copyright 2013, gabrielle dunne

A GEOLOGICAL AND SEDIMETOLOGICAL APPROACK TO INFER PALEOCLIMATE FROM BURIED SOILS PROFILES WITHIN PLAYA FILLS,

SOUTHERN HIGH PLAINS, TEXAS.

by

Gabrielle Dunne BSc

A Thesis

In

Arid Land Studies

Submitted to the Graduate Faculty of Texas Tech University in

Partial Fulfillment of the Requirements for

the Degree of

Master of Science

Approved

Dr Dustin Sweet Chair of Committee

Dr Gad Perry

Dr Anthony Parsons

Dominick Casadonte Interim Dean of the Graduate School

May, 2013

Texas Tech University, Gabrielle Dunne, May 2013

ii

Acknowledgments

I am very grateful to Dr. Dustin Sweet, my thesis advisor, for his advice and

guidance throughout this program. I would like to express my gratitude to Dr.

Melanie Barnes for her help and instruction in the geochemistry lab. I would

like to give my deepest appreciation to Dr. Wayne Hudnall, who gave up his

precious time to assist me in the field and allowing me to use his coring

equipment. I would also like to thank Andrew Whitesides and Juske Horita for

their assistance in the field. I acknowledge Dr. Gad Perry and Dr. Anthony

Parsons for their input while serving in the graduate committee and finally I

thank Hollee Baird for her assistance in the preparation of samples.


iii

Table of Contents

Acknowledgements ii

List of Tables ix

List of Figures xi

Abstract xiv

1. Introduction to the Southern High Plains 1

1.1 Physical Properties of the Southern High Plains 4

1.1.1 Geological Setting and Stratigraphy 4

1.1.2 The Ogallala formation 7

1.1.3 The Blackwater Draw Formation, Tahoka Formation and the Randall Clay

7

1.2. Playa Wetlands 8

1.2.1 Playas 8

1.2.2 Playa Morphology 9

1.2.3 Playa Hydrology 10

1.2.4 Playa Formation 13

1.2.5 Playas as Climate Proxies 15

1.3 Climate of the Southern High Plains 15

1.3.1 The Southern High Plains in Modern times 15

1.3.2 The Southern High Plains in Pleistocene-Holocene times 19


iv

1.4 Soils 1.4.1 Modern Soil 25

1.4.2 Soil Horizons 26

1.4.3 Soil Structure 26

1.4.4 Soil and climate 31

2. Materials, Methods and Sampling

2.1 Materials and Methods 34

2.1.1 Core Samples 34

2.1.2 Site Description 34

2.1.3 Coring 41

2.2 Physical Sampling

2.2.1 Sample preparation 42

2.2.2 Grain Size 42

2.2.3 Thin Section 43

2.3. Geochemical Sampling

2.3.1 Sample Preparation 48

2.3.2 Loss on Ignition (LOI) 48

2.3.3 Fusions 49

2.3.4 ICP/ICP-MS 47

3. Results 51

3.1. Key physical properties used in assigning soil horizonation 51

3.1.1 Bailey Playa -1 57


v


3.1.3 Floyd Playa -1 65

3.1.4 Floyd Playa -2 69

3.2 Geochemistry 73

3.3 Major Oxides 74



3.3.3 Floyd Playa-1 83


3.4 Minor Elements 89





4. Weathering Profiles 103

4.1 Weathering Ratios 105

4.1.1 Barium/Strontium Ratio 105

4.1.2 Titanium / Zirconium Ratio 105

4.1.3 Aluminum/Silica Ratio 106

4.1.4 Alkalines / Titanium Ratio 107

4.1.5 Potassium + Sodium / Aluminum Ratio 107


vi

4.1.6 Summation of Bases/Aluminum Ratio 107

4.1.7 Titanium/Aluminum Ratio 108

4.1.8 Carbonates 111

4.1.9 Iron-Manganese Nodules 113

4.2 Weathering Profiles of Playa Sediments in Bailey County

and Floyd County 113

4.2.1 Bailey Playa-1 113




4.2.5 Other Elemental Weathering Trends

136

4.2.6 Soil Characteristics

136

4.3 Correlation and Soil Types 139

4.3.1 Bailey Playa 139

4.3.2 Floyd Playa 143

4.3.3 Playa formation considerations

147

4.4 Temporal Constraints 148

5. Climate Proxies 158

5.1 Climo-functions 158

5.1.1 Method (1) 158


vii

5.1.2 Method (2) 159

5.1.3 Method (3) 161

5.1.4 Method (4) 161

5.2 A Summary of Climate 163

6. Summary and Conclusions 168

References 170

Appendix 181


viii

List of Tables

1.1 Proposed Processes for Playa Initiation and development 13

1.2 Major Soil Horizons 27

1.3 Soil Sub Horizons 28

1.4 Ped Structures 29

1.5 Soil Orders 32

3.1 Soil Core Nomenclature 52

3.2 Major Oxides, BP-1 75

3.3 Major Oxides, BP-2 76

3.4 Major Oxides, FP-1 77

3.5 Major Oxides, FP-2 78

3.6 Minor Elements, BP-1 89

3.7 Minor Elements, BP-2 90

3.8 Minor Elements, FP-1 91

3.9 Minor Elements, FP-2 92

4.1 Molecular Weathering and Pedogenesis Ratios 104

4.2 Stages of Carbonate accumulation in soils 112

4.3 Surface Horizons 137

4.4 Subsurface Horizons 138

5.1 Quantification of Climo-functions 158

5.2 Summary of paleotemperature 160

5.3 Summary of paleoprecipitation 162


ix

5.4 Paleoprecipitation calculated using depth to Bk 163


x

List of Figures

1.1 Study Location 6

1.2 Playa Morphology 12

1.3 Precipitation Variability 18

1.4 18O curve 20

1.5 Climate summary of the last 10 ky 23

2.1 Aerial view of Bailey Playa 36

2.2 Aerial view of Floyd Playa 36

2.3 Bailey Playa Drainage Network 38

2.4 Bailey Playa 3D model 38

2.5 Floyd Playa Drainage Network 40

2.6 Floyd Playa 3D model 40

2.7 Coring 41

2.8 Thin Sections 46

2.9 Billets 47

3.1 Stratigraphic logs 54

3.2 Grain Size BP-1 56


xi

3.3 Grain Size BP-2 64

3.4 Grain Size FP-1 68

3.5 Grain Size FP-2 71

3.6 Major Oxides BP-1 80

3.7 Major Oxides BP-2 82

3.8 Major Oxides FP-1 86

3.9 Major Oxides FP-2 88

3.10 Minor Elements BP-1 95

3.11 Minor Elements BP-2 97

3.12 Minor Elements FP-1 100

3.13 Minor Elements FP-2 102

4.1 Ti/Al parent material 110

4.2 BP-1 Weathering Ratios - I 115

4.3 BP-1 Weathering Ratios - ii 119

4.4 BP-2 Weathering Ratios - I 122

4.5 BP-2 Weathering Ratios - ii 124

4.6 FP-1 Weathering Ratios - I 128


xii

4.7 FP-1 Weathering Ratios - ii 130

4.8 FP-2 Weathering Ratios - I 132

4.9 FP-2 Weathering Ratios - ii 134

4.10 Bailey Playa Correlation 142

4.11 Floyd Playa Correlation 146

4.12 Grain Size Map 151

4.13 S-N transect 153

4.14 SW-NE transect 155

5.1 Summary of climate trends 167


xiii

Abstract

The Southern High Plains (SHP) is a large plateau with ubiquitous

playas accumulating sediment with little to no erosion for the past 1.6 Ma. The

small size and ephemeral nature of playas make them sensitive to climatic

fluctuations and often record high resolution archives. To date, climatic

studies on the SHP largely pursued pedogenic, sedimentologic and/or isotopic

data sets. Here we present whole-rock geochemical climatic signatures as a

new paleoclimate proxy for future playa studies on the SHP. Many whole-rock

geochemical ratios within soil horizons are largely driven by pedogenic

processes. Moreover, whole-rock geochemical signatures are

interchangeable between many modern soils and paleosols. Four cores (up to 4.5 m deep) were recovered from two playas on the

eastern half of the SHP (Bailey County Playa) and the western margin of the

SHP (Floyd County Playa). 2-3 buried paleosols (~1-1.5 m thick) were

recognized within each core by traditional observational techniques. Each

core shows an upward progression of buried soil type from aridisol (30-40

kyBP), to inceptisol (~21 kyBP), to mollisol (~11 kyBP) representing a

decrease in aridity. Whole-rock geochemical proxies largely follow this

progression and indicate much higher CaO and salinized zones in the lower

paleosols and an increase in leached or illuviated zones in higher paleosols.


xiv

Thus, pedogenic processes observed through traditional observation methods

and geochemical data sets agree.

Using empirically derived equations that utilize whole-rock geochemical

data, precipitation and mean annual temperature increased upward in

paleosols from ~275 mm/yr to 440 mm/yr (SE ± 147 mm/yr) and from ~ 12 to

16°C (SE ±0.6°C). Modern precipitation levels range from 330-450 mm/yr and

mean annual temperature is 18.6°C. Thus, from the oldest paleosol to the

present, these data sets indicate that precipitation increased by 50-175 mm/yr

while mean annual temperature increased by ~6°C. Our age model utilizes

previous published radiocarbon dates from nearby playas and suggests

temperature has steadily increased during soil forming events for the past ~30

ky, whereas precipitation largely increased between 21ky and 11ky soil

forming episodes. These results are similar to coeval temperature and

precipitation changes estimated elsewhere on the Great Plains.


1

Chapter 1 Introduction to the Southern High Plains

Paleoclimate can be used as a frame work for predicting variability and

thresholds of future climate change. The small size and ephemeral nature of

inundation make playa wetlands highly sensitive to climatic fluctuations and

consequently playas may be able to provide a high resolution terrestrial

archive of paleoclimate (Bowen and Johnson, 2012). Holliday et al., (1996)

study playa wetlands on the Southern High Plains which are

contemporaneous with the Blackwater Draw Formation. The multiple buried

soil profiles observed in these playas may extend back 1.6 million years,

giving them the potential to be utilized as quaternary climate proxies.

Previous studies that use playa lake sediments as a paleoclimate proxy

(Bowen and Johnson, 2012, Holliday et al., 2008, Holliday et al., 1996) focus

on carbon dating, stratigraphy and analysis of soil profiles.

Paleosols preserved in continental settings may be able to provide a

long term, continuous climatic record, equal in resolution to marine isotope

records (Retallack, 2007), especially under aggradational conditions.

Paleosols form at the Earth’s surface in direct contact with the atmosphere,

giving them potential as one of the most powerful tools in paleoclimate

interpretation (Sheldon and Tabor, 2009). Sheldon and Tabor (2009)

summarize whole-rock geochemistry methods to study paleosols in a range of

depositional setting. Geochemical ratios and trends observed within major

oxides and selected trace elements indicate pedogenic processes in

paleosols such as, weathering, leaching and illuviation that are largely

climatically driven (Sheldon & Tabor, 2009). Whole-rock geochemistry is


2

interchangeable between paleosols and modern soils allowing comparative

studies and inferences to be made regarding the conditions under which

paleosols formed (Dreise et al., 2005).

The aim of this study is to determine whether the well-established

geochemical methods of paleosol analysis as described by Sheldon and

Tabor (2009) can be successfully applied to the buried soil profiles of playa

wetlands, an area where this type of study has not been previously explored.

The objective is to apply these methods to data collected from playa wetlands

on the Southern High Plains to;

• Assess the degree of weathering within the buried soil profiles.

• Assess the grain size distribution within the soil profile.

• Assess the variability in buried soil profiles between the playa floor and

playa edge.

• Asses the variability in buried soil profiles between the eastern and

western margins of the Southern High Plains.

Comparisons between our finding and the findings of others working in the

same area which date their sediments e.g. Bowen and Johnson (2012,

Holliday et al., (2008) and Holliday et al., (1996) can be used to determine if

the whole-rock geochemistry of playa sediment can be used as a viable proxy

for interpreting quaternary climate on the Southern High Plains. Absolute

age control of the cores was not assessed; however, we utilize grain size

distribution data in comparison with the well-established northerly fining trend


3

observed in the Blackwater Draw Formation to assess reworking and thus, a

relatively younger age. Results indicate that buried soils grain size

distributions are inconsistent with the range expected within the Blackwater

Draw Formation, thus we infer that these paleosols were developed on

reworked Blackwater Draw Formation sediments, and thus younger than ~

40,000 years. Furthermore, C14 dates from nearby playas are used to bolster

the grain size comparison trends and suggest that the buried soils analyzed

range from ~11-20 ky.

The cores were obtained from the center and edge of two playas in

Texas, one located in Floyd County, which is on the edge of the eastern

escarpment and the other from Bailey County, which is further to the west (Fig

1.0). The cores crossed between two and three buried soil profiles. Samples

were obtained from each core at 100 mm intervals for analysis. For each

sample data on grain size, major elements (Wt %) and minor elements (PPM)

was collected. This data was plotted against depth and trends were analyzed

to infer the boundaries of the buried surfaces and different horizons within the

buried soil profiles. To determine the degree of weathering within each profile

ratios of mobile versus immobile elements were plotted against depth. The

pedogenic processes that we attribute as the cause, of the physical and

geochemical properties within our core, can be compared with modern

pedogenic processes resulting in similar characteristics to infer climatic

conditions at the time of their formation.


4

1.1 Physical Properties of the Southern High Plains 1.1.1 Geological Setting and Stratigraphy

The Southern High Plains also known as the Llano Estacado, is an

extensive semi-arid plateau spanning northwest Texas and eastern New

Mexico, covering an area of approximately 80,000 km2 (Holliday et al., 2008).

It lies south of the Canadian River and east of the Pecos River (Fig 1.1). The

Southern High Plains are approximately 400 km long (N-S) and 200 km wide

(E-W) and have an elevation ranging between 750 m – 1500 m (Lotspeich &

Everhart, 1962).

The development of the Pecos and Canadian river valleys are

attributed to the dissolution of salts and underlying Paleozoic evaporates by

groundwater, which led to subsidence and in turn controlled the position of the

river valleys (Gustavson, 1988). Moreover, uplift associated with the

formation of the Rocky Mountains created the hydraulic head which initiated

groundwater dissolution of the evaporites (Wood, 2002). This fluvial incision

has since isolated the Southern High Plains such that no hyrdrological

recharge outside of the Southern High Plains is currently underway. Thus,

the Southern High Plains can be thought of as an isolated plateau with no

fluvial source exterior to the region since isolation at around 1.6 Ma (Holliday,

1989).

The topography of the plateau is very flat and is interrupted only by

several dune fields and many small playa wetlands and their associated


5

lunettes (Holliday, 1989). The basal bedrock unit of the playa-lunette systems

is formed from sand and gravel eroded from the Rocky Mountains, this is

known as the Ogallala Formation (Bowen and Johnson, 2012). The Ogallala

Formation forms the largest aquifer in the U.S.A. and provides the primary

water supply for the semi-arid regions of Texas and New Mexico (Fryar et al.,

2001). A thick carbonate-rich zone forms a cap rock above the Ogallala

formation (Bowen and Johnson, 2012) this is overlain by the aeolian derived

sands and silts of the Blackwater Draw Formation (Holliday, 1989). Holliday

et al., (2008) observe playa fill on the Southern High Plains to be composed of

a pale olive green to gray clay which maybe calcareous, this it termed the

Tahoka Formation (Reeves, 1990). Above this lies the Randall Clay which is

a dark black/ gray mud (Holliday et al., 2008).


6

Figure 1.1: Location of the two study sites; Bailey Playa and Floyd Playa on the Southern High Plains (modified from Holliday, 1989).


7

1.1.2 The Ogallala Formation

The Ogallala Formation (Darton, 1905), averages 100m thick (Wood,

2002) and is Miocene-Pliocene age (Holliday et al., 1996). It forms a massive

piedmont alluvial plain on the eastern side of the southern Rocky Mountains

and forms the bedrock of the High Plains, from South Dakota to south–

eastern New Mexico (Reeves, 1972). The Ogallala Formation lies

unconformably above Permian, Triassic, Jurassic and Cretaceous strata and

is capped by a pedogenic calcrete which defines the three sides of the

Southern High Plains (Sabin and Holliday, 1995). The formation consists of a

series of alluvial deposits which filled incised bedrock valleys with clay, sand

and gravels derived from the Rocky Mountains (Hawley et al., 1976).

1.1.3 The Blackwater Draw Formation, Tahoka Formation and Randall Clay

The Blackwater Draw Formation termed by Reeves (1976) is formed

from Pleistocene cover sand, which directly overlay The Ogallala Formation.

The Blackwater Draw Formation forms a 25-30m thick sequence which is the

principal surficial deposit across much of the Southern High Plains (Hawley,

1976). The Blackwater Draw is characterized as an eolian deposit consisting

of fine sand, silt, and clay, which fine from south-west to north-east, a

relationship that suggests sediments were derived from the Pecos River

Valley (Holliday, 1989). The formation includes up to six well developed

buried soil horizons which indicate periods of episodic sedimentation


8

separated by times of landscape stability. The eolian deposition is inferred to

have occurred during times of prolonged aridity and the stability and

pedogenesis most probably occurred in periods of sub-humid to semi -arid

conditions (Holliday, 1989).

Two formations comprise the basin fill of playa wetlands on the

Southern High Plains. The Tahoka formation which is Wisconsin in age,

using pollen and vertebrate fossil analysis Reeve’s (1976) date the formation

between 20-14 ky BP. The Tahoka is comprised of two fill facies; sand –

gravel found at the basin margin, this is interpreted to be fluvial/deltaic

sediment (Evans & Meade, 1945). The other facies is found in the center of

the playa floor and is composed of a clay dominated lacustrine mud (Evans &

Meade, 1945). Above the Tahoka formation lays a surficial deposit - The

Randall Clays, a dark black smectite mud composed of silts and clays

(Holliday et al., 2008) these are thought to form under ponded conditions or

heavily vegetated sub-aerial conditions (Holliday et al., 2008).

1.2 Playa Wetlands

1.2.1 Playas

Playas are small, internally drained, ephemerally inundated wetlands

that are common throughout many arid and semi-arid regions across the

world (Bowen and Johnson, 2012). Playa wetlands are a prominent feature of

the Southern High Plains of Texas and New Mexico, it is estimated that there


9

are approximately 25,000 - 30,000 of these ephemeral lakes, which occur

above the present zone of saturation (Osterkamp and Wood, 1987a; Holliday

et al., 1996). The playas of the Southern High Plains lie on top of the

widespread Blackwater Draw Formation and lie locally above the Ogallala

Formation (Holliday et al., 1996). Small, isolated, eolian dunes called lunettes

often form downwind of playa basins (Holliday, 1997; Bowen and Johnson,

2012). Lunettes, first named by Hills (1940) are relatively low dune ridges

(<10m), and usually have a crescentic form. On the Southern High Plains the

material forming the lunettes is generally material derived from the deflation of

both the Blackwater Draw Formation and sediments from the associated

playa basin floor (Sabin and Holliday, 1995; Holliday, 1997). Playa-lunette

systems provide an array of vital roles such as groundwater recharge (Wood,

2002), surface water storage and nutrient cycling (Bowen and Johnson,

2012). A thick unsaturated zone which underlies much of the Southern High

Plains is a result of increased groundwater movement to the southeast as

seeps and springs from the escarpment edge (Wood & Osterkamp, 1987a).

