Geomorphology and Geoarchaeology of Galveston Bay

8/14/2019 Geomorphology and Geoarchaeology of Galveston Bay

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COMPREHENSIVE HISTORIC PRESERVATION PLANHOUSTONGALVESTON NAVIGATION CHANNELS,TEXAS PROJECT, GALVESTON, HARRIS, LIBERTY ANDCHAMBERS COUNTIES, TEXAS.

ByStephanie L. PerraultandCharles E. Pearson

with contributions byMargaret S. HensonKay HudsonandPaul Heinrich

Submitted to:U.S. Army Corps of EngineersGalveston District(Contract No. DACW6491D0010,Delivery Order No.1)

Submitted by:Coastal Environments, Inc.1260 Main StreetBaton Rouge, Louisiana

MARCH 1993


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TABLE OF CONTENTSEXECUTIVE SUMMARy..................................................................... iiLIST OF FIGURES ............................................................................. viiLIST OF TABLES ............................................................................... viii

CHAPTER 1: INTRODUCTION .......................................................... 1-1Purpose of the Historic Preservation Plan.. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1The Galveston Bay Navigation System............ .................... 1-2Goals............. ..................... ..... ............ ................ 1-8Policies................................... ................... ........... 1-9Priorities.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. . .. .. .. . .. .. .. . .. . 1-10Organization of the Historic Preservation Plan........................ 1-12CHAPTER 2: OVERVIEW............................................................... 2-1

G a l v e s t < ~ n ,I?i.stricts, Corps of Engineers Needs andResponsibIlities ......................... " . . . . . . . . . . . . . . . . . .. . . .. . . .. . . . 2-1Cultural Resources Management Needs......................... 2-1Legal Responsibilities.............................................. 2-2Summary of Geological History and Natural Setting ofGalveston Bay........................................................... 2-7Climate .............................................................. 2-16Biota ............................................................... 2-16Summary of Cultural History of the Galveston Bay Area ......... 2-18Previous Archaeological Research. . .. .. .. .. .. . .. .. . .. .. .. .. .. .. . 2-18Underwater Archaeology .......................................... 2-30Native American Culture History ................................ 2-31The Prehistoric Period. .. . . . .. . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . .. 2-31The Paleoindian Period ....................................... 2-31The Archaic Period ............................................ 2-33Late Prehistoric Period. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2-34Historic Native American Cultures .......................... 2-37Euro-american Culture History .................................. 2-38Early Exploration and Settlement Prior to 1800............ 2-38Early-Nineteenth-Century Occupation and Settlement,1800-1836 ...................................................... 2-39Texas Independence to the Civil War ....................... 2-41The Civil War, 1861-1865 .................................... 2-42

CHAPTER 3. HISTORIC CONTEXTS .............................................. 3-1The Historic Context Concept.. .. .. .. ... .. .. .. .. . . . .. .. .. . .. .. .. .. .. .. 3-11. Late Quaternary Environments, Paleogeography,and the Archaeological Record.................................... 3-2Introduction and Perspectives.. .. .. .. . .. .. . .. .. . .. .. .. .. .. .. . 3-2Geological Setting. . . . . . . . . . .. . . .. . . . . . . . .. . . . . . . . . . . . . . . . . . . . . 3-6Geological Features and Geomorphic Processes.. .... 3-6Upland Surfaces and Process ................................ 3-15Coast-Parallel Terraces ................................... 3-16Prairie Complex. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3-17Prairie Terrace. . .. . . . . . . . . . . . . . . .. . . . . . . . .. . . . . . . . . . . . . . . .. 3-17Beaumont Formation - Beaumont Alloformation .......... 3-20Surface Modification ...................................... 3-22

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Surface Modification ...................................... 3-22Effects on Human Adaptation ............................ 3-25Effects on the Archaeological Record. . . . . . . . . . . . . . . . . .. 3-26Stratigraphy and Chronology of Fluvial Sequences ....... 3-27Trinity and San Jacinto River Valleys .................. 3-28Galveston Bay ............................................. 3-39Fluvial Complexes Beneath Galveston Bay ............ 3-43Sea Level Rise: Processes and Chronology ............... 3-47Effects on Human Adaptation ............................ 3-50Effects on the Archaeological Record ................... 3-533. Hunter-Gatherer Adaptations to SoutheasternCoastal Texas, The Galveston Bay Region,10,000 - 1700 B.C ................................................ 3-57Introduction ..................................................... 3-57Overview of the Regional Database ......................... 3-57Major Problems ................................................ 3-59Research Needs and Goals ............................... 3-60A Model of Paleoindian and Archaic Hunter-Gatherer Adaptation. . . .. . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3-61Adaptation to Changing Coastal and EstuarineHabitats and Resources.. .. . .. .. . .. .. .. . . .. .. .. .. .. .. .. ... 3-62Cultural Property Types ...................................... 3-63Resource Characteristics and Criteria for Evaluation ...... 3-63Stresses on the Resources Base .............................. 3-64Treatment Goals, Objectives, and Tools .................... 3-644. Effects of European Contact on NativePopulations in Southeastern Coastal Texas,The Galveston Bay Region, A.D. 1529 - 1850 ................ 3-65Introduction ..................................................... 3-65Overview of the Regional Database ......................... 3-67

Major Problems ................................................ 3-70Patterns of European/Aboriginal Interaction.. . .. .. . .. .. .... 3-71The Results of European Contact and theArchaeological Record .................................... 3-73Cultural Property Types ...................................... 3-74Resource Characteristics and Criteria for Evaluation ...... 3-74Stresses on the Resources Base .............................. 3-75Treatment Goals, Objectives, and Tools .................... 3-75Special Problems and Suggested Study Units .............. 3-755. Navigation and Maritime Uses of the GalvestonBay Region During the Historic Period ......................... 3-78Introduction ..................................................... 3-78

Overview of the Regional Databaseand ..................... 3-78Major Problems and Research Needs and Goals .......... 3-80Navigation in the Galveston Bay Region: 1529 tothe Present. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . .. . .. 3-81Navigation and Commerce prior to 1800 to 1861 ..... 3-83Mexican Texas 1821-1835 and Anglo AmericanSettlement.. .. .. .. .. .. .. .. .. .. .. . .. .. . .. . . .. . .. .. .. .. . .. .... 3-87Republic of Texas 1836 - 1846.......................... 3-93State Hood 1846 - 1860 .................................. 3-98

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Recommended Procedures for the Protection ofCultural Resources in the Galveston Bay Area...................... 6-9A Research Design for the Management of CulturalProperties in the Galveston Bay Area.... .... .. .. .. .. .. .. .. .. .. .. .... 6-11Research Themes ................................................... 6-12Buried and Submerged Cultural Resources ..................... 6-13Archaeological Sites. . . . . . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . .. . . .. 6-13Shipwreck Sites ................................................ 6-15Terrestrial Archaeological Sites.. . .. .. .. .. .. .. .. . . .. . .. .. . .. .. .... 6-18

REFERENCES ..................................................................... R-l

APPENDIX 1: National Historic Preservation Act of 1966 . . . . . . . . . . Al-lAPPENDIX 2: Army Regulation 420-40 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2-1APPENDIX 3: 36 CRF Part 800: Protection of Historic Properties

A3-1

APPENDIX 4 Abandoned Shipwreck Act of 1987 andNPS Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A4-1

APPENDIX 5: National Register Bulletin 20 . . . . . . . . . . . . . . . . . . . . . . . . . . . A5-1

APPENDIX 6: Programmatic Agreement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A6-1APPENDIX 7: Annotated Listing of Shipwrecks

in the Galveston Bay Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A7-1

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the management of the property. Any such contract will contain tenns andconditions necessary to protect the interests of the United States as well asinsure adequate preservation of the historic property.

The development of a HPP satisfies these responsibilities for a Federal agencysuch as the COE.

Guidelines for the fulfillment of these responsibilities have been developed by theNational Park Service and the Advisory Council on Historic Preservation. In recognition ofthese responsibilities, the Department of the Army has also developed its own guidelines forbranches such as the COE. Anny Regulation 420-40 (Historic Preservation) prescribesmanagement responsibilities and standards for the treatment of historic properties. It alsopresents a format and suggested contents for the development of a Historic Preservation Plan(HPP) in consultation with the ACHP and the appropriate SHPO. The guidelines establishedin Regulation 420-40 (presented as Appendix B) were followed in the development of thisHPP.

The Archeological Resources Protection Act of 1979 (P.L. 96-95) was designed toprotect cultural resources on public or Indian lands. This law defines the prohibited activities(excavation, removal, damage, or defacement) on public lands and the associated criminalpenalties that are enforced by this law. This act requires a pennit for any excavation or removalof archaeological resources from public or Indian lands which is not sponsored by the Federalagency. Any such excavation must be of a scientific nature and all resources removed remainthe property of the Federal government. The permit granting authority usually belongs to theland manager responsible for the property.

