ada278553 soil-geomorphic and pa leo climatic characteristics of the fort bliss maneuver areas,...

8/8/2019 ADA278553 Soil-Geomorphic and Pa Leo Climatic Characteristics of the Fort Bliss Maneuver Areas, Southern New M

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SOIL-GEOMORPHIC AND PALEOCLIMATIOFORT BLISS MANEUVER AREAS,SOUTHERN NEW MEXICO

AND1WESTERN TEXASAD-A278 553

H.Curtis MongerWith contributions by

r H.H~iordanklice j>' CuItuRafeoresa7tinc~yt ofmig 'Ago,0


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DISCLAIIIEI NOTICE

THIS DOCUMENT IS BESTQUALITY AVAILABLE. TH E COPYFURNISHED TO DTIC CONTAINEDA SIGNIFICANT NUMBER OFPAGES WHICH DO NOTREPRODUCE LEGIBLY.


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DEPARTMENT OF THE ARMYHEADQUARTERS, U.S. ARMY AIR DEFENSE ARTILLERY CENTER AN D FORT BLISSFORT BLISS, TEXAS 79916-0058

REPLY TOATTENTION Of

Directorate of Environment March 7, 1994Cultural/Natural Resources BranchFort Bliss, Texas 79916-6816

To: Addressee,Fort Bliss is pleased to provide th e following report on workcompleted on a project sponsored by the cultural resources program. Thereport is part of th e *Historic and Natural Resources Report" seriessponsored by Fort Bliss.

No. 10: Monger, H. Curtis. Soil-Geomorphic and PaleoclimaticCharacteristics of th e Fort.Bliss Ma neuver Areasg_ SouthernNew Mexico and Western Texas.

Five (5) other reports are being provided separately. Four (4) areprovided in one package including:No. 5: Jamieson, Perry. A. Su..rvey History of Fort .B.SSL 1890-1940.No. 6: Harris, Charles H. and L.R. Sadler. Bast.io.n. on. th e Border.1,1854-'194.'3'.No. 7: Foster, Michael S. Archaeologi._ca_ Investig.ations at Pueblo..S..i~~~~~~~~~~n.~~ ..saF_ Z3.. ._t.com O . ........... .eI __~.......oS n. C sas tF8?73) _ tjicoponent it~e I the Huec oB~~............... ....... ..............Bolson, Fort Ba-iss. TeasNo. 8: Mauldin, Raymond. The DIVAD Archaeological Project

One report is provided in another package. This report is:No. 9: MacNeish, Richard S. (Editor). Preliminary investigations ofthe_ Archaic in th e Region o_f Las Cr uc__s_ New Mexic .

Fort Bliss will have several additional reports ready for distributionduring 1994 and early 1995. Please write or call if you do not wish toremain on th e mailing list or if your address has changed. Finally, if youknow of other persons or institutions that may wish to receive copies ofreports in this series, then ask them to write or call, (915)568-5140, sothey can be added to th e mailing list.

Glen DeGarmo, Ph.D.' 7 Archaeologist


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SOIL-GEOMORPHIC ANDPALEOCLIMATIC CHARACTERISTICSOF THE FORT BLISS MANEUVERAREAS, SOUTHERN NEW MEXICOAND WESTERN TEXAS

byH. Curtis Monger

with contributions byDavid R. Cole, John Kipp, Jannifer W. Gish, Mohammad H. Nash, Sa'eb Khresat,

Brenda J. Buck, Thomas H. Giordano, Alice Janavaris, Linda S. Cummings

Publication of this report was supported by funding from theLegacy Resource Management Programof the

Department of Defense

Historic and Natural Resources Report No. 10Cultural Resources Branch

Environmental Management DivisionDirectorate of EnvironmentUnited States Army Air Defense Artillery CenterFort Bliss, Texas

IC 1993

SB 94""APR 2e .


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WSMR Contract No. DAAD07-89-D-0050, D.O. 23HSR Project 9029

Human Systems Research, Inc.Tularosa, New Mexico1993


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TABLE OF CONTENTS

LIST OF FIGURES ...................................................... viLIST OF TABLES ....................................................... ixACKNOWLEDGEMENTS ................................................ xFOREW ORD ........................................................... xiABSTRACT ........................................................... xiiCHAPTER I Introduction ................................................. ICHAPTER II M ethods ................................................... 7M apping ............................................................. 7Soil Characterization ................................................... 7Isotope Analysis ....................................................... 8

PART ISOIL-GEOMORPHIC CHARACTERISTICSCHAPTER III Geomorphic Surfaces on Maneuverand Adjacent Areas of Fort Bliss ..................................... 11General Landform s ................................................... I IGeom orphic Surfaces .................................................. I ILa Mesa (basin floor deposits of early to middle Pleistocene age) ............... 13Jomada I (fan deposits of late middle Pleistocene age) ....................... 19Jomada II (fan deposits of late Pleistocene age) ............................. 19Petts Tank (basin floor deposits of late Pleistocene age) ...................... 19Fault Com plex ....................................................... 24

Isaacks' Ranch (fan deposits of earliest Holocene-latest Pleistocene age) ......... 28Fort Selden Complex (erosional surfaces and fans of late Pleistoceneto Holocene age associated with the Camp Rice Fluvial Facies) ............. 28Lake Tank (basin floor deposits of late Pleistocene and Holocene age) ........... 28Organ (eolian and alluvial deposits of Holocene age) ......................... 28Historic Eolian and Arroyo Deposits ..................................... 30CHAPTER IVEolian Alteration of Soil Strata on Maneuverand Adjacent Areas of Fort Bliss ..................................... 35Mapping Unit 1: Modem Deflational Surfaces .............................. 35Mapping Unit 2: Dunes with Interdune Sheet Deposits ....................... 37

Mapping Unit 3: Depositional Areas Composed of Sand Sheet Deposits ......... 38Mapping Unit 4: Areas Where Soil Strata Are Modified Little by Wind .......... 38

ill


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CHAPTER VGeomorphic Investigation of a Possible Paleolakeon McGregor Range ................................................... 41Introduction .............................................................. 4 1Materials and M ethods ..................................................... 42Laboratory Analysis ........................................................ 45Profile Descriptions ........................................................ 46Results and Discussion ..................................................... 48Particle Size Distribution .................................................... 49Sedim entary Structures ..................................................... 57Secondary Calcium Carbonate ............................................... 58pH and Electrical Conductivity ............................................... 58Organic M atter ............................................................ 58M ineralogy ............................................................... 58Soil M icromorphology ..................................................... 61Stable Isotopes ............................................................ 64Geom orphology ........................................................... 64Summary and Conclusion ................................................... 66

CHAPTER VI Radar Analysis of the Fort Bliss Study Area .......................... 69

PART 11LATE QUATERNARY CLIMATIC AND ENVIRONMENTAL CONDITIONSCHAPTER VII Stable Isotopes in Pedogenic Carbonates of Fan-Piedmont Soilsas an Indicator of Quaternary Climate Change ............................... 75Abstract ................................................................ 75Introduction ............................................................. 75

M aterials and M ethods ..................................................... 77Results and Discussion .................................................... 78Sum mary ............................................................... 86CHAPTER VIII Radiocarbon and Stable Isotopes in the BasinFloor Soils on Fort Bliss ................................................ 89CHAPTER IX Pollen Results from Three Study Localities on Fort BlissM ilitary Reservation, New Mexico ........................................ 93Introduction ............................................................. 93M ethods and Data Presentation .............................................. 95Pollen R esults ........................ ................................... 97

C onclusion ............................................................ 114CHAPTER X Phytolith Analysis of Buried Soils in the FortBliss Reservation, El Paso, Texas ........................................ 117Introduction ............................................................ 117M ethods ............................................................ 117

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Interpretation ........................................................... 120Conclusions ........................... ............................... . 12 1Phytolith Analysis of Three Locations on the Fort Bliss MilitaryReservation, New Mexico: A Feasibility Study ............................. 129

Introduction ............................................................ 129Discussior . ............................................................. 129Summary and Conclusions ................................................ 130

CHAPTER XI Sedimentation and Soil Formation in Maneuver andAdjacent Areas on Fort Bliss ........................................... 133Organ Fan-Piedmont Alluvium ............................................. 133Maneuver Areas IB, 2C, and 2D ............................................ 133McNew Pipeline and State Line Roadcut ..................................... 136

