Starting at Rock Bottom: A Peculiar Central Texas PreClovis Culture

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Posy Foster
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1 Starting at Rock Bottom: A Peculiar Central Texas PreClovis Culture Background Brushy Creek grades, overall, west-northwest (WNW) to east-southeast (ESE) through the easternmost portions of the central Texas Hill Country, in southern Williamson County. The headwaters originate ca. 15 miles west of the Balcones Escarpment, and the creek moderately grades out of the Hill Country and onto the Texas Blackland Prairies, ca. 5 miles to the east of the escarpment. Brushy Creek gently grades through the Blackland Prairies, eventually draining into the Brazos River. The Brazos River meanders through the Gulf Coast Prairies,eventually draining into the Gulf of Mexico, ca. 190 miles southeast of the Brushy Creek headwaters. Until recently, most of Brushy Creek, in the area of this author s research, was unexplored, mainly due to private ownership of very large tracts of farm and ranch land, bordering the northwest and southeast banks of the creek. One very significant archeological excavation, which occurred ca. 8 miles upstream, on Brushy Creek, conducted by the Texas Archeological Research Laboratory (TARL), and formally reported on in 1998, is The Wilson-Leonard Site. Dr. Michael Collins and an entourage of archeologists, osteologists, geologists and other specialists produced an immense amount of information concerning this long inhabited creek: The site occurs as multiple cultural levels buried in layers of natural valley fill, which accumulated to a thickness of six meters (19.5 feet) over approximately the last 12,000 years. This is the most complete cultural sequence at any single site in central Texas and one of the more complete in North America. Chronological control is based on more than seventy radiocarbon dates. Deepest in the site is a sparse cultural assemblage assignable to the Clovis horizon. Above this is a bone bed of extinct bison with a small assemblage of artifacts, including an engraved stone, resembling those of Folsom affiliation. Dr. Collins formal report fills 5-ca. 350-page manuals: Wilson-Leonard, An 11,000 Year Archeological Record of Hunter-Gatherers in Central Texas, Volumes I-V. Dr. Collins has also written a Current Research in the Pleistocene article concerning this unique creek habitat: Stratigraphic, Chronometric, and Lithic Technological Evidence for PreClovis at Wilson-Leonard, Texas. Current Research in the Pleistocene. This article briefly reports on artifacts recovered from the preclovis gravel strata (Igl)

2 This author s research continues Dr. Michael Collins, Texas Archeological Research Laboratory s (TARL), and Texas Department of Transportation s (TxDOT) research on this archeologically productive, central Texas creek. This research focuses on where Brushy Creek has recently dissected an alluvium in several locations. These dissections have exposed several complete geologic columns, quite similar to the geologic column documented 8 miles upstream, at Wilson-Leonard. Wilson-Leonard is located ca. 5 miles west of the Balcones Escarpment, while The Brushy Creek Site is positioned ca. 3 miles east of the escarpment. The Brushy Creek Site has been subdivided into 7 units, each located where a portion of the alluvium has been dissected. The units are separated by an average of 275 meters. Starting with the dissection farthest upstream (southwest) and ending with the dissection farthest downstream (northeast), the units have been termed: Lima, Lima B; Tango; Tango C; Tango B; Foxtrot B, Foxtrot; and Romeo. Figure 1 Brushy Creek Site Units Lima, Lima B, Tango, Tango B, Tango C, Foxtrot B, Foxtrot and Romeo. Note that the portion of Brushy Creek, where the site is located, deviates from the creek s overall WNW-ESE course, draining southwest (SW) to northeast (NE).

3 This local deviation is caused by the easternmost outcropping of the Edwards Plateau, creating the southeastern boundary of Brushy Creek in the immediate area. Downstream from the outcropping, the creek resumes it s overall WNW-ESE course.