Summary of Geological History and Natural Setting of Galveston BayA considerable amount of research has been directed at the geology and natural

environment of the Galveston Bay area such that it is reasonably well known. The followingsection presents a summary of the area's natural setting and its geological history pertinent togaining an understanding of the major geological and geomorphic features and how they havedeveloped. More detailed discussions on specific aspects of the geology and geomorphologyof the study area are provided in following chapters. In particular, these later discussions view

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the geology and geomorphology of the bay area from the concept of "allostratigraphy," anapproach which seems to have particular utility in the study of archaeological phenomena_

Galveston Bay, and its associated smaller lakes and bays, is located in the Gulf CoastProvince in the upper Coastal Zone of Texas, a region characterized by "several active, naturalsystems of environments--f1uvial and deltaic systems, marine barrier-strandplain-cheniersystems, [and] bay estuary-lagoon systems . __ " (Fisher et al. 1971 :11)_ Additionally, relictfeatures representative of similar systems active during the Pleistocene are found throughoutthe region_ Today, a nearly continuous series of marginal, estuarine embayments separatedfrom the Gulf of Mexico by barrier islands and spits characterize the Texas coastline_ TheGalveston Bay complex is the largest of these estuarine systems with an area of about 1680square kilometers (see Figure 1-1, Figure 2-1)_ This estuarine complex consists ofa roughlyT-shaped embayment composed of five major elements known as East, Galveston, SanJacinito, Trinity, and West bays_ A large barrier island, Galveston Island, and major spit,Bolivar Peninsula separates the Galveston Bay complex from the Gulf of Mexico (Lankfordand Rehkemper 1969:1; White et aL 1985)_

The Galveston Bay bay-estuary-Iagoon system is Holocene in age, created as rising sealevels have flooded older, incised stream valleys in the past 10,000 years or so_ The higherterrain surrounding the bay complex consists of the remains of Pleistocene-age fluvial-deltaicsystems, the upper portions of which is termed the Beaumont Formation or Beaumont Terrace(Aronow, 1971; Bernard 1950; Bernard and LeBlanc 1965; Fisk 1944; Saucier 1974,1977)_Two factors have been the primary controls on producing the current geometry of the Holoceneand Pleistocene deposits in the region: 1) inland uplift and seaward subsidence and 2) glacialcycles of the Pleistocene and resultant changes in sea level (Lankford and Rogers 1969:2)_Fluctuations in sea level have produced the most dramatic impacts on the landscape and theseare considered in some detail below.

Galveston, San Jacinito, and Trinity bays compose the vertical segment of the "T" ofthe modern estuarine complex which extends inland about 48 km perpendicular to the coast.This estuarine-bay complex is characterized by a mixing of marine and fluvial processesdescribed in detail by Fisher et aL (1972) and White et aL (1985). The dominance of eithersystem is a function of an array of factors, including river discharge, tidal interchange, waterdepth, and the location along the axis of the bays between the river mouth and tidal inlet. TheTrinity and San Jacinito rivers and other small streams discharge into the heads and along theflanks of these bays. Two shallow, flat-bottomed bays, Galveston and Trinity bays, with an

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average depth of 2 to 3 m comprise the bulk of this estuarine-bay complex. These bays wereonce separated by the east-west trending Red Fish Bar. The bottoms of these bays deepensharply immediately adjacent to their margins, except for the gently sloping bottoms of thenorthern heads of San Jacinito and Trinity bays (Lankford and Rehkemper 1969:1-2;Rehkemper 1969a:6-12).

Currently, the Trinity River Delta is filling in the head of Trinity Bay. It is a modern,typical bayhead delta dissected by numerous distributary and tidal channels and covered byfresh to brackish marsh. This modern feature has a deltaic plain that covers an area of about15.5 square kilometers on the eastern side of the Holocene fluvial-deltaic plain of the TrinityRiver. The construction of this deltaic plain has isolated part of Trinity Bay to form LakeAnahuac. Behind the modern deltaic plain, the progradation of older deltaic plains and theirriver courses have formed a fluvial-deltaic plain about 10.5 km wide over the last 3,100 years(Rehkemper 1969a:9; Aten 1983).

Unlike the Trinity River, the other major stream flowing into the Galveston Baysystem, San Jacinito River, lacks a mappable delta at its head because of its small sedimentload. Apparently, there has been some accumulation of sediment and resulting shoaling in SanJacinito at the mouth of San Jacinito River. However, extensive dredging, associated dredgedmaterial disposal on its banks and islands, and over 4 m of subsidence have obliterated anybayhead delta that may have existed (Lankford and Rehkemper 1969: 1-2; Rehkemper1969a:9).

The cap of the "T" is oriented parallel to the coastline and consists of East and Westbays. These bays constitute a coast-parallel lagoon measuring approximately 88 km long and1.5 to 6.5 km wide. They are quite shallow and flat with an average depth of about 2 m. Shellreefs oriented perpendicular to the axis of the lagoons are scattered throughout both bays. Eastand West bays are strongly influenced by marine processes and gulf waters through tidal inletsand hurricane overwash. Along both bays, fresh to brackish water marshes extend as far as6.5 km inland from their shoreward edge. The lagoons and associated marshes are strips ofthe adjacent Pleistocene coast-parallel terrace which have been flooded by the Holocenetransgression and separated from the Gulf of Mexico by the development of Galveston Islandand Bolivar Peninsula (Lankford and Rehkemper 1969:1-2; Rehkemper 1969a:6-12).

Galveston Island and Bolivar Peninsula separate the Galveston Bay complex from theGulf of Mexico. This barrier island and spit complex averages about 1.5 to 2.5 km wide and

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has a straight or smoothly arcuate gulf shoreline. Its lagoonal shoreline is highly irregularbecause of a series of washover deltas. old tidal inlets, storm passes, and distal ends ofrecurved spits. Well-preserved ridge and swale topography formed by the lateral progradationof this barrier island and spit complex characterize the surfaces of both Galveston Island andBolivar Peninsula. The ridges and swales parallel the gulf shoreline. Three tidal inlets breachthe Bolivar-Galveston barrier complex. These inlets provide limited hydrologic communicationbetween Galveston Bay and the Gulf of Mexico. (Lankford and Rehkemper 1969:2-3; Fisher etal. 1972). The largest of these is Bolivar Roads, a natural pass between Galveston Island andBolivar Peninsula which connects Galveston Bay with the Gulf of Mexico.

The Galveston Bay complex has been extensively modified in a number of ways inhistoric times. First, over the last century, channel dredging and attendant formation ofshallow spoil banks and islands, e.g., the Houston and Texas City ship channels, hassignificantly modified the natural setting and conditions of the Galveston Bay complex.Second, dredging and the removal of oyster shell over the past century has locally deepenedparts of this estuarine-bay complex by as much as 2.5 to 3 m. Third, the removal ofgroundwater for industrial and urban usage has caused as much as 1.5 m of subsidence at thehead of San Jacinito Bay to less than 0.2 m of subsidence within East Bay between 1943 and1975. This subsidence has significantly increased local rates of shoreline erosion and landloss. Finally, urbanization and dam construction has significantly changed the volume andtypes of sediment and dissolved solids and gases being delivered by the Trinity and SanJacinito rivers to the Galveston Bay complex. (Rehkemper 1969:11-\3; Fisher et al. 1972;White et al. 1985).

The coastal plain surrounding the Galveston Bay complex consists of two majorgeomorphic terraines. One terraine consists of broad, coast-parallel terraces. These terracesare composed ofrelict alluvial and deltaic plains of Late Quaternary fluvial systems ancestral tothe Brazos, Trinity, and San J acinito rivers and a coastal sand ridge system known as theIngleside sand ridge. The other terraine consists of coast-perpendicular fluvial valleys of theserivers entrenched into these relict systems which have active floodplains flanked by a series offluvial terraces. As noted earlier, the upper segment of these Late Quaternary alluvial anddeltaic plain terrace features are identified as either Beaumont Formation or Beaumont Terrace.There is some controversy over the age of the Beaumont, but recent interpretations argue thatdeposition of this formation began during the Sangamon Interglacial (prior to 80,000 B.P.) andthe uppermost deposits are probably associated with the Mid-Wisconsinan, FarmdalianInterstadial (Saucier 1977).

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A variety of relict deltaic and fluvial features of the Beaumont can be seen at the surfacein the vicinity of the study area. As shown in Figure 22, a number of distributary channelswhich represent ancient fluvial systems can be seen in the vicinity of Galveston Bay. Theserelict channels represent various meander belts of the Pleistocene-age Brazos and Trinity riverswhich may be contemporary to the Deltaic Plain phase (ca. 30,000 to 25,000 B.P.) (Aronow1971; Aten 1983b, Weinstein 1991b:5). These features were apparently formed during theFarrndalian Interstadial, when sea level was at or near its present level.

Subsequent to the Farmdalian high-sea stand, about 25, 000 years ago, sea level beganto drop in the wake of Woodfordian glaciation (Fisher et al. 1972:11). Approximately 18,000years ago, sea levels reached their lowest levels, about 450 ft below the present sea level(Saucier 1981; Saucier and Fleetwood 1970). In response to the fall in sea level, Pleistocenerivers and streams initially extended their floodplain seaward. However, the fall eventuallybecame so dramatic that progradation could not be maintained and streams began to incise theirchannels into the underlain Pleistocene deposits (Fisher et al. 1972:13). Following the glacialmaximum, sea levels began a slow rise, eventually, inundating most of the valleys formedduring the low stand. This inundation resulted in the eventual filling of the old river valleys asa progression of deltaic and estuarine systems developed within the valleys and wide-spreaddeposition occurred. Most of presentday Galveston and Trinity bays constitute the filledPleistocene age valleys of the Trinity and San Jacinto rivers.

A slight reversal in sea level rise occurred between 11,000 and 10,000 years ago (Aten1983b). This drop was less dramatic than the previous fall, but it was sufficient to causeentrenchment in coastal streams (Weinstein 1991b:5). After about 10,000 years ago, sea levelbegan to rise, with most arguing that it reached its present level about 40-00 to 3500 years ago(Aten 1983b; Lankford 1971; Pearson et al. 1986; Rehkemper 1969). As sea level rose, thevalleys of the various rivers in the Galveston Bay area became drowned, and the GalvestonBay estuary developed.