PART IIIARCHAEOLOGICAL IMPLICATIONS AND SUGGESTIONS FOR FUTURE STUDY

CHAPTER XII Archaeological Implications .................................... 13 9Geomorphic Implications of this Study ....................................... 13 9Paleoclimatic Implications of this Study ...................................... 13 9CHAPTER XIII Suggestions for Future Study ................................... 143APPENDIX A: Laboratory Analysis and Soil Profile Descriptions ................... 145APPENDIX B: Statistical Analysis of Soil Properties ............................. 193REFEREN CES ............................................................ 203

Aooesslon ForDTI,' 7,A13 El

-Diet 8-~a1vA ___ _i


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LIST OF FIGURESFigure I-I Fort Bliss Soil-Geomorphic and Paleoclimatic Study Plan ................ 2Figure 1-2 Study Sites and Maneuver Areas on Fort Bliss North .................... 3Figure 1-3 Study Sites and Maneuver Areas on Fort Bliss South .................... 4Figure II-I General Landforms of Fort Bliss North .............................. 12Figure 111-2 General Landforms of Fort Bliss South .............................. 13Figure 111-3 Alluvial Fan Deposits in the AreaSoutheast of the Organ Mountains .................................. 14Figure 111-4 La Mesa Geomorphic Surface Distribution on Fort Bliss North ........... 15Figure 111-5 La Mesa Geomorphic Surface Distribution on Fort Bliss South ........... 16Figure 111-6 Geomorphic Surface Ages andAssociated Deposits on Fort Bliss .................................. 17Figure 111-7 Soil Carbonate Morphogenetic Sequences ........................... 18Figure 111-8 Jornada I Surface Distribution on Fort Bliss .......................... 20Figure 111-9 Jornada 11 Surface Distribution on Fort Bliss North .................... 21Figure III-10 Transect of Backhoe Trenches in theDoha Ana Range Camp Area ...................................... 22Figure 111-I 1 Petts Tank Surface Distribution on Fort Bliss ......................... 23Figure 111-12 Deposit Relationships in the AreaSouth of Doiha Ana Range Camp ................................... 24Figure 111-13 Fault Complex Mapping Unit Distribution on Fort Bliss ................ 25Figure 111-14 Cross Section of Soils Associated with theFault Complex Mapping Unit ..................................... 26Figure 111-15 Tectonic Map of Southern New Mexico ............................. 27Figure 111-16 Isaacks' Ranch Geomorphic SurfaceDistribution on Fort Bliss North ................................... 29Figure 111-17 Fort Selden Complex Mapping UnitDistribution on Fort Bliss North .... ......................... 30Figure 111-18 Lake Tank Geomorphic Surface Distribution on Fort Bliss .............. 31Figure 111-19 Organ Fan-Piedmont Alluvium Distribution on Fort Bliss ............... 32Figure 111-20 Index Map of Geomorphic Surfaces ................................ 33Figure IV-I Eolian Alteration Mapping Unit Soil Profiles ......................... 36Figure IV-2 Index Map of Soil Strata Eolian Alteration ........................... 39Figure V-I Study Area .................................................... 43Figure V-2 Geological Cross Section of Study Site .............................. 44Figure V-3 Particle Size Distribution for Soil Profile 1 ........................... 51Figure V-4 Particle Size Distribution on a Clay-Free Basis for Profile I ............. 52Figure V-5 Particle Size Analysis for Soil Profile 2 ............................. 53Figure V-6 Particle Size Distribution on a Clay-Free Basis for Profile 2 ............. 54Figure V-7 Particle Size Distribution for Soil Profile 3 ........................... 55Figure V-8 Particle Size Distribution on a Clay-Free Basis for Profile 3 ............. 57Figure V-9 X-ray Diffraction Patterns of Bulk Soil Sample for Profile I ............. 59Figure V-10 X-ray Diffraction Patterns of Bulk Soil Sample for Profile 2 ............. 60Figure V-I I X-ray Diffraction Patterns of Bulk Soil Sample for Profile 3 ............. 61Figure V-12 Clay Skins Surrounding a Quartz Grain in Profile 2 .................... 62Figure V-13 Clay Skins Surrounding the Sand Grains in Profile 3 ................... 62

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Figure V-14 Rhyolite, Plagioclase, and Quartzin a Calcite Matrix of Profile I .................................... 63Figure V-15 Quartz Grains in a Stage II I Calcium Carbonate of Profile 3 ............. 63Figure V-16 Major Soils of the Study Area ..................................... 65Figure VI-I Photograph of SLAR Image Near Center of Training Area IB ........... 70Figure VI-2 Photograph of SLAR Image of Old Coe Lake ......................... 71Figure VI-3 Photograph of SLAR Image of the SouthwesternPart of Training Area 5B ......................................... 72Figure VIi-! Site Locations on Fan-Piedmont ofOrgan and Franklin Mountains .................................... 76Figure VII-2 Isotopic Composition of Pedogenic Carbonateand Schematic Diagram ofTrench 90-1 ............................. 78Figure VII-3 Isotopic Composition of Pedogenic Carbonatesand Schematic Diagram of Trench 91-i ............................. 81Figure VII-4 Isotopic Composition and Inorganic RadiocarbonDates of Pedogenic Carbonates at the Laminar Calcrete Site ............. 83Figure VII-5 Isotopic Composition of Pedogenic Carbonate and SchematicDiagram of the Franklin Mountain Arroyo Site ....................... 84Figure VII-6 Stable Isotopic Signatures and Pollen Contentin Soil Strata at the Booker Hill Gully Site ........................... 85

Figure VII-7 V'3C Values Versus Time for Study Sites:Trench 90-1, 91-1, and Booker Hill Gully ........................... 86Figure VII-8 8"'O Values Versus Time for Study Sites:Trench 90-1, 91-1, and Booker Hill Gully ........................... 87Figure VIII-1 Stable Carbon and Oxygen Isotopes Plotted Against Time .............. 91Figure VIII-2 Isotopic Composition of Pedogenic Carbonate andSchematic Diagram of the Old Coe Lake Gully Site .................... 92Figure X-I Percent Phytoliths Determined by Weight in Ray's Trench ............. 118Figure X-2 Percent Phytoliths Determined byW eight at Booker Hill Gully ..................................... 118Figure X-3 Percent Phytoliths Determined byWeight at Franklin Mountain Arroyo .............................. 119Figure X-4 Percent Phytoliths Determined by Weight at Old Coe Lake ............. 119Figure X-5 Percent Phytoliths Determined by Weight for Other Samples ........... 120Figuic X-6 Square/rectangle Phytoliths from theFranklin M ountain Arroyo Site ................................... 12 2Figure X-7 Square/rectangle Phytoliths from theFranklin M ountain Arroyo Site ................................... 123Figure X-8 Serrated Rod-shaped Soil Phytolithsfrom the Franklin Mountain Arroyo Site ............................ 124Figure X-9 Probable Silicious Perforated Root Plateletsof the Franklin Mountain Arroyo Site .............................. 125Figure X-10 Unknown "Hooked" and "Bulbous" Phytolithsfrom Surface Coppice-dune Samples ............................... 126Figure X-I 1 Possible Dumbbell-shaped Phytolith anda Square/rectangular Phytolith .................................... 12 7

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Figure X-12 SE M Photograph of a Sq uare/rectangularPh?,tolith from the Booker Hill Gully Site .......................... 12 8Figure XI-I Suil Stratigraphy in the Tobin Well Area ........................... 13 5Figure XI-2 Soil Stratigraphy at the McNew Tank Pipeline Trench ................. 13 6Figure Xii-I Distribution of Organ Fan-piedmont Alluvium ....................... 140Figure XII-2 Distribution of Lake Tank Alluvium ............................... 141Figure XII-3 A Comparison of Landforms on Fort Bliss Northand Early/Middle Archaic Components ............................. 142

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LIST OF TABLESTable 1-1 Quartemary Ages ................................................ ITable 1-2 Data Collected at Study Sites on Fort Bliss North ...................... 5Table 1-3 Data Collected at Study Sites on Fort Bliss South ...................... 6Table VII-I Study Area Carbonate Morphology and Agesof Alluvial Fan Deposits ......................................... 77Table VII-2 Stable isotope Values for Pedogenic Calcite .......................... 80Table VIII-1 C-14-dated Inorganic Carbon and Stable Isotopes ..................... 89Table VIII-2 Radiocarbon Ages and Corresponding