Playa wetlands in this area do not occur beyond the escarpment edge of the

Southern High Plains (Wood 1987a).

1.2.2 Playa Morphology

Playa-Lunette systems tend to be characterized by several distinct

zones; (Figure 1.2). The playa floor, this area is intermittently inundated with


10

water and is underlain by hydric soil that is locally able to support aquatic

vegetation (Smith, 2003). The annulus is the sloping region between the rim

of the depression and the playa floor. Between the depression rim and the

lunette, there is a generally flat grass bench area. The lunette is a stratified

dune that forms downwind of the playa and is derived largely from calcareous

playa fill (Sabin and Holliday, 1995). The inter-playa is an upland, typically flat

region which is often mantled by loess and covers an expansive area (Bowen

and Johnson, 2012).

1.2.3 Playa Hydrology

Playas significantly influence the surface and groundwater hydrology of

the Southern High Plains by providing surface water drainage and major

zones of recharge to the Ogallala aquifer (Stone, 1990). Precipitation and

runoff are the primary surface processes acting on playa basins influencing

the shape of playa basins through the interplay between centripetal flow and

erosion by sheet wash, rill wash, and small streams that transport sediments

to the playa (Reeves, 1990).

Playas significantly influence the surface and groundwater hydrology of the

Great Plains by providing surface water drainage and major zones of

recharge to the Ogallala aquifer (Stone, 1990). Precipitation and runoff are the

primary surface processes acting on playa basins influencing the shape of

playa basins through the interplay between centripetal flow and erosion by


11

sheet wash, rill wash, and small streams that transport sediments to the playa

(Reeves, 1990).


12

Figu

re 1

.2: a

dapt

ed fr

om B

owen

and

John

son

(201

2) sh

ows t

he k

ey m

orph

olog

ical

feat

ures

of a

pla

ya w

etla

nd.


13

1.2.4 Playa Formation

Playa wetlands occur where water can periodically collect in

depressions of the lands surface. There is some degree of debate

surrounding the processes by which playa wetlands form; proposed

processes include, differential compaction (Johnson, 1901), wind deflation

(Reeves, 1966), piping (Reeves, 1966), animal activity (Reeves, 1966), and

collapse through dissolution (Gustavson and Finley, 1981). See Table 1.1,

adapted from Holiday et al., (1996).

Osterkamp and Wood (1987b) propose a mass transport model for

playa development and expansion where an initial depression, most likely

formed by removal of material by eolian processes, is inundated with surface

Table 1.1 Proposed Processes for Playa Initiation and development

Process References

Deflation Evans and Meade (1945), Reeves (1966), and Reeves and Parry (1969), Kaczrowski (1977)

Dissolution of underlying evaporites

Johnson (1901), Baker (1915), Patton (1935), Price (1944), Reeves (1971), Gustavson et al. (1980), Reeves and Temple (1986),Paine (1994)

Animal activity , (see Gilbert, 1895), Gould (1907), Baker (1915), Reeves (1966) Leaching of calcic soils and calcretes and deflation Judson (1950, 1953) Piping of fines, eluviation, and calcrete dissolution Wood and Osterkamp (1984), Osterkamp and Wood (1987) Differential compaction Johnson (1901)


14

run off from precipitation. Downward transport of fine grained clastic and

organic material occurs, oxidation of the organic material at depths which

forms carbonic acid when combined with groundwater, allows for rapid

dissolution of carbonates in the unsaturated zone; ultimately leading to more

subsidence.

Playas expand from the center outwards (Wood & Osterkamp, 1987a)

fine grained deposits on the playa floor lead to low permeability. Thus, the

annulus is the main zone of groundwater recharge (Wood & Osterkamp,

1987a). During periods of ponding piping of water and fine clastic material

into the unsaturated zone along with the eluviations of silts and clays by

ground water leads to further expansion of the playa (Wood & Osterkamp,

1987b). The size of a playa is a function of its catchment area, once the

supply of runoff is insufficient for further illuviation and dissolution, expansion

will cease (Wood & Osterkamp, 1987a).

Holliday et al., (1996) examined the lacustrine, eolian and alluvial fill of

multiple playas on the Southern High Plains, and proposed fluvial erosion and

deflation as the primary playa formation mechanism. Holliday et al., (1996)

observe that variations in the texture and grain size of the Blackwater Draw

Formation are a controlling factor in the size and distribution of Playas.

Coarse sandy areas form the most erodible substrates, followed by finer

clayey areas, where the clays form sand sized aggregates (Chepil & Woodruf,


15

1963). This supports the hypothesis for playa formation and maintenance by

deflation and erosion rather than dissolution and subsidence as proposed by

Wood and Osterkamp (1989a). Holliday et al., (1996) also suggest that the

dissolution of carbonate occurs as a result of the playa basin rather than

being the cause of the playa basin.

1.2.5 Playas as Climate Proxies

The small size and ephemeral nature of inundation make playas highly

sensitive to climatic fluctuations and consequently they may be able to

provide a high resolution terrestrial archive of palaeoclimate on the high plains

(Bowen and Johnson, 2012). It is possible that playa wetlands contain

sediment reaching as far back as 1.6 Ma, this period covers Marine Isotope

Stage (MIS) 3 and possibly reaches as far back as MIS 5 (Bowen and

Johnson, 2012). Playas on the Great Plains contain terminal Pleistocene and

Holocene fills. Thus they have the potential for providing clues to regional

landscape evolution and environmental changes (Holliday et al., 2008).

1.3 Climate of the Southern High Plains 1.3.1 The Southern High Plains in Modern Times

Russell (1945) describes the Great Plains as climate type BScDw, this

is characterized as dry, steppe, mesothermal (average temperature of coldest

month 0 - 18°C) climate, with occasional microthermal years (average


16

temperature of coldest month below 0°C) (Lotspeich & Everhart, 1962). The

continental setting of the Southern High Plains reduces the climate

modulating effects of the oceans resulting in greater seasonal variations. The

Southern High Plains experiences an average annual temperature range

between -9°C and 34°C, with a mean annual temperature (MAT) of 18.6°C

(High Plains Regional Climate Centre, 2009).

Temperatures on the Southern High Plains are generally high with 70 -

100 days per year experiencing conditions greater than 32°C (USGCRP,

2009). The average July temperature in Floyd County (Fig 1.1) is 26.5°C

(SRCC) average December temperature for Floyd County is 3°C (SRCC)

however temperatures do frequently drop below freezing.

Precipitation on the Southern High Plains is variable, it is lower during

the winter months, and higher during the summer. The average annual rainfall

of Lubbock is 473 mm; with 540 mm falling in May, 760 mm in June, 600 mm

in August and 650 mm in September (NOAA). The mean annual precipitation

(MAP) on the Southern High Plains ranges from 450 mm/year in the north

east to 330 mm/year in the south west (Bolen et al., 1989). 80% of total

precipitation falls between the months of May to October; during the winter

cold air masses from Polar Regions move south, blocking moister air masses

from the Gulf of Mexico (Llano Estacado Regional Water Plan, 2010).

Precipitation is highest during spring due to the frontal lifting of warm air


17

masses (Johnson, 2007a). During the summer months droughts often occur

as subsiding air leads to high pressure over the region, summer precipitation

tends to occur during intense convectional storms (Johnson, 2007a). Figure

1.3 shows the inter-annual variability of rainfall on the Great Plains.


18

Figu

re 1

.3: a

dapt

ed fr

om W

este

r (20

07) u

ses N

OA

A d

ata

colle

cted

from

Lub

bock

, Tex

as to

dem

onst

rate

the

inte

r-an

nual

var

iabi

lity

in ra

infa

ll on

the

Hig

h Pl

ains


19

Winds blow almost continuously across the Great Plains with gust

commonly exceeding 95 km/h (Lotspeich & Everhart, 1962). Winds speeds

tend to be greater in the early spring and autumn, with average wind velocities

in March being 50% greater than those in August (Lotspeich & Everhart,

1962). These increased wind velocities in spring and autumn often generate

localized dust storms (LERWP, 2012).

Modern Vegetation on the Great Plains is short grass prairie,

dominated by Blue Grama (Bouteloua gracilis), Buffalo Grass (Buchlöe

dactyloides) and Honey Mesquite (Prosopis glandulosa) (Johnson, 2007a).

Sand Sagebrush and Yucca are also common, while more aquatic species

such as Curltop Smartweed are able to colonies playas which are frequently

inundated after rainfall (LERWP, 2010).

1.3.2 The Southern High Plains in Pleistocene – Holocene times

During Marine Isotope Stage (MIS) 2-4 (Fig 1.4) The Laurentide ice

sheet extended across much of North America, this was known as the

Wisconsin Glaciation. At 18 ky, during MIS 2, conditions reached the Last

Glacial Maximum (LGM). During this time tundra and boreal forest extended

hundreds of miles south of the ice sheet and temperate forest retreated as far

south as Texas (Wilkins, 1991). MIS 1, 11ky ago, saw the end of the Younger


20

Figure 1.4: adapted from Porter (1989) shows the shifts in 18O

isotopes from benthic foraminifera. The peak in oxygen isotopes at

MIS2 (18,000 years ago) corresponds with the LGM. MIS stages 2-

4 correspond with the Wisconsin Glaciation.


21

Dryas and transition from the Pleistocene to the Holocene, this was

accompanied by increasing temperatures (Fritz, 2001).

Fritz (2001) examined lake records from several locations across North

America, including the Southern High Plains, Northern Great Basin and

Arizona. The records demonstrate that the whole of North America

experienced millennial scale fluctuations in climate linked with insolation and

shrinkage of the Laurentian ice sheet during MIS1. During the early

Holocene, 10 ky ago, lowered lake levels observed in the Pacific Northwest

and Northern Great Basin indicate increase aridity, this is linked with the

increased summer insolation leading to the intensification of the Pacific sub-

tropical high, preventing inflow of moist air from the west (Barnosky, 1987).

Van Devender et al., (1987) propose precipitation levels greater than today

but lower than the Pleistocene maximum around 9ky ago. This is likely due to

the southerly displacement of the jet stream. After 9ky, northward migration

of the jet stream led to a decrease in winter precipitation and drying of climate

(Fritz, 2001). At 5 Ky ago, a reduction in insolation lead to an increase in

moisture across North America, greater fluctuations in winter precipitation

were a result of shifting westerly storm tracks, high pressure cells and a shift

in the position of the winter jet (Stine, 1994).


22

Bowen and Johnson, 2012, Holliday et al., 2008, Holliday et al., 1996

have carried out stratigraphic analysis of soil profiles from playa basins

spanning MIS 5-1. Bowen and Johnson (2012) find that playa wetland

sediments suggest that during MIS 3 climate was similar to today, with warm

temperatures and low effective moisture. Sediments which correspond to the

extended inundation of the playa floor indicate a relatively cool climate and

are found in the stratigraphic record at depth corresponding to MIS 2 (Bowen

& Johnson (2012). Towards the end of MIS 2 (11-13 ky), Holliday et al.,

(2008) observe eolian sands at the base of several playa sequences on the

Southern High Plains, interpreted to be indicative of regional aridity.

MIS 1, 11 ky ago, saw the end of the Younger Dryas and the transition

from the Pleistocene to Holocene. At the Pleistocene-Holocene transition a

soil, dated between 11.8 and 9.4 ky is thought to coincide with a warming of

climate which continued through the Holocene (Bowen and Johnson. 2012).

Holliday (1989) observes lacustrine deposits followed by desiccation, dated

between 8.5 and 5.5 ky ago and infer peak aridity during this time. Between ~

9 to ~4 ky ago, Holliday (2008) observes a slowing in mud deposition which is

also linked to the warming of climate, this continued throughout the Holocene

period. Figure 1.5 adapted from Fritz (2001) provides a summary of climate

on the Southern High Plains over the last 10 ky.


23

Figure 1.5: adapted from Fritz (2001) is a summary of climate on

the Southern High Plains over the last 10ky based on

stratigraphic and sedimentological observations of Holliday

(1989).


24

It has been said that recent drought on the Southern High Plains such

as the 1930s “Dustbowl” (Worster, 1979) pale in insignificance when

compared to the “mega-droughts” experienced during the Holocene

(Woodhouse and Overpeck, 1998). One such drought occurred during the

Medieval Period ~AD 900-1300, when the Northern Hemisphere experienced

much higher temperatures than all but the most recent decades (Woodhouse

et al., 2010). This period of severe and persistent drought has been linked

with a peak in solar irradiance (MacDonald et al., 2008). Laird (2003)

suggests that atmospheric circulation was also different during this period,

with a change in shape and location of the jet stream causing a change in

associated storm tracks, shifting the moisture regime from wet to dry.

Graham et al. (2007) attributed medieval drought to sea surface temperature

(SST) anomalies i.e. strong cooling in the Pacific Ocean related to La Nina-

like conditions. Further research using the Community Atmospheric Model

(CAM) suggests that warm conditions in the North Atlantic may also be an

important factor influencing drought, particularly its aerial extent. It is thought

that a combination of both Pacific and Atlantic SST anomalies controlled the

longevity and severity of drought in the medieval period (Feng et al., 2008).

Regardless of the control, the concept of punctuated shifts in climate regime

for the Southern High Plains is important to keep in mind when evaluating

potential climate proxies in the stratigraphic record.


25

Grasslands have dominated the Southern High Plains since Miocene-

Pliocene times (Fox & Koch, 2003). Studies based on pollen analysis have

shown this to fluctuate between parkland and savannah and interspersed

short periods of deciduous woodland (Johnson, 2007a). Johnson (2007a)

uses pollen records associated with playa wetlands on the Southern High

Plains to reconstruct vegetation since the LGM. During the LGM, the region

was dominated by sagebrush grassland indicating a cool dry climate, this

transgresses into tall grass prairie towards the end Pleistocene typical of a

cooler humid environment (Johnson, 2007a). At the onset of the Holocene,

the grasslands were mixed prairie to Savannah this coincides with climatic

warming and increased aridity. Short grass ecosystems dominate from the

mid Holocene onwards (Johnson, 2007a).

1.4 Soils 1.4.1 Modern Soil

Climate is one of the most important factors influencing the formation of

soil, different soil types are restricted to different climate zones, each soil has

a specific climatic range, and features of such soils can be used to infer

paleoclimate (Retallack, 1990). Paleosols can be used in order to provide a

relatively detailed reconstruction of MAT, MAP, provenance and weathering

intensity (e.g. Sheldon & Tabor, 2009). Paleosols are also able to provide

information about atmospheric and soil gas composition including CO2 and O2

(Cerling, 1984). Soils record nutrient flux in and out of the soil, and may


26

reveal clues about moisture balance during pedogenesis, vegetation cover

and paleo-altitude (Sheldon and Tabor, 2009).

1.4.2 Soil Horizons

Paleosols profiles are divided into horizons according to color,

structure, root trace concentration, and translocation of authogenic minerals

(Tabor et al., 2008). The presence of a horizon indicates that soil forming

processes operated on a relatively stable substrate for a period of time

sufficient to allow for the reorganization of parent materials into zones of

accumulation and removal (Retallack, 1990). Table 1.2 adapted from Brady &

Nyle, (1984) summarizes the major horizons.

The master horizons are often divided into subcategories; a designated

lower case letter follows the horizon e.g. Bk or Bt, the sub horizons observed

in this study are summarized in Table 1.3 adapted from Brady & Nyle, (1984.)

1.4.2 Soil Structure

The structure of a soil is determined by the arrangement of soil

particles, and binding together into larger clusters called peds. Peds are

aggregates of soil which occur between roots cracks and burrows (Retallack,

1990). Peds can be classified into several different types, these are

summarized in Table 1.4 (adapted from Brady & Nyle (2008).


27

Table 1.2- Major Soil Horizons

Horizon Properties

O The O horizon is an organic layer made of wholly or partially decayed plant and animal debris. The O horizon generally occurs in undisturbed soil, since plowing mixes the organic material into the soil. In a forest, fallen leaves, branches, and other debris make up the O horizon.

A The A horizon, called topsoil by most growers, is the surface mineral layer where organic matter accumulates. Over time, this layer loses clay, iron, and other materials to leaching. This loss is called eluviation. Materials resistant to weathering, such as sand, tend to remain in the A horizon as other materials leach out. The A horizon provides the best environment for the growth of plant roots, microorganisms, and other life.

E The E horizon, the zone of greatest eluviation, is very leached of clay, chemicals, and organic matter. Because the chemicals that color soil have been leached out, the E layer is very light in color. It usually occurs in sandy forest soils in high rainfall areas.

B The B horizon, or subsoil, is often called the "zone of accumulation" where chemicals leached out of the A and E horizon accumulate. The word for this accumulation is illuviation. The B horizon has a lower organic matter content than the topsoil and often has more clay. The A, E, and B horizons together are known as the solum. This part of the profile is where most plant roots grow.

C The C horizon lacks the properties of the A and B horizons. It is the soil layer less touched by soil-forming processes and is usually the parent material of the soil.

R The R horizon is the underlying bedrock, such as limestone, sandstone, or granite.


28

Table 1.3 - Soil Sub Horizons

Suffix Properties

b Buried horizon. Such a soil layer is an old horizon buried by sedimentation or other processes.

c Concretions or hard nodules. a nodule is a hard "pocket" of a substance like gypsum in the soil.

g Strong gleying. Such a horizon is gray and mottled, the color of reduced (nonoxidized) iron, resulting from saturated conditions

h

Illuvial accumulation of organic matter. The symbol is used with the B horizon to show that complexes of humus and sesquioxides have washed into the hoizon. Includes only small quantities of sesquioxides. May show dark staining.

k Accumulation of carbonates. Indicates accumulation of calcium carbonate (lime) or other carbonates.

m

Cementation. The symbol indicates a soil horizon that has been cemented hard by carbonates, gypsum, or other material. A second suffix indicates the cementing agent, such as "k" for carbonates. This is a hardpan horizon; roots penetrate only through cracks

t Accumulation of silicate clays. Clay may have formed in horizon or moved into it by illuviation.

w Development of color or structure. The symbol indicates that a horizon has developed enough to show some color or structure but not enough to show illuvial accumulation of material.


29

Table 1.4 - Ped Structures

Spheroidal Plate-like Block-like Prism-like

Granular Crumb Angular sub-

angular Columnar Prismatic

Characteristic of subsurface A horizon, usually porous. Subject to wide and rapid changes.

Common in E horizons, but may occur in any part of the profile. Often inherited from the parent material, or caused by compaction.

Common in B horizons, particularly in humid regions, may occur in A horizon. Promote drainage, aeration and root penetration.

Usually found in B horizons. Common in arid and semi-arid regions.


30

The aggregation of soil particles allows for openings and hollows within

the soil. This is important for movement of air and water, these openings may

form interconnect networks called packing voids, a vuggy structure occurs

when air spaces are irregular, near spherical air spaces produce a vesicular

structure ( Retallack, 1990).