Prior to its inundation, the entrenched valley of the Trinity River followed a meanderingcourse through what is now Galveston Bay. The San Jacinto River joined the Trinity betweenwhat is presently Smith Point and San Leon, the combined rivers extended southward throughthe Bolivar Roads area across the Continental Shelf to the Gulf. Lankford and Rogers

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ANCIENTBRAZOS

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tFigure 2-2. Locations of Pleistocene deltas of Brazos and Trinity rivers(after Barton 1930).

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(1969:41) indicate that the valley was fairly narrow, about 6 miles, and that "Pleistoceneoutliers isolated by meandering channel erosion stood as hills and ridges above the valleyfloor." They indicate that the combined Pleistocene age Trinity-San Jacinto had incised itschannel to maximum depth of about 130 ft at the entrance to Galveston Bay, and that thePleistocene Trinity channel reaches a depth of 60 ft at the upper end of Trinity Bay beneath themodern Trinity Delta (Figure 2-3) (Lankford and Rogers 1969:41). Others suggest that thevalley entrenchment was deeper. For example, Fisher et a!. (1972) indicate that cores taken inthe bay indicate the depth to the now buried and filled relict valley is as much as 260 ft.

As sea level rose and the valley of the Trinity-San Jacinto was inundated, large "pointbar sand bodies and extensive overbank mud sheets were deposited" within the valleys by themeandering river (Fisher et a!. 1971: 13). Considerable areas of these Holocene meander beltdeposits are exposed in the submerged, but as yet unfilled, portions of the Trinity and SanJacinto valleys. By 8,000 years ago, rising sea levels were forming an estuary in what is nowGalveston Bay. At that time, infilling of the smaller streams tributary to the bay by locallyderived sediments started to occur, a process which continues along some to this day(Lankford 1971:362). Concomitant with the infilling was the development of bars and barriersacross the mouths of tributary valleys and within parts of Galveston Bay (Lankford 1971:362-363).

During the past 4500 years or so, since sea level reached its approximate present level,several changes have occurred in the natural systems and features in the Galveston Bay system.As Fisher et al.( 1971:14) note these are:

(1) Deeper parts of the Trinity and San Jacinto estuaries began to fillwith sediment eroded from the walls of drowned valleys; (2) the Trinity andSan Jacinto bay-head deltas began their slow filling of the uppermost part of theestuaries; (3) headward erosion by short streams continued within Pleistoceneinterdistributary areas where significant compaction of mud is occurring; (4)East Bay and West Bay developed as elongate lagoons behind BolivarPeninsula, which grew southwestward by spit deposition and shorefacedeposition from eroded deltaic headlands near High Island, and behindGalveston and Follets Islands, which developed as coalescing, exposedoffshore bars that also grew seaward by shoreface deposition; and (5) marshesencroached upon subsiding Pleistocene delta deposits and bay areas that werefilled by storm-washover fans and bay-margin deposits.

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_11..,.'L ..., ... H U Y " ~ ""'_uc.O ,_nor. . . .. .

Figure 2-3. Contour map of top of Pleistocene in Galveston area.Pleistocene deposits after Henry, 1956.

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Climate

The climate of the Galveston Bay area represents the only truly humid bay system withincoastal Texas (Shew et al. 1981:12). Similarly, Galveston Bay receives the most rainfall of anyarea along the coast, with most precipitation falling during the spring and summer months,eventually reaching a peak during late summer. This peak is then followed by a rapid decrease inOctober, resulting in a relatively low rate of precipitation throughout the remainder of the fall andwinter months (Shew et al. 1981: 13, Fig. 1).

Temperatures in the Galveston Bay area are moderated by winds from the Gulf of Mexico,causing mild winters and relatively cool summer nights (Wheeler 1976:2). Mean annual airtemperature is 20.5 degrees Celsius at Houston (NOAA 1973, cited in Shew et al. 1981:13), witha maximum in August and minimum in January.

Prevailing winds are from the south and southeast, "except in January when frequent highpressure areas bring invasions of polar air and prevailing northerly winds (Wheeler 1976:2).About one-fourth of the days each year are clear, with October having the greatest number of cleardays. Cloudy days are frequent from November through May, and partly cloudy days are frequentfrom June through September (Wheeler 1976:2).

Biota

The Galveston Bay system as a whole has an average salinity of 17.3 parts per thousand,the lowest salinity rate of any bay system on the coast of Texas (Martinez 1975 [cited in Shew etal. 1981 :29]). This low salinity is largely a result of the great quantity of freshwater discharged into the system by the Trinity and San Jacinto rivers in combination with the high volume of localrunoff from smaller tributary streams produced by the region's high precipitation rates. This issignificant, because several faunal species thrive best in areas where salinity is relatively low andhigh levels of freshwater inflow occurs. Examples include Rangia clams, an important dietaryresource to aboriginal populations, and other species which may have played an important part inthe aboriginal diet, such as the blue crab (Callinectes sapidliS) and white shrimp (Panaeussetiferus), although evidence for prehistoric exploitation of these species is minimal.

Several recent summaries of the flora and fauna of the Galveston Bay and Trinity Riverdelta areas have appeared (Dillehay 1975a; Fisher et al. 1972; Gilmore 1974; Mercado-Allinger etal. 1984; Shew et al. 1981; Stokes 1985). In this ovelview it is sufficient simply to provide a briefreview of the more important species known from the area. Mercado-Allinger et al. (1984:3-4),

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citing data supplied by Dillehay (1975a:166-178), Fisher et al. (1972:70), Gilmore (1974:22), andthe Houston Audubon Society and Preservation of Armand Bayou Committee (1974), offer asummary of the species of the region and their study is quoted below:

Although the natural vegetation of the project region has been severely alteredby twentieth-century agriculture and urbanization, it is possible to define threevegetational assemblages which may have occurred in the area prehistorically:(I) in the Pleistocene uplands, a prairie grassland with species such as littlebluestem (Schizachyrium scoparium), big bluestem (Andropogon gerardi),indiagrass (Sorghastrum avenaceum), and eastern gramagrass (Tripsacumdactyloides); (2) along portions of Clear Creek, the south side of Clear Lake,and especially the north side of Clear Lake, a fluvial woodland with plants suchas pecan (Carya illinoensis), willow oak (Quercus phellos), water oak (Quercusnigra), overcup oak (Quercus lyrata), bottomland post oak (Quercus simiUs),water hickory (Carya aquatica), southern red oak (Quercus falcata), Americanelm (Ulmus americana), Texas sugarberry (Cetis laevigata), palmetto (Sabalminor), American hornbeam (Cmpinus caroliniana), red mulbelTY (MOrliSrubra), American beauty berry (Callicarpa americana), flatwood plum (Prunusumbellata), possum-haw (/lex decidua), greenbriar (Smilax spp.), and grapes(Vitis spp.); and (3) along parts of Clear Creek and its tributaries, a brackish tofreshwater marsh with plants such as coastal sacahuista (Spartina spartinae),marsh hay cordgrass (Spartina patens), big cordgrass (Spartina cynosuroides),rushes (Juncus spp.), bulrushes (Scirplls spp.), and cattail (Typha latifolia).Likewise, present-day faunal assemblages are only partly representative ofthose that existed prehistorically. It is clear, however, that the environmentsdescribed above supported a number of faunal species that were importantprehistorically. Animals which occur most commonly in the archaeologicalrecord of the region .. .include brackish water clam (Rangia cuneata and R.flexuosa), oyster (Crassostrea virginica), gar (Lepisosteus sp.), catfish(lctalurus sp.), freshwater drum (Aplodinotus grunniens), black drum(Pogonias cromis), sheepshead (Archosarglts probatcephallts), various turtles,alligator (Alligator mississippiensis), various waterfowl, bison (Bison bison),whitetail deer (Odocoileus virginianus), black bear (Ursus americanus), raccoon(Procyon 1010r), opossum (Didelphis marslIpialis), muskrat (Ondatra zibelhica),

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mink (Mustela vison), skunk (Mephitis mephitis), and rabbits (Sylvilagllsfloridanus and S. aquaticus).

Summary of Cultural History of the Galveston Bay AreaThis section is to place the cultural history of the Galveston Bay area in its appropriate

cultural and chronological framework. This section contains only a summary of the region'sculture history, not an in depth treatment of the topic and its intent is to provide CaE managerswith a handle on the scope and history of cultural resources research within the Galveston Bayarea as well as a basic understanding of the prehistoric and historic cultural setting. As noted inArmy Regulation 42040, the overview serves to "determine if the installation [in this case theGalveston Bay Navigation System] has or is likely to have historic properties that may beadversely affected by Army undertakings." This discussion also serves as a platform for themore detailed discussions on specific aspects of the area's culture history contained in thehistoric contexts presented in the next chapter. A considerable amount of archaeological andhistorical research has been undertaken in the Galveston Bay region from which informationcan be drawn. Much of the information presented in this summary has been taken from studiesmade by Aten (1979; 1983b), Gadus and Howard (1990), Howard et al. (1991), MercadoAllinger, et al. (1984), Weinstein (1991b),and Weinstein et al. (1988; 1989), to name a few.