Morphology of Soil Carbonate Samples ............................. 90Table IX-I Pollen Sample Proveniences for Fort Bliss ........................... 93Table IX-2 Scientific and Common Botanical and Palynological Names ............. 96Table IX-3 Pollen Results from Old Coe Lake Gully ............................ 98Table IX-4 Pollen Results from Booker Hill Gully ............................. 103Table IX-5 Pollen Results from Franklin Mountain Arroyo ...................... 106Table IX-6 Other Pollen Results from Fort Bliss ............................... 113Table X- I Provenience Data .............................................. 131Table X-2 Old Coe Lake Gully Site Phytoliths ............................... 131Table XI-I Holocene Eolian Deposits and Their Diagnostic Features .............. 134

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ACKNOWLEDGEMENTSThis study was funded by the Fort Bliss Directorate of Environment in contract with Human SystemsResearch, Inc. and New Mexico State University. Th e writer wishes to acknowledge Glen DeGarmo, John

Hawley, and LeRoy Daugherty for making it possible for the writer to conduct this study as a post-doctorateresearch project at New Mexico State University (NMSU). Appreciation is expressed to Karl Laumbach,David Kirkpatrick, and other staff members of Human Systems Research as well as Robert Burton of theWhite Sands Missile Range for their support. Discussions with Leland H. Gile were very helpful fordescribing the soil-geomorphic and paleoclimatic processes occurring in southern New Mexico. RaymondMauldin and Jeff Leach provided information and many ideas that have contributed to this report. Field tripsand discussions with Kevin Von Finger, Richard MacNeish, Mike McFaul, and Jerry William also havecontributed to the understanding of soil-geomorphic processes on the Fort Bliss Maneuver areas.The writer wishes to acknowledge the contributions of David R. Cole of the Oak Ridge National Lab forhis analysis of stable isotopes in pedogenic carbonates, John Kipp for his mapping and editorial assistance,Jannifer W. Gish of Quaternary Palynology Research for analyzing pollen, Mohammad H. Nash for soil

sample analysis at NMSU, Sa'eb Khresat for investigating a suspected paleolake on the McGregor Range aspart of his dissertation at NMSU, Brenda J. Buck of the Department of Agronomy and Horticulture at NMSUfor phytolith analysis, Thomas H. Giordano of the Department of Geological Sciences at NMSU for hiscontribution to understanding the geochemistry of pedogenic isotopes, Alice Janavaris for her lab work onsoil samples as well as the manuscript, and Linda Cummings of the PaleoResearch Lab for phytolith analysis.Support for David R. Cole was provided by the Division of Engineering and Geosciences, Office of BasicEnergy Sciences, U.S. Department of Energy, under contract DE-AC05-84OR21400 with Martin MariettaEnergy Systems, Inc.H. Curtis Monger

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FOREWORDThis report describes the results of a study of the geomorphological and paleoclimatic variabilitydocumented in the maneuver areas on Fort Bliss. It was mentioned in the Foreword to Dr. Michael Foster'sPuebloSin Casas (FB6273),A MulticomponentSite in the Hueco Bolson. FortBliss. Texas, Report Number7 in this series.The identification and mapping of stable land surfaces in some areas of the post is of considerableinterest to the Cultural Resources Management Program on Fort Bliss. Evidence of some subsets of activitiesconducted during most of the archaeological periods that comprise the archaeological record on theinstallation may lie exposed on these surfaces.Identification of other areas where prehistoric occupational surfaces may be buried confirms the generalfinding that sites in some areas are visible only in road beds lower than the surrounding surface of the landupon which no archaeological materials are visible. Knowledge of the probable extent and age of thesurfaces will be very useful in future years.Th e identification of multiple episodes of eolian deflation and deposition adds to the complexity of theproblems of attempting to interpret surface evidences of the archaeological record on the post. A projectcurrently being conducted by Dr. Monger is concentrated upon dating and mapping the evidence of theseepisodes. It is anticipated that the results of this work will be useful for attempts to understand thechronological relationships between sites exposed upon these eolian surfaces and the stratigraphy of sites inlocations where episodes of deposition and deflation are preserved.The documentation of a major deflational and climatic event that occurred sometime between 10,000and 7,000 years ago is of considerable importance. The event, now documented with additional data fromFort Bliss, appears to be one that occurred throughout the Southwest. It probably caused considerabledamage to the archaeological record that existed prior to the event. As suggested in Chapter XII of thisreport, it may be very difficult to find intact Paleo-Indian and early Archaic sites on Fort Bliss. One of the

questions being investigated by the current study of eolian phenomena on Fort Bliss is whether there areareas on the post where these early parts of he archaeological record still remain.

GLEN DEGARMO, PH.D.Cultural Resources Management ProgramFort Bliss, Texas

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ABSTRACT

Soil-Geomorphic CharacteristicsBy the early Quaternary period (2 million years ago) the ancestral Rio Grande had spilled throughFillmore Pass between the Organ and Franklin Mountains and was filling the Hueco Bolson with riversediments (Hawley et al., 1969). By middle Pleistocene, when the ancestral Rio Grande entrenched into itsmodem valley (400 to 300 ka, Gile et al., 1981), it had been diverted back to the west of the FranklinMountains, probably as the result of uplifting of the Organ-Franklin Mountain chain (Seager 1981). Sincethe mid-Pleistocene, landscape evolution on Fort Bliss has been restricted mainly to (I) alluvial fandeposition, (2) land displacement along faults, and (3) eolian activity.Alluvial fan deposition has involved at least four generations of alluvial fans on the piedmont aprons thatskirt the mountains. The fans range in age from approximately 400 ka to the present arroyo mouth deposits.Land displacement along faults has occurred throughout the late Pleistocene and Holocene. Sediments that

fill linear depressions caused by extensional faulting are the result of both tectonic movement andclimatically driven sedimentation that presumably corresponds to periods of aridity. Eolian activity hasmodified existing soil strata in areas that were not sheltered from wind erosion by desert pavement,vegetation, or younger deposits. Most of the soilscape on Fort Bliss has experienced multiple periods ofdeflation and reburial by locally derived eolian sediments. There are at least four eolian deposits in the basinfloor that range in age from early Holocene to Historical blowsand deposits.

Late Quaternary Climatic and Environmental ConditionsBased on 8`'O in soil carbonates, the mean annual temperature appears to have been only slightly coolerduring the late Pleistocene than the Holocene. A major shift toward aridity, however, occurred between 9

and 7 ka, based on four lines of evidence: (1) By 7 ka the latest generation of alluvial fans (the Organalluvium) began to be deposited. The onset of this erosion-sedimentation event appears to have beentriggered by the decline of vegetation in response to aridity. (2) The V'C in soil carbonates on thefan-piedmont area of the Organ Mountains shifts toward lower values at approximately 8 ka. This shiftimplies a change from C4 grassland to C-3 desert scrub. (3) Fossil pollen analysis from a site in the samefan-piedmont area reveals a decline in grassland pollen and an increase in Cheno-am pollen during the sameearly-Holocene period. (4) At several locations in the basin floor area of Fort Bliss, pedogenic carbonatenodules and Rio Grande pebbles are concentrated into a layer that appears to be a paleo-deflational surfacesimilar to deflational surfaces on Fort Bliss today. Inorganic radiocarbon dates of lag nodules indicate thedeflational event occurred after 10 ka. Radiocarbon dates of hearths confirm that the event occurred before 4ka and probably happened prior to 7 ka, based on radiocarbon dates of soil calcite. This desertification eventis presumed to correspond to the onset of Organ sedimentation as well as the isotope and pollen changes thatoccurred approximately 8 ka.

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Chapter IINTRODUCTION

Th e purpose of his study wa s to describe and interpret soil-geomorphic features on Fort Bliss in southernNew Mexico and western Texas in order to obtain information about landscape evolution and paleoclimaticconditions during the late Quaternary. This information is intended to assist Fort Bliss archaeologists inevaluating archaeological site locations and conditions in terms of their geomorphic and paleoclimaticcontext. To obtain this goal, backhoe trenches were dug and maps were made of the geomorphic surfacesand deflated depositional areas. In addition to soil-geomorphic evidence of paleoclimatic and environmentalconditions, stable isotopes, fossil pollen, and phytoliths were examined (see Figure I-1).