Loosely packed spherical peds cemented by organic matter produce a

granular structure, this is common in the A horizon. Large peds, with platy,

prismatic or blocky types dominate the B horizon. Platy structure results from

disruption of original bedding and addition of cement (Retallack, 1990).

Prismatic and blocky structures are often the result of continual wetting and

drying which causes swelling and shrinking of the peds, these peds are held

together by clays, carbonates, iron oxides and organic matter (Gardiner &

Miller, 2004).

Cutans are the modified surfaces of peds and come in various forms;

clay coatings (Argillans), Iron stained surfaces (ferrans), Iron/Aluminum oxide

coatings (sesquan) and calcite coatings (calcans) (Retallack, 1990). Cutans

may also form during digenesis, these tend to be much thicker than the thin

irregular cutans of the original soil (Retallack, 1990).

Isolated glaebules are another common feature of soil structure, they

possess a wide range of shapes and form from a similar variety of materials to

cutans, one example are the calcareous nodules commonly found in desert


31

soils (Retallack, 1990). Fe-Mg concretions may also form glaebules these are

generally associated with finer grained, clayey sediments with restricted

permeability and drainage (Stiles et al., 2001).

1.4.3 Soil and Climate

Paleosols can provide a direct means of reconstructing past climate,

soils form at the Earth's surface in direct contact with the atmospheric and

climatic conditions during the time of their formation thus they are in

equilibrium (Sheldon and Tabor, 2009). Paleosols contain many diagnostic

indicators of environment; different soil orders are formed under different

climatic regimes, and physical properties these are summarized in Table 1.5

(adapted from Brady & Nyle (2008).

Color can indicate the soil moisture regime in modern soils, gley colors,

(typically blue, green and-grey) and/or mottling indicates reduced conditions

typical of saturation 25-50% of the year. Gleyed soils form in restricted

horizons within the soil profile or where iron pans low down in the soil profile

and prevent run off. (Daniels et al., 1971). Thus, it can be inferred that

paleosols demonstrating similar features formed under conditions analogous

to those forming modern soils (Tabor et al., 2008).

Another indicator of climate is the calcium carbonate content of paleosols, the

presence of calcium carbonates in the Bk horizon is observed in sub-humid to

semi – arid environments (Tabor et al., 2008). In humid climates, calcium-


32

Table 1.5 - Soil Orders

Name Major characteristics

Alfisol Argillic, nitric or kandic horizons; high to medium base saturation.

Andisol From volcanic ejecta, dominated by allophone or Al-humic horizons

Aridisol Dry soil, ochric epipedon, sometimes argillic or nitric horizon

Entisol Little profile development, ochric epipedon common.

Gelisol Permafrost, often with cryoturbation Histosol Peat or bog; > 20% organic matter.

Inceptisol Embtyonic soils with few diagnostic features, Ochric or umbric epipedon, cambric horizon

Mollisol Mollic epipedon, high base saturation, dark soils, some with argillic or nitric horizons

Oxisol Oxic horizon, no argillic horizon, highly weathered.

Spodosol Spodic horizon commonly with Fe, Al oxides and humus accumulation.

Ultisol Argillic or kandic horizons, low base saturation

Vertisol High in swelling clays, deep cracks when soil is dry.


33

bearing minerals, which are easily weathered, are hydrolyzed and disappear

as calcium cations in the groundwater (Retallack, 1990). In semi-arid

environments, moisture is insufficient to remove calcium cations, evaporation

of soil-water at the wetting front can result in the precipitation of a low-

magnesium calcite in the subsurface (Bk) horizon i.e. calcic horizon (Brady &

Weil, 2008). Pedogenic calcrete precipitation is rarely observed in regions

which receive precipitation exceeding 70 mm per year (Royer, 1999),

therefore it can be interpreted that the presence of pedogenic calcrete

indicates a climate with low effective moisture.

In regions which experience seasonal rainfall, argillic and vertic (high

clay content) horizons are often observed within the calcisol (Tabor et al.,

2008). Argillic horizons are recognized by subsurface accumulations of illuvial

lattice layered clays, which appear as a waxy coating on ped surfaces (Mack

et al., 2003). In modern environments, argillic horizons develop under

conditions with free drainage and moderate seasonality (Tabor et al, 2008).


34

Chapter 2

Materials, Methods and Sampling

2.1 Materials and Methods 2.1.1 Core samples

Two cores were obtained from each playa, one from the center of the playa

floor and one from the edge of the playa floor so that any variation in

sediments between the playa center and playa edge may be sampled i.e.

sediments may be more clayey in the centre relative to the edge (Wood &

Osterkamp, 1987a).

2.1.2 Site description

The cores were taken from two playa wetlands; one in Floyd County on the

eastern margin of the Southern High Plains and one in Bailey County on the

western border of the State of Texas (Figure 1.1). A satellite image of Bailey

Playa denotes the locations of cores BP-1 and BP-2 (Fig 2.1). A satellite

image of Floyd Playa denotes the locations of cores FP-1 and FP-2 (Fig 2.2).

Figure 2.3 and 2.4, adapted from Netthisinghe (2008), display the watershed

and drainage network of Bailey Playa and a 3D view of Bailey Playa,

respectively. Figure 2.5 and Figure 2.6, adapted from Netthisinghe (2008),

display the watershed and drainage network of Floyd Playa and a 3D view of

Floyd Playa, respectively.


35

Figure 2.1: (top) Aerial photograph (from Google Earth) of the Bailey

County Playa. The two yellow pins show the location of core 1, near

the center and core, 2 at the playa edge.

Figure 2.2: (bottom) Aerial photograph (from Google Earth) showing

the location of the cores taken from Floyd County Playa. The yellow

pins show the location of core 1, towards the center of the playa and

core 2 on the eastern edge of the playa floor.


36

400 m

BP-1: 34° 1’ 14.80” N, 103° 1’ 4.02” W

BP-2: 34° 1’ 19.14” N, 103° 1’ 10.06” W

250 m

FP-1: 34° 5’ 43.60” N, 101° 7’ 0.60” W

FP-2: 34° 5’ 42.52” N, 101° 6’ 52.96” W


37

Figure 2.3: (top) adapted from Netthisinghe (2008), Digital Elevation

model of the Bailey Playa drainage network.

Figure 2.4: (bottom) adapted from Netthisinghe (2008) is a 3D model

of Bailey Playa.


38


39

Figure 2.5: (top) adapted from Netthisinghe (2008), Digital Elevation

model of Floyd Playa drainage network.

Figure 2.6: (bottom) adapted from Netthisinghe (2008) is a 3D model

of Floyd Playa.


40

• FP-1 • FP-2


41

2.1.3 Coring

A trailer mounted, concord hydraulic corer was used to obtain the four

cores (Fig 2.7). The depth of sampling ranged between 3 and 4.8 m, passing

through multiple buried soil horizons. The soil cores were encased in plastic

tubing, capped, labeled, marked with the way up and stored for lab analysis.

Figure 2.7 Field photograph of coring in Bailey Playa


42

2.2. Physical Sampling 2.2.1 Sample Preparation

The plastic tubing was split and the cores were laid out on the table for

analysis, important morphological features such as color, according to the

Munsel® Color Chart, changes in grain size, roots and nodules were recorded

on stratigraphic columns, each core was also photographed.

Samples of the core were taken every 100 mm, starting from the

bottom of the core working up to the top (i.e. modern surface). Two samples

were taken from each interval one for grain size analysis and one for

geochemical analysis. The grain size used approximately 1 g of material

which was stored in a glass vial and filled with Calgon® which acts as a

deflocculating agent.

The samples for geochemical analysis were weighed, oven dried at

50°C for 24 hours in order to remove pore water, and weighed again so loss of

water mass could be calculated. The samples were then ground to a fine

powder using a mortar and pestle and stored in glass vials for later

geochemical analysis.

2.2.2 Grain size

Samples were sonicated for a minimum of 20 minutes in order to

disaggregate clay flocculation, in some cases further dilution with Calgon®


43

solution was necessary. Once disaggregated, grain size distributions were

measured using a Beckmann-Coulter LS13320 laser particle analyzer. Grain

size variations throughout the cored soil profiles were analyzed. The D50

fraction, i.e. 50% of material is coarser and 50% finer than that grain diameter,

was measured this represents the mean. The D75 fraction i.e. the coarsest

75th percentile and D25 i.e. finest 25% of grains were also measured.

The D50 and D75 were plotted to gauge the variability in the coarse

fraction, useful for denoting deltaic sands. The symmetrical D25 fraction was

not shown because the variation from paleosol to paleosol was minimal.

Grain size distributions were plotted against depth to determine changes

between horizons and various sand fraction measurements were used to

analysis reworking of the Blackwater Draw Formation.

2.2.3 Thin sections and Billets

Several samples from the cores were made into thin sections and

examined under a microscope. These were used to identify Fe-Mn nodules,

carbonate nodules, grain coatings and illuviation (Fig 2.8). Billets were also

used to identify similar features (Fig 2.9). Nodules are 3D bodies which occur

in the ground mass, in the playa cores these are formed by calcite or Fe-Mn.

Calcite nodules are generally indicative of arid soils (Barchhardt &

Lienkaemper, 1999) while Fe-Mn nodules tend to form in soils subject to

intense seasonal change (Stiles, 2001). Illuviation is the re-deposition of


44

clays, organic matter and other material, mobilized by water from

precipitation, from one horizon into another which is generally lower in the soil

profile (Brady & Nyle, 2008). Clay coatings or cutans (Retallack, 1990) form

as a result of illuviation, when drier, deeper horizons are reached water is

suctioned into microvoids resulting in the deposition of clays which form a thin

coating on peds.


45

Figure 2.8: Photomicrographs showing key physical soil features in

each core. A) Taken from BP-1-125 and shown in plane light, vertical

section cutting through several carbonate nodules, some of which

display clay coatings. B) Horizontal section taken from BP2-270 in

cross polar light displays a Fe-Mn nodule with a clay coating. C)

Taken from BP-1-215 and shown in plane light, horizontal view

displaying Fe-Mn staining of the matrix. D) Viewed in plane light is a

horizontal section taken from FP-2-395 cm, photomicrograph displays

accumulations of Fe with diffused boundaries surrounding the grains.

E) Taken from BP-1-320 is a horizontal view in cross polar light, the

lighter colored area demonstrates clay illuviation with Fe-Mn staining

of the clay portion. F) Taken from FP-2-285 under plane light, vertical

view of an illuviation pipe. G) Taken from BP2-150 shows a vertical,

plane light view of clay illuviation. H) Taken from BP-1-335 cm

under cross polar light displaying cutans surrounding the grains.


46


47

Figure 2.9: Photographs of billets taken from BP-2, A) shows a

horizontal view through a calcium carbonate nodule with a diffused

margin; B) shows evidence of illuviation and clay-filled paleo-root

traces; C) is a vertical view of root traces; D) is a horizontal view

across a an illuviation pipe.


48

2.3. Geochemical Sampling 2.3.1 Sample Preparation

The samples for geochemical analysis were weighed, oven dried at

50°C for 24 hours in order to remove pore water, and weighed again so loss of

water mass could be calculated. The samples were then ground to a fine

powder using a mortar and pestle and stored in glass vials for later

geochemical analysis.

2.3.2. Loss on Ignition (LOI)

Porcelain crucibles are heated in a muffle furnace at 1000°C for 20

minutes, and left to cool in a desiccator for 15 minutes before they are

weighed and the mass is recorded. ~2 g of sample is added and the crucible

is weighed again. The sample is then heated in the muffle furnace at 1000°C

for 30 minutes, and allowed to cool in the desiccator for a further 15 minutes

before being weighed again. The LOI is the calculated using the following

equation (Eqn 1). This data can be found in Appendices 1. LOI data is used

when calculating the totals for each sample, the sum of the Wt% of each

element and the LOI should equal 100.

LOI = [(crucible + wet sample)-(crucible + dry sample)/ (1)

(crucible + wet sample) - crucible] x 100


49

2.3.3 Fusions

For each sample, 0.6000 +/- 0.0006 g of Lithium metaborate flux is

measured out in a porcelain crucible and poured into a platinum crucible.

0.2000 +/- 0.0002g of sample is then weighed in the porcelain crucible and a

further 0.6000 +/- 0.0006 g of Lithium metaborate flux is added. This is

thoroughly mixed and added to the platinum crucible. The M4 Claisse Fluxer

is then set up to run, 3 samples can be run at a time. Using a repipeter,

Teflon beakers are filled with 80 ml of 5%HNO3 and 1%HCl V/V acid. 20 µl of

Lithium Iodide are then dropped into the centre of the sample in the platinum

crucible. Each crucible containing sample is then clipped into the M4 Fluxer

and the Teflon beakers of acid are place in the tray below. Fluxer program P6

is selected and the samples are run, the samples are heated until molten and

then poured into the acid and stirred using magnets. Once the program is

finished, samples are transferred into 125 ml wide mouthed bottles and

labeled for trace element analysis. Samples for major element analysis are

diluted; 20 ml of sample are pipetted into a 125 ml wide mouth bottle

containing 40 ml of 5%HNO3 and 1%HCl V/V acid.

2.3.4 ICP/ ICP-MS

Using a Teledynen Leeman Labs Prodigy ICP (inductively coupled

plasma) the samples were analyzed for Si, Ti, Al, Mn, Mg, Fe, Ca, Na, K, P,

Sr, Ba, Zr and Y. A calibration for major elements was set up using the


50

following in house rock standards; BLANK, BHVO, BCM, MHA, RGMT and

1.5 BCM these standards have been analyzed using USGS rock standards at

five different labs using two techniques (XRF and ICP). The instrument was

recalibrated using these standards, which were run as samples, when data

drifted outside of 5% of this range. All samples fell within 5% of the highest

value for that element.

For the Minor elements, the following in house standards were used;

BLANK, BHVO, BCM, MHA, RGMT, STM, SCo and GSP. The instrument was

recalibrated when elements drifted outside of 10% of the calibration range.

We found recalibration was more efficient than drift calculations; therefore the

resulting data set is within 5% of the actual value for major elements and 10%

for minor elements, realistically most samples are within 3% for major

elements. The detection limit for this instrument is 4 ppm, elements which are

below this may fall below the lower limit of quantification, all of my values fall

above this limit.


51

Chapter 3 Results

The physical and geochemical properties of the playa cores are

presented in this section. Physical properties such as color, structures,

nodules and root traces are presented as graphic and photographic logs.

Grain size data is plotted against depth and is spatially matched with the

graphic log. The various wt% and ratios of major and minor elements within

the core are also plotted against depth and matched spatially with the graphic

logs. Thus, it is possible to infer the various soil horizons.

Figure 3.1 shows graphic and photographic logs from the four cores,

BP-1, BP-2, FP-1 and FP-2. Each core was analyzed for the presence of

buried soils using standard pedological practices, two to three distinct

intervals with different pedological characteristics were found. Table 3.1

provides a summary of the nomenclature used.

3.1 Key physical properties used in assigningsoil horizonation


52

Table 3.1 - Soil Core Nomenclature Symbol Description

Modern soil

b Buried soil * S Buried soil surface**

A A Horizon B B Horizon

C C Horizon

Lowercase suffix indicate sub-horizon***

* followed by number, beginning at 1 with the first buried horizon ** followed by number, beginning at 1 with the first buried surface *** See table 1.4


53

Figure 3.1: Photographic and stratigraphic logs for the four cores,

depth in cm is marked down the side. Colors are assigned according to

the Munssel® color chart and other key physical properties are

depicted. Buried soil surfaces are denoted S and buried soils are

denoted b.


54


55

Figure 3.2: Grain size in µm is plotted against depth in cm and matched with

the stratigraphic log. An increase in grain size corresponds with S3 and

remains increased through b2 until the Btkb2 horizon. Above S2 grain size

becomes much finer. Refer to Figure 3.1 for a key to symbols on the

stratigraphic log.


56


57

3.1.1 Bailey Playa-1

BP-1 (Fig 3.1) has three buried surfaces, S1, S2 and S3. S1 occurs at

a depth of 120 cm, S2 at 215 cm and S3 at 320cm. This section contains four

distinct intervals based on varying pedogenic characteristics. Each interval is

separately described and interpreted below. This core was found to; the

modern soils and three buried soils, b1, b2 and b3.

Modern Soil

The first horizon is dark in color, N3, due to its increased organic

content and also contains many organic woody roots. The lower horizon (20-

120 cm) contains vertically oriented pipes of finer grained material and

organics.

This horizon is interpreted to be the modern soil, the upper horizon

forms the A horizon (top soil) (Table 1.2) as indicated by abundance of

organic woody roots. The lower horizon also contains organic roots, but to a

lesser degree, and the vertical pipes of fines are indications of illuviation.

Thus, the interval is best inferred as a Bht horizon (Table 1.3).

Buried Soil 1

Interval b1 (Fig 3.1) is color 10YR4/2, at the top (120-140 cm) there is

a sub horizon containing carbonate nodules (Fig 2.9: A) this horizon


58

demonstrates vertical piping of fine grained material. Below this (150-175 cm)

is a sub horizon which is characterized by further vertical piping of fine

grained material, this horizon also contains some organic root traces. In the

deepest horizon of b1 (175-215 cm), small black concretions and organic root

traces are observed along with some vertical pipes which display a difference

in color from the surrounding material. Grain size remains relatively low

throughout b1 (Fig 3.2).

The horizonation observed throughout b1 leads to the inference of a B

horizon (Table 1.2). The piping of fines observed in the upper sub horizon is

interpreted as the illuviation of clays. The presence of clay illuviation and

carbonate nodules in this horizon are interpreted as a Btk horizon (Table 1.3).

The piping of fines in the middle horizon is again interpreted as illuviation of

clays, thus a Bt horizon is inferred (Table 1.3). The dark concretions

observed in the deepest horizon are inferred as Fe-Mn nodules. The color

variation is interpreted as development of color structure these characteristic

are best described by a Bwc horizon (Table 1.3).

Buried Soil 2

Interval b2 (Fig 3.1) is color 10YR4/2, and contains 3 sub-horizons.

The upper horizon (215-250 cm) contains black nodules and some vertical

piping of fines. In this unit a small peak is observed in the D75 portion of the

grain size (Fig 3.2). Below this (250-260 cm) a thin sub horizon occurs which


59

contains calcite nodules and further piping of fines. D75 and D50 portions of the

grain size increase in this unit (Fig 3.2). The lower unit (260-320 cm) contains

black nodules towards the top of the unit (Fig 2.8: C) and some cementation

of the grains. D75 and D50 portions of the grain size remain high at the top of

this sub horizon but decrease toward the bottom (Fig 3.2).

Horizonation within this soil leads to its interpretation as a B horizon

(Table 1.2). In the upper horizon the dark concretions are interpreted as Fe-

Mn nodules, the piping of fines is interpreted as clay illuviation, thus a Btc

horizon best fits this soil (Table 1.3). In the middle horizon the piping of fines

is interpreted as the illuviation of clays. The presence of clay illuviation and

carbonate nodules in this horizon are interpreted as a Btk horizon (Table 1.3).

In the deepest horizon the dark concretions are interpreted as Fe-Mn nodules,

the presence of concretions and cementation leads to the inference of a Bmc

horizon (Table 1.3).