Previous Archaeological ResearchThere have been numerous archaeological investigations in the Galveston Bay area of

Chambers, Harris, and Galveston counties, many of them funded by the Galveston DistrictCaE. This abundance can be attributed largely to the appearance of federally mandated culturalresource surveys, site assessments, and data-recovery projects within the last 20 years, inconjunction with the boom in construction related to residential development in and around theGalveston Bay area. One bias that should be noted is that the emphasis of most of the previousresearch has been on prehistoric sites and the prehistoric period, relatively little attention hasbeen paid to non-aboriginal cultural resources. The one exception to this is in the area ofhistoric shipwrecks; a topic of particular importance to this HPP. A number of studies,primarily remote-sensing surveys in and in the vicinity of Galveston Bay, have beenundertaken specifically to locate shipwreck remains. These studies are noted in the followingdiscussions. The area under consideration in this review includes all of Chambers andGalveston counties, Harris County east of Houston, Galveston Island and Bolivar Peninsula,

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CHAPTER 3

HISTORIC CONTEXTS

The Historic Context ConceptOne element in the management of cultural resources, is the "historic context". The

term historic context refers to the grouping of resources defined by theme, geographic limit andchronological period. The U.S. Department of the Interior (USDI) has developed specificstatements about how historic contexts are to be used in the preservation planning process.Their Standards and Guidelines for Archeology and Historic Preservation state:

Decisions about the identification, evaluation, registration, and treatment ofhistoric properties are most reliably made when the relationship of individualproperties to other similar properties is understood. Information about historicproperties representing aspects of history, architecture, archeology, engineering,and culture must be collected and organized to define these relationships. Thisorganizational framework is called an "historic context." The historic contextorganizes information based on a cultural theme and its geographical andchronological limits. Contexts describes the significant broad patterns ofdevelopment in an area that may be represented by historic properties. Thedevelopment of historic contests is the foundation for decisions aboutidentification, evaluation, registration, and treatment of historic properties [USDIn.d.].The Guidelines go on to state that a series of preservation goals should be

systematically developed for each historic context. These goals are to be prioritized andintegrated into the overall preservation planning effort for a given geographic area. Thefollowing section presents discussions on five basic historic contexts deemed pertinent to thestudy and management of cultural resource properties within the Galveston Bay NavigationSystem. These discussions provide relevant historical information pertinent to understandingthe position of the cultural resources within these contexts. The primary goal in developing


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of archaeological deposits, assessments will be made concerning the preservation potential ofarchaeological deposits. Finally, this review of the geomorphology and Quaternary geology ofthe Galveston Bay area is intended to help guide future geomorphological andgeoarchaeological research within the Galveston Bay region. The basis of the followingdiscussions relies on the concept of allostratigraphy in the definition of geological deposits. Itis felt that the use of allostratigraphy as a guiding concept in geological interpretation willultimately prove to be of significant value in the development of models of site archaeologicalsite distributions. In light of this, a rather detailed discussion of allostratigraphy is presented.

Allostratigraphy. The use of allostratigraphy in Gulf Coast geoarchaeologicalresearch is new application for this stratigraphic technique. Allostratigraphy is a methodologythat can be used to interpret seismic profiles, foundation borings, and other typical offshoregeologic data for geoarchaeological studies within the Galveston Bay area and the adjacentcontinental shelf. Allostratigraphy is a very important and useful, but often either ignored ormisunderstood, stratigraphic tool for geoarchaeological research within the Texas CoastalPlain. Allostratigraphy uses the "allofonnation" as the basic unit of analysis. An allofonnationis a mappable body of sedimentary rock or unconsolidated sediments that is defined andidentified on the basis of bounding discontinuities. A bounding discontinuity can be either anerosional unconformity or a construction surface (North American Commission onStratigraphic Nomenclature 1983:865-868). Using this methodology, it is possible to definemappable geomorphic surfaces and sedimentary units that can be used to predict the age,preservation potential, and potential for the occurrence of archaeological deposits withinHolocene sediments of Galveston Bay Area and the remainder of the Texas Coastal Plain andContinental Shelf.

In order to accomplish the goal of this Historic Context, an extensive review of the LateQuaternary geology and geomorphology of the Galveston Bay complex was conducted for tworeasons. First, although Galveston Bay has been the object of intensive sedimentological andarchaeological research, a proper stratigraphic framework is lacking and had to be constructed,because it was lacking. In part, this framework was lacking, because only recently has amethodology, allostratigraphy, been refined by Autin (1989, 1992) Autin et al. (1990, 1991),and Bhattacharya (1992) which has utility for the naming and mapping of Late Quaternarysedimentary deposits within Southeast Texas. Also, the lack of this framework results fromthe sedimentological orientation of geological research which resulted in the exclusive use ofanother stratigraphic methodology, sequence stratigraphy, which is powerful way to interpretsedimentary sequences context of relative sea level change, but is inadequate for the purpose of

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defining and mapping these deposits. Finally, contradictory interpretations by Aten (1983),LeBlanc (1991a), Gagliano (1991), Thomas (1991) and others concerning the alluvial depositscommonly called the "Deweyville Terraces or Formation" had to be resolved using a testablehypothesis. Although it was initially thought that certain researchers were wrong and othersright, it was discovered that each researcher observed a fundamental part of what became aproposed solution to this problem.

With this framework provided by the geological and geomorphological data, theprogress of environmental change in the Galveston Bay region since the coming of humanpopulations can be assessed. Further, with this diachronic model, shifting patterns of humanadaptation can be more accurately examined as can the resultant archaeological record.

The Holocene and Late Pleistocene sediments within many parts of the United Statesexist as only a thin veneer of sediment or topsoil overlying either unconsolidated sediments orbedrock that predates the human occupation of North America. As a result, these depositstypically are restricted to a thin, relatively uncomplicated, layer of alluvium, colluvium, orresiduum. The stratigraphy of such deposits, for the most part, can be described in simplestratigraphic terms without recourse to the complex assemblage of stratigraphic methodologyemployed normally by geologists.

However, the Texas Coastal Plain consists of large coast-parallel terraces comprised ofdelta, alluvial, and other plains that are the surface expression of thick, unconformity-bounded,sequences of Pleistocene and Holocene deltaic, fluvial, and eolian sediments (Figure 3-1).Within the Galveston Bay region, the Trinity, Brazos, and San Jacinto rivers and the shiftingshoreline of the Gulf of Mexico have created thick and intricately stacked sequences ofPleistocene and Holocene shallow marine, estuarine, coastal, deltaic, and fluvial sediments.As a result, multiple systems of independent and formally defined stratigraphic classificationsystems, e.g., lithostratigraphy, allostratigraphy, and pedostratigraphy, are an essential part ofthe interdisciplinary research approach used to describe, correlate, and interpret the complexsuccession of Pleistocene and Holocene sedimentary deposits which have accumulated withinthe Texas Coastal Plain (Autin et al. 1990,1991; Barton 1930; Bernard et a1.l970; DuBar et al.1991; Winker 1979).

I f this stratigraphic analysis is going to be of use to both archaeological research and themanagement of known and unknown archaeological properties within the Texas Coastal Plain

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oIo

5. " 10.15 20 15.

TRINITYBAY

NI

20mi25 ' (Hm

EXPLANATIONHOLOCENE SYSTEMS

Fluvial/deltaicsand and mudBarrier islandsond ond shellMarsh

pI EISTOCENE SYSTEMSFluvial/deltaic mud "nosand .Barrier slronaptalnsand (lnQfeside)

HUMAN ACTIVITIES Spoil and mode land

Figure 3-1. Generalized geologic map of the Galveston Bay system (source: Paine andMorton 1986:8).

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in general and the Galveston Bay area in particular, the stratigraphic nomenclature must bemore precisely applied than it has been in the past. For example, criteria, e.g., subsurfacestratigraphy and soil geomorphology, in addition to elevation and morphology need to be usedto map the distribution of geomorphic surfaces and the sedimentary deposits that underlie them.In addition, a geomorphic surface should not be assumed automatically to have the same ageand distribution as the sedimentary strata that underlie it. Furthermore, the different types ofstratigraphic units, geomorphic surfaces and formations, should be recognized as separateentities and not hybridized as many previous studies of the geomorphology and geology of theTexas Coastal Plain have consistently done. Finally, the use of models that propose simpleonetoone correlations between the formation of individual paleosols, coast-parallel terraces,delta plains, alluvial plains, and formations with glacial cycles or sea level fluctuations to dateor explain the origin of these stratigraphic units should be avoided (Autin et al. 1990, 1991).

Five types of stratigraphy, namely morpho stratigraphy (geomorphic surfaces),lithostratigraphy, allostratigraphy, pedostratigraphy, and chronostratigraphy, are important tothe definition, correlation, and dating of Pleistocene and Holocene deposits within the TexasCoastal Plain. Three of these types of stratigraphy, geomorphic surfaces, lithostratigraphy,and allostratigraphy, are specifically important to understanding the geomorphology of theTexas Coastal Plain. Two of these types of stratigraphic units, chronostratigraphy andpedostratigraphy, are discussed by Autin et al. (1990, 1991) and the North AmericanCommission on Stratigraphic Nomenclature (1983).Geological Setting

Geological Features and Geomorphic ProcessesWithin the Texas Coastal Plain, a variety of geomorphic surfaces can be recognized.

For geoarchaeological and geomorphological research, these geomorphic surfaces can beclassified as coast-parallel terraces, fluvial terraces, delta plains, and alluvial plains. Alluvialplains can be further subdivided into meander belts and backswamps.

Terraces. A terrace is a relatively flat geomorphic smface that is separated fromadjacent geomorphic surfaces by a constructional or erosional scarp. Within the Texas CoastalPlain, two different types of terraces, coast-parallel and fluvial terraces, can be recognized.The coast-parallel terraces are low-relief, gulf-ward sloping geomorphic surfaces separated bylow, irregular coast-parallel scarps; they parallel the coast and can be tens of kilometers wide.

