SURVEY AT A FOLSOM SITE IN THE BRAZOS RIVER DRAINAGE ON THE SOUTHERN PLAINS

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Introduction
. The site lies within the margin of an extensive dune field containing active and stabilized dunes. Aeolian dune sands apparently buries the sites shortly after it was abandoned (Holliday, 1997:161).
As part of the continuing investigation into hunter-gatherer use of the Adair-Steadman site, fieldwork for the past five years (2015-2019) consisted of annual 1-day pedestrian surveys to map and collect newly exposed artifacts. An unmanned aerial vehicle (UAV) drone was flown over the site (2017) to create a detailed 3D model for future research and monitoring. Luminescence dating of sediment samples collected in 2013 was completed in 2016 (Hurst and Johnson, 2016a). Results of this work provided important clues to the impact of bioturbation at Adair-Steadman.

PHYSIOGRAPHIC SETTING
Adair-Steadman is situated on the Rolling Plains of Texas that is characterized by low topographic relief. The Brazos River is the largest drainage in the region and extends from the Llano Estacado to the northwest to the Gulf of Mexico in the south.
Prior to historic farming, the area is characterized by short or mixed grass prairies with cottonwood and willow along streams and riverbanks. Drought resistant species of brush and scrubby woodland would have been found in the upland areas, away from water sources (Shelford, 1963).
Grey wolf and black bear once were common but were extirpated from the area, as was black-footed ferret. The carnivore guild also contained coyote, gray fox, mountain lion, bobcat, ringtail, raccoon, badger, and skunk. Bison, pronghorn, and deer were the most common large game herbivores (Schmidly, 2004;Jones et al., 1985). In addition to mammals, numerous species of lizard, reptile, and bird also could be found.
The climate today is strongly continental, meaning it has large temperature ranges that are not influenced by large bodies of water. Currently, the region receives ~61cm of rainfall annually, most of which falls in the spring through autumn (Bomar, 1995).
Summer rains occur primarily in the form of severe thunderstorms that arise as a result of daytime heating and the absence of high pressure. Summer droughts, however, also occur due to high pressure that can dominate the region (Barry, 1983;Haragan, 1983:67). Precipitation in the form of winter snowfall is minimal. Conditions are much wetter during the late Pleistocene with an increase in sea, river, and lake levels (Baker, 1983;Friedman, 1983;Smith and Street-Perrott, 1983). This rise is due to an increase in effective precipitation and a reduction in the rate of evaporation presumably due to climatic changes.  By the end of the Pleistocene, a drying trend was underway. Conditions still were much moister than those in the region today. Water levels, however, were beginning to drop and lakes were becoming seasonal (Smith and Street-Perrott, 1983;Reeves, 1973). Between 12,000 and 11,000 radiocarbon yrs BP, an equitable, humid, maritimelike paleoclimate existed that lacked season extremes, with a lower mean annual temperature than today, cooler summers, and warmer winters that lacked extended freezing conditions (Johnson, 1991). A winter rainfall pattern was coupled with cool dry summers. Savannas or scrub grasslands existed throughout the Southern Plains (Bryant, 1977;Lundelius et al., 1983).
The time of 11,000 radiocarbon yrs BP marks the biotic and ecosystemic end of the Pleistocene conditions on the Southern Plains (Baker, 1983;Lundelius et al., 1983;Johnson, 1986Johnson, , 1987Johnson, , 2017Ferring, 2001). Available moisture and humidity levels continue to decrease, reflecting the intensification of the warming and drying trend and more marked seasonality. Mild winters persist with occasional periods of freezing conditions. Yearly precipitation is decreasing although enhanced winter rains appeared to have continued. Native trees form a component of the vegetation community, generally restricted to wooded waterways. The grassland is a mixed prairie, albeit with a different composition than today's mixed prairie (Humphrey and Ferring, 1994;Nordt et al., 1994;Holliday, 1995;Holliday et al., 2008;Fredlund et al., 2003;Johnson, 2007).
Ancient bison emerges in the early Holocene fauna as the major grazing herd herbivore, with deer and pronghorn continuing as large browsers.

THEORETICAL PERSPECTIVE
The Lubbock Lake Landmark regional research approach is focused on people-land relationships (Johnson, 1987(Johnson, , 1991(Johnson, , 2002 Within the broader regional research program, cultural continuity and change within hunter-gatherer economic systems are being examined in relationship to changing ecosystems. The major hunter-gatherer subsystems reflected in the archaeological record are subsistence and technology. The basic cultural assumption is that inferences concerning hunter-gatherer technology and subsistence can be made from analysis of the lithic, faunal, and floral materials. The approach to people-land relationships is in the context of a technologicalenvironmental explanation given the concept that culture is a people's adaptation to the environment. The interaction, therefore, between culture and environment is facilitated by technology (Bettinger, 1980;Hayden, 1981). A landscape approach is used in examining the interaction between people and their environments and land use patterns as people generally are involved actively in a dynamic relationship with the landscape.
This perspective is a mechanism to determine the way people perceive, interact with, and transform the environment (Savage, 1990). A landscape approach provides a framework in which to assess land use and regional patterns and examine resource exploitation (Rossignol and Wandsnider, 1992).