Buried Soil 3

Interval b3 (Fig 3.1) is color 10YR5/4, only the top portion of this unit

was retrieved in the core. This horizon demonstrates vertical piping of fines,

with black staining (Fig 2.8 E), thin coatings are also observed surrounding

the grains (Fig 2.8: H). The area of finer grained dark material is interpreted

as a clay illuviation pipe, stained by Fe-Mn, the coatings on the grains are


60

interpreted as cutans (Retallack, 1990) both of these features are indicative of

clay illuviation thus a Bt horizon is inferred (Table 1.3).

3.1.2 Bailey Playa -2

In BP-2, (Fig 3.1) three surfaces are identified; surfaces are inferred at

depths of 145 cm (S1), 215 cm (S2) and 315 cm (S3). This section contains

four distinct intervals based on varying pedogenic characteristics interpreted

to be; the modern soils and three buried soils, b1, b2 and b3.

The modern soil

The first interval contains 3 sub-horizons, it is dark in color, N3 at the top,

toward the bottom of this soil a color change to 5YR6/1 is observed. The

upper horizon of this section (0 -20 cm) contains organic root fragments. The

middle horizon (20-60 cm) displays some vertical piping of fine grained and

organic material and contains organic root fragments. In the deepest unit (60-

145 cm) root fragments display orange coatings, some areas of sediment

display blue/grey to green/grey discoloration, vertical piping of fines are also

noted.

This soil is interpreted to be the modern soil, the upper horizon forms

the A horizon (top soil) (Table 1.2) as indicated by abundance of organic

woody roots. The middle horizon also contains organic roots, but to a lesser

degree, and the vertical pipes of fines and organics are indications of


61

illuviation. Thus, the interval is best inferred as a Bht horizon (Table 1.3). In

the deepest horizon the orange discoloration of roots is interpreted as a result

of oxidation, the blue/grey to green/grey discoloration is likely the effect of

gleying and the piping of fines indicate illuviation, thus a Btg horizon is

inferred (Table 1.3).

Buried Soil 1

Interval b1 (Fig 3.1), has a color 5YR6/1 and contains two sub-

horizons. The upper sub-horizon (145-200 cm) contains dark concretions and

prominent piping of lighter colored fines (Fig 2.8: G). In the horizon below

(200-215 cm) carbonate nodules become prominent and an abrupt peak in

D75 and D50 portions of the grain size is observed (Fig 3.3).

In the upper unit, the dark nodules are identified as Fe-Mn nodules,

piping of fines is interpreted as illuviation, thus a Btc horizon is inferred (Table

1.3). The dominance of carbonates in the lower unit is interpreted as a Bk

horizon (Table 1.3).

Buried Soil 2

Interval b2 (Fig 3.1), has a color 5YR6/1 and contains two sub-horizons. The

upper unit (215-230 cm) is thin and demonstrates vertical piping of fines. The

lower unit (230-310 cm) contains black concretions (Fig 2.8: B) and carbonate


62

nodules. Grain size then increases and fluctuates between 50 µm and 100

µm throughout b2 (Fig 3.3).

In the upper unit, piping of fines is interpreted as illuviation, thus a Bt

horizon is inferred (Table 1.3). The black concretions in the lower horizon are

interpreted as Fe-Mn nodules, the presence of nodules and carbonate leads

to its classification as a Bck horizon (Table 1.3).

Buried Soil 3

Interval b3 (Fig 3.1) has a color 10YR5/4, and contains two sub-

horizons. Only the top part of this unit was retrieved in this core. The upper

unit (310-335 cm) contains black concretions and spots of orange

discoloration. The lower unit 335 cm – end of core) is dominated by calcite

nodules. At S3, an abrupt decreases in the D50 and D75 fractions is observed,

grain size remains relatively low through b3 (Fig 3.3).

In the upper unit, the black concretions are interpreted as Fe-Mn

nodules, the orange discoloration is likely due to oxidation, thus a Bc horizon

is inferred (Table 1.3) The dominance of calcite nodules in the lower horizon

leads to the inference of a Bk horizon (Table 1.3).


63

Figure 3.3: Grain size in µm is plotted against depth in cm and

matched with the stratigraphic log. A small increase in the D75 portion

corresponds with S1. A larger increase in grain size corresponds with

S2, below S3 a reduction in grain size occurs. The D75 portion

fluctuates through b1 and b2. Refer to Figure 3.1 for a key to symbols

on the stratigraphic log.


64


65

3.1.3 Floyd Playa-1

FP-1 (Fig 3.1) is largely homogenous in appearance and contains

missing data between 255 cm and 215 cm where the core was unrecovered.

There are two inferred buried surfaces one at a depth of 200 cm (S1), and

one at 310 cm (S2). There are three distinct intervals based on varying

pedogenic characteristics observed within this core, these are interpreted as;

the modern soil and two buried soils, b1 and b2. Figure 3.4 shows the grain

size data for core FP-1, the fluctuations of grain size within this core are very

small when compared with the other three cores.

The modern soil

The upper interval contains 3 sub-horizons. The upper unit (0-45 cm)

has a color 5YR2/2, and contains woody organic root structures. The horizon

below (45-165 cm) is 10YR2/2 color and demonstrates vertical piping of fines

and organic matter, woody roots are observed. The lower unit (165-200 cm)

is 5YR6/1 color and also contains woody root material and demonstrates

piping of fines. A small peak in grain size occurs just above within the modern

soil just above S1 (Fig 3.4).

This soil is interpreted to be the modern soil, the upper horizon forms

the A horizon (top soil) (Table 1.2) as indicated by abundance of organic

woody roots. The middle horizon also contains organic roots, but to a lesser

degree, and the vertical pipes of fines and organics are indications of


66

illuviation. Thus, the interval is best inferred as a Bht horizon (Table 1.3). In

the lower unit piping of fines is interpreted as illuviation of clays, thus a Bt

Horizon is inferred (Table 1.3).

Buried Soil 1

Interval b1 (200-305 cm) (Fig 3.1) is 10YR4/2 color, no sub-horizons

were observed and a section of this horizon could not be retrieved. This unit

contains black nodules towards the bottom, piping of fines is also observed.

The concretions are interpreted as Fe-Mn nodules and piping of fines

indicates illuviation, thus a Btc horizon is inferred (Table 1.3).

Buried Soil 2

Only the top of b2 (Fig 3.1) was retrieved, this unit is 10YR4/2 color, it

is dominated by carbonate nodules and contains weakly developed pipes

which display small variations in color and grain size. These variation

structures are not developed well enough to be interpreted as illuviation, thus

it is interpreted as a Bwk horizon (Table 1.3).


67


matched with the stratigraphic log. An increasing trend is seen in b2,

whereas above S2 a decrease in grain size is observed. Throughout b2

the size of grains appears to fluctuate and a peak corresponds with S1.

Grain size seems to decrease as it moves into the modern soil profile.

Refer to Figure 3.1 for a key to symbols on the stratigraphic log.


68


69

3.1.4 Floyd Playa -2

FP-2 (Fig 3.1) is the deepest core reaching a depth of 485 cm and

contains two buried surfaces at depths of 230 cm (S1) and 385 cm (S2). This

core contains three distinct intervals based on varying pedogenic

characteristics, interpreted to be; the modern soil and two buried soils, b1 and

b2.

The modern soil

The upper interval contains three sub-horizons. The upper unit (0-

30cm) has a color 5YR2/2, and contains woody organic root structures. The

horizon below (30-185 cm) is 10YR2/2 color and demonstrates vertical piping

of fines and organic matter and contains woody root traces. The lower unit

(185-230 cm) is 5YR6/1 color and demonstrates piping of fines. At around

205 cm, the interval exhibits a moderate decrease in grain size (Fig 3.5).

This interval is interpreted to be the modern soil, the upper horizon

forms the A horizon (top soil) (Table 1.2) as indicated by an abundance of

organic woody roots. The middle horizon also contains organic roots, but to a

lesser degree, and the vertical pipes of fines and organics are indications of

illuviation. Thus, the unit is best inferred as a Bht horizon (Table 1.3). In the

lower unit, piping of fines is interpreted as illuviation of clays, thus a Bt

Horizon is inferred (Table 1.3).


70


matched with the stratigraphic log. A large increase in grain size is

seen above S2, which corresponds with the C horizon. Another

increase is observed around S1. Refer to Figure 3.1 for a key to

symbols on the stratigraphic log.


71


72

Buried Soil 1

Interval b1 (Fig 3.1) contains three sub-horizons; the upper unit (230-

270 cm) is 10YR4/2 in color and demonstrates piping of fines. The middle unit

(270- 310 cm) is also 10YR4/2 in color and vertical piping of fines, which are

much darker in color than the surrounding material, are observed (Fig 2.9: F).

Downward tapering structures with calcite coatings are present in this unit.

The lower unit (310-385 cm) is a very pale, 5Y8/1, sandy unit which contains

relatively unweathered material this unit corresponds with an increase in grain

size (Fig 3.5).

In the upper horizon, piping of fines is interpreted as clay illuviation,

thus a Bt horizon is inferred (Table 1.3). In the middle horizon, pipes of fine

grained, darker material are interpreted as clay illuviation with Fe-Mn staining.

The downward tapering structures are interpreted as calcified root traces.

This unit is inferred as a Btk horizon (Table 1.3). The lower horizon appears

to be relatively unweathered sand, thus it is interpreted as a C horizon (Table

1.2).

Buried Soil 2

Interval b2 (Fig 3.1) contains three sub-horizons, the upper horizon

(385-405 cm) has a very orange color, 5YR4/4, (Fig 2.8: D) with a more sandy

than clayey texture, and contains black concretions. The horizon below (405-

440 cm) is 10YR5/4 in color and dominated by calcite nodules, towards the


73

bottom of the unit a few black concretions are observed. The lower unit (440

cm – end of core) is also 10YR5/4 in color and is dominated by black

concretions, weakly developed pipes of smaller grains which are lighter in

color are observed.

In the upper unit, the orange discoloration is attributed to staining by

oxidized iron, the black concretions are interpreted as Fe-Mn nodules thus a

Bc horizon is inferred (Table 1.3). Black concretions in the middle unit are

also interpreted as Fe-Mn nodules. This unit is inferred as a Bck horizon

(Table 1.3). Fe-Mn nodules are also present in the deepest unit, the

development of pipes is considered too weak to be illuviation, thus a Bwc

horizon is inferred (Table 1.3).

3.2 Geochemistry

The following section describes the geochemical trends and ratios

observed in the ICP data. These are plotted as a Wt% of the oxide against

depth for all of the major oxide elements. The major oxides are SiO2, Al2O3,

Fe2O3, TiO2, MnO, MgO, CaO, Na2O, K2O and P2O. Other major elements

are Sr, Ba, Zr and Y these are plotted in Parts Per Million (PPM). The Minor

elements are; Zr, Zn, V, Cr, Ni, Co, Cu and Sc are plotted in (PPM) against

depth.


74

Tables 3.2 through to 3.5 contain the major oxide data for all four cores.


Figure 3.6 shows each of the major oxides plotted against depth in

core BP-1. Within the modern soils SiO2 fluctuates around 60%, abundance

of Al2O3, Fe2O3, in K2O, MgO and CaO increase towards the surface. Small

peaks in MgO and CaO occur at S1. Throughout b1, Al2O3 and Fe2O3 show

an increasing upward trend, contrasted by a decreasing upward trend in SiO2.

After S2, the decreasing trend in SiO2 and increasing trend in Al2O3 and

Fe2O3 becomes less pronounced. In b2, SiO2 begins to decrease while Al2O3

and Fe2O3 both increase and form an almost identical trend line. Small

increase in K2O, MgO and CaO also occur. Within b3, SiO2 shows a small

increase until S3. This is mirrored by small decreases in Al2O3 and Fe2O3

until S3. K2O and MgO also show similar decreasing trends through b3.


Figure 3.7 is the major oxides plot for core BP-2. All of the major elements

show little fluctuation within the modern soil. Below S1 a slight increasing

trend in SiO2, with a corresponding decreasing trend in Al2O3 is observed

through b1. A large spike in CaO is also observed towards the bottom of b1,

with a small corresponding spike in K2O. Throughout b2, SiO2 increase

steadily while Al2O3 and Fe2O3 remain relatively unchanged, CaO fluctuates

3.3 Major Oxides


75

Table 3.2 -Major Oxides, BP-1

Depth (cm) Element

SiO2 TiO2 Al2O3 MnO MgO Fe2O3 CaO Na2O K2O P2O5 Sr Ba Zr Y

0

58.91 0.73 16.39 0.08 1.54 5.49 1.09 0.50 2.87 0.22 99 582 198 35

10

66.93 0.67 13.99 0.20 1.26 4.76 0.98 0.58 2.76 0.18 96 657 261 32

20

67.03 0.67 13.67 0.10 1.23 4.58 0.96 0.58 2.71 0.15 94 567 250 31

30

69.42 0.64 12.89 0.09 1.16 4.28 0.93 0.57 2.59 0.15 93 546 256 31

40

65.47 0.66 13.32 0.12 1.20 4.44 0.95 0.59 2.65 0.15 96 594 259 31

50

66.12 0.67 13.47 0.10 1.21 4.49 0.97 0.59 2.71 0.17 97 580 266 32

60

66.63 0.66 13.23 0.06 1.17 4.33 0.94 0.60 2.67 0.15 95 512 257 30

70

66.63 0.66 13.42 0.09 1.19 4.40 0.95 0.61 2.70 0.15 97 560 258 31

80

66.32 0.65 13.19 0.08 1.17 4.36 0.93 0.59 2.66 0.15 96 533 255 30

90

67.14 0.65 13.10 0.06 1.16 4.27 0.92 0.59 2.65 0.15 95 520 263 30

100

67.22 0.64 12.95 0.05 1.14 4.16 0.90 0.58 2.61 0.15 95 518 251 30

110

67.19 0.64 12.86 0.05 1.13 4.15 0.89 0.58 2.61 0.14 95 517 269 29

120

66.73 0.63 12.85 0.08 1.13 4.20 0.90 0.57 2.61 0.15 95 548 249 29

130

67.50 0.65 12.98 0.14 1.26 4.48 0.97 0.59 2.63 0.18 96 619 256 30

140

67.41 0.61 12.17 0.05 1.18 4.14 0.92 0.58 2.53 0.16 92 489 256 29

150

68.45 0.63 12.72 0.05 1.23 4.31 0.94 0.60 2.64 0.16 94 482 244 29

160

70.13 0.61 12.21 0.04 1.18 4.14 0.90 0.58 2.54 0.16 91 466 254 27

170

69.63 0.62 12.45 0.06 1.22 4.22 0.92 0.59 2.58 0.16 94 495 253 28

180

67.41 0.63 12.53 0.06 1.21 4.23 0.91 0.60 2.60 0.15 94 489 255 28

190

68.60 0.61 12.14 0.05 1.18 4.08 0.93 0.59 2.55 0.18 93 472 248 27

200

66.56 0.61 12.35 0.05 1.19 4.12 0.89 0.61 2.57 0.14 94 479 269 27

210

67.95 0.59 11.89 0.06 1.15 3.97 0.86 0.59 2.50 0.14 92 530 270 26

220

68.60 0.56 11.05 0.04 1.07 3.67 0.87 0.56 2.35 0.19 88 498 270 25

230

73.29 0.56 11.05 0.05 1.04 3.66 0.78 0.57 2.44 0.14 88 515 286 25

240

73.72 0.56 10.97 0.05 1.05 3.65 0.90 0.54 2.41 0.21 96 1162 290 25

250

74.59 0.55 10.68 0.06 1.02 3.56 0.99 0.54 2.37 0.29 100 1664 276 24

260

78.35 0.49 9.41 0.03 0.96 3.30 0.77 0.47 2.08 0.18 79 717 285 23

270

78.95 0.47 8.77 0.03 0.90 3.09 0.78 0.44 2.01 0.21 72 365 326 24

280

79.67 0.44 8.03 0.02 0.80 2.77 0.60 0.44 1.87 0.11 67 337 315 21

290

78.56 0.46 8.73 0.02 0.89 3.01 0.70 0.45 2.02 0.15 71 354 285 22

300

79.10 0.42 7.45 0.05 0.79 2.57 0.76 0.45 1.83 0.23 67 358 316 19

310

78.58 0.42 7.16 0.05 0.76 2.41 0.71 0.46 1.78 0.21 67 354 335 20

320

81.67 0.39 6.64 0.03 0.66 2.07 0.61 0.50 1.78 0.17 72 688 344 18

330

77.06 0.51 9.24 0.03 0.93 2.90 0.63 0.60 2.16 0.07 80 393 312 22

340 77.74 0.51 9.04 0.04 1.00 3.16 0.68 0.63 2.16 0.10 84 602 337 23


76

Table 3.3 -Major Oxides, BP-2

Depth (cm)