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These surfaces represent relict coastal plains consisting of relict, Pleistocene alluvial, delta, andstrand plains (Barton 1930; Bernard et al. 1962). A fluvial terrace is a narrow geomorphicsurface of purely fluvial origin that parallels an adjacent, modern stream or river. Typically, afluvial terrace trends perpendicular to the modem coastline and lies between the walls of anentrenched valley and modem meander belt that occupies it.

Many investigators studying the Texas Coastal Plain confuse geomorphic surfaces,e.g., fluvial and coast-parallel terraces, with the sediments that form them. As a result,stratigraphic units, e.g., terrace and formation, and names, e.g., Prairie; Deweyville;Montgomery; and Williana, are used interchangeably to refer to both geomorphic surfaces andthe underlying sedimentary strata.

Plains. The Prairie and Lissie coast-parallel terraces are complex geomorphic surfaceswhich consist of an assemblage of smaller constructional geomorphic surfaces formed by theperiodic aggradation of fluvial systems and the periodic progradation of either deltaic orstrandplain systems. A constructional geomorphic surface, formed by either an active or relictfluvial or deltaic system, is designated as a "plain." Within the Louisiana Coastal Plain, Autinet al. (1988, 1991) demonstrate that the coast-parallel terraces consist of assemblages of relictalluvial, delta, and strandplains. Mapping by Van Siclen (1985, 1991) shows that this isapparently true of the coast-parallel terrace of the Texas Coastal Plain within the project area.Within the older coast-parallel terraces, surficial processes have either greatly modified orobliterated the constructional surface that once formed the surface of the older two coastparallel terraces.

An alluvial plain is a geomorphic surface that consists of the active meander belt of ariver or stream and its associated flood basins and abandoned meander belts. A meander belt isa surface that consists of an assemblage of constructional landforms created by the meanderingof a river while occupying a single course. These constructional landforms include the ridgeand swale topography of point bars, natural levee ridges, crevasse splays, abandoned meanderloops, and abandoned river courses. A flood basin, also called "backswamp," is an areaconsisting of swamp, lakes, or combination of both that comprise the low alluvial plainbetween meander belts (Saucier 1974:10-11).

A delta plain is the constructional surface of a delta complex. A delta complex consistsof the set of delta lobes fed from a common trunk channel. A delta lobe consists of a set ofsubdeltas and minor distributaries fed from a major distributary (Coleman and Gagliano 1964;

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Frazier 1967). Recent studies, e.g., Penland et al. (1987:1692), within the Mississippi RiverDelta region have confused geomorphic surfaces and subsurface sediments by incorrectlyextending the definition of a "delta plain" to include both the surface of the delta and sedimentsthat form this surface. By definition, a plain of any type is strictly a geomorphic surfaceconsisting of level or nearly level land. Also, the term "plain" lacks any reference to thedeposits that form it. Therefore, in this report, the term "delta plain" is reserved solely for thesubaerial, constructional surface of a delta complex.

Lithostratigraphy. The basic unit of lithostratigraphy is the formation. A formationis defined as a mappable body of sedimentary, volcanic, metamorphic, or plutonic rock whichcan be distinguished and delineated on the basis of its physical character, lithology, andstratigraphic position without reference to its cultural and paleontological content or age. Bydefinition, a formation is recognized by only the physical properties of the lithified orunlithified sediments that compose it (North American Commission on StratigraphicNomenclature 1983).

Within the coastal plain of Southeast Texas and adjacent Louisiana, various attempts,e.g., McFarlan and LeRoy (1988) and Van Siclen (1985:531,1991:651), have been made tosubdivide Pleistocene strata into formations which correlate directly with previously definedand mapped coast-parallel terraces. However, these attempts have repeatedly failed toconsistently recognize formations as defined by the rules of stratigraphic nomenclature anddemonstrate their correlation with the coast-parallel terraces (DuBar et al. 1991:584; Winker1979:22-24). Typically, the formations and members defined by such studies, e.g., Bernardand LeBlanc (1965), McFarlan and LeRoy (1988:424-426), and Van Siclen (1985:531,1991:651), fail to be true lithostratigraphic units (i.e., formations and members) because theyare defined as unconformity-bounded, depositional sequences and not by any distinctive andmappable differences in gross lithologic characteristics that would characterize a true formation.Additionally, these three coast-parallel terraces lack any one-to-one correspondence with the 11high frequency, high amplitude sea level fluctuations that have accompanied the Pleistoceneglacial cycles of the last 1.8 million years (Wornardt and Vail 1991:742). Finally, the coastparallel terraces are not the simple depositional surfaces envisioned by Bernard and LeBlanc(1965), Bernard et al. (1962), Doering (1935), Fisk (1939; 1944), and others. Rather, like theHigh, Intermediate, and Prairie Terraces of adjacent Louisiana, the coast-parallel terraces areapparently very complex geomorphic surfaces, consisting of mUltiple alluvial and deltaic plainsformed by separate periods of deltaic progradation and and fluvial aggradation (Aronow1988:15; Van Siclen 1985:531, 1991:651). The cyclic deposition of fluvial, deltaic, and other

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coastal sediments during the Holocene and Pleistocene Epochs have resulted in sedimentsconsisting of a complex set of interbedded sands, muds, and clays_ The heterogeneous natureof these sediments generally precludes the recognition of stratigraphic units based on gross orunique lithologic characteristics (Dubaret aL 1991; Winker 1979). Therefore, lithostratigraphyis generally an unusable stratigraphic tool within the Plio-Pleistocene sediments of the TexasCoastal Plain. However, on the scale of a site, lithostratigraphic units such as the Layer asdefmed by Stein (1990) are useful in archaeological research.

Bounding Discontinuities. Within the Texas Coastal Plain, the four major types ofbounding discontinuities that can be used to define and map allostratigraphic units aregeomorphic surfaces, fluvial erosion surfaces, flooding surfaces, and ravinement surfaces. Aspreviously discussed, geomorphic surfaces, e.g. coast-parallel terraces, fluvial terraces,meander belts, and delta plains, are the upper bounding discontinuity of depositional sequencesof Late Quaternary sediments. Typically, these surfaces are plains formed by the accumulationof alluvial, deltaic, or eolian sediments which exhibit landforms indicative of the processeswhich formed them, e.g. Bernard and LeBlanc (1965:Figure 4 and 5) and Van Siclen (1985).However, prolonged subaerial exposure of relict constructional plains to weathering and othersurficial processes will eventually obliterate any constructional landforms and form a subaerialerosional plain. Where buried intact, a geomorphic surface will be detectable by either laterallypersistent paleosols or truncated weathering horizons and abrupt changes in sedimentary facies(Autin et aL 1991:Figure 4, personal communication 1991; Winker 1979:Figure 9).

Complexes. Within the Texas Coastal Plain, few of these allostratigraphic units havebeen either adequately defined or named. In case formal stratigraphic units exist, an informalallostratigraphic unit, the "complex," is used. A complex consists of a single geomorphicsurface or temporally related surfaces and associated depositional sequence or sequences. Thedepositional sequence consists of the deposits of one or more depositional environments andpossesses distinct, regionally mappable bounding discontinuities. Typically, the complex isnamed for the geomorphic surface which forms part of it, although this practice is discouragedby the formal rules of stratigraphic nomenclature for the naming of formal alloformations.After it is named and described as a formal allostratigraphic unit, the use of a complex shouldbe abandoned (Whitney J. Autin, personal communications 1990; Autin et aL 1990; 1991).

Coast-Parallel Allostratigraphic Units. A coast-parallel complex is anallostratigraphic unit whose surface consists of a coast-parallel terrace. For example, theuppermost coast-parallel complex within eastern Brazoria County consists of a 10 to 25 m thick

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stratiform body of unfossiliferous silty clay with scattered elongated bodies of sand that trendroughly perpendicular to the coast and elongate bodies of shelly sands that parallel the coast.The lower bounding discontinuity of a coast-parallel complex is the paleosol developed withinthe buried coast-parallel terrace of an underlying terrace or the erosional unconformity at thebase of either a buried entrenched valley or meander belt. Gulfward, the fluvial facies gradelaterally into coastal and marine deposits (Autin et al. 1991, Winker 1979:44, 50).

A fluvial erosion surface is typically an undulating surface cut by either theentrenchment, lateral migration, or both of the thalweg of a river channel. This type of surfaceis an erosional bounding discontinuity that forms the base and sides of allostratigraphic unitsassociated with fluvial terraces and meander belts. Terrace scarps are subaerially exposededges of fluvial erosion surfaces (Figure 3-2) (Autin 1989, 1992).

A flooding surface is a local disconformity either at the base of or within estuarinedeposits created by a permanent rise in sea level. Within the Holocene valley fill beneathGalveston and the other coastal bays of Texas, two types of flooding surfaces, the baylineflooding and intermediate flooding surfaces, have been recognized (Figure 3-3). A bay lineflooding surface is a disconforrnity which separates either fluvial or older upland deposits fromoverlying estuarine deposits across which there is evidence for a permanent rise in sea level.Typically, a bayline flooding surface separates marsh or swamp deposits from overlying baysediments. An intermediate flooding surface is a disconforrnity which separates younger fromolder estuarine deposits across which there is evidence of an abrupt increase in water depthwithout any significant accompanying erosion. The intermediate flooding surfaces are markedby abrupt changes in faunal assemblages, color of sediments, geotechnical properties, andsometimes in lithology and seismic facies (Anderson and Siringan 1992: 10-11; Bhattacharyan.d.; Thomas 1990:99-100; Thomas and Anderson 1989:565).

