Dr. Rolfe D. Mandel, Executive Director Odyssey Research ProgramKansas Geological Survey

University of Kansas

Using Soils to Reconstruct Climate

Five Soil Forming Factors

• Climatic Factor• Biotic Factor• Topographic Factor• Parent Material• Time Factor

When using soils to reconstruct climate, it is useful to consider the concept of “pedogenic pathways.”

A pedogenic pathway is a set of pedogenicprocesses leading to a given soil morphology.

Soils in different bio-climatic regions follow different pedogenic pathways.

A good way to understand the relationship between bio-climates and pedogenic pathways is to consider modern analogs.

Pedogenic pathways in the modern grasslands of the dry-subhumid to semi-arid Great Plains.

• Accumulation of organic matter and other plant nutrients in the A horizon. The organic carbon content and thickness of the A horizon generally decreases as mean annual precipitation decreases.

• Accumulation of calcium carbonate in the subsoil.

Tallgrass prairie in the Flint Hills of eastern Kansas

Mean Annual Precipitation: 26-28 inches

Mixed grass prairie on the High Plains of central Kansas

Mean Annual Precipitation: 22-24 inches

Short grass prairie on the High Plains of northwestern Kansas

Mean Annual Precipitation: 17-19 inches

Short grass prairie on the High Plains of southwestern Kansas

Mean Annual Precipitation: 11-13 inches

Pedogenic pathways in moist sub-humid to humid coniferous forests of North America.

Podzolization – A process that involves a pronounced downward translocation of iron, aluminum, and organic matter to form a silica-enriched eluvial E horizon above a spodic or Bt horizon enriched in some combination of Fe, Al, and organic matter (Birkeland, 1999:108).

• Thin A horizon.• Thick E horizons with low organic carbon, Fe, Al, and clay content• Thick B horizons with high Fe, Al, and OM content

Southern Pine forest of SE Texas

Alfisol

Pedogenic pathways in tropical climates.

Evolution of Oxisolic or lateritic profiles – Thick (meters), deeply weathered profiles composed of highly weathered material (Birkeland, 1999:121). Characterized by:• Massive enrichment of Fe, Al, or both, and associated oxide, hydroxide, and oxyhydoxide minerals.• Massive depletion of silicates (few original minerals are left)• Extensive depletion of bases• Formation of 1:1 layer clay minerals, especially kaolinite• Part of the profile may harden irreversibly on drying (laterite)

Oxisol in Hawaii

Oxisol in Brazil

Laterite in Brazil

In soil science, paleosols are defined as soils that formed under past environmental conditions; the chemical and physical characteristics of paleosols are not products of the modern bio-climate. There are three types of pleosols:

• Relict paleosol – at the surface• Buried paleosols• Exhumed paleosols

Buried soils represent previous land surfaces (landscapes) that were stable for long enough periods to develop recognizable soil profile characteristics.

Buried Soils

20,080 ± 56020,080 ± 560

32,850 ± 53032,850 ± 530

13,960±±150

2003 Excavation in Lower Mammoth/Camel Level2003 Excavation in Lower Mammoth/Camel Level

Lower Mammoth/Camel Bone Level, June 2003

12,215 ± 3512,215 ± 35

14SN105, Area A

92409240±70±70

97509750±70±70

10,37010,370±20±20

10,95010,950±60±60

12,21512,215±35±35

Folsom Folsom ComponentComponent

Clovis Clovis ComponentComponent

Pre-Clovis Pre-Clovis ComponentComponent ??

The following fossils may be preserved in soils and can provide valuable information about climate change:

PhytolithsGastropods

There is almost always some organic carbon preserved in soils – Stable carbon isotope (13C) analysis.

• Particles of hydrated silica formed in living plants

• Plant absorbs soluble silica from groundwater, deposited as solid SiO2 in cell walls, cell interiors, and intracellular spaces

Phytolith = “Plant Stone”

Why do plants produce phytoliths?