Element


90

69.86 0.62 12.13 0.07 1.17 4.21 0.94 0.57 2.50 0.16 115 436 267 26

100

71.52 0.62 12.15 0.18 1.17 4.22 0.95 0.56 2.49 0.17 113 439 279 27

110

71.50 0.63 12.33 0.06 1.19 4.21 0.95 0.58 2.56 0.15 103 430 287 26

120

71.08 0.61 11.92 0.07 1.16 4.06 0.92 0.59 2.50 0.16 102 438 285 26

130

70.99 0.62 12.21 0.06 1.20 4.15 0.95 0.60 2.55 0.16 106 450 277 27

140

72.93 0.63 12.29 0.04 1.21 4.13 0.99 0.62 2.61 0.18 102 420 256 26

150

71.80 0.62 12.20 0.05 1.18 4.06 0.93 0.61 2.58 0.14 108 683 282 27

160

72.50 0.62 12.17 0.06 1.19 4.06 0.95 0.62 2.57 0.16 106 920 278 28

170

72.33 0.63 11.96 0.06 1.18 4.00 0.94 0.62 2.55 0.16 103 460 289 27

180

73.09 0.63 12.29 0.05 1.22 4.07 0.97 0.65 2.65 0.17 100 460 289 26

190

73.72 0.61 11.73 0.07 1.17 3.88 0.93 0.62 2.54 0.16 96 440 323 27

200

71.44 0.59 11.26 0.05 1.35 3.95 2.40 0.64 2.46 0.18 97 471 307 26

210

77.05 0.62 11.77 0.04 1.30 4.06 0.99 0.66 2.57 0.19 99 591 288 27

220

75.39 0.60 11.37 0.06 1.26 3.93 0.96 0.64 2.50 0.18 98 465 275 27

230

75.30 0.59 11.14 0.06 1.26 3.85 1.50 0.64 2.46 0.17 104 442 273 27

240

74.92 0.59 10.98 0.04 1.23 3.78 1.36 0.64 2.42 0.16 97 567 274 28

250

70.96 0.58 10.96 0.05 1.25 3.78 1.84 0.64 2.41 0.17 99 518 301 28

260

71.92 0.60 11.19 0.05 1.31 3.86 2.36 0.64 2.48 0.18 96 523 281 29

270

71.34 0.60 11.27 0.25 1.27 3.95 1.80 0.64 2.47 0.18 96 515 301 28

280

69.52 0.59 11.17 0.11 1.31 3.84 2.74 0.63 2.44 0.19 95 493 268 28

290

65.77 0.57 10.75 0.04 1.28 3.69 2.74 0.60 2.30 0.16 96 503 298 29

300

70.11 0.60 11.33 0.04 1.28 3.84 2.35 0.64 2.47 0.17 94 494 283 29

310

71.06 0.59 10.85 0.05 1.22 3.66 2.11 0.62 2.40 0.15 91 509 262 27

320

70.71 0.58 10.73 0.05 1.22 3.62 2.47 0.61 2.39 0.15 93 501 275 28

330

67.46 0.59 11.28 0.04 1.34 3.79 3.77 0.65 2.46 0.16 92 669 253 29

340

66.50 0.58 11.09 0.05 1.36 3.75 4.30 0.62 2.41 0.16 91 507 273 28


77

Table 3.4 -Major Oxides, FP-1

Depth (cm) Element


90

64.48 0.71 13.68 0.08 1.25 4.67 1.02 0.56 2.66 0.18 87 527 271 32

100

63.91 0.71 13.49 0.03 1.23 4.58 1.01 0.55 2.62 0.18 86 474 276 31

110

64.43 0.71 13.56 0.08 1.25 4.59 1.03 0.56 2.63 0.18 87 524 271 31

120

65.03 0.72 13.65 0.07 1.23 4.57 1.02 0.56 2.68 0.18 88 525 274 31

130

64.83 0.71 13.63 0.11 1.24 4.57 1.05 0.57 2.67 0.19 90 589 278 32

140

64.28 0.72 13.69 0.05 1.26 4.59 1.04 0.56 2.65 0.18 89 492 274 31

150

64.57 0.71 13.67 0.06 1.25 4.61 1.04 0.56 2.67 0.19 89 519 274 32

160

64.39 0.72 13.75 0.07 1.27 4.59 1.07 0.57 2.68 0.20 90 525 279 32

170

62.87 0.70 13.49 0.05 1.25 4.49 1.03 0.56 2.63 0.18 89 495 264 31

180

64.37 0.72 13.80 0.06 1.29 4.56 1.06 0.58 2.73 0.19 91 527 272 32

190

63.72 0.71 13.77 0.05 1.29 4.56 1.05 0.58 2.69 0.18 91 523 276 31

200

64.86 0.73 14.19 0.07 1.36 4.76 1.10 0.60 2.80 0.20 94 572 270 32

210

64.79 0.73 14.01 0.06 1.32 4.68 1.07 0.59 2.75 0.19 93 525 268 32

220

65.04 0.73 14.12 0.07 1.33 4.70 1.09 0.59 2.76 0.19 94 535 271 32

230

- - - - - - - - - - - - - -

240

- - - - - - - - - - - - - -

250

- - - - - - - - - - - - - -

260

63.95 0.72 13.84 0.05 1.31 4.58 1.05 0.60 2.73 0.18 93 513 277 31

270

64.93 0.72 13.96 0.05 1.33 4.64 1.06 0.60 2.77 0.18 94 524 269 31

280

62.79 0.72 14.06 0.06 1.36 4.70 1.10 0.58 2.75 0.19 95 513 259 32

290

63.30 0.72 14.03 0.08 1.35 4.67 1.11 0.59 2.76 0.19 95 553 267 32

300

63.12 0.72 14.17 0.04 1.36 4.67 1.62 0.59 2.78 0.21 97 494 261 32

310

64.10 0.73 14.22 0.04 1.36 4.69 1.23 0.60 2.79 0.19 97 495 272 32

320

65.35 0.75 14.63 0.05 1.40 4.83 1.20 0.63 2.90 0.20 100 517 277 33

330

64.50 0.74 14.48 0.04 1.36 4.75 1.18 0.62 2.87 0.19 100 523 269 33

340 63.95 0.74 14.45 0.07 1.37 4.76 1.27 0.61 2.85 0.18 100 519 265 32


78

Table 3.5 -Major Oxides, FP-2

Depth (cm) Element


130

75.89 0.50 9.62 0.04 0.89 3.20 0.66 0.64 1.92 0.10 59 359 336 23

140

76.93 0.50 9.70 0.04 0.88 3.22 0.65 0.64 1.96 0.09 60 367 334 24

150

76.71 0.53 10.11 0.03 0.93 3.33 0.68 0.66 2.03 0.09 62 364 340 24

160

76.64 0.53 10.22 0.04 0.94 3.38 0.69 0.67 2.06 0.09 63 383 350 24

170

79.40 0.51 9.51 0.03 0.89 3.10 0.64 0.62 1.91 0.08 60 361 332 23

180

80.13 0.50 9.19 0.08 0.88 3.10 0.63 0.61 1.91 0.07 60 393 344 23

190

80.83 0.50 9.11 0.15 0.86 3.06 0.63 0.62 1.92 0.08 61 509 343 24

200

79.85 0.53 9.56 0.06 0.92 3.12 0.69 0.67 1.96 0.07 66 400 366 24

210

79.00 0.50 9.21 0.04 0.88 3.04 0.66 0.64 1.87 0.07 62 367 362 23

220

79.41 0.53 9.53 0.04 0.93 3.10 0.71 0.69 1.93 0.08 68 381 360 26

230

77.45 0.52 9.52 0.04 0.92 3.13 0.79 0.77 1.91 0.09 68 384 363 25

240

79.98 0.54 9.54 0.06 0.93 3.12 0.69 0.67 1.97 0.07 69 399 337 23

250

80.74 0.50 8.59 0.04 0.83 2.78 0.62 0.60 1.81 0.07 63 370 376 23

260

79.87 0.53 9.23 0.05 0.89 2.95 0.93 0.90 1.93 0.08 70 388 347 23

270

80.00 0.50 8.44 0.03 0.80 2.65 0.91 0.89 1.79 0.11 67 361 361 24

280

84.80 0.46 7.56 0.03 0.70 2.35 0.63 0.62 1.66 0.08 59 335 411 22

290

79.89 0.50 9.43 0.02 0.94 3.06 1.20 1.17 1.83 0.09 66 341 367 23

300

78.58 0.51 9.68 0.02 0.97 3.19 1.21 1.17 1.87 0.08 66 347 367 23

310

76.00 0.52 10.36 0.04 1.05 3.60 1.52 0.35 1.94 0.08 67 361 349 24

320

91.76 0.30 4.81 0.01 0.45 1.42 0.43 0.17 1.06 0.03 35 216 427 16

330

92.34 0.27 4.44 0.02 0.41 1.30 0.31 0.17 1.01 0.03 35 212 436 17

340

87.09 0.36 6.40 0.03 0.61 2.08 0.55 0.25 1.38 0.05 47 275 404 20

350

88.38 0.35 5.80 0.01 0.49 1.65 0.44 0.27 1.35 0.05 46 283 374 17

360

90.12 0.31 5.24 0.01 0.44 1.33 0.44 0.26 1.27 0.04 44 264 356 17

370

88.21 0.34 5.48 0.01 1.04 1.46 1.03 0.27 1.35 0.07 47 269 410 19

380

72.70 0.55 10.88 0.05 1.02 4.54 0.73 0.40 2.21 0.10 69 361 303 23

390

70.89 0.53 10.65 0.06 1.15 5.47 0.72 0.39 2.16 0.16 68 363 311 21

400

68.67 0.59 11.87 0.09 1.12 4.19 1.83 0.44 2.40 0.15 77 409 311 28

410

62.54 0.57 11.51 0.18 1.24 3.91 6.38 0.43 2.30 0.18 80 448 277 27

420

67.12 0.62 12.84 0.10 1.28 4.46 1.18 0.47 2.55 0.11 81 423 296 28

430

67.31 0.66 13.42 0.19 1.33 4.66 0.88 0.51 2.72 0.09 85 488 298 29

440

66.13 0.66 13.79 0.17 1.38 4.87 0.94 0.52 2.76 0.12 87 482 294 31

450

67.81 0.63 12.81 0.13 1.26 4.45 0.80 0.47 2.55 0.07 80 451 280 27

460

67.41 0.66 13.53 0.07 1.33 4.33 0.86 0.52 2.70 0.09 85 421 316 28

470 66.66 0.66 13.61 0.05 1.34 4.49 0.95 0.52 2.69 0.14 86 412 299 32


79

Figure 3.6: Major oxides elements are plotted in Wt% against depth in

cm in core BP-1. The stratigraphic log and inferred surfaces highlight

the key trends in each buried soil. A key for the symbols shown in the

stratigraphic log can be found on Figure 3.1. Soil b2 demonstrates

increasing aluminum oxide and iron oxide, while silica oxide is

decreasing. A small peak in CaO also occurs in b2.


80

Depth (cm)


81

Figure 3.7: Major oxides elements are plotted in Wt% against depth in

cm for core BP-2. The stratigraphic log and inferred surfaces highlight

the key trends in each buried soil. A key for the symbols shown in the

stratigraphic log can be found on Figure 3.1. CaO show major

fluctuations throughout the core, with a large decrease in b2 and a Bk

horizon towards the bottom of b1.


82

Depth (cm)


83

heavily, but shows an overall decreasing trend. A small spike in MnO is

observed at 270 cm. S3 is marked by a small drop in MgO and the change in

CaO trend from rapidly decreasing to increasing. Through b3, CaO

decreases heavily. SiO2 shows a small increase until S3. This is mirrored by

very small decreases in Al2O3 and Fe2O3 until S3.

3.3.3 Floyd Playa-1

Major oxides data for core FP-1 is shown in Figure 3.8, this core is

fairly homogeneous and contains two buried surfaces; S1 at a depth of 200

cm and S2 at 310 cm. The modern soil shows very little geochemical

fluctuation. Very small peaks in SiO2, Al2O3, Fe2O3 and K2O occur at S1.

Below this, b1 shows no major geochemical trends only a small spike in CaO

at 300 cm. S2 is linked with a change to a very slight increasing trend in SiO2

and decreasing trend in Al2O3 and Fe2O3.

3.3.4 Floyd Playa-2

FP-2 (Figure 3.9) contains the most variability of all the cores and two

buried surfaces; S1 at 270 cm and S2 at 385 cm. CaO, Na2O and K2O

fluctuate heavily throughout the bottom part of the modern soil, whereas the

Wt% of all other elements remains fairly constant with little fluctuation

throughout the upper part of the unit. In the lower part of b1, an abrupt

increase in SiO2 content is observed this is mirrored by a negative jump in

Al2O3 and Fe2O3. A negative double peaked perturbation is also exhibited in


84

the abundances of unit K2O, MgO TiO2, MnO and Na2O; this unit is inferred

as C horizon. Above the C horizon, all elements show values similar to those

observed in b2. A small increasing trend in SiO2 content, which is mirrored

by decreasing trends in Al2O3 and Fe2O3, is observed in b2. Throughout this

unit, K2O, MgO TiO2, MgO and Na2O also show a decreasing trend. At 410

cm, there is a large spike in CaO which reaches 6.1 Wt% this coinciding and

confirming a Bk horizon interpretation.


85

Figure 3.8: Major oxides elements recorded in FP-1 are plotted in

Wt% against depth in cm. The stratigraphic log and inferred surfaces

highlight the key trends in each buried soil. A key for the symbols

shown in the stratigraphic log can be found on Figure 3.1. This core is

fairly homogenous but demonstrates a Bk horizon towards the bottom

of b1.


86

Depth (cm)


87

Figure 3.9: Major oxides elements recorded in FP-2 are plotted in Wt%

against depth in cm. The stratigraphic log and inferred surfaces

highlight the key trends in each buried soil. A key for the symbols

shown in the stratigraphic log can be found on Figure 3.1. Major

geochemical changes occur through this core, most notably those

associated with the C horizon in b1. There is also a significant CaO

spike associated with a Bk horizon in b2.


88

Depth (cm)


89

Tables 3.6 through to 3.9 show for the minor element abundances in ppm.

Table 3.6 - Minor Elements, BP-1 Depth (cm)

Sc V

Cr Ni

Cu Zn Zr

Co

0

6 46 39 16 18 45 349 11

10

6 48 37 13 17 52 323 10

20

4 33 26 10 14 38 358 8

30

5 38 28 16 16 43 354 10 40

5 40 31 18 14 46 332 11

50

6 42 36 13 21 55 282 9

60

6 38 30 12 16 51 316 8

70

6 44 39 14 16 61 330 10

80

7 47 35 20 18 65 286 11

90

8 53 42 24 18 74 279 14

100

8 54 46 28 18 76 296 15

110

8 51 43 22 10 77 285 15

120

8 51 44 20 13 79 270 14

130

9 54 42 20 19 79 283 14

140

9 55 45 21 24 82 281 14

150

9 54 45 24 18 79 252 13

160

10 57 45 23 19 84 264 15

170

10 57 44 21 19 84 261 15

180

9 55 45 22 15 84 263 14

190

10 57 47 22 16 89 252 15

200

9 55 43 22 14 86 261 15

210

10 61 45 25 20 92 259 20

220

10 59 46 23 21 93 247 19

230

10 58 46 21 16 90 270 15

240

10 58 45 22 12 88 247 16

250

10 59 46 23 13 93 264 18

260

10 60 49 24 17 95 253 19

270

9 60 48 27 11 100 242 19

280

8 51 45 25 11 76 276 14

290

9 58 48 25 11 97 244 18

300

9 60 49 27 14 100 247 20

310

9 61 48 27 10 100 246 22

320

6 39 34 12 8 55 279 9

330

10 62 48 26 10 101 261 20

340

10 65 51 28 13 106 250 22

350

10 68 51 32 14 111 251 28

360 12 83 59 37 13 124 189 23

3.4 Minor Elements


90

Table 3.7 - Minor Elements, BP-2 Depth (cm)

Sc V

Cr

Ni

Cu Zn Zr

Co

90

8 54 49 25 17 93 261 17

100

8 56 46 21 16 90 237 22

110

8 52 45 17 13 87 258 13

120

8 52 51 26 18 86 249 16

130

8 52 46 17 14 86 273 14

140

8 51 44 15 13 85 286 12

150

8 52 45 16 15 86 253 13

160

8 52 43 17 17 85 290 13

170

8 52 44 16 16 81 268 14

180

8 53 48 20 16 83 291 13

190

8 50 40 15 16 76 256 14

200

9 54 45 14 18 80 293 12

210

8 53 40 14 18 77 284 12

220

8 52 39 17 19 116 303 13

230

8 52 39 14 20 73 328 12

240

8 51 43 14 16 71 354 10

250

8 53 38 13 16 71 308 12

260

8 53 40 15 23 73 301 11

270

8 61 41 24 20 75 282 22

280

8 57 40 18 20 73 296 16

290

8 54 42 14 20 73 279 11

300

8 54 38 14 19 71 288 11

310

8 53 38 13 21 69 302 11

320

8 52 41 12 20 67 305 11

330

9 55 39 13 24 70 296 11

340

8 55 36 14 22 66 280 11


91

Table 3.8 - Minor Elements, FP-1 Depth (cm)

Sc V

Cr

Ni

Cu Zn Zr Co

90

10 53 33 12 15 76 244 13

100

11 57 36 10 16 78 276 9

110

10 60 38 14 15 78 264 14

120

11 65 42 14 21 80 279 14

130

11 68 43 16 18 79 278 16

140

12 70 45 15 24 88 281 12

150

10 64 36 11 19 80 275 15

160

11 68 42 14 21 83 282 15

170

12 70 42 34 22 86 272 15

180

12 65 44 17 24 89 314 16

190

12 65 44 18 20 87 331 15

200

- - - - - - - -

210

- - - - - - - -

220

- - - - - - - -

230

11 66 46 19 191 106 302 17

240

11 67 45 17 27 91 312 17

250

11 67 45 18 23 89 309 18

260

11 66 44 16 24 89 312 15

270

11 67 44 16 32 91 288 17

280

11 69 45 16 24 85 276 16

290

11 72 46 18 23 92 277 18

300

11 70 45 15 19 89 260 15

310

11 72 45 14 23 86 273 15

320

11 73 45 19 24 88 281 15

330

11 75 48 17 29 91 277 15

340 11 75 47 19 39 92 273 16


92

Table 3.9 - Minor Elements, FP-2

Depth (cm) Sc V Cr Ni Cu Zn Zr Co 140 7.9 57 39 12 17 65 366 9 150 8.2 56 40 11 17 65 367 9 160 8.8 57 39 12 21 68 392 9 170 8.5 62 39 13 20 72 387 11 180 7.3 54 40 12 23 57 331 9 190 7.4 55 41 15 18 55 357 12 200 7.6 56 36 15 18 54 368 15 210 8.6 61 40 13 18 56 421 11 220 7.9 57 38 13 21 56 399 9 230 7.9 60 50 16 18 55 382 9 240 8.5 62 41 12 54 61 438 8 250 8.1 61 39 15 21 54 388 11 260 7.8 57 35 19 18 51 448 10 270 7.4 65 37 13 21 60 362 9 280 6.7 61 33 10 16 50 374 7 290 6.0 55 30 8 16 42 416 6 300 7.4 73 37 10 15 57 373 7 310 7.8 81 40 12 18 63 370 9 320 8.0 81 39 18 18 60 342 9 330 3.8 35 20 5 7 25 417 3 340 3.7 32 20 5 12 23 436 3 350 6.4 46 31 7 18 38 465 5 360 5.4 34 25 7 30 34 434 4 370 4.8 30 20 5 11 27 403 3 380 5.1 29 23 7 15 29 460 4 390 8.7 61 35 16 27 68 318 13 400 8.3 90 50 17 23 67 319 19 410 10.0 68 49 22 28 77 330 22 420 9.3 64 41 21 24 72 296 18 430 11.3 56 40 24 23 83 287 15 440 10.4 59 40 19 25 81 281 15 450 10.6 68 42 18 31 83 298 14 460 9.5 75 48 15 27 79 264 17 470 10.9 73 46 14 22 81 325 13 480 11.1 73 47 14 22 84 314 13


93


Figure 3.10 shows the minor element abundances for core BP-1.

Within the modern soil, Zn, V and Cr show a decreasing trend while Zr shows

an increasing trend. At S1, negative peaks in Cu and Zr occur. In b1, Zn, V

and Cr all show a decreasing trend while Zr shows a heavily fluctuating

increasing trend. Throughout b2, Zn, V, Cr, Ni, Co, Cu fluctuates and display

small peaks at a depth of 270 cm. Zr also fluctuates with a positive peak at

270 cm. Zn, V, Cr, Ni, Co, Cu all demonstrate a strong negative peak at S3,

Zr mirrors this, with a strong positive peak at S3. Zn, V, Cr, Ni, Co, Cu all

decrease in abundance throughout b3, Zr mirrors this and in increases

abundance throughout b3.


Figure 3.11 shows the minor element abundances for core BP-2, the

modern soil displays peaks in Cr and Ni at a depth of 120 cm, Zn shows an

increasing trend while Zr shows a decreasing trend. S1 is marked by a

negative peak in Zr. In b1, Zn and Cr show an increasing trend while Zr

shows a decreasing trend. S2 is marked by a large positive spike in Zn. In b2

Co, Ni and V all show a small increase at a depth of 260cm. Zr shows an

overall increase throughout this unit, but demonstrates a decrease in

abundance around 260 cm and a large increase at 240 cm. Cu, V and K all


94

Figures 3.10: Minor elements for BP-1 are plotted in PPM against

depth in cm. The stratigraphic log and inferred surfaces highlight the

key trends in each buried soil. A key for the symbols shown in the

stratigraphic log can be found on Figure 3.1. This data shows an

overall decreasing trend upward through the core and an increasing

trend in Zr.