The continued exploration into the record of cultural occupations on the Southern
Plains had at least one goal and several objectives. objective 1: to delineate the lifeways of the aboriginal hunter-gatherer peoples through landscape utilization and household maintenance tasks.
objective 2: to examine subsistence strategies through optimal foraging theory, risk management, and nutritional parameters by inferred behavioral patterns revealed in excavated materials using precise recovery techniques, mapping, and documentation.
objective 3: to analyze site type, landscape and resource utilization, movement patterns, and timing of activities to provide information on the structural organization of hunter-gatherers.

Field Methodology
The areal extent of investigation at Adair-Steadman covered 2.92ha (7.22ac).
The fieldwork consisted of 100% pedestrian survey. Lubbock Lake Landmark methodology (Johnson, 1987) was followed.
Pedestrian survey was completed by crew members walking ~2m linear transects across the entire site. Artifacts were flagged, their provenience recorded using a Trimble R8 GPS base station. The GPS data points contained sub-centimeter accuracy.
A UAV was used to document the Adair-Steadman landscape. A DJI Inspire 1 UAV carrying a high resolution 16 megapixel Zenmuse X5 camera was flown over the site at ~30 m. Images were captured across the entire site with a 70-80% overlap at an oblique angle. Agisoft Metashape software was used to convert the images into a 3D dense cloud model. The software also was used to create a digital elevational model and georeferenced orthomosiac image of the site's surface to delineate topographic features.

Analytical Methodology
Lithic material was sorted into two categories, either tool or debitage, and a basic analysis was completed. Tools were measured (length, width, and thickness) and material type and source were recorded. Diagnostic tools were identified and placed within the regional cultural typology. Non-diagnostic tools were categorized as uniface, biface, or core.
Debitage was divided further into flakes (debitage with intact platforms) and debris (debitage without intact platforms) (Crabtree, 1972;Cotterell and Kamminga, 1979;Sullivan and Rozen, 1985;Andrefksy, 1998). Regardless of the completeness of the flake, measurements of maximum length, width, and thickness were taken for all identified flakes. Platform maximum length and width measurements were obtained using digital calipers (Mitutoyo Corp. 0.01-150mm).
A basic nominal flake platform (adapted from Andrefksy, 1998) was followed.
Platform type was assigned to one of five categories, these being flat, complex, Cluster analysis. Clusters then were mapped within Quantum GIS. A cluster was defined arbitrarily as 10 or more lithics within a 5m area.

RESULTS
The 2015 through 2019 work consisted of an annual 1-day surface survey (Table 1). A total of five field workdays, therefore, was completed. The purpose of the field work was to map and recover any additional artifacts exposed over the year from erosion in order to investigate further the spatial distribution of artifacts.           Biface TTU-A7-67791 ( Figure 7; Table 7) was a mid-section of a bifacial core or tool. It was completely flaked on both sides with no cortex remaining.

Field Season
A crew of four people completed a 100% pedestrian survey during the 1-day 2018 season. Six lithic debitage were mapped and collected throughout the Adair-Steadman site area (Figure 12; Tables 10-11). Five pieces of debitage (60%) were chert that was sourced to the Edwards Formation. One piece (20%) of debitage was chert that was sourced to the Ogallala Formation gravels. The debitage consisted of three flakes and three pieces of debris. The flake platforms were classified as abraded (n=2; 67%) and flat (n=1; 33%). The presence of both abraded and flat platforms indicated that these flaked were detached from both bifacial and blocky core types (e.g., Andrefsky, 1998).

Field Season
A crew of two people completed a 100% pedestrian survey during the 1-day 2019 season. No objects were found during survey. A thunderstorm that had just finished precipitated a significant amount of rainfall onto to the site prior to the survey. The rain most likely impacted the ability to view lithic material on the surface.

Spatial Analysis
The spatial distribution of lithic artifacts (n=47)   Test excavation at Adair-Steadman from 2011-2013 in unit 36N11E uncovered a clay band that consisted of a layer of lamellae within sandy sediments. Clay bands were a pedogenic feature that is characteristic of soils formed in sand (Holliday, 2004:112).
The presence of the clay band in the Adair-Steadman dune indicated that the dune had remained stable at some point in time in order for the clay to accumulate as a layer. To test this hypothesis, OSL samples were collected above and below the clay band (Figures 14, 15). This unit was chosen for sampling because it was the most deeply excavated unit.
The OSL samples were collected by hammering light-tight PVC cylinders into the side of the test-unit profile (e.g., Feathers et al., 2006). A wooden block was used to buffer the impact of hammer blows at the end of the pipe. Both ends of the PVC cylinders were capped and tapped to ensure the sediment samples were not impacted by light. Optical stimulated luminescence was applied to 180-212µm quartz grains. The sensitivity of the quartz grains was not high resulting in equivalent dose values of UW 3016 (n = 54), UW 3017 (n = 63), UW 3018 (63), and UW 3019 (60). The average acceptance rate was 5.4%, and sample UW 3016 was lower at 3.7% due to its location closer to the surface. All of the samples were bi or tri modal either from mixing or partial bleaching (Figures 16, 17, 18, and 19).
The youngest grains represented by the first component was 20th-century in age for UW2016 and a 500 year age for UW3019. The first component of these samples were likely sand grains being transported downward from the surface.
In all of the samples, the second and third components were distinct, with no higher precision points between them. Very old grains were represented by the third and fourth components. These older grains within the sample were likely derived from upward admixture of grains from a lower stratum. A likely source for the third component of sample UW3016 is from upward movement of sand grains from the lower sand layers below the clay lamellae.