• Structural functionsStructural functions: silica provides plant rigidity

• Physiological functionsPhysiological functions: lessens effects of heavy metals

• Protective functionsProtective functions: against herbivores, insects, pathogenic fungi

Grass phytoliths are:abundant, durable, morphologically different, taxonomically identifiable…

Excellent for reconstructing paleoenvironments, including climate!

Major grass subfamilies:

•Chloridoideae: short-grass prairie, C4

Saddle-shaped

Blue grama and Buffalo Grass

•Panicoideae: tall-grass prairie, C4

Bilobate and cross-shaped

Big Bluestem, Indian Grass

•Pooideae: northern prairie, C3

Wavy, trapezoidal

Needle grasses, Western Wheatgrass

Some diagnostic trees & shrubs

Celtis occidentalis

(Hackberry)Diagnostic seed covering of sedges

Stable Isotope Geochemistry

• Stable Carbon Isotopes in Soil Organic Matter

• Stable Carbon and Oxygen Isotopes in Soil Inorganic Carbon

• Oxygen Isotopes in Faunal Remains

Stable Carbon Isotope Analysis

• SOM contains 13C/12C isotope ratio that reflect the photosynthetic pathways of C3 and C4 plant communities

• The δ13C value: the difference between the 13C/12C ratio and a known standard

– expressed in ‰

• C3 values range from -32‰ to -22‰

• C4 values range from -17‰ to -9‰ From Koch, P.L., 1998,

Isotopic Reconstructionof Past ContinentalEnvironments:Ann. Rev. Earth Planet.Sci. 26:573-615.

δ13C value differences trees (C3) vs. grasses (C4)

CO2

C-3 C-4

δ13C= -26 to - 22 δ13C= -16 to -12

PhotosynthesisPhotosynthesis

Soil Organic Matter-26 -24 -22 -20 -18 -16 -14 -12

Gastrocopta contracta

(2.4 mm)

Carychium exiguum

Discus whitneyi Gastrocopta contracta

Land Snails

Discus whitneyi and Gastrcopta contracta are typical of moist, woodland setting. Carychium exiguum demands a moist environment and is common near springs or seeps.

14SN105, Area A

92409240±70±70

97509750±70±70

10,37010,370±20±20

10,95010,950±60±60

12,37512,375±35±35

Folsom Folsom ComponentComponent

Clovis Clovis ComponentComponent

Pre-Clovis Pre-Clovis ComponentComponent ??

a = Charcoale = Burnt phytolith

B and C = Sporormiella spore

10,350+25

9240+70

6025+40

12,375+40

Carychium exiguum The analysis of the Kanorado gastropod assemblage has not been completed, but preliminary results are as follows:

Ca. 12,400-11,000 14C yr B.P.An abundance of aquatic gastropods, and the presence of Carychium exiguum, indicates ponded water (perhaps seasonal).

Ca. 11,000-10,300 14C yr B.P.Aquatic species gradually decline in number at the expense of terrestrial species. It is getting drier at Kanorado.

Ca. 10,300-9200 14C yr B.P.Aquatic species disappear from the assemblage and are replaced by terrestrial land snails that prefer dry environments. James L. Theler, Department of Sociology and Archaeology, University of Wisconsin-LaCrosse

Kanorado at ca. 12,500-11,000 14C yr B.P.

Kanorado at ca. 10,500 14C yr B.P.

Kanorado at ca. 9000 14C yr B.P. (minus the vehicles, billboard, and portable toilet)

14SN105, Area A

92409240±70±70

97509750±70±70

10,37010,370±20±20

10,95010,950±60±60

12,37512,375±35±35

Folsom Folsom ComponentComponent

Clovis Clovis ComponentComponent

Pre-Clovis Pre-Clovis ComponentComponent ??

JVC Device

Md. A Core

Let’s look at some soil and learn something about climate change!