95


96

Figure 3.11: Minor elements for BP-2 are plotted in PPM against


key trends in each buried soil. A key for the symbols shown in the in

the stratigraphic log can be found on Figure 3.1.


97


98

show small decreases at S3, Zr shows an increasing trend through b3 which

peaks at S3.

3.4.3 Floyd Playa-1

FP-1 (Figure 3.12) is perhaps the most variable of the minor element

data. The modern soil shows an overall decreasing trend in Zr, Zn shows a

small peak at 140 cm and V, Cr and Ni show decreases at 150 cm. Zr shows

another positive spike at 190 cm. S1 is marked by a very large spike in Cu

with a corresponding smaller spike in Zn and a small negative shift in Zr. It is

difficult to interpret trend in b1 due to the missing data, however it appears

that Zr showed an overall increase. Fluctuations occurred in Zn and V, Cu

demonstrates an increasing trend between S2 and 330 cm. An increasing

trend in Zr is observed in b2, while decreasing trends are apparent in Cu, Zn

and V.

3.4.4 Floyd Playa-2

Figure 3.13 shows the minor element abundances for core FP-2. The

modern soil shows few variations other than a spike in copper at 240cm, this

is likely related to human activity such as pipes. Zr fluctuates throughout this

unit. Soil b1 shows a large decrease in Zn and V associated with the

presence of the C horizon, at this horizon Zr increases. Few trends are

observed in b2, other than a decrease in V associated with the Bk horizon.


99

Figure 3.12: Minor elements for FP-1 are plotted in PPM against



stratigraphic log can be found on Figure 3.1. A large spike in Cu and a

smaller spike in Zr correspond with S1.


100

Depth (cm)


101

Figure 3.13: Minor elements for FP-2 are plotted in PPM against



stratigraphic log can be found on Figure 3.1.


102


103

Chapter 4

Weathering Profiles

If one element is considered to be immobile relative to another

element, geochemical ratios can be used to assess the relative gains and

losses of materials in paleosols during weathering and pedogenesis

(Chadwick et al., 1990). The degree of weathering is increased with

increasing precipitation and temperature (Sheldon et al., 2002). A summary

of commonly applied major element ratios used to determine pedogenic

processes is given in Table 4.1 (adapted from Sheldon and Tabor, 2009).

Although paleosols are unable to preserve the base saturation and

cation exchange due to post burial alteration, the bulk geochemical

composition remains unaltered by diagenesis (Retallack,1991) making these

ratios viable climo-functions. However the precision of these as absolute

values for temperature or precipitation may be slightly lacking, thus emphasis

is placed on observing the climatic trends i.e. warming and wetting rather than

the absolute values (Retallack, 2000).


104

Table 4.1 - Molecular Weathering and Pedogenesis Ratios

Ratio Formula Summary Pedogenic process

Ʃbase/Al Ca+Mg+Na+Ca/Al

Ʃbases lost to Al during pedogenesis

Hydrolysis

Base loss Base/Ti Bases lost during weathering, Ti accumulates

Leaching

Clayeyness Al/Si Al accumulates as clay minerals form

Hydrolysis

Provenance Ti/Al Ti is more readily removed by physical weathering, Al by chemical weathering

Acidification

Salinization K+Na/Al Alkali elements collect as soluable salt and are not removed

Salinization

Leaching Ba/Sr Sr more soluable than Ba - Sr is preferentially removed

Leaching


105

Ratios between different elements can be used to evaluate pedogenic and

weathering processes in paleosols (Sheldon & Tabor, 2009). The following

paragraphs provide a summary of these relationships.

4.1.1 Barium/Strontium Ratio

Ba/Sr ratios can be used to estimate the intensity of leaching (Sheldon,

2006) and also the intensity of weathering (Kahmann et al., 2008). Higher

values of Ba/Sr indicate more leaching is taking place. Sr is significantly more

soluble than Ba and is therefore more readily leached (Sheldon and Tabor,

2009). Heavily leached paleosols are commonly characterized by a low Ba/Sr

ratio at the top of the horizon and a high Ba/Sr ratio at the bottom of the

horizon (Sheldon and Tabor, 2009). The ratio of Ba/Sr increases with the

duration of weathering and the degree of drainage, this ratio can range from

2; common in most rocks, up to 10; which is indicative of strongly leached

soils (Retallack, 1997).

4.1.2 Titanium/Zirconium

Ti and Zr are both relatively immobile elements (Sheldon and Tabor,

2009). This is due to the insoluble nature of the minerals in which they are

hosted i.e. Zr in Zircon (ZrSiO4) and Ti in rutile (TiO2) (Stiles, 2003). Zr is

more abundant in coarser fractions of sediment such as sands, while Ti is

more common in finer, clayey sediments; thus there exists a grain size factor

4.1 Weathering Ratios


106

on the ratio. Lower values of Zr are therefore indicative of removal through

physical weathering and the preferential removal of larger grains (Stiles,

2003). Zr is chemically immobile and only able to be redistributed and

accumulate through physical weathering processes, i.e. small additions of Zr

to the upper portion of soil are commonly the result of introduction of detrital

zircon by eolian processes (Stiles, 2003). Conversely, Ti elevated ratios are

indicative of illuviation of fine grained material downward through a soil profile

(Stiles, 2003). Ti/Zr ratios are also able to provide information on provenance,

a scatter plot of Zr against Ti which displays a linear trend would be indicative

of a homogeneous source (Kahmann et al., 2008). However, scatter plots of

data collected from our cores showed no significant correlations due to the

overprinting of grain size effects.

4.1.3 Aluminum/Silica

The Al/Si ratio indicates the degree of clay production by feldspar

weathering and clay translocation i.e. illuviation (Kahmann et al., 2008).

These values tend to range between 0.1 and 0.3, they may be very close to 0

in very sandy soils and above 0.3 in very clayey soils (Retallack, 1997);

largely due to the increased abundance of Al in clay minerals relative to a

silicate parent mineral (Sheldon and Tabor, 2009). Syn-formational addition

of Si may be attributed to the addition of eolian sediment (Sheldon and Tabor,

2009). These can be distinguished by other commonly observed trend in


107

eolian sediment i.e. increased Zr and by comparison to the element suite

observed in the Blackwater Draw Formation.

4.1.4 Alkaline/titanium ratios

These ratios indicate leaching, during weathering Na, K and Ca are leached

while the chemically immobile Ti remains (Sheldon and Tabor, 2009). In arid

setting, leaching is limited due to lack of moisture, in humid settings the

leaching of bases will be enhanced (Retallack, 1997) thus more leached soils

indicate humid conditions while less leached soils indicate arid conditions.

4.1.5 Potassium + Sodium/Aluminum

This ratio is used as an indicator of salinization, a subsurface enrichment of K

+ Na relative to Al is commonly found in paleosols which form in arid to desert

regions (Retallack, 1997). This indicator of aridity is often accompanied by

other aridity indicators such as the presence of carbonate nodules or other

evaporite minerals (Sheldon and Tabor, 2009).

4.1.6 Summation of Bases/Aluminum Ratio

This ratio uses ∑bases (i.e. Ca + Mg + Na + K), which are the primary

cations lost during weathering, plotted against Al. This indicates weathering

of paleosols through hydrolysis (Sheldon and Tabor, 2009). As climate

becomes warmer and wetter alkali earth elements become depleted at the

expense of refectory elements such as Al (Tabor et al., 2002).


108

4.1.7 Titanium/Aluminum

This ratio is most commonly used to determine provenance of the

parent material, but has also been linked to climatic variations (Boyle, 1983).

The Ti content varies significantly between different rock types while the

concentration of Al remains relatively stable (Sheldon and Tabor, 2009).

Mafic rocks generally display a high Ti/Al ratio while sandstones and

mudstones have a low Ti/Al value (Fig 4.1) adapted from Sheldon and Tabor,

(2009). Ti is often lost towards the top of soil profiles as a result of physical

weathering through processes similar to those discussed under the Ti/Zr ratio

(Sheldon and Tabor, 2009). In the marine realm, higher Ti/Al values have

been linked with oxygen isotopic excursions and have been found to correlate

to cold climates (Boyle, 1983). This largely reflects the addition of coarser,

wind-blown silt material during glacial periods.


109

Figure 4.1: Average Ti/Al ratios for paleosols with sandstones parent (Diamond), mudstone parent (triangles) and basalt parent (square). The highlighted section covers the range in which our results fall, adapted from Sheldon and Tabor (2009).


110


111

4.1.8 Carbonates

The presence of CaCO3 indicates aridity, CaCO3 is highly soluble thus

it is readily mobilized in ground water and soil solution, therefore it is removed

from the soil profile under humid conditions (Sheldon and Tabor, 2009). Table

4.2 adapted from Gile et al., (1966) demonstrates the various stages of

development of carbonates within arid and semi-arid soils. Using this

classification, soils with carbonate horizons in the playa cores studied are best

characterized as type II carbonate accumulations.

Nodular concretions of calcium carbonate form when Ca2+ ions from

precipitation of minerals in the soil combine with CO32- from precipitation, soil

minerals or root respiration (Barchardt and Lienkaemper, 1999). This process

is enhanced in arid and semi-arid climates; short periods of precipitation

encourage the dissolving stage these are followed by prolonged periods of

evapotranspiration which concentrate the nodules (Barchardt and

Lienkaemper, 1999). An abundance of carbonate in a horizon is termed a Bk

Horizon (Brady and Nyle, 2008).


112

Table 4.2 - Stages of Carbonate accumulation in soils

Stage Properties

I Didpersed powdery and filamentous carbonate.

II Few to common carbonate nodules and veinlets, with powdery and filamentous carbonate in places between nodules.

III Carbonate forming a continuous layer formed by coalescing nodules; isolated nodules and powdery carbonate outside the main horizon.

IV Upper part of the solid carbonate layer with a weakly developed platy or lamellar structure capping less pervasivley calcareous parts of the profile.

V Platy of lamellar cap to the carbonate layer strongly expressed; in places brecciated with pisolites of carbonate

VI Brecciation and recementation, as well as pisoliths, common in association with the lamellar upper layer.

adapted from Gile et al. (1966)


113

4.1.9 Iron-Manganese Nodules

Visible nodules of ferromanganese precipitated from extant pools of Fe

and Mn in the soil occur most commonly in finer grained, clayey sediments

with restricted permeability and drainage, in temperatures ranging from

continental warm to subtropical (Stiles et al., 2001). The formation of nodules

is controlled by seasonal wetting and drying in the vadose zone, Fe-Mn

nodules initially form as hydrous-phase assemblages in micropores and

accrete outwards (Stiles, 2001). The nodules form through dissolution and

precipitation along a redox gradient, MnO is first precipitated subsequent

oxidation of Fe2+ by the MnO results in the accretion of Fe3+ (Golden et al.,

1988).

The following section applies the theory described in the above section

to the results observed in these samples.


Figure 4.2 represents core BP-1, the Ba/Sr ratio remains fairly constant

throughout the modern soil and b1. Ba/Sr peaks in b2 in the Btcb2 horizon

above a Bk horizon, it is likely that re-deposition occurred on the surface of

4.2 Weatehring Profiles of Playa Sediments in BaileyCounty and Floyd County


114

Figure 4.2: Weathering ratios in BP-1 plotted against depth in cm, a

key for the symbols used in the stratigraphic log can be found in Figure

3.1. This core is fairly homogenous but shows leaching in the Ba/Sr

profile. The absence of leaching in the K, Na and Ca/Ti profiles is

indicative of arid conditions.


115


116

the Bk. The Ba/Sr ratio is lower at the top (~5) of Btcb2 and higher (>10) at

the bottom of Btcb2, this is indicative of a heavily leached soil (Sheldon and

Tabor, 2009). Another smaller peak is observed at S3 indicating that the soil

Bmcb2 may also be leached. The values in this core are moderately high >5

this indicates that leaching is likely taking place throughout the soil profiles.

Ti/Zr shows fluctuation throughout the modern soil, moving up through

b2 and b1 Ti increases in abundance relative to Zr indicating physical

weathering processes. Zr is contained in larger sandy grains thus, it may be

inferred that preferential removal of these sandy grains by eolian processes

account for the depletion in Zr. Soil b3 shows a large influx of Zr at the

surface, this may be due to an increase in illuviation of Ti bearing fines at this

time. Alternatively, and more likely, this increase in Zr may be due to an influx

of eolian material containing detrital zircon (Stiles, 2003). Ti /Zr can also be

used as an indicator of provenance however much of the literature (e.g.

Holliday, 1989) report that the Blackwater Draw Formation is the primary

sediment source in this area. Differences observed in the Ti/Zr ratios of each

horizon may be an artifact of changes in grain size i.e. larger grains higher Zr

concentration, smaller grains higher Ti concentration. The increase in grain

size observed through soil b2 is tracked by enrichment in Zr.

Al/Si demonstrates enrichment of Al relative to Si in b3, towards the top

of Btb3 the Al/Si value is <0.1, this is considered to be very sandy (Retallack,


117

1997). Above S3, a prolonged positive trend of Al enrichment relative to Si is

observed which continues across S1 and S2 all the way up to the upper 15cm

(modern soil) where the positive trend steepens indicating an increase in clay

content of the soils above S3.

Na, K and Ca all become enriched relative to Ti at S3 indicating a small

degree of leaching took place at this time. Leaching of these bases requires

moisture (Retallack, 2001b), however minimal moisture is likely in this interval

due to the low degree of leaching. Throughout the rest of the core no

leaching profiles are observed this may indicate that moisture levels are

insufficient for the leaching of these soluble bases.

Figure 4.3 shows the K+Na/Al, Ʃbases/Al andTi/Al ratios. The increase

in K + Na relative to Al observed at S3 indicates that salinization may have

occurred through b2 and the K and Na accumulated on S3.

Ʃbases/Al show an increase in abundance of Ʃbases relative to Al

above S3 indicating hydrolysis occurred through the formation of b2. Thus,

moisture must have been sufficient to dissolve Mg, Ca, Na and K ions from

the parent silicate mineral. Above S2, no trends are seen indicating little to no

hydrolysis was taking place, thus arid conditions may have been likely.

The presences of Bk horizons indicate arid to semi-arid conditions as CaCO3

is too soluble to remain in humid conditions (Sheldon and Tabor, 2009).


118

Figure 4.3: Weathering ratios in BP-1 plotted against depth in cm, a


3.1. These again show few major trends. Salinization may be

observed at S3.


119


120

The presence of ferromanganese nodules between 280 cm and 190 cm is

troubling as they are largely reported under wetter climate regimes (Stiles et

al., 2001) and reasons for the seemingly inconsistent carbonate and Fe-Mn

intercalated nodule bearing horizons is unclear. Soil horizons such as this

which contain both carbonate and Fe-Mg nodules have been observed to infer

seasonality in monsoonal climates, where carbonate nodules form during the

dry season and Fe-Mn nodules for during the wet season (Sehgal and

Stoopes, 1972).


Figures 4.4 and 4.5 represent the weathering profiles of core BP-2. The

Ba/Sr ratio demonstrates leaching in Bcb3 and Bkb1 i.e. higher ratios at the

bottom of the horizon relative to the top. The Btcb1 horizon demonstrates a

large peak at the top of this horizon; this accumulation may be the result of

illuviation.

Ti/Zr fluctuates throughout the core and is likely a function of grain size;

observed increases in grain sizes can be correlated with an increase in the

abundance of Zr relative to Ti. Al/Si remains relatively constant throughout

the whole core. The Al/Si value is around 0.2 indicating that the sediment is a

mixture of sand and clay (Reatallack, 1997) consistent with the grain size

distributions presented earlier.


121

Figure 4.4: Weathering ratios in BP2 plotted against depth in cm, a key

for the symbols used in the stratigraphic log can be found in Figure

3.1. This core from the playa edge shows more variation then BP-1

from the playa center. Leaching profiles are observed in the Ba/Sr

ratio and small amounts of leaching are also observed in the base

cations. Strong peaks in Ca are associated with the presence of Bk

horizons.


122


123

Figure 4.5: Weathering ratios in BP2 plotted against depth in cm, a key

for the symbols used in the stratigraphic log can be found in Figure

3.1. An overall depletion of the ∑bases relative to Al is observed

indicating conditions were too moist for salinization to occur.


124


125

The Na/Ti, K/Ti and Ca/Ti are fairly constant indicating that little

leaching has taken place. Thus, it can be inferred that moisture was

insufficient for the removal of these bases i.e. conditions were arid.

Accumulations of Ca are associated with the presence of Bk horizons, again

indicate climatic aridity (Sheldon and Tabor, 2009).

Salinization trends are observed through b2, b1 and the modern soil

i.e. K + Na is enriched relative to Al towards the bottom of each profile. Thus

arid desert like conditions with a low Mean Annual Temperature may be

inferred (Sheldon and Tabor, 2009).

Fluctuations observed in Ʃbases/Al are most likely an artifact of the

fluctuations in Ca related to the presence of Bk horizons. The overall trend in

the core is a depletion in bases relative to Al upward through b2 and b3

indicating a warming and wetting of climate (Sheldon et al., 2002). Ti/Al is

used to determine provenance, Ti/Al values are low, <0.1 this is indicate that

the likely source is a sandstone or mudstone (Fig 4.1).

Carbonate nodules are present in three of the horizons; Bkb3, Bckb2

and Bkb1 indicating some degree of aridity. Ferromanganese nodules are

present in Bcb3, BcKb2 and Btcb1 indication poorly developed drainage

(Stiles 2001.) Soil horizons such as Bckb2 which contain both carbonate and

Fe-Mg nodules formed by intermittent intergrowth have been observed to infer

seasonality in monsoonal climates, where carbonate nodules form during the


126

dry season and Fe-Mg nodules for during the wet season (Sehgal and

Stoopes, 1972).

4.2.3 Floyd Playa-1

Figure 4.6 and 4.7 show the weathering profiles for core FP-1 which is

from the center of the playa floor in Floyd County. This core is very

homogenous and exhibits little signs of weathering. The Ba/Sr profile shows

some leaching occurred through the Btcb1 and Bt Horizons. Ti/Zr shows

small fluctuations, these are likely an artifact of changes in grain size. K/Ti,

Na/Ti and Ca/ Ti remain constant, other than enrichment in Ca associated

with the Bk horizon. This indicates insufficient moisture for leaching of these

cations (Retallack, 1997). Al/Si gives a consistently low value indicative of a

sandstone or mudstone source (Sheldon and Tabor, 2009).

4.2.4 Floyd Playa-2

Figures 4.8 and 4.9 demonstrate the weathering profiles for the core

FP-2. The Ba/Sr ratios are indicative of leaching, particularly in the Bht

horizon of the modern soil. Strongly leached horizons tend to exhibit

accumulations of Ba/Sr relative to Sr towards the bottom of a horizon

(Sheldon and tabor, 2009) consistent with the large spike observed at 190 cm.