An area on McGregor Range in the vicinity of Benton Well was investigated to determine if the area wasoccupied by a late Pleistocene pluvial lake. If so, the lake might have been significant to the possible latePleistocene inhabitants of Pendejo Cave and would provide further paleoclimatic information about the latePleistocene-early Holocene time period. Quaternary ages in this report are based on the assigned dates inTable I-I.

Table I-I. Quaternary Ages (after Gile et al. 1981)ftri" 01 oruTheim" OrSpi'a *ftd Yons AV (kiQuaternary Historical 1850 A.D. to present

Holocene late 2.5 to presentmid 2.5 to 7.5early 7.5 to 10

Pleistocene late 10 to 250mid 250 to 900early 900 to 2000

Twenty-four sites, in the forms of backhoe trenches, hand-dug pits, and natural exposures, were studiedon Fort Bliss North (see Figure 1-2), and sixteen sites were studied on Fort Bliss South (see Figure 1-3). Thegathered data included radiocarbon dates, stable isotopes, fossil pollen, phytoliths, particle size analysis,organic carbon (OC), calcium carbonate, and thin sections (see tables 1-2 and 1-3).


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2\ SOIL-GEOMORPHIC CHARACTERISTICS OF THE FORT BLISS MANEUVER AREAS

Longitudinal studies of soil strataacross maneuver areas: backhoe

trenching and hand-dug pits

aoMapf geomnorphicMaofdlatsurfaces based on depositional areassoil stratigraphyoil_ .st..atindytolth

Radlometric dating,stable isotopes, pollen,

'Paleolake study:-'geornorphic features, .Evidence forIsotopes, pollen, dates paleocillraticconditions -

This study Is intended to assist Fort Bliss archaeologists in (1) evaluatingthe conditions of archaeologlc sites, and (2) understanding the location ofS sites In terms of geomorphic and paleo climatic conditions.

Figure1-l. Fort Bliss Soil-Geomorphic and Paleoclimatic Study Plan


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Lutroductiem A3

~4

uiz

kot


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4D01 Pit 6 fallhn Pit 4

I EI A70 75 80 85

8-40 -

Eoian Pit 11 Eolian Pi t 12i& I1A 2A 2B

35--

A 2C 2DTrench 91-6 Tr'Irth 5Trenchn

Tobin Well Pitp-

13B A Trench 160 Eollan Pit 13- 2 Fault Trenchl 2/ 25.--2 -

20- Trench 91-7

Figure1-3. Study Sites and Maneuver Areas on Fort Bliss South


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Introduction /5

Table 1-2. Data Collected at Study Sites on Fort Bliss North

Lii3!

Trench 90-1 559574 X X X X X X X X XTrench 90-2 565571 X X X X X XTrench 90-3 568566 X X X X X XTrench 90-4 564555 X X X X X XTrench 90-5 565545 X X X X X XTrench 91-1 641634 X X X X X X X XTrench 91-2 648644Trench 91-3 634649 X X X X X XTrench 91-4 688659 X X X X X XTrench 91-5 703660 X X X X X X

McNew Pipeline 880858Trench

Old Coe Lake 667625 X X X X X X X X X XGully SiteJomada 1 601572 X X

Laminar SiteBooker Hill 530580 X X X X X X X X X XGully Site

Franklin Mt. 520513 X XArroyo SiteEolian Pit 1 626551 X X X X XEolian Pit 2 705534 X X X X XEolian Pit 3 772521 X X X X XEolian Pit 4 845495 X X X X XEolian Pit 5 604538 X X X X XEolian Pit 6 808493 X X X X XEolian Pit 7 861544 X X X X XEolian Pit 8 849675 X X X X XEolian Pit 9 839795 X X X X X


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Table 1-3. Data Collected at Study Sites on Fort Bliss South

a I Jji JIlTrench 91-6 691299 X X X X XTrench 91-7a 799205 X X X X X XTrench 91-7b 799205 X X X X X X

Trench 5 881302 X X X X X X XTrench 7b N 885295 X X X X X X XTrench 7b M 855295 X X X X XTrench 7b S 855295 X X X X XTrench 16 863284 X X X

lxi Pit 855296 X X XFault Trench 775261 X XArmy Trench 767299 X X X

Tobin Well Pit 704274 X X XEolian Pit 10 831441 X X X XEolian Pit 11 823385 X X X XEolian Pit 12 935384 X X X XEolian Pit 13 809267 X X X


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Chapter IIMETHODS

MappingMaps of geomorphic surfaces and eolian alteration were made using a combination of aerial photographyand field identification. Geomorphic surfaces were identified by soil development and their geomorphicposition (see Chapter III). Eolian alteration maps were based on vegetative clues, such as the occurrence ofcoppice dunes and grasslands, in addition to augering, digging backhoe trenches, and systematically drivingroads and perusing aerial photographs looking for exhumed, indurated caliche fragments (see Chapter IV).Stereo-pair aerial photographs were used to identify three dimensional topographic features. Thephotographs were 1984 United States Geological Survey (USGS) high-altitude program (HAP)color-infrared, scale 1:58,000. The 1:50,000 Fort Bliss North and South topographic maps were used as basemaps. Mapping unit delineations were drawn on transparent overlays covering the aerial photographs. These

lines were transferred to the 1:50,000 base maps, which were photocopied in sections.Soil Characterization

The step-by-step procedure for analyzing soil organic carbon and particle size distribution is given below.Analysis of calcium carbonate follows the procedure described in Soil Survey Staff (1982).Bulk Sample Preparation1. Air dry soil sample approximately two days.2. Crush with wooden rolling pin and weigh whole soil sample.3. Sieve with 2-mm sieve to separate coarse fragments.

4. Weigh coarse fragments and calculate their percentages.Organic Carbon(after Nelson andSommers 1982)1. Sieve the < 2-mm soil with a 0.5-mm sieve.2. Weigh 1g of sieved soil into a 400-mL beaker or Erlenmeyer flask.3. Add 10 mL of IN K2Cr 2O7 and swirl. (Prepare K2Cr2O7 solution by dissolving 49.04 g ofreagent-grade K2Cr 2O7 in 1000 mL of water.)4. Add 20 mL of conc H2SO4mix by swirling, then let cool.5. Add 200 mL of water (filter suspension if experience shows that titration endpoint cannotbe clearly discerned otherwise.)6. Add 2-3 drops of o-phenanthroline indicator.7. Titrate the solution with 0.5 N FeSO4.(Prepare FeSO4 solution by dissolving 140 g of reagent,

add 15 mL of conc sulfuric acid, cool, dilute to 1000 mL.)8. As endpoint approaches, the solution becomes green then blue. At this point, titratedrop by drop until the color changes from blue to maroon.9. Calculate results according to the following formula:Organic Carbon = (meq.K2Cr2, - meq FeSO)(0.003)(100)(1.30)g air dry soil


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ParticleSize Analysis (afterGee and Bauder 1986)1. Add between 40 to 80 g of< 2-mm soil to 250-mL Pyrex centrifuge bottle (sandy soils requiremore sample than clayey soils). Add 100 mL of water.2. Remove carbonates by adding I M HCI dropwise with stirring until pH 3.5 or 4.0, leavesample overnight and recheck pH , adding more acid if necessary (Jackson 1956).3. Wash sample by centrifuging at 1500 rpm for 10 min and decanting clear supernatant untilsample is near neutral pH .4. Remove organic matter by adding 25 mL H20 2 . Heat sample on hot plate to increase reactionrate. Continue to add H20 2until frothing is minimal.5. Wash sample by centrifugation and decanting clear supernatant.6. Transfer sample to I000-mL sedimentation cylinder. Ad d 100 mL of 5-percent sodiumhexametaphosphate, plunge and let soak over night.7. Plunge sample several times and take readings at* 30 seconds* 60 seconds* 1.5 hour0 24 hours8. Determine oven-dry sample weight by transferring sample into pre-weighed oven bags, and dryingat 105" C until dry. Let sample cool and equilibrate with ambient moisture, which is reachedwhen the weight becomes constant. Record weight.