A ravinement surface is a regional marine erosional surface produced by the erosionalretreat of the shoreface. The formation of this erosional surface consumes a thickness ofunderlying sediments of up to several meters thick, the subaerial dune and beach deposits, andthe upper shoreface of the barrier island to which the shoreface belongs. Within the GalvestonBay area, where a landward moving shoreline intersects the former subaerial interfluves andother coastal headlands, the ravinement surface cuts a few meters into the sediments of the

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'-''""''""'

'".. ?O~ ~ 5

10

5"J:: '-- -J.',,::Pb

Abandoned RiverChannelsI ib \

Pb

2015

10

5""

'\SF" - "1 '\P b ~ n D f f i " - E r o s i o n ~ o I Bounadanes 0oLEGEND 1 Width (Kilometers) 2,,"",."""" = acies boundary- =Bounding disconfonnityT77 =Paleosol or soil (depth ofstrips indicates development)

Al =Undifferentiated AlluviumBa =Backswamp Faciesc =Channel Fill FaciesOb =Overbank FaciesPb =Point Bar Facies

3

Figure 3-2. Hypothetical fluvial alloformations associated with an entrenched valley (source:Heinrich nd).


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i'====:::t:@w;;:::------ Modem SeaLevel------l

~ l t ! ~ ~ ~ LEGENDAF = AllofonnationAM = AllomemberBFS =Bayline Flooding SurfaceIFS = Intennediate Flooding SurfaceRS = Ravinement Surface"" ayhead Deltas D EsturaineSediments .., ', "

Figure 3-3. Allostratigraphy of estuarine sediments within the entrenched valley of theTrinity and San Jacinto rivers beneath Galveston Bay and on the adjacentContinental Shelf (modified from: Thomas 1990:Figure 2-22).

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coast-parallel terraces. Where landward moving shoreline intersects the valley fill underGalveston Bay, the ravinement surface cuts several meters deeper into the softer estuarinevalley fill (Numrnendal and Swift 1987:244-148; Swift 1968; Thomas 1990:211).

Fluvial Allostratigraphic Unit. A fluvial complex or alloformation IS anallostratigraphic unit composed of unconformity-bounded package of fluvial deposits lyingwithin an entrenched alluvial valley. Its upper bounding discontinuity consists of a terrace,which might be buried or partially buried, an erosional unconformity, or a combination of both(see Figure 3-2). The upper bounding discontinuity of an allostratigraphic unit associated withan active river channel is an alluvial plain or meander belt. Both units consist of a basalbounding discontinuity, a body of fluvial sediments that lies between the boundingdiscontinuities, and an upper bounding discontinuity. Typically, the basal boundingdiscontinuity is an erosional unconformity formed by scour at the channel bottom and, at thebank, collapse of cutbank of a channel (Autin 1989; 1992).

Fluvial sediments deposited by this channel overlie the basal unconformity. Generally,but not always, these sediments consist of a lower part composed of point bar sands andgravels, overlain by finer-grained and vertically accreted natural levee and overbank sediments(Walker 1984). Typically, the upper bounding discontinuity consists of both an exposed orburied fluvial terrace and an erosional unconformity formed during the formation of a youngeralloformation (Autin 1989, 1992).

The scarp that defines a fluvial terrace is the exposed edge of the basal boundingdiscontinuity (see Figure 3-2). As a result, a scarp, as reflected by differences in surfacemorphology, soil development, and thickness of overbank deposits, separates geomorphicsurfaces of differing ages. Also, the terrace scarp separates the fluvial complexes consisting offluvial sediments that can, but not always, differ in type and distribution of facies (Autin 1989;1992).

Two general models have been used to explain the origin of fluvial complexes andalloformations. First, many investigators, e.g., Thomas (1990) and LeBlanc (1991a) haveinterpreted fluvial terraces and, by implication, their associated fluvial allostratigraphic units interms of the classic model of Fisk (1944, 1939) for the creation of coast-parallel and otherterraces. Fisk (1944) concluded that a terrace is the result of fluvial aggradation followed by aperiod of fluvial entrenchment. This model implies that the aggradation of a fining-upwardsequence in response to a rising base-level, typically a relative rise in sea level, constructs a

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floodplain. The floodplain becomes a terrace when it is abandoned by the fluvial system as aresult of entrenchment in response to a dropping base-level, typically a relative drop in sealevel. According to this model, each fluvial terrace and its associated allostratigraphic unit isinterpreted to represent the fluvial response to a single rise and fall in base level, which iscommonly assumed to be sea level (Autin 1992:241).

Finally, Autin (1989, 1992) and Blum (1990:80-81) have demonstrated that theformation of fluvial complexes and alloformations is the result of geomorphic processes morecomplex than simple changes in base levels. Within the Amite River Valley of Louisiana,Autin (1992:240) found that a temporal clustering of cutoffs initiates a period of meander beltinstability. This response results from changes in one or more geomorphic influences, e.g.,climate, base-level, etc., which cause an imbalance between river hydrology and sedimentdelivery. Because of the increased rates of channel cutoffs, the channel pattern locallystraightens which favors channels avulsion over lateral accretion. Avulsion creates a newchannel which truncates the older alluvium and produces the initial lateral boundaries of analloformation. After a few decades to centuries of instability, a new stable meander belt isestablished with a channel pattern and slope equilibrium with the new conditions of riverhydrology and sediment delivery (Autin 1992:240). Significantly, Autin (1989, 1992) andBlum (1990:80-81) demonstrate that to simply interpret all fluvial alloformations, fluvialcomplexes, and their terraces solely as the result of rises and falls of sea level is a grosslysimplistic explanation that can be wrong as often as it is right.

Estuarine Allostratigraphic Units. A estuarine complex or alloformation is anallostratigraphic unit composed of unconformity-bounded package of fluvial deposits lyingwithin an entrenched alluvial valley (see Figure 3-3). Landward of the shoreface of associatedbarrier island, its upper bounding discontinuity consists of the bottom of the bay and the deltaplain of the bayhead delta filling the flooded valley. Seaward of the of the shoreface ofassociated barrier island, the upper bounding disconformity is the ravinement surface formedby the trangressing shoreface. The basal bounding disconformity consists of the baylineflooding surface which separates the sediments of this allostratigraphic units from those of theunderlying fluvial allostratigraphic units.

Subregional bounding disconformities, previously defined as intermediate floodingsurfaces, occur within an estuarine deposits that lie between the bayline flooding surface andthe ravinement surfaces (see Figure 3-3). An intermediate flooding surface is typicallyassociated with correlatable seismic reflector, nearly flat stmcturally with less than 4 m of relief

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on it, and pinches out against the bayline flooding surface where the structural elevations ofboth surfaces are equal. The intermediate flooding surface subdivides an estuarineallofonnation into into a series of discontinuity-bounded sedimentary packages, equivalent toallomembers. Each of these packages consist of eustarine-bay deposits with a wedge ofbay head delta deposits at its landward edge directly underlying this flooding surface. At theseaward end of the intennediate flooding surface, it commonly truncates barrier island, spit,and tidal inlet deposits where i t merges with the ravinement surface.

Upland Surfaces and ProcessesFisk (1939,1944) and Fisk and McFarlan (1955) considered each of the coast-parallel

terraces, called "coast-wise terraces," to be the result of alluviation followed by a period ofextensive fluvial entrenchment. Fisk's model implied that coast-parallel terraces developed bythe aggradation of a single depositional sequence in response to rising base level. Lowering ofbase level was presumed to cause renewed entrenchment, leaving the abandoned coastal plainas a coast-parallel terrace. Thus, the model of Fisk (1939,1944) claims that each coast-parallelterrace and the sedimentary deposits which fonn it are the product of a single depositional cycleand represent an individual sea level cycle (Winker 1979).

Based upon Fisk's model many investigators have assumed as fact that each of themapped coast-parallel terraces which have varied in number between 3 to 4 are fonned by asingle depositional cycle. Furthennore, it has been presumed that each of these depositionalcycles consists of a lithostratigraphic unit, i. e., fonnation, that should be recognizable on thebasis of gross lithologic characteristics. As a result, numerous investigators, e.g., Bernard etal. (1962; 1970), Guevara-Sanchez (1974), Murray (1961), and Solis (1981) have attempted tosubdivide the Pleistocene strata that underlie the coast-parallel terraces of Texas and adjacentLouisiana into fonnations that directly correlate with each of of these terraces. However, theseattempts have failed to consistently define any such fonnations within the subsurface anddemonstrate any correlation with the coast-parallel terraces (DuBar et al. 1991; Winker 1979).Also, the fonnations and members defined in some studies, e.g. Bernard et al. (1962; 1970)and Van Siclen (1985, 1991), fail to be true lithostratigraphic units (i. e. formations andmembers) as they are defined on the basis of either depositional cycles or boundingdiscontinuities rather than any distinctive and mappable differences in gross lithologiccharacteristics of these stratigraphic units.

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In addition to problems with the subsurface stratigraphy, the coast-parallel terraces lackthe proposed one to one correspondence with glacial, eustatic sea level fluctuations envisionedby Fisk (1939, 1944) and Fisk and McFarlan (1955). A review of the Midwest glacial recordby Richmond and Fullerton (1986) demonstrates that there has been at least 13 Pleistocene and3 Pliocene glacial-interglacial cycles instead of the previously accepted 4 glacial cycles.Wornardt and Vail (1991) demonstrate that at least II high frequency, high amplitude sea levelfluctuations have accompanied the Pleistocene glacial cycles of the last 1.8 million years.