The Ti/Zr ratio exhibits enrichment in Zr associated with the C horizon this is

an artifact of grain size as horizon C contains predominantly sand material


127

Figure 4.6: Weathering ratios in FP-1 plotted against depth in cm, a


3.1. This core from the playa center is very homogenous. Leaching is

present in the Ba/Sr profile.


128


129



3.1. Due to the cores homogeneity no significant trends are observed.


130


131



3.1. Significant changes in the weathering profile are observed in the

C horizon as this is largely unweathered material. Above the C

horizon, a large accumulation of Na is observed with a smaller

accumulation of Ca. This may be the result of arid conditions,

insufficient moisture allowed these soluble cations to accumulate.


132


133



3.1. These plots again show the difference in degree of weathering

within the C horizon. The accumulation of alkali bases is again shown

above the C horizon. The Al/Si ratio indicates a clayey unit above the

C horizon and the trend observed indicates that the C horizon may

provide the parent material for the soils above this horizon.


134


135

The Al/Si also shows an increase at the C horizon that can be attributed to a

higher proportion of silicate sand material.

Above the C horizon, the Na/Ti shows an accumulation of Na at the

bottom of the Btkb1, Btb1 and Bt horizons. This is likely due to leaching of

soluble salts such as Na from horizons above and their accumulation at intra-

soil horizon boundaries. K/Ti and Ca/Ti show similar yet less pronounced

trends. A strong peak in Ca/Ti is associated with Bkb2, the presence of this

Bk horizon indicates aridity.

Increases in the concentrations of Na+K/Al at the base of the Btkb1

horizon are likely the result of hydrolysis indicating climate was warm and

moisture was sufficient to dissolve the soluble K+ and Na+ cations and

redeposit them above the C horizon.

The Ʃbases/Al show that weathering through hydrolysis occurred in horizons

Btkb1 and Btb1 the Ʃbases become depleted with respect to Al up the profile

suggesting a warming and wetting of climate. The spike in the Bkb2 horizon

is related to the abundance of carbonate nodules which form the Bk horizon.

The Ti/Al ratio through the b1 soil shows a general decrease upward in Ti.

The highly elevated Al values just atop the C horizon are likely the result of

accumulation of illuviated clay minerals. However, if those values are

disregarded due to the illuviation mechanism rather than weathering, then the

Ti/Al trend forms a fairly consistent linear decrease upward; an expected trend


136

from parent material to daughter soil (Fig. 4.1, Sheldon and Tabor, 2009).

Thus, the b1 soil in FP-2 is the only soil horizon recovered, from any core, that

appears to show the relatively unweathered parent material and overlying soil.

4.2.5 Other Elemental Weathering Trends

BP-1 (Fig 3.10) displays an overall decrease in Zn, V and Cr towards

the surface. Zn and Cr are commonly associated with organic matter, along

with smaller quantities of V and may provide a proxy for former organic matter

in the paleosol profile (Retallack, 1990). Thus, this trend may be interpreted

as a decrease in organic matter moving up the profile. FP-1 (Fig 3.12) shows

a major spike in Cu and a smaller associate spike in Zn at S1, this spike in Cu

seems un-naturally large and is confined to a very small zone in the soil. It is

reasonable to assume this is a result of human activity i.e. copper pipes rather

than a pedogenic process.

4.2.6 Soil Characteristics

The horizons observed may also be classified as diagnostic horizons,

also known as epipedons which include both the darker, organic upper part of

the soil and the upper eluvial horizon (Brady & Weil, 2008). These are

summarized in table 4.3 and table 4.4, adapted from Brady & Weil (2008).


137

Table 4.3 - Surface Horizons

Diagnostic Horizon

Major features

Anthropic (A)

Human modified, mollic-like horizon, high in available P.

Folistic (O) Organic horizon saturated for <30 days/ normal year.

Histic (O) Very high in organic content, wet during some parts of the year.

Melanic (A) Thick, black, high in organic content (>6% organic C) common in volcanic ash soil.

Mollic (A) Thick, dark-colored, high base saturation, strong structure.

Orchic (A) Too light-colored or too low in organic content to be Mollic, may be hard and massive when dry.

Plaggen (A)

Human made soda-like horizon created by years of manuring.

Umbric (A) Same as Mollic except low base saturation.


138

Table 4.4 - Subsurface Horizon

Diagnostic Horizon

Major features

Argic (A or B) Organic and clay accumulation just below plow layer resulting from cultivation.

Albic (E) Light-colored, clay and Fe and Al oxides mostly removed. Argillic (Bt) Silicate clay accumulation. Calcic (Bk) Accumulation of CaCO3 or CaCO3.MgCO3 Cambic (Bw, Bg)

Change or altered by physical movement or chemical reactions, generally non-illuvial.

Duripan (Bqm)

Hard pan, strongly cemented silica.

Fragipan (Bx) Brittle pan, usually loamy textured, dense, coarse prisms. Glossic (E) Whiteish eluvial horizon that tongues into Bt Gypsic (By) Accumulation of gypsum. Kandic (Bt) Accumulation of low-activity clays. Natric (Btn) Argillic, high sodium, columnar or prismatic structure.

Oxic (Bo) Highly weathered, primarily mixture of Fe, Al oxides and nonsticky-type silicate clays.

Petrocalcic (Ckm)

Cemented calcic horizon

Petrogypsic (Cym)

Cemented gypsic horizon.

Placic (Csm) Thin pan cemented with Fe alone, or with Mn .or organic matter Salic (Bz) Accumulation of salts. Sombric (Bh) Organic matter accumulation. Spodic (Bh, Bs)

Organic matter, Fe, Al oxide accumulation

Sulfuric (C) Highly acidic with Jarosite mottles.


139

4.3.1 Bailey Playa

The modern soil and b1 soil in the Bailey Playa are primarily Bt or Bk

with some modifications such as nodules (c), color structure (w) or illuvial

accumulations (h) and (t). These are interpreted as Mollisols. Molisols

generally form on flat low lying land, with sub-humid to semi-arid climates and

support grassland vegetation (Retallack, 1990). Leaching near the

subsurface and illuviation leading to clay enrichment in the Bt horizon, along

with the removal of Ca+, Na+, K+ and Mg+ by hydrolysis indicate that a

Lessivage soil forming regime may be present (Retallack, 1990). Additionally,

the b1 soil contains calcic sub horizons suggesting that the climate during that

interval was slightly more arid than the modern climate. The characteristics of

the soils observed within the modern profile are very similar to those observed

by Holliday et al., (2008) in the Randall Clay, present in nearby playas. Thus

we infer the modern profile is part of this formation. The characteristics of the

soil in b1 is similar to those observed by Holliday et al., (2008) in the Tahoka

Formation of playa located close by, thus it can be inferred b1 is part of the

Tahoka Formation.

Soil b2 observed in the Bailey Playa cores is less well developed and

contains some degree of subsurface clay accumulation, but overall poor

horizonation. Thus, these soils are best characterized as Inceptisols.

4.3 Correlation and Soil Types


140

Inceptisols are able to form in a range of climates and vegetation, but

commonly form in open grasslands (Retallack, 1990). Moreover, both the BP-

1 and BP-2 cores contain fairly well developed Bk and less developed Bt

horizons indicating more aridity than the overlying soils. The characteristics of

this soil are again similar to the Tahoka Formation described by Holliday et

al., (2008) thus we b2 is inferred to form part of the Tahoka Formation.

Soil b3 in the Bailey Playa is largely characterized as a well-developed

Bk horizon in the BP-2 core and a Bt horizon in the centrally located BP-1

core. The entire soil profile was not penetrated during coring, but based on

the well-developed Bk horizon in the BP-2 core, an aridisol soil series is

inferred for the interval. This soil is likely derived from the Blackwater Draw

Formation as Holliday et al., (2008) observe the Tahoka Formation lies atop

Blackwater Draw sediments.

In summary, the Bailey Playa soils observed in core change from

Aridisol to Inceptisol to Mollisol upwards (Fig 4.10). This trend in soil series

types can generally be related to an increase upward in precipitation and

possibly temperature.


141

Figure 4.10: Correlation between sediments from the center of the

playa floor and sediment from the playa margin for the Bailey County

Playa. A key to the symbols used in the stratigraphic log can be found

in Fig 3.1.


142


143

4.3.2 Floyd Playa

The modern soil in the Floyd Playa are primarily Bt or Bht, these are

interpreted as Mollisols thus flat low lying land, with sub-humid to semi-arid

climates and grassland vegetation may be inferred (Retallack, 1990).

Leaching near the subsurface and illuviation leading to clay enrichment in the

Bt horizon along with the removal of Ca+, Na+, K+ and Mg+ by hydrolysis

indicate that a lessivage soil forming regime may be present (Retallack,

1990).

The characteristics of the soils observed within the modern profile are

very similar to those observed by Holliday et al., (2008) in the Randall Clay,

present in nearby playas. Thus we infer the modern profile is part of this

formation.

Soil b1 observed in the Floyd county playa exhibits clay accumulation,

the development of horizonation decreases with depth through b1. These

soils are characterized as Mollisols at the top, thus climates which support

grassland may be inferred (Retallack, 1990). However, the S2 surface likely

indicates a second soil forming episode with poor horizonation and is inferred

as an Inceptisol. The sandy unit observed in FP-2 is interpreted as an influx

of fluvial deltaic sediment, similar to the gravel/sand member of the Tahoka

Formation observed by Hall (2001). The clay portion of this unit displays

characteristics very similar to those observed by Holliday et al., (2008) in the


144

Tahoka Formation of playa located close by, thus it can be inferred b1 is part

of the Tahoka Formation.

Soil b2 in the Floyd contains well-developed Bk horizon, Fe-Mn concretions

are also present. The entire soil profile was not penetrated during coring,

but based on the well-developed Bk horizon, an aridisol soil is inferred for this

interval. This soil is likely derived from the Blackwater Draw Formation as

Holliday et al., (2008) observe the Tahoka Formation atop Blackwater Draw

sediments.

Floyd Playa soils also exhibit a change from Aridisol to Inceptisol to

Mollisol upwards (Fig 4.11). This trend in soil series types can generally be

related to an increase upward in precipitation and possibly temperature as

well.


145

Figure 4.11: Correlation between sediments from the center of the

playa floor and sediment from the playa margin for the Floyd County

Playa. A key to the symbols used in the stratigraphic log can be found

in Fig 3.1.


146


147

4.3.3 Playa formation considerations

Figure 4.10 demonstrates the correlation between the facies observed

at the playa center and playa edge for the Bailey Playa. The Randall Clay

appears to be thicker at the playa edge (BP-2) than in the playa center (BP-1).

This may be the result of increased accommodation space at the playa edge

relative to the playa center, this is concurrent with Wood and Osterkamp’s

(1987a) model of playa enlargement through dissolution, whereby playas

enlarge from the center outwards, thus the annular becomes the main zone of

recharge (Wood & Osterkamp 1987a). Randall Clays are known to form

under ponded conditions or heavily vegetated sub-aerial conditions (Holliday

et al., 2008).

The Tahoka Formation which forms soils b1 and b2 is thicker at the

center of the playa indicating greatest subsidence here this may be a result of

dissolution of carbonate below by precipitation and ground water runoff which

may have accumulated in the initial depression (Wood & Osterkamp 1987a).

The Pale olive gray clays observed in this section of the Tahoka Formation

are lacustrine muds which may have formed during periods of playa

inundation (Holliday et al. 2008). Below this both cores reach the Blackwater

Draw Formations uppermost Aridisol.


148

Figure 4.11 demonstrates the correlation between the facies observed

at the playa center and playa edge for the Floyd County Playa. The Randall

Clay appears to be thicker at the playa edge (FP-2) than in the playa center

(FP-1). This may be the result of increased accommodation space at the

playa edge relative to the playa center, and is again concurrent with Wood

and Osterkamp’s (1987a) model of playa enlargement through dissolution at

the annulus. Both facies of the Tahoka Formation are present in b1, FP-1 is

composed only of the lacustrine muds, FP-2 however exhibits an influx of

sand and gravel known to occur in the playa margin this is interpreted as a

fluvial-deltaic sediment (Evans & Meade, 1945). Below the Tahoka formation,

FP-2 extends in to the Blackwater Draw Formations uppermost Aridisol.

The Blackwater Draw Formation exhibits a well-established northerly

fining trend (Fig 4.12) adapted from Holliday, (1989). Various grain size

relationships show remarkable correlation (often R2 = .88 to .94) with distance

from the Pecos River located to the south of the Southern High Plains (Fig.

4.13 & 4.14; Holliday, 1989). Deviations from this trend would indicate either a

different source than the Blackwater Draw Formation or hydrological

reworking of the Blackwater Draw Formation after deposition. However,

within the study areas the Blackwater Draw Formation is the only viable

source as it represents the surface that the playas formed on and exterior

4.4 Temporal Constraints


149

sediment sources to the Southern High Plains have not existed since the

Pecos River down-cut to the west and isolated the region around 1.6 Ma

(Holliday, 1989). Therefore, grain size parameters that are significantly

deviated from the well-established trends shown in the Blackwater Draw

Formation would indicate reworking of the Blackwater draw Formation and

thus, a relatively younger age.

In the Bailey Playa cores, grain size data was taken from 40-100 cm

below the S2 surface and results indicate that the BP-1 core is significantly

elevated (i.e. close to or more than 1 σ) in sand percentage and mean sand

size (Fig. 4.13). Moreover, the BP-2 data shows a standard deviation less

very fine sand to silt ratio. In the Floyd Playa cores, grain size data was taken

from 70-130 cm below the S1 surface and results here indicate that both

cores show significant departure from the observed trend in the Blackwater

Draw Formation (Fig. 4.14).


150

Figure 4.12 adapted from Holliday, 1989 demonstrates the northerly

fining of grains size with distance from the Pecos River.


151


152

Figure 4.13: S-N transect of a) % sand (R2 = 0.88), b) mean sand (mm;

R2 = 0.93) and c) very fine sand versus coarse silt (vfs/silt; R2 = 0.31)

against distance (km) from the Pecos River. BP-1 (green square) and

BP-2 (orange square) are plotted along with margins of ±1σ (dashed

lines).


153


154

Figure 4.14: SW-NE transect of a) % sand (R2 = 0.94), b) mean sand

(mm; R2 = 0.94) and c) very fine sand versus coarse silt (vfs/silt; R2 =

0.58) against distance (km) from the Pecos River. FP-1 (green square)

and FP-2 (orange square) are plotted along with margins of ±1σ

(dashed lines)


155


156

Results relatively consistent with the trends are not meaningful to

interpret as either original Blackwater Draw Formation or reworked Blackwater

Draw Formation because both scenarios could produce results on that trend.

However, results outside of the ±1σ are significant and hard to reconcile as

original Blackwater Draw Formation. Thus, the most likely scenario is the b2

soil in the Bailey Playa is post-youngest age for the Blackwater Draw

Formation. Thermoluminescence and radiocarbon dating typically bracket a

minimum age for the Blackwater Draw Formation between 40 and 30 ky

(Holliday, 1989; Holliday et al., 1996; Holliday et al., 2008) .Thus, the

paleosols studied here are younger than ~ 40ky.

A more refined temporal constraint can be derived from the

comparison of our soils with similar soils of other studies. Holliday et al.,

(2008) carried out a sedimentological study of 30 different playa fills on the

Southern High Plains. Two of the playas which they sampled were very

close in location to our sample locations; Colston Playa (11) is ~18 km

north of Floyd Playa and Radcliffe Playa (19) is ~18 km southwest of

Bailey Playa. Both of the Bailey and Floyd Playas contain horizons

sedimentologically similar to the Tahoka Formation observed in the

Colston and Radcliffe Playas. Holliday et al., (2008) use 14C dating to

provide an estimate for the age of the Tahoka Formation. The Tahoka

Formation clays in Colston Playa were dated at 11,570 14C yrs BP in the


157

upper part of the section, thus is may be possible that uppermost Tahoka

Formation in the Floyd and Bailey Playas are of a similar age. In the

Radcliffe Playa, the lowermost part of the Tahoka Formation were dated at

21,360 14C yrs BP, thus it may be possible that the lower section of the

Tahoka Formation in Bailey and Floyd Playas are of a similar age.


158

Chapter 5Climate Proxies

Several of the weathering ratios described in chapter 4 have been

empirically quantified through study of modern soil types in order to provide

estimates of paleoclimate such as precipitation and temperature, these

methods are summarized in table 5.1. These methods may only be used in

presence of certain soil types and horizons.

Table 5.1 - Quantification of Climo-functions

Ratio (x) Climo-function Equation Reference

Si/Al Temperature (°C) (2) T = 46.9 x + 4 Sheldon, (2006c)

*K+Na/Al Temperature (°C) (3) T = -18.516 x+ 17.298 Sheldon et al., (2002)

*Ca/Al Precipitation (mm)

(4) P= -130.9ln x + 467 Sheldon et al., (2002)

Depth to Bk

Precipitation (mm)

(5) P= -0.013 x2 + 6.45 x +137.2

Retallack (2005)

5.1.1 Method (1)

The Al/Si ratio which determines clay content can be used to calculate

paleotemperature, (Sheldon, 2006c) relates mean annual temperature (MAT)

(T) to clayeness (C) with equation 2, which has standard error of +/- 0.6 °C

and an R2 value of 0.96 (Sheldon et al., 2006).

T (°C) = 46.9C + 4 (2)

5.1 Climo-Functions


159

This method is applicable only to the Bt and Bw horizons of inceptisols

(Sheldon, 2006c). Thus, the method can be applied to the Bt and Bw

horizons of buried soil 2 in cores BP-1 and BP-2 and buried soil 2 in FP-1

(Table 5.2).

5.1.2 Method (2)

Sheldon et al., (2002) relate salinization trends to MAT °C (T) using the

molecular ratios of Na2O +K2O/Al2O3 (S) (equation 3). Na and K tend to

accumulate in desert environments thus a low MAT would be expected for

horizons which demonstrate salinization (Sheldon & Tabor, 2009). This

method has a standard error of +/- 4.4 °C, an R2 value of 0.37 and is

significant to the 99.9% level (Sheldon et al., 2002).

T (°C) = -18.516(S) + 17.298 (3)

This method is only applicable to lowland soils formed within the last

100 ky under climates that have a MAT range of 2-20°C (Sheldon et al., 2002)

thus it will be applicable to this study. The equation may only be applied to Bt

and Bw horizons that exhibit significant salinization trends i.e. a subsurface

enrichment of Na + K relative to Al, and yields best results when applied to

Inceptisols (Sheldon et al., 2002). The only horizon suitable for this analysis

is Btcb2 in core BP-1 (Table 5.2).