Isotope AnalysisAll samples used for isotope analysis were taken from freshly excavated profiles. Pedogenic carbonate,which is generally composed of calcite crystals I to 5 gm in diameter (Monger et al. 1991), wereconcentrated by sieving with a 53 gim sieve. Stable isotope measurem ents were carried ou t by convertingpedogenic calcite to CO 2 liberated by reacting the sieved soil samples with 100% phosphoric acid. Resultsare reported in the (per mil) notation where

S=(R, p!C/Rtafdfrd)- 111000and R.,, and Rsadad refer to the "3C/' 2C or "S0/"60 ratio in a sample and standard, respectively. The 8values are generally reproducible to 0.1 for carbon and 0.2 for oxygen.Stage I carbonate filaments from the lxi pi t (UTM 855296, Fig. 3) were concentrated by microscopicallysiphoning the filaments into a flask of deionized water. Approximately 100 grams of the carbonate-richmaterial were oven dried and sent to Beta Analytic, Inc., for inorganic radiocarbon dating and stable isotope

analysis.


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Part ISOIL-GEOMORPHIC CHARACTERISTICS


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Chapter IIIGEOMORPHIC SURFACES OF MANEUVERAND ADJACENT AREAS OF FORT BLISSBy H. Curtis Monger

General LandformsSix major landforms were delineated within the study area of Fort Bliss North and South (see figuresIII-1 and 111-2).Th e La Mesa Basin floor occupies the Hueco Bolson. Th e upper portion of this basin fill depositcomprises the Camp Rice Formation of Strain (1966) which is the upper subdivision of the Santa Fe Group(Hawley et al. 1969). Th e La Mesa geomorphic surface is the constructional top of the Camp Rice Formationand is of early to middle Pleistocene age (Gile et al. 1981).Th e sediment apron surrounding mountains in the study area makes up the fan-piedmont landform. Thefan-piedmont landform is composed of alluvial fans, interfan valleys, and coalescent fans (bajadas).Within the La Mesa Basin floor are younger deposits occupying depressions (Seager et al. 1987). In thisstudy, these deposits are referred to as youngest basin ill. These deposits are associated with the Petts Tankand Lake Tank geomorphic surfaces of C;,le et al. (1981).The bedrock landform occurs in the upper Organ, Jarilla, Franklin, and Hueco mountain areas no tcovered with quaternary sediments. This landform is composed of various igneous and sedimentary rockswith minor amounts of metamorphic rocks (cd Hardie 1958; Harbour 1972; Seager 1981; Kelly and Matheny1983; and Seager et al. 1987).Although most of the study area, especially the basin floor, is covered with coppice dunes and eoliansheet deposits, a few areas are covered with enough deep eolian sediments to merit delineation as a separatelandform. These areas of deep sand (several meters) and sparse interdune areas were designated the duneslandform.Th e fault complex landform is composed of fault scarps, associated linear basins, and downthrownblocks. Soils associated with the fault complex vary in age, thickness, and pedogenic development. Erodedsoils, which are often buried by H istorical eolian sediments, are common on the scarps. Sequences of buriedsoils are comm on in the trough-shaped basins.

Geomorphic SurfacesGeomorphic surfaces contain evidence of landscape evolution that, on Fort Bliss, has been drivenprimarily by climate change during the Holocene and late Pleistocene. Geomorphic surfaces are landformsurfaces defined in terms of geologic ag e and pedologic development (Gile et al. 1981). A geomorphicsurface is a mappable landscape element formed during a discrete time period and has distinctive materials,


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12k SOIL-GEOMORPHIC CHARACTERISTICS OF THE FORT BLISS MANEUVER AREAS

topographic features, soil profiles, and weathering characteristics (Bull 1991). A single geomorphic surfacescan be composed of both erosional and constructional (depositional) phases (Daniels and Hammer 1992).

The fan-piedmont landform southeast of the Organ Mountains (see Figure I11-I) contains examples ofgeomorphic surface application. A portion of this landform is subdivided into four geomorphic surfacesbased on alluvial fan deposit ages. Geomorphic surface ages are indicated by the degree of pedogenicdevelopment (see Figure 111-3).

Names of geomorphic surfaces used in this study were borrowed from the neighboring Desert Project, asoil-geomorphic study conducted on a 400-square-mile area surrounding Las Cruces, New Mexico, by theUnited States Department of Agriculture (USDA) Soil Conservation Service (Gile and Grossman 1979). TheDesert Project area was studied by a team of soil scientists and geologists from 1957 to its formal completionin 1972. Significant soil-geomorphic research, however, continues to be conducted in the Desert Project area(e.g., Gile 1987a, b; and Gile 1990).

Figure II-!. General Landfornis of Fort Bliss North


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14 \ SOIL-GEOMORPHIC CHARACTERISTICS OF THE FORT BLISS MANEUVER AREAS

Jomneds 1 91-1

il +

Figure 111-3. Alluvial fan deposits that comprise a portion of the fan-piedmont landform in the area southeastof the Organ Mountains. Older geomorph ic surfaces, such as the .ornada I surface, have associated soils withadvanced pedogenic development (e.g., indurated caliche). In contrast, soils associated with youngergeomorphic surfaces, such as the Organ surface, exhibit weaker pedogenic development (e.g., stage Icarbonate filaments of Gile et al. 1966).


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Geomorpbic Surfaces on Maneuver an d Adjacent Areas /15

r% It65 -, I.-,,,.., n." .f

65

75 -U

41;

70 HI Vtj65

V 11R44 I

tr-

W N1414 0 5OW

METERS

Figure111-4. La Mesa Geomorphic Surface Distribution (shaded area) on Fort Bliss North


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16N SOIL-GEOMORPHIC CHARtACTERISTICS OF THE FORT BLISS MANEUVER AREAS

45-

Figrel-. L Mea Gomopi ufc i t iuin(hddaes nFr ls ot


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Geomorphic Surfaces on Maneuver an d Adjacent Areas /17

Organ III 0. 1-1. 1 (C-14)YOrgan II 6-10(4) 1.1-2.1 (C- 14)oOrgan I 2.2-7 (C-14)(')Isaacks Ranch 8-15(b) 9.5 (C- 14)(d)

25-31(a) 22 15 (MT1)(aJornada II 62(')(young phase)Jornada II 95(s) 130 20 (UT)' (a) Machete, 1985

(main phase) 180? (K-Ari) (b) Gile, 1987Jornada I 306c*) (c) Gile et al., 1981

(young phase)290 +20 (LJYa) (d) Blair et al., 1990

Jornada I 388(") (e) Izett and Wilcox, 1982(old phase)La Mesa 500(&) (f) Hawley et al., 1969

- - _ _620 (K-Ar)"."' (g) Seager et al., 1975Figure111-6. Geomorphic Surface Ages and Associated Deposits on Fort Bliss


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IS\ SOIL-GEOMORPHIC CHARACTERISTICS OF THE FORT BLISS MANEUVER AREAS

AIII IV

K21mK2K22mK22mK3 K3

.;.-...K21m-- K12 K22m

Stage and General Character Diagnostic Carbonate MorphologyGravelly Soil Nongravelly Soil

Weakest expression of Thin, discontinuous Few filaments ormacroscopic carbonate pebble coatings faint coatingsIICarbonate segregations separated Continuous pebble coatings, Few to common

by low-carbonate material some interpebble fillings nodulesIIICarbonate essentially continuous; Many interpebble fillings Many nodules andplugged horizon forms in last part internodular fillingsIV

Laminar horizon develops Laminar horizon overlying plugged horizonVThick laminae (>1 cm ) and thin to thick pisolites. Vertical faces and fractures

are coated with laminated carbonate (case-hardened surface).Figure 111-7. Soil carbonate morphogenetic sequences of Gile et al. (1966) and Machette (1985). (a)Schematic diagram of the diagnostic morphology of stages I to IV in gravelly and nongravelly material. (b)Table of morphogenetic definitions (from Gile and Grossman 1979; and Machette 1985).