Finally, the coast-parallel terraces are not the simple depositional surfaces envisionedby Fisk (1939; 1944), Doering (1935), and Bernard et al. (1962, 1970), and others. Ratherthey are complex geomorphic surfaces, each of which has been formed by multiple periods ofdeltaic and alluvial deposition. Recent research within the Mississippi Alluvial Valley and thecoastal plain of Louisiana demonstrates that the individual coast-parallel terraces areallostratigraphic complexes that consist of multiple, geomorphic surfaces. Each of thesegeomorphic surfaces forms the surface of unconformity-bounded sedimentary sequences,called "alloformations." Because a complex consists of mUltiple components of varying origin,simple casual relationships between the formation of a complex and eustatic sea level events arenot valid (Autin et a11990, 1991).

Van Siclen (1985,1991) assumes that the aggradation of the alluvial-deltaic plains thathe has mapped occurs during rising sea level and subsequent high stands. Current modelsconcerning the development of stratigraphic sequences strongly indicate that plain-wise alluvialaggradation actually occurs during the maximum high stand and between it and the inflectionpoint offalling sea level, the "F inflection point" of Posamentier and Vail (1988: 131). Duringrising sea level, net alluvial aggradation is limited to the confines of a preexisting entrenchedvalley as is currently is occurring within the modem Texas Coastal Plain (Posamentier and Vail1988:143-145).

Coast-Parallel Terraces

Starting with Doering (1935), the coastal plain of Southeast Texas has been recognizedas consisting of a series of geomorphic surfaces called "coast-parallel terraces." Typically,researchers have mapped these coast-parallel terraces on the basis of topographic expression,degree of seaward slope, degree of preservation of constructional topography, types of soilcatenas, and chronologic sequence. Erosional escarpments and depositional on laps form theboundaries between coast-parallel terraces (Winker 1979:15-20). The original coast-parallel

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terraces of Doering (1935) have been redefined and remapped many times as detailed byWinker (1979:15-20). Currently, DuBar et al. (1991:585-587) and Winker (1991) recognizethree such terraces, the "Beaumont," "Lissie," and "pre-Lissie" coast-parallel terraces, alongthe Texas coast. Within Louisiana, their Beaumont Terrace includes the Prairie Terrace of Fisk(1939), Saucier and Snead (1989), and others.

Prairie ComplexThe lowest of these coast-parallel terraces forms the surface of a coast-parallel complex,

designated as the "Prairie Complex" by Autin et al. (1991:556-558) and Saucier and Snead(1989). As previously explained, a coast-parallel complex is an informal allostratigraphic unitthat consists of a set of related geomorphic surfaces which form a coast-parallel terrace and thedepositional sequences associated with these surfaces. The lowest of the coast-parallelterraces, called the "Prairie Terrace" for this study, by definition forms the surface of thePrairie Complex. The Beaumont Formation (alloformation?) consists of the deltaic, fluvial,and coastal depositional sequences that form this coast -parallel terrace.

Prairie TerraceWithin Louisiana and Texas, Autin et al. (1991:556-558) considers the lowest coast

parallel terrace that forms the surface of the Prairie Complex to be properly called the "PrairieTerrace." However, with the exception of a small, inland portion of it within Louisiana,Winker (1979:28, 1991) maps this same coast-parallel terrace as the "Beaumont Terrace"within both Louisiana and Texas. These papers agree that the Prairie-Beaumont division ispurely arbitrary and only one name should be used for the entire coastwise terrace within itsextent across Mississippi, Louisiana, and Texas. However, they disagree on whether thisprominent coast-parallel terrace should be called either the "Beaumont Terrace" or the "PrairieTerrace" in its entirety.

In this report, the designation of this coast-parallel terrace in its entirety as the "PrairieTerrace" by Saucier and Snead (1989) is used. Initially, Hayes and Kennedy (1903:27-29)originally defined the "Beaumont" on the basis of its lithology. Later, Deussen (1914, 1924)and Sellards et al. (1932) described the Beaumont as a lithostratigraphic unit. Doering (1935)later informally extended the designation "Beaumont" to the geomorphic surface presumed tobe associated with the Beaumont Formation. In contrast, the Prairie Terrace was defined byFisk (1939) as a geomorphic surface purely on the basis of surface morphology. Fisk (1944)

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later extended the designation "Prairie" to the sediments underlying this terrace withoutformally describing, defining, and naming it as a valid stratigraphic unit. Because of theoriginal usage of these names and the lack of a formal definition for both the Prairie Formationand Beaumont Terrace, "Prairie" is used to designate the coast-parallel terrace and "Beaumont"is used to designate the sediments that form it. Besides allowing for the consistent designationof this prominent coast-parallel terrace across the entire Gulf Coastal Plain, it also resolvesproblems with the usage of the term "Beaumont" for both a geomorphic surface and thesediments underlying it noted by Winker (1979:23-24). Finally, it allows for the consistentrecognition of the Beaumont Formation which extends eastward into Louisiana as far asJefferson Davis Parish.

The Prairies Terrace is the outermost, lowest, and widest of the coast-parallel terraceswhich extends from the coastal plain of Mississippi, across Louisiana, Texas, and into Mexico.The continuity of the Prairie Terrace is only interrupted where the floodplains of theMississippi, Brazos, Colorado, Trinity, Sabine and other rivers cut through it and the SouthTexas eolian sand sheet buries it. Well-preserved depositional topography that includes relictmeander belts, relict delta lobes, and a strandplain and barrier island system characterize thePrairie Terrace. This coast-parallel terrace is crossed by numerous low-relief, silty to sandymeander belts, which often exhibit relict high-sinuosity channel patterns and spread in a radialpattern. The relict high-sinuosity channel systems are often associated with well-definedmeander belt ridges (Figure 3-4). Rarely, these channel systems end in recognizable deltaplains. However, the majority of this coast-parallel terrace consists of relict flood basins,backswamps, and interdistributary bays in which clayey soils, often vertisols, have developed.Numerous, enigmatic circular to elliptical hillocks commonly called "pimple mounds" cover thePrairie Terrace. A discontinuous series of coastal sand ridges interpreted to be either a relictstrandplain or barrier island complex extends across the Prairie Terrace from Mexico along theTexas coast into Southwest Louisiana. These sand ridges have been designated by a variety ofnames such as "Ingleside Terrace," "Ingleside Barrier trend," Ingleside Strandplain", and"Ingleside Barrier." For this report, it will be simply designated in a nongeneric fashion as theIngleside sand ridge (Aronow 1971, 1988, 1990; Barton 1930; Bernard et al. 1962, 1970;Dubar et al. 1991; Morton 1988; Price 1933, 1958; St. Clair et al. 1975; Van Siclen 1985,1991; Winker 1979).

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J)

.... .GULF OF

MEXICO

'.-, LEGENDIV = Oberlin alluvial plainV = Almeda alluvial plainVI = Eunice alluvial plainVIII = Modern alluvial and deltaic plians

o . ~ : : ~ I t ~ : ~ ~ . ~ ? .. :-"o.f'...,-- U l ~ O O I l U OIII1EU-< ~ ' s " , . c : , : " ' : l ; ~ :'-ont, ...... TU'IU.(;oE. C O ~ U C f t

f; ~ . . . . , . . . . . , . . . , 1""11 ...7'$, >, . fro,. ,"!W".,.... , ~ . . . . .

~ < , : f : k / . : : . : ~ I . d ~

Figure 3-4. Ma p of meander belt and distributary ridges within the westernGalveston Bay region (modified from Van Siclen nd).

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The Prairie Terrace is a complex geomorphic surface composed of smaller geomorphicsurfaces such as alluvial plains, delta plains, and the Ingleside sand ridges (see Figure 34).Within the Prairie Terrace, Van Siclen (1985, 1991) has mapped 3 alluvial-deltaic plains,which he calls "coastal terraces," within the Houston-Galveston, Texas region. He interpretsthese alluvial-deltaic plains to represent the surface expression of members within of theBeaumont Fonnation. However, because the Beaumont Formation consists of unifonn,randomly interstratified sands, silts, muds, and clays, it is highly unlikely that lithostratigraphicunits such as members can be recognized within it. These plains, if correctly mapped, morelikely are geomorphic surfaces that fonn the upper boundary of allostratigraphic subdivisionssimilar to those recognized within the Prairie Complex of Louisiana by Autin et al (1991:556-558). However, a considerable amount of additional detailed subsurface research will beneeded to confinn, define, name, and map the allostratigraphic subdivisions associated withthese plains.

Beaumont Formation - Beaumont AllojormationAt this time, confusion exists as to how the Beaumont Fonnation, should be defined.

The confusion arises, because it was never properly defined with either a designated typesection, an accepted thickness, or a specific basal lithologic identifier (Aronow 1988b:3). Inaddition, within Southeast Texas, the subsurface Pleistocene strata, except for a fairly laterallypersistent, thick sand, consist of fairly unifonn, randomly interstratified sands, silts, muds,and clays. On the basis of gross lithology, only two major lithostratigraphic units have beenconsistently recognized in the subsurface Pliocene-Pleistocene sediments of the literature. Thelaterally persistent sand has been infonnally named as the "Alta Lorna sand" within SoutheastTexas by hydrogeologic studies such as Rose (1943) and Kreitler et al. (1977). These stud.ieshave consistently assigned the 150 to 500 m of interstratified sands, silts, muds, and clays thatoverlie the Alta Lorna sand to the Beaumont Formation (Winker 1979:22-23; DuBar et al.1991 :585-586).