160

Table 5.2 - Summary of paleotemperature

Method: (1) Al/Si T (°C) = 46.9C + 4

Core Horizon Depth (cm) Temperature (°C) BP-1 Btcb2 220 14.2

230 14.2

240 13.6

Average 14

Btkb2 250 13.9

260 13.2

Average 13.6 BP-2 Btb2 220 12.0

230 11.9

Average 11.95 FP-1 Bwkb2 310 15.8

320 15.9

330 15.9

340 16.0

Average 15.9 Method: (2) Salinization T (°C) = -18.516(S) +

17.298

Core Horizon Depth (cm) Temperature (°C) BP-1 Btcb2 230 13.5

240 13.5

Average 13.5 FP-2 Btb1 230 12.9

240 12.9 250 12.9 260 12.6 270 12.4 Btkb1 280 12.6 290 12.5 300 12.6 310 12.5 Average 12.6

mailto:BP-@


161

5.1.3 Method (3)

Sheldon et al., (2002) propose a proxy for MAP which utilizes the molar

ratio of Ca/Al (C) (Equation 4). This method has a standard error of +/- 156

mm and an R2 =0.59. This relationship is applicable only to Mollisols in the B

horizon where significant variation from the weathering ratio of the parent

material is observed (Sheldon et al., 2002). Following these limitations this

method may be applied the horizons Btb1 and Btkb1 in core FP-2 (Table 5.3).

P (mm/yr) = -130.9ln (C) + 467 (4)

These relationships are applied on to Bt and Bw horizons as they form

over longer time periods and are in equilibrium with the climate (Sheldon &

Tabor, 2009). The longer period of formation also ensures that short time

climate trends such as those associated with El Nino events do not impose on

the long-term trends (Sheldon &Tabor, 2009).

5.1.4 Method (4)

The depth of the Bk horizon (D) is also correlated with the MAP this

relationship is quantified by equation 5 adapted from Retallack, (2005). This

relationship was determined using data collected by Jenny and Leonard

(1935) from 807 globally distributed soils. This method has a standard error

of ±147 mm yr−1, and R2=0.52 (Retallack, 2005).

P (mm/yr) = -0.013D2 + 6.45D +137.2 (5)


162

In sub-humid regions the Bk horizon is generally deep but in arid

regions Bk horizons are much shallower (Retallack, 2005). In warm and wet

climates, bases such as Calcium are readily removed, in more arid regions

moisture is insufficient to remove Calcium cations, thus they accumulate at

the upper surface of Bk horizons (Sheldon et al., 2002).

This method has been applied to soils ranging in age from the Paleozoic to

the Quaternary (Retallack, 2001b). When applying this relationship pre-burial

erosion, post-burial compaction and atmospheric CO2 levels must be

considered, however these are generally not an issue when dealing with post-

Cretaceous soils (Berner and Kothavala, 2001). This relationship may only be

applied to moderately developed soils which contain calcite nodules in

Table 5.3 - Summary of paleoprecipitation

Method (4) P = -130.9ln (Ca/Al) + 467

Core Horizon Depth (cm)

Precipitation (mm/yr)

FP-2 btb1 230 181

240 163

250 162

260 206

Average 178

Btkb1 270 215

280 182

290 237

300 234

310 255

Average 225


163

lowland setting with limited human disturbance (Sheldon &Tabor, 2009), thus

this method will be applicable to all the cores which contain Bk horizons

(Table 5.4).

The modern MAT on the Southern High Plains is 18.6°C (High Plains

Regional Climate Centre, 2009). Using Method 1 to calculate temperature

results in a temperature range between ~12-16°C, these are cooler than

modern temperatures (Fig. 5.1). Method 2 gives results which are very

consistent with those observed at the same depth in BP-1, the average

temperature for soil b1 is 13.5°C this is ~ 5°C cooler than present. The

convergence of the two methods around a similar temperature strengthens

the argument that the numbers are valid. The sediments from which these

values were calculated form part of the Tahoka formation, dated around

Table 5.4 - paleoprecipitation calculated using depth to Bk Method (4): P (mm/yr) = 0.013D2 + 6.45 D+137.2

Core Horizon Depth (cm) Depth to Bk(cm) Precipitation (mm/yr)

BP-2 Bkb1 200-215 53 443

Bckb2 230-310 15 231

Bkb3 335-345 23 279

FP-2 Bkb2 400-440 22 273

5.2. A Summary of Climate


164

21,360 14C yrs BP to 11,570 14C yrs BP in playas located close to Bailey

and Floyd Playas (Fig. 4.15 and 4.16) (Holliday et al., 2008). This is

contemporaneous with the LGM which occurred around 18-21 ky ago until its

demise at ~10 ky (Bowen & Johnson, 2012). If this age model is correct, our

BP-1 soil b1 ( ~ 21,360 ky) results are comparable with those of Johnson et

al., (2007b) who also report temperatures 5°C cooler than present, based on

δ13 C analysis, of the Upper Gilman Formation, Central High Plains which is

dated ~25,580 ky. Although this location is at higher latitude, these locations

are still reasonably comparable. The values calculated for Floyd Playa are

higher than those calculated for the possibly older b2 soil in Bailey Playa.

Thus, a warming trend towards the present day climate might exist (Fig 5.1).

However, the magnitude of the warming shown by these calculations ranges

broadly from ~12-16°C indicating that over the last ~ 11 ky there has been a

minimum of ~2.5°C. Nordt et al., (2007) carry out δ13 C analysis of 61

different buried soils across the High Plains, they estimate that early Holocene

temperatures (10-7.5 ky) were 1-2 °C cooler than present, this is fairly

consistent with our results.

The modern MAP on the Southern High Plains ranges between 330-

450mm/year (Bolen et al., 1989). Method 3 which is applied only in FP-2

gives an average precipitation value of 203 mm/year. The b1 soil occurs

within the upper Tahoka Formation. If the correlation with nearby playas is

correct, then this horizon is dated ~11, 547 ky BP (Fig. 4.15 and 4.16).


165

Method 4 gives a range in precipitation between 231-443 mm/yr for

various soil horizons in the BP-2 and FP-2 cores (Table 5.4; Fig. 5.1).

However, the b2 and b3 soils in these cores range from 231-279 mm/yr

whereas the b1 soil is estimated at 443 mm/yr and approaches modern

conditions. The b2 and b3 values correlate best to the lower Tahoka

Formation and Blackwater Draw Formation, respectively, whereas the b1 soil

is more likely upper Tahoka Formation. Therefore, using the age model

developed on (Fig. 4.15 and 4.16), the climate appears to have become more

humid sometime between ~21 and ~11 ky, possibly by up to ~200 mm/yr (Fig.

5.1). Between 15 - 9 ky Bowen and Johnson (2012) observe an increase in

sediments associated with more humid climate, an increased effective

moisture, which stabilized the landscape would fit well with transition from

Inceptisol (poorly developed) up into a Mollisol within the Tahoka Formation

(Fig 4.15 and 4.16). Although this example is further removed, Barchardt and

Lienkaemper calculate precipitation using depth to Bk, in Union City

California, these horizons are then dated using 14C of associated charcoals.

They report rainfall in early Holocene times, between 10 and 7 ka was

probably had half the present (~470mm), this is in keeping with our result in

which double from 11Ky to present, thus indicating that the magnitude of

change we observe may be of a reasonable value.


166

Figure 5.1 provides a summary of climate progression using methods (1) to (4) based on the age model derived from Holliday et al., (2008)

dates for the Tahoka Formation.


167


168

Chapter 6Summary and Conclusions

This study applies well-established methods in geochemistry to assess

the applicability on the Southern High Plains in order to produce an estimate

of climate over the last 40,000 years.

Four cores were taken from two playa basins on the Southern High

Plains, Texas. Within each core three to four soil profiles were observed.

Geochemical analysis and analysis of the physical properties of the soils

correlate well and revealed that significant weathering of the buried soil

profiles has occurred in a climate that was more arid than present. Equations

were applied to assess past MAP and MAT. Climo-functions suggest;

Temperature has increased by 5°C from bottom of the core to top.

Precipitation increased by approximately 100-150 mm/yr from bottom of the

core to top.

Analysis of the grain size distribution within the soil profile allowed for

the development of an age model based on the well known northerly fining

trend of the Blackwater Draw formation. The observed deviation from this

trend suggests that sediments have been reworked, thus an age younger than

the Blackwater Draw (~40 Ky) is inferred. A comparative age control was also

carried out using 14C dates from playas studied by Holliday et al. (2008), these

yielded dates of 21,360 14C yrs BP for soil b2 in Bailey Playa and 11,547

21,360 14C yrs BP for soil b1 in Floyd Playa.


169

The MAT and MAP were combined with the age model to suggest that

climate became warmer and wetter towards present. Thus, this study

suggests that temperature and precipitation both increased during soil forming

events by 5°C and 100-150 mm/yr, respectively, over the last 30-40 ky. This

trend is concurrent with several other studies. It can therefore be assumed

that this method of paleoclimate analysis can successfully be applied to playa

wetlands in order to produce a relatively high resolution climatic record.


170

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181

Appendix

Loss On Ignition Data BP-1

Sample # Crucible Number

Crucible Weight (g)

Cruc.+ Wet Wt.

(g)

Cruc. + Fused Wt. (g)

LOI

BP1 - 0 1.00 8.84 10.84 10.71 6.46

BP1- 10 2.00 7.84 9.79 9.66 6.28

BP1 - 20 3.00 7.81 9.84 9.74 4.49

BP1- 30 4.00 8.08 10.18 10.08 4.97

BP1- 40 5.00 8.25 10.26 10.15 5.18

BP1 - 50 6.00 7.76 9.74 9.63 5.76

BP1-60 1.00 9.69 11.62 11.50 5.86

BP1-70 2.00 8.93 10.90 10.77 6.77

BP1-80 3.00 8.41 10.41 10.27 6.90

BP1-90 4.00 9.28 11.21 11.05 7.84

BP1-100 5.00 8.12 10.18 10.01 8.30

BP1-110 6.00 8.66 10.68 10.51 8.20

BP1-120 1.00 9.69 11.63 11.46 8.65

BP1-130 2.00 8.93 10.95 10.76 9.34

BP1-140 3.00 9.28 11.26 11.07 9.57

BP1-150 4.00 8.41 10.41 10.22 9.39

BP1-160 5.00 8.12 10.16 9.96 9.84

BP1-170 6.00 8.66 10.66 10.47 9.39

BP1-180 1.00 8.84 10.69 10.52 9.29

BP1-190 2.00 7.84 9.75 9.56 9.80

BP1-200 3.00 7.80 9.83 9.63 9.67

BP1-210 4.00 8.08 10.10 9.89 10.16

BP1-220 5.00 8.25 10.20 10.00 10.62

BP1-230 6.00 7.76 9.77 9.57 10.19

BP1-240 1.00 7.84 9.77 9.57 10.22

BP1-250 2.00 7.76 9.79 9.58 10.20

BP-260 1.00 9.69 11.42 11.24 10.32

BP-270 2.00 8.93 10.59 10.42 10.35

BP1-280 3.00 9.28 11.27 11.07 10.30

BP1-290 4.00 8.66 10.63 10.42 10.72

BP1-300 5.00 8.41 10.42 10.21 10.57

BP1-310 6.00 8.12 10.16 10.00 7.95

BP1-320 1.00 8.66 10.66 10.47 9.56

BP1-330 2.00 8.41 10.45 10.26 9.39

BP1-340 3.00 9.28 11.18 10.91 14.02

BP1-0 R 3.00 7.80 9.92 9.78 6.59


182

BP1-80 R 4.00 8.25 10.39 10.24 6.89

BP1-110 R 5.00 8.08 10.15 9.98 8.28

BP1-180 R 6.00 8.84 10.67 10.50 9.37

BP1-310 R 4.00 8.12 10.28 10.10 8.04

BP1-80 R 5.00 9.69 11.41 11.29 6.96

BP1-110 R 6.00 8.93 10.76 10.61 8.12

BP1-280 R 5.00 7.81 9.94 9.71 10.49

R - Repeat


183

Loss On Ignition Data BP-2


Crucible Weight (g)

Cruc.+ Wet Wt.

(g)

Cruc. + Fused Wt.

(g)

LOI

BP2-0 1.00 7.80 9.86 9.61 11.98

BP2 - 10 2.00 7.84 9.79 9.56 11.97

BP2 - 20 3.00 8.25 10.12 9.91 11.27

BP2 - 30 4.00 8.84 10.81 10.61 10.11

BP2 - 40 5.00 7.76 9.73 9.51 10.86

BP2 - 50 6.00 8.08 10.06 9.84 11.35

BP2 - 60 1.00 8.41 10.34 10.12 11.42

BP2 - 70 2.00 8.93 10.84 10.64 10.50

BP2 - 80 3.00 8.12 10.10 9.90 10.52

BP2 - 90 4.00 8.66 10.43 10.25 10.24

BP2 - 100 5.00 9.28 11.04 10.91 7.05

BP2 - 110 6.00 9.69 11.62 11.49 6.89

BP2 - 120 1.00 8.12 10.13 10.00 6.51

BP2 - 130 2.00 8.93 10.90 10.77 6.31

BP2 - 140 3.00 8.66 10.56 10.42 7.42

BP2 - 150 4.00 9.69 11.52 11.37 7.95

BP2 - 160 5.00 8.41 10.45 10.30 7.57

BP2 - 170 6.00 9.29 11.47 11.30 7.77

BP2 - 180 1.00 7.76 9.85 9.69 7.70

BP2 - 190 2.00 7.80 9.91 9.72 8.96

BP2 - 200 3.00 7.84 9.72 9.57 7.82

BP2 - 210 4.00 8.08 9.82 9.68 8.28

BP2 - 220 5.00 8.84 10.44 10.30 8.89

BP2 - 230 6.00 8.25 10.30 10.09 10.45

BP2 - 240 1.00 9.29 11.09 10.90 10.49

BP2 - 250 2.00 8.41 10.20 10.02 10.40

BP2 - 260 3.00 8.93 11.03 10.87 7.56

BP2 - 270 4.00 8.66 10.62 10.46 8.01

BP2 - 280 5.00 9.69 11.52 11.37 8.07

BP2 - 290 6.00 8.12 10.25 10.07 8.19

BP2 - 300 1.00 7.84 9.80 9.63 8.49

BP2 - 310 2.00 8.25 10.16 9.99 8.78

BP2 - 320 3.00 8.08 10.01 9.85 8.67

BP2 - 330 4.00 7.77 9.83 9.63 9.39

BP2-0 R 1.00 9.28 11.18 10.95 12.07

BP2-110 R 6.00 8.84 10.87 10.73 6.89

BP2-130 R 2.00 8.41 10.32 10.20 6.33

BP - 300 R 3.00 8.93 10.98 10.81 8.54

BP2-200 R 4.00 8.66 10.55 10.40 7.68

BP2-130 R 5.00 9.69 11.44 11.33 6.36

BP2-300 R 6.00 8.12 9.99 9.83 8.56


184

Loss On Ignition Data FP-1


Crucible Weight (g)

Cruc.+ Wet Wt. (g)

Cruc. + Fused Wt.

(g)

LOI

FP1 - 0 1.00 9.29 11.22 11.00 11.44

FP1- 10 2.00 8.66 10.75 10.52 11.32

FP1 - 20 3.00 8.41 10.48 10.25 11.45

FP1 - 30 4.00 8.93 10.95 10.72 11.53

FP1- 40 5.00 8.12 10.14 9.91 11.79

FP1 - 50 6.00 9.69 11.72 11.49 11.45

FP1 - 60 1.00 7.80 9.86 9.62 11.72

FP1- 70 2.00 7.84 9.88 9.65 11.41

FP1 - 80 3.00 8.25 10.61 10.33 12.02

FP1 - 120 4.00 8.84 10.98 10.67 11.47

FP1- 130 5.00 8.08 10.17 9.93 11.29

FP1 - 140 6.00 7.76 9.95 9.70 11.45

FP1 - 150 1.00 8.93 10.94 10.71 11.42

FP1- 160 2.00 9.69 11.60 11.38 11.55

FP1 - 170 3.00 8.12 10.14 9.90 11.66

FP1 - 180 4.00 8.66 10.61 10.38 11.61

FP1- 190 5.00 8.41 10.47 10.19 11. 71

FP1 - 200 6.00 9.28 11.46 11.21 11.78

FP1 - 210 1.00 7.84 9.89 9.64 11.83

FP1- 220 2.00 7.80 9.91 9.65 12.56

FP1 - 230 3.00 8.84 10.83 10.59 12.31

FP1 - 240 4.00 7.76 9.71 9.47 12.29

FP1 - 250 5.00 8.25 10.25 10.00 12.65

FP1- 260 6.00 8.08 10.01 9.78 12.14

FP1 - 270 1.00 7.84 9.81 9.55 13.40

FP1 - 280 2.00 7.76 9.75 9.49 13.26

FP1 - 290 3.00 8.08 10.20 9.91 13.25

FP1 - 300 4.00 7.80 9.83 9.57 13.12

FP1 - 310 5.00 8.84 10.92 10.64 13.19

FP1 - 320 6.00 8.26 10.48 10.19 12.75


185

Loss On Ignition Data FP-2


Crucible Weight (g)

Cruc.+ Wet Wt. (g)

Cruc. + Fused Wt. (g)

LOI

FP2 - 0 1.00 7.77 9.71 9.51 10.23

FP2 - 10 2.00 8.08 10.02 9.82 9.98

FP2 - 20 3.00 7.80 9.77 9.58 9.64

FP2 - 30 4.00 7.85 9.85 9.65 10.22

FP2 - 40 5.00 8.25 10.31 10.10 10.19

FP2 - 50 6.00 8.84 10.86 10.66 10.03

FP2 - 60 1.00 9.70 11.62 11.36 13.49

FP2 - 70 2.00 9.28 11.31 11.12 9.74

FP2 - 80 3.00 8.41 10.44 10.27 8.78

FP2 - 90 4.00 8.93 10.94 10.77 8.57

FP2 - 100 5.00 8.12 10.17 10.09 4.00

FP2 - 110 6.00 8.66 10.64 10.57 3.44

FP2 - 120 1.00 8.83 10.93 10.83 4.62

FP2 - 130 2.00 8.25 10.32 10.22 4.68

FP2 - 140 3.00 7.84 9.83 9.78 2.52

FP2 - 150 4.00 7.80 9.93 9.87 2.80

FP2 - 160 5.00 8.08 10.06 9.93 6.72

FP2 - 170 6.00 7.76 9.98 9.72 12.11

FP2 - 180 1.00 9.69 11.64 11.53 5.72

FP2 - 190 2.00 8.41 10.71 10.60 4.55

FP2 - 200 3.00 8.93 10.96 10.86 5.04

FP2 - 210 4.00 9.28 11.28 11.16 5.58

FP2 - 220 5.00 8.66 10.63 10.52 5.33

FP2 - 230 6.00 8.12 10.42 10.29 5.53

FP2 - 240 1.00 8.83 10.79 10.68 5.87

FP2 - 250 2.00 8.25 10.35 10.22 6.33

FP2 - 260 3.00 7.76 9.94 9.79 6.61

FP2 - 270 4.00 7.80 9.93 9.79 6.57

FP2 - 280 5.00 7.84 9.81 9.67 6.92

FP2 - 290 6.00 8.08 10.02 9.89 6.42

FP2 - 300 1.00 8.12 10.16 10.02 6.58

FP2 - 310 2.00 8.93 10.72 10.59 7.42

FP2 - 320 3.00 8.66 10.59 10.45 6.92

FP2 - 330 4.00 9.28 11.22 11.07 7.63

FP2 - 340 5.00 9.69 11.64 11.48 8.38

copyright 2013, gabrielle dunne

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