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Geomorphic Surfaces on Maneuver and Adjacent Areas /19Jornada I (fan deposits of late middle Pleistocene age)

Jornada I is the oldest fan-piedmont deposit in the study area (400 to 250 ka, Gile et al. 1981). TheJornada I surface occurs in the upper and middle piedmont slopes of the Organ Mountains and occupiesnearly the entire piedmont areas of the Northern Franklin, Jarilla, and Hueco mountains (see Figure 111-8).The Jornada I surface caps the Camp Rice piedmont facies (Gile et al. 1981). In the higher elevations of thefan-piedmont, Jornada I occupies the highest geomorphic position with younger fans inset below.Basinward, the Jornada I becomes buried by younger fans (Seager 1981).In addition to being the geomorphically highest fans in the study area, the Jornada I surface can beidentified by its well-developed soil profiles which include well-developed reddish Bt argillic horizons, ifuneroded, and stage IV carbonate morphology. Jornada I also can have stage III carbonate morphology innongravelly sediments (Gile et al. 1981). The Jornada I surface has a steeper gradient than younger fans,parallel drainage, and boulders on the surface that are more highly weathered than younger fans (Seager,1981). Dissection of Jornada I alluvium commonly has a ridge-and-ravine (ballena) topographic pattern asdescribed by Bull (1991).In areas having large watersheds and sediment sources, such as the Organ Mountains, multiple alluvial

fan generations can be distinguished (e.g., Jornada I and Jornada II). In contrast, multiple fan generations areabsent on the fan-piedmont areas of smaller mountains, such as the Hueco Mountains. The piedmont of smallmountains have a large Jornada I component, as identified by the well-developed stage IV calcrete, butyounger fans probably exist also. The younger fans, however, are thin and merge with older fans, and thusare not easily discernable on aerial photographs.Jornada II (fan deposits of late Pleistocene age)

The Jomada II surfaces occur mainly in the Organ Mountain fan-piedmont area (see Figure 111-9 ) wherethey occupy an intermediate geomorphic position. The Jornada II is estimated to range in age from 150 to 25ka (Gile 1987b). Most of Jornada IIprobably was deposited during the previous interglacial period (Hawleyet al. 1976). Jornada II is an important surface for stable isotope (see Chapter VII) and fossil pollen (seeChapter IX) research, where it is buried by younger deposits.The Jornada II surface is inset below the Jornada I surface and above the Isaacks' Ranch and Organsurfaces (see Figure 111-3). Carbonate morphology in Jornada 11 can range from incipient stage IV in gravellysediments to stage IInodules in fine-textured sediments (Gile et al. 1981). Where the soil is uneroded, it hasa well-developed Bt argillic. The Jornada II,a piedmont-fan surface, grades into its basin floor equivalent,the Petts Tank surface, at the boundary between distal fans and basin floor sediments (see Figure 111-10).Boulders on the Jornada II fans are less decomposed than boulders on the Jornada I fans (Seager 1981).Unlike Jornada I fans, which have parallel drainage, Jornada II fans exhibit distributary drainagecharacteristics.

Petts Tank (basin floor deposits of late Pleistocene age)Petts Tank alluvium occurs in closed depression on both Fort Bliss North and South (see Figure 111-1 1).Petts Tank is correlative with Jornada II but, in some locations, may be even older than Jornada II based onits well-developed stage III carbonate morphology in fine-grained sediments. The relationship among PettsTank and neighboring deposits in the Dofia Ana Range Camp area is illustrated in Figure 111-12.


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20\ SOIL-GEOMORPHIC CHARACTERISTICS OF THE FORT BLISS M ANEUVER AREAS

66 -1 681

7A L7

GO as so 906D 7C 7D

TO 4ASA 5B!,a

485C

v4C

3A3B Q SE

TO 7 5 80

-40-2A

54 1A 2!j 1:- 35- 'iT; 22-AM2C / 1

V L N

-7 18 2E 0 sow t5-- METE N-2

Figure111-8. Jornada I Surface Distribution (shaded areas) on Fort Bliss North (top)and Fort Bliss South (bottom)


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Geomorphic Surfaces on Maneuver and Adjacent Areas /21

6BA7

GO0 70 75 80 85 906C 6D 17C 7

954A~ 5A 5-B

4B

DN3A ----

31 54D 5E0 5000

50- -- METERS

Figure111-9. Jornada I1Surface Distribution (shaded areas) on Fort Bliss North(Jornada 11 did not occur to a mappable extent on Fort Bliss South.)


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.7.

m. -1. ,......... ..['55 _______

N -"_Elevation (m ) Pedon

1265 90-1 Organ Alluvium"LL Pedon I

1255 90-2 Pedon93 Pedon1245 90-41235- Jornada 11 Potts Tank 90d5.. I . Alluvium

Alluvium ake ank Alluvium1225- Jornada I1215 AlluviumI 1 I I I I0 2.0 3.0(km)

Deposit Ages (based on Gile et al. 1981)Deposit Age (yearsB.P.)Lake Tank Present to late PleistoceneOrgan 100 to 7000Petts Tank 25,000 to 150,000Jornada I 25,000 to 150,000Jornada I 250,000 to 400,000

Figure III-10. Transect of backhoe trenches (black ovals on map) in the Dofila Ana Range Camp area. Datafor studied pedons are in Appendix A. This transect revealed that Organ and Jomada alluvium facies changefrom gravelly material in higher elevations to finer material basinward.


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Geomorphic Surfaces on Maneuver and Adjac~ent Areas/23

- i-, h

6A so IIT

8C 6D 17E 7D

7 070 7 I) 0

4 8 5CA

4C 2

4--2

Figre-1 . et san 75racsrbto(soae ares) nFr ls ot t4n 2Ar 28sS u h b tt m

| IA


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24 \ SOIL-GEOMORPHIC CHARACTERISTICS OF THE FORT BLISS MANEUVER AREAS

Little oollan alteration)

Stage I

(various degrees of eoliandeflation and deposition)

Figure 111-12. Deposit Relationships in theArea South of Dofra Ana Range Camp (vicinity of UTM 5755)Fault Complex

The fault complex mapping unit is not a true geomorphic surface because it has formed during a broadtime range and has several soil profiles associated with it. The fault complex, nevertheless, is included as amapping unit because it is a distinctive landscape feature identifiable by its linear topographic configuration.The Fault Complex occupies relatively large areas in both Fort Bliss North and South (see Figure 111-13).The fault complex mapping unit is composed of (1) fault scarps, which are the steep slopes formed bylandscape displacement (Bates and Jackson 1987); (2) associated basins, which contain sediments resultingfrom both tectonic movement and eolian activity; and (3) downthrown blocks. Depending on the degree oferosion and sediment age, the fault complex can have a variety of associated soil types (see Figure 111-14).East of the Organ and Franklin mountains are tectonic and neotectonic activity areas that contain numerousfaults (Seager 1981; Seager et al. 1987; and Figure 111-15). The fault complex mapping unit contains PettsTank and Lake Tank mapping units where those units were too small to map separately on the 1:50,000-scalebase map.


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Geomorphic Surfaces on Maneuver and Adjacent Areas /2S

37A 7

1 , T _ i- ,-o- 7o0 - 4 8- I z

29

2D

N I METERS N

Figure111-13. Fault Complex Mapping Unit Distribution (shaded area) on Fort Bliss North (top)and Fort Bliss South (bottom)


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2A SOIL-GEOMORPHIC CHARACTERISTICS OF THE FORT BLISS MANEUVER AREAS

Area 662502 Fault Complex

Stage IVW [ C Stage IV BCoppice Dunes [Bk Stage I Btk Stage I

Figure111-14. Cross section of soils associated with the fault complex mapping unit. In many locations, theleeward western edge of the fault complex is buried by wind-blown sands, in contrast to the more-deflatedwindward eastern slopes.


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Geomorphic Surfaces on Maneuver and Adjacent Areas /27low10"ll

area

PSP

T~0 Tipi

Tt .'6

Pits

106W0- ~SYMBlOL$

I. .k.AA Rwnkottws, f.,Irs ut-,sdAsiaofar-ortwtned"-170EXPLANATION lrdAU1

Af m a Appoeiratg sWeb @5ofose Aft. an ne.cosG.l.aisr'r~sy bs.. iri caee con o,nae1409neogribfud, fill anid flite deposits; deeper portions of b..i,,%are darker shaded1. shallow oortl~on iightttst htrlo, 9itlolo to I .nnadisto-tornpo~ltiort. hishl,iwl olutlonlCth rM*Yhyoiti.,ontr .. o..st, ,ul.& cpftcpitla agsorn.and tTertiar rgoinofthe Oatrul h avnaoMPgg. cassioncrliatd with ".leok. Mesozoic, and fewar Tertiary sedimeWntary r~oksGood. ght-Codo, Hills1 daprelpion FT*Pim~y volcanic rocks and asmsociated WdiRttiaty rocks M PI'acgri,b11i. rocks. tt"tt ranits

Figure 111-15. Tectonic Map of Southern New Mexico (showing large number of faultsin the Fort Bliss North Study Area; from Seager et al. 1987)


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Isaacks' Ranch (fan deposits of earliest Holocene-latest Pleistocene age)The Isaacks' Ranch surface appears to be 15,000 to 8,000 years old (Gile et al. 1981). It occurs on theOrgan Mountains fan-piedmont (see Figure 111-16) where it occupies a geomorphic position below Jomada IIand above Organ (see Figure 111-3). Isaacks' Ranch can be identified by its stage II carbonate morphology. If

uneroded, it has a Bt argillic but the argillic is less pronounced and not as red as the Jornada 11 and Jornada Iargillic horizons. Isaacks' Ranch alluvium slopes are less steep than older deposits (Seager 19 8 1).