Other researchers, e.g., Bernard et al. (1962; 1970), McFarlan and LeRoy (1988:424-426), and Murray (1961:Figure 8.26), have defined the Beaumont Formation and equivalentPrairie Fonnation as the deposition cycle that forms the lowest of the three coast-parallelterraces. As defined by these studies, the Beaumont Formation consists of a sequence ofsediments recognized not on the basis of its gross lithologic characteristics, but rather by itsbounding discontinuities. As a result, their Beaumont and Prairie Formations fail to belithostratigraphic units, e.g., a formation, but rather they are allostratigraphic units such as

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alloformations or allogroups (North American Commission on Stratigraphic Nomenclature1983:865-866)_

By such definitions, the Beaumont alloformation forms only the upper portion of thePleistocene sediments that lie above the Alta Lorna sand. For example, Aronow (1991:9)presumes the Beaumont alloformation to consist of the uppermost fluvial depositional sequenceand contemporaneous deltaic and coastal deposits that underlie each of the plains which formthe Prairie Terrace. By this definition, the Beaumont alloformation consists only of the upper15 to 20 m of the Pliocene-Pleistocene sediments that overlie the Alta Lorna sand instead of thisentire 150 to 500 m thick sequence. If the Beaumont alloformation is presumed to consist ofone to three stacked depositional fluvial sequences, then it would comprise the upper 30 to 60m of the sediments overlying the Alta Lorna sand (Aronow 1988b:3). Within southern HarrisCounty, the allostratigraphic unit which Bernard and LeBlanc (1965:174) and Bernard et al.(1962:Figure 14) call the Beaumont "Formation" is 40 m thick.

Either the Beaumont alloformation or the uppermost part of the Beaumont Formationconsists predominantly of clayey, fine-grained sediments. These clayey deposits contain thin,discontinuous beds of sands, silts, and clayey sands and silts and thick, often stacked channelsands. The clayey sediments deposited by the Brazos River often have reddish colors inheritedfrom eroded Permian and Triassic "red beds" within Northeast Texas. Within the fluvialfacies, slickenslides, pedogenic carbonate, and plinthite concretions associated withdiscontinuous, truncated paleosols are common characteristic of these sediments (Aronow1988b, 1990a, 1990b, 1991a; Winker 1979).

The determination of a firm estimate of the age of the Prairie Complex will be aunresolvable controversy until a consensus is developed concerning a specific definition of theBeaumont Formation. For example, as defined by Rose (1943) and Kreitler et al. (1977), theBeaumont Formation probably represents fluvial-deltaic and coastal deposits which haveaccumulated over the latter part of the Pliocene and all of the Pleistocene Epochs. As definedby Aronow (1991:9), the Beaumont alloformation consists of fluvial-deltaic and coastaldeposits which have periodically accumulated during the Sangamonian, Early Wisconsinan,and Middle Wisconsinan Substage (Dubar et al. 1991; Thomas 1990; Winker 1979).Individual depositional sequences and alluvial plains likely accumulated in response to themaximum high stand of sea level during the Sangamonian and the lower than present highstands during the Wisconsinan much like depositional sequences within the Prairie Complex ofLouisiana (Autin et al. 1991:558).

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As demonstrated for the Prairie Terrace of Louisiana by Autin et al. (1991:556-558),the Prairie Terrace of the Texas Coastal Plain undoubtedly consists of geomorphic surfaces thatformed during both the Wisconsinan and Sangamonian Stages with older geomorphic surfacesand deposits possibly being present. As a result, the question concerning the age of theBeaumont Formation (or alloformation) and associated Prairie Terrace should not be whetherthey formed during either the Sangamonian or part of the Wisconsinan Stages, but rather whenduring the Sangamonian and Wisconsinan Stages it formed. However, it has been definitelyestablished that the Prairie Terrace and the sediments which form it were created prior to to thehuman occupation of the Texas Coastal Plain.

Possible Unnamed Stratigraphic UnitOngoing work by Frederick (1991, personal communication 1991) infers that eolian

sediments covers large portions of the Prairie Terrace of Southeast Texas and SouthwestLouisiana. He proposes that this eolian blanket consists of silty sands within the middlecoastal plain of Texas which decrease progressively eastward in grain size to almost 100percent pure silts within southwestern Louisiana. Presumably these eolian deposits have beenreworked by various processes to form the innumerable pimple mounds which cover the coastparallel terraces. Similarly, Aronow (1992:2) concludes that the sand and silty sand epipedonsgreater than 1 m thick and characteristic of grossarenic soils, e.g. the Kennedy and Boy soilsseries, are nonpedogenic, possibly eolian, in origin. Aronow (1992:2) claims that these soilsare associated with subdued, stabilized dune-like topography. Frederick (1991) concludes thatthese sediments accumulated during Middle and Late Holocene times. Aronow (1992:2)proposes that the sediments formed during periods of aridity between either 6,500 to 4,500 or1,000 to 800 radiocarbon years B.P. Additional research, including detailed sedimentologicaland pedological studies are needed to determine the validity, distribution, and age of thisunnamed stratigraphic unit.

Surface ModificationAs the preceding discussion demonstrates, the landscape of the Prairie Terrace consists

of relict landforms. With the cessation of coastal processes and the abandonment of individualalluvial and deltaic plains within it, the Prairie Terrace has started to evolve into an erosionalcoast-parallel terrace. Pedogenic processes, sheet flood erosion and deposition, eolianprocesses, the development of entrenched drainage systems, and lateral retreat of valley wallshave substantially modified the surface of this terrace. The overall effects of these processes is

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to obscure and, eventually, obliterate preexisting constructionallandfonns_ Some of the morecontroversial and archaeologically significance products of this modification are enigmaticlandforms called "pimple mounds" and the previously discussed possible unnamedstratigraphic units (Aronow 1988a, 1990a:3l; Gustavson 1975; Fisheret al. 1972).

Pimple MoundsPimple mounds are innumerable, enigmatic circular to elliptical hillocks that are a

common landfonn found not only on the surface of Pleistocene coast-parallel terraces such asthe Prairie and Lissie Terraces, but also on the Holocene floodplains of Clear Creek, BuffaloBayou, Greens Bayou, and other drainages within Harris County. These hillocks areapproximately 15 to 60 m in diameter and rise as much as 1.2 m above the intennound terracesurface. Typically, the relief of a pimple mound results from the thickening of the A and Ehorizons of their sola (Aronow 1988:103, 1990:37-41). The pimple mounds which occurupon the floodplain of modem floodplains have been called by other names such as "floodplainmounds" and "sandy mounds." Because clear differences in size, shape, or structure betweenthe mounds which occur upon floodplains and the coast-parallel terraces have yet to bedocumented, all of these sandy hillocks found within Southeast Texas are designated "pimplemounds" for this study.

Discussions concerning the origin of pimple mounds has generated a immense anddiverse literature as documented by Aronow (1990a:37-44) and Washburn (1988). Thetheories concerning the origin of pimple mounds include: 1. residual hillocks left after eitherwind or sheetflood erosion possibly with a core of tree-bonded surficial material; 2.accumulations of wind-transported sediment around around clumps of vegetation similar tocoppice dunes; 3. eolian accumulations whose sites were started by, or topographicallyenhanced by, erosional processes; 4. fluvial bedfonns later modified by eolian erosion anddeposition; 5. mounds fonned by the "fluffing up" of, or the decreasing the bulk densities ofsolum materials and centripedal transport of surface materials by burrowing animals; and 6.complex polygenetic landfonns that result from the middle to late Holocene modification of apreexisting eolian drape. At this time, neither a commonly accepted nor solidly documentedexplanation exists for the origin of pimple mounds (Aronow 1990a, Frederick 1991; Voellingeret al. 1987:91-93).

At least two major hypotheses can be discounted for the origin of pimple moundswithin Southeast Texas. Numerous paleoclimatic studies all agree that even during the most

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severe glacial period, e.g., the Wisconsinan glacial maximum between 22,500-14,000radiocarbon years B.P., paleoclimates were insufficiently cold to form patterned ground(Bryant and Shafer 1977:7-13; Bryant and Holloway 1985). Also, Berg's (1990) proposalthat seismic vibrations from earthquakes produced pimple mounds can be discounted, becauseof the lack of significant seismicity within Southeast Texas (Algermission 1969). Moreimportant, the interfering waveforms which produced the simulated "pimple mounds" areartifacts of Berg's (1990) modeling technique that any earthquake within Southeast Texaswould fail to produce (Bridget Jensen, personal communication 1992).

Possible Unnamed Stratigraphic UnitThe possible unnamed stratigraphic unit is an important modification of the surface of

the Prairie Terrace. Because it is might be Holocene in age and, thus, may contain buriedPaleo-Indian and Archaic archaeological deposits. In addition, these deposits likely resultedfrom climatic events significant enough to have impacted subsistence human patterns. Also, itis this unit that forms the bulk of pimple mounds. It is uncertain whether the origin of pimplemounds and this stratigraphic unit are concomitant as is the case of many constructionallandforms. Therefore the existence and formation of this unit is a research question that shouldbe addressed separately from questions concerning pimple mound formation (Frederick 1991,personal communication 1992; Voellinger et al. 1987:91-93).

Entrenched Drainage SystemsBuffalo Bayou, Clear Creek, and Double

Geomorphology and Geoarchaeology of Galveston Bay

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