4 Figures 2 and 2a Brushy Creek Site Unit Lima.

6 Figures 3 and 3a Brushy Creek Site Unit Lima B.

8 Figures 4 and 4a Brushy Creek Site Units Tango and Mike ( Very Large Archaic Midden).

10 Figures 5 and 5a Brushy Creek Site Unit Tango B.

12 Figures 6 and 6a Brushy Creek Site Unit Foxtrot-B.

14 Figures 7 and 7a Brushy Creek Site Unit Foxtrot.

16 Figures 8 and 8a Brushy Creek Site Unit Romeo. Wilson-Leonard was thoroughly documented, archeologically, from just above the buff gravel stratum (Bed Igl), throughout the clay and silt paleosols (Beds Icl and Isi), and on up through the silt and clay topsoil (Isi(c)-III). The buff gravel stratum (Igl) was only researched superficially at Wilson-Leonard. This author s research focuses on Bed Igl, downward through the underlying 2-3 cementation strata (Bed Ice), 8-12 caliche stratum (Bed Ica), and ends at the surface of the creek valley s Edwards Formation limestone bedrock (Bed Ked).

Geology The relevant geology for human habitation on Brushy Creek begins somewhere between the Edwards Formation limestone s (Bed Ked) diagenesis (Lower Cretaceous) and the earliest remaining, local

17 Geology The relevant geology for human habitation on Brushy Creek begins somewhere between the Edwards Formation limestone s (Bed Ked) diagenesis (Lower Cretaceous) and the earliest remaining, local Cenozoic deposits (Beds Ica, Ice and Igl). Some unknown amount time after the diagenesis of the Ked limestone, in the Early Cretaceous, a prolonged hot, dry climate existed locally, as evidenced by ca of hard, cemented caliche (Bed Ica) riding uncomformably on Bed Ked, at Brushy Creek s southern valley margin. Overlying Bed Ica is a ca. 2-3 stratum of cemented alluvial gravel and sand ( Bed Ice): Figure 9 Highlighted close up of Beds Ked, Ica, Ice and Igl

18 Figure 10 Close up of Beds Ked, Ica, Ice and Igl Marking the end of the drought, which preceded Bed Igl s deposition, is significant valley scouring of Bed Ked:

19 Figure 11 Valley scouring of Bed Ked, ca. 100 meters upstream from Unit Lima. View is to the northeast. Note the remnants of Bed Ica on the southern valley margin ( to the right in this image).

20 Figure 12 Dissected Beds Igl, Ice and Ica.

22 Figures 13 and 14 Complete geologic column (Unit Lima), illustrating the position of Bed Igl within the entire sequence of strata. The ca. 5 strata, overlying Bed Igl, are several paleosols (Beds Icl, Isi and II). The upper ca. 2 of strata in the profile are soils consisting, predominantly, of black clay loam (Bed III). More than 70 radiocarbon assays from Wilson-Leonard indicate the following time periods for each strata s deposition: 1. Edwards Formation Limestone Bedrock ( Bed Ked- Lower Cretaceous): Older than 11,000 BP- PreClovis 2. Caliche (Bed Ica): Older than 11,000 BP- PreClovis. 3. Cementation Strata (Bed Ice): Older than 11,000 BP- PreClovis. 4. Buff Gravel Stratum (Bed Igl): Older than 11,000 BP- PreClovis. 5. Paleosols (Beds Isi and Icl ): Older than 11,000 BPClovis time frame and perhaps a bit older. 6. Silt and Clay Topsoil (Beds Isi(c)-III): 11,000 BP to present. As discussed earlier, this research focuses on the lower four strata, beginning with Bed Ked (Edwards Formation limestone- Lower Cretaceous) and ending with the upper

23 portions of Bed Igl (Pleistocene). Hence, the title for this report: Starting at Rock Bottom.

Starting at Rock Bottom

Starting at Rock Bottom At rock bottom of the Brushy Creek site s geological column lies the first clue to human habitation: A smelting and heattreating furnace, and mold, carved into Bed Ked: Figure 15