Fort Selden Complex (erosional surfaces and fans of late Pleistoceneand Holocene age associated with the Camp Rice Fluvial Facies)

The Fort Selden Complex occurs in Fort Bliss North where Rio Grande downcutting (west of FillmorePass) and tectonic uplift has exposed the Camp Rice fluvial facies (see Figure 111-17). The age of the FortSelden unit in the Las Cruces area, where it contains components of Leasburg and Fillmore surfaces (Hawley1965), is 15,000 to 100 B.P. (Gile et al. 1981). The Fort Selden mapping unit in the study area ischaracterized by soils with slight pedogenic development (Entisols) and the abundance of Rio Grande sandsand mixed-rounded gravels. This unit primarily consists of erosional surfaces.

Lake Tank (basin floor deposits of late Pleistocene and Holocene age)Lake Tank alluvium occurs in closed depressions on both Fort Bliss North and South (see Figure 111-18).Lake Tank can be differentiated from Petts Tank because it has experienced less soil development. In mostcases, Lake Tank has only stage I carbonate filaments. In the closed depression south of Old Coe Lake,however, Lake Tank deposits contain powdery stage II nodules that produced radiocarbon dates of 8220 120B.P. (see Chapter VIII). The Lake Tank alluvium appears to be older than Holocene in some locations, suchas the Davis Tank area just north of the Fort Bliss-White Sands boundary, which contains tusks, teeth, andbones of Pleistocene megafauna. In most cases, Lake Tank occurs in depressions that appear to have resultedfrom faulting. Some isolated depressions, however, lack the linearity typical of fault-produced depressionsand may have an eolian origin. Vertisols occur in the Lake Tank alluvium in the Old Coe Lake and StewartLake depressions.

Organ (eolian and alluvial deposits of Holocene age)The Organ geomorphic surface associated with fan-piedmont sediments occurs mainly in Fort BlissNorth with minor amounts in Fort Bliss South (see Figure 111-19). Organ alluvium, which is well dated withradiocarbon, ranges in age from 7,000 to 100 B.P. (Gile et al. 1981). The Organ alluvium can be identified byits braided-channel pattern and lowest geomorphic position, which is graded very close to the modern arroyo

system (Seager 1981) (see Figure 111-3). The Organ alluvium contains soil profiles less-developed soilprofiles than do older alluvium. Organ generally has stage I filaments and may contain reddish-brownargillic or cambic horizons (Gile et al. 1981).Much of the La Mesa basin floor is buried with eolian sediments of Organ age. These eolian depositsvary in thickness from less than a meter to a few meters. Unlike the fan-piedmont Organ sediments,


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Geomorphic Surfaces on Maneuver and Adjacent Areas /29Organ-age eolian sediments are not readily mappable because (1) there is no land surface expression of thesubsurface material and (2) the occurrence and thickness of these deposits within a small area variesextensively.

Th e Organ alluvium has paleoclimatic significance because its deposition appears to represent an earlyHolocene shift toward aridity. Organ alluvium has been subdivided into three members-Organ I, II, andIII-(Gile et al. 1981). Future studies of the three members may help refine ou r understanding ofpaleoclimatic conditions during the Holocene in the Fort Bliss area.

-85-

6B A B80- 6A , .

6D 65 70 75 so 85 90-7 5 TI 6C 6D 7 7D

915

""a- 4A DhNno 5B

4B5iD

METERS

Figure1II-16. Isaacks' Ranch Geomorphic Surface Distribution (shaded areas) on Fort Bliss North(No Isaacks' Ranch was mapped on Fort Bliss South.)


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30\ SOIL-GEOMORPHIC CHARACTERISTICS OF THE FORT BLISS MANEUVER AREASHistoric Eolian and Arroyo Deposits

Historic eolian and arroyo deposits are widespread across the Fort Bliss study area. Deflation and eoliansedimentation are active processes that currently are modifying the Fort Bliss landscape. Army artifactsburied beneath a couple of meters of eolian sediments testify to the rapid rate of deposition. Eolian depositionis most active in the spring when soil m oisture is low and wind velocities are high (Blair et al. 1990).

Arroyo systems continue to drain and deposit sediments in relief areas, such as the mountainous regionsand along faulted terrain. Arroyos are most active during the summ er thunderstorm season.

--- 85 -;" :

6B 7A 7B- 6A I

75- 65 70 75 80 8590o-76----C D7C

95

70- 4A .

4B 5

3 4C -

.w50 - -,--- .. m-.

Figure II-17. Fort Selden Complex Mapping Unit Distribution (shaded areas),limited to Fort Bliss North


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GA 0

/J 4C

a s

6C 6D 'C 17 ,,

4 NMEER4C20C

Figure/1]-18.ake Tank Geomorphic Sufac itiuin(hddaes31Ars oth(o)adFr l isSuh(otm

I IA


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S7A7 22 3B

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9E3525545000N

+ IB 2E


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34\ SOIL-GEOMORPHIC CHARACTERISTICS OF TH E FORT BLISS MANEUVER AREASMap Legend:

Symbol Mappimg Unit (see preceding text in this chapterfor mapping unit descriptions)LM La Mesa Geomorphic SurfaceJI Jornada I Geomorphic SurfaceJIl Jornada II Geomorphic SurfacePT Petts Tank Geomorphic SurfaceFC Fault Complex Mapping UnitIR Isaacks' Ranch Geomorphic SurfaceFS Fort Selden Complex Mapping UnitLT Lake Tank Geomorphic SurfaceOR Organ Geomorphic SurfaceBR Bedrock

Areas that have an intricate association of two mapping units are signified by combining the symbols,such as OR/IR. Th e first symbol indicates the dominant mapping unit.


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Geomorpkic Surfaces on Maneuver an d Adjacent Areas /33

,wC... 6D 7C 7D7

4 , 5 5B5 5c

4 5 C 2DD

9E352503545000NR

Fiue1120 ne a o 3oophcSrae


50/276

i -w

34%SOIL-GEOMORPHIC CHARACTERISTICS OF THE FORT BLISS MANEUVER AREASMap Legend'Symbol Mapplig Unit (see preceding text in this chapterfor mapping unit descriptions)LM La Mesa Geomorphic Surfaceii Jornada I Geomorphic Surface

JlI Jornada 11 Geomorphic SurfacePT Petts Tank Geomorphic SurfaceFC Fault Complex Mapping UnitIR Isaacks' Ranch Geomorphic SurfaceFS Fort Selden Complex Mapping UnitLT Lake Tank Geomorphic SurfaceOR Organ Geomorphic SurfaceBR Bedrock

Areas that have an intricate association of tw o mapping units are signified by combining the symbols,such as OR/JR. Th e first symbol indicates the dominant mapping unit.


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Chapter IVEOLIAN ALTERATION OF SOIL STRATA ON MANEUVERAND ADJACENT AREAS OF FORT BLISSBy H. Curtis Monger

The purpose of this investigation was to (1) identify areas where deflation (wind erosion) probably hasaltered the stratigraphic characteristics of soils causing the archaeological stratigraphy to collapse vertically,and (2) identify areas where deposition may have protected archaeological sites.Vegetative, topographic, and color patterns of the Fort Bliss land surface were identified on USGScolor-infrared aerial photographs (1:58,000) taken in May, June, and September of 1984. Th e land surfacepatterns were delineated and related to subsurface features as revealed in backhoe trenches, hand-dug pits,auger holes, and road cuts (see figures 1-2 and 1-3). Th e aerial photographs provided high-quality stereo-pair

coverage in which even relatively small coppice dunes appeared topographically higher than adjacent deflatedinterdune areas.Much of Fort Bliss has been deflated to various degrees and reburied numerous times. As a result, there

are many types of soil profiles (see Figure IV-1). Four mapping units were devised to group soils in amanner reflecting deflational and depositional characteristics. Mapping Unit I includes deflated dune andnondune areas exposed at the modern land surface. Mapping Unit 2 includes areas buried by historicalblowsand in the form of dunes with interdune sheet deposits. Mapping Unit 3 is similar to Mapping Unit 2except the historical blowsand occurs as large sheet deposits. Mapping Unit 4 includes areas that have beenmodified little by wind activity because soils have been protected by an armor of desert pavement or highclay content.lapping Unit 1: Modern Deflational Surfaces

This mapping unit -, areas of the modern land surface that have been deflated. These areas wereidentified by the occurrence of lag layers of indurated caliche fragments, which indicates a deflated soilprofile (see Figure IV-I). Generally these areas are not buried, or are buried by less than approximately 30cm of eolian sediments. This mapping unit occurs in patches and most commonly is associated with faultscarps and areas where tank traffic has been extensive. Mapping Unit I is similar to the mapping unit "ZoneP"of Davis and Nials (1988) in their study of the Santa Teresa area in south-central New Mexico.

Caliche fragments, which are diagnostic for this mapping unit, are composed of stage 1I carbonatenodules and petrocalcic horizon fragments. The lag accumulation of these nodules signifies the deflationaldestruction of a former soil profile containing this material and the vertical collapse of the nodules.Petrocalcic horizon fragments accumulate on the land surface as the result of a La Mesa soil being truncatedby deflation. Petrocalcic horizons, however, need not be exhumed totally before fragments beginaccumulating on the land surface. Soil profile exposures in many Fort Bliss locations reveal petrocalcichorizons begin to disintegrate when they are about 40 cm from the surface as the result of root and wettingfront penetration. Once released, fragments of the petrocalcic horizon begin an upward migration to the landsurface.


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36\ SOIL-GEOMORPHIC CHARACTERISTICS OF TH E FORT BLISS MANEUVER AREAS

EOLIAN ALTERATION la Historic Blow Sand (C horizon)MAPPING UNITS1

tokorizon) of Carbonate Nodules(B:orizon)

(Bkm h rBzm2a

A

Btk" Nodular Lag Laye 2CBkm 3Bk

DeetPavement Relatively High ClayContent In Depression Soils

.__ AS~~Bt..

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Figure IV-J. Eolian Alteration Mapping Unit Soil Profiles(FSoilhorizon nomenclature is that used by the U.S. Cooperative Soil Survey-Soil Survey Staff 1992.)


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Geomorphic lnvestigatiom of aPossible Paleolake /37(]a): LargeDunes (generallygreater han I m) with Collapsed nterdune Strata

This mapping unit occurs to a minor extent on both Fort Bliss North and South. Many areas of la in FortBliss North appear white on aerial photographs. The large dunes generally have little interdune vegetation.

(Ib): Small Dunes (generally ess than I m) with CollapsedInterduneStrataThis mapping unit is similar to Mapping Unit la except dunes here are smaller. These areas generallyhave some interdune vegetation and commonly are associated with areas of faulting and tank traffic.

(lc): DeflatedNondune AreasThese are deflated areas that do not contain dunes. These areas often are disturbed by land use andcommonly contain a snakeweed cover.

Mapping Unit 2: Dunes with Interdune Sheet DepositsMapping Unit 2 is the most extensive type of eolian alteration unit on both Fort Bliss North and South.This unit is composed of historical blowsand in the form of dunes with interdune sheet deposits. It is

subdivided into units 2a (dunes generally greater than I--m high) and 2b (dunes less than Ii-m high). Thesehistorical eolian deposits bury landscapes containing soils that have undergone various degrees of deflation(see Figure IV-l). On one extreme, historical blowsand covers paleodeflational surfaces in whicharchaeological stratigraphy would have collapsed. In contrast, many buried landscapes have undeflated soilprofiles in which archaeological stratigraphy would be intact.In a study area west of the Jarilla Mountains, Blair et al. (1990) described the various thicknesses of

historical eolian deposits. Their fence diagram illustrates that in most cases historical blowsand overliesHolocene Organ material. The same is true for large areas on Fort Bliss.Good profile exposures of Mapping Unit 2 occur along Area 8's southern boundary (a road). Much of thenortheastern section of Fort Bliss North is covered with Mapping Unit 2a, in which dunes are aligned in anortheast-southwest direction. Mapping Unit 2 is similar to Mapping Unit "Zone 3" of Davis and Nials(1988).

(2a): Large Dunes (generallygreater han I m) with InterduneSheet DepositsWind ripples are common in this unit and indicate active sand movement. Interdune vegetation is sparse.

(2b): Small Dunes (generally es s than 1 m) with InterduneSheet DepositsThis mapping unit is transitional between mapping units 2a and 3. Dunes here generally are smaller than1 m in height. Interdune grasses are common.


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Mapping Unit 3: Depositional Areas Composed of Sand Sheet DepositsMany areas of Fort Bliss, especially the grassland areas, are buried by sheet deposits of historical eoliandeposits. These sheet deposits cover both deflated land surfaces and areas that have intact soil stratigraphy(see Figure IV-1). Mapping Unit 3 is similar to Mapping Unit "Zone 2" of Davis and Nials (1988).

Mapping Unit 4: Areas Where Soil Strata Are Modified Little by WindMany of the fan-piedmont and depressional basin floor areas contain soils modified little by windactivity. The fan-piedmont soils commonly are protected by an armor of desert pavement (see Figure IV-1).Depression soils in the basin floor generally have higher clay concentrations than do neighboring soils.Apparently the clay protects these soils from wind erosion.


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Geomorphic Investigation of a Possible Paleolake /39bN+ 6B 7A 781 + 23

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Figure IV-2. Index Map of Soil Strata Eolian Alteration


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40\ SOIL-GEOMORPHIC CHARACTERISTICS OF TH E FORT BLISS MANEUVER AREAS

Map Legend:Th e following symbols, described earlier in this chapter, were used to indicate the various categories ofsoil strata eolian alteration.

Symbolla See text in this chapter for descriptionslb See text in this chapter for descriptionsIc See text in this chapter for descriptions2a See text in this chapter for descriptions2b See text in this chapter for descriptions3 See text in this chapter for descriptions4 See text in this chapter for descriptions

Areas that have an intricate association of two or more mapping units are signified by combining thesymbols, such as la/2a. Th e preceding symbol indicates the dominant mapping unit. Arrows indicatelocations where coppice are aligned and the direction of alignment. Arrows pointing NE do not necessarilyimply movement in that direction.


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Chapter VGEOMORPHIC INVESTIGATION OF A POSSIBLEPALEOLAKE ON McGREGOR RANGE

By Sa'eb A. Khresat

IntroductionArcheological and paleoenvironmental studies of a cave in the Hueco Mountains east of Orogrande, NewMexico, have revealed the possibility of paleo-lndian existence before 12,000 B.P. An intermontane basinwest of the paleo-lndian site contains eolian, fan-piedmont, and possibly lacustrine deposits that couldcontain information relevant to archeological studies. The purpose of this study is to investigate the soilsdeveloped in the intermontane basin deposits in order to reconstruct the geomorphic evolution of the area.The results show the basin was not occupied by a late Pleistocene paleolake as suspected. Alluvial plaindeposits were the major deposits in the basin. Haplargids were found on older surfaces while

Torripsamments were found on younger and unstable surfaces.The first question addressed in this study was: Was there a lake in this basin in the late Pleistocene? Ifnot, what is the basin's geomorphic history? This information is very important for archaeologists,geomorphologists, and land-resources planners. Th e second part of this study called fo r the establishment of

a relationship between the geomorphic surfaces of the basin and soil genesis. Such a relationship is a key tounderstanding soil behavior; consequently allowing for better utilization an d proper planning.This study is based on observations of particular landforms in the intermontane basin that may help

determine the processes and methods that contributed to

ada278553 soil-geomorphic and pa leo climatic characteristics of the fort bliss maneuver areas,...

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