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Stratigraphy, Site Formation, and Geochronology at the San Esteban Rockshelter, Southwestern Texas
Niquette, Richard Mason
Niquette, Richard Mason
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Abstract
The San Esteban site (41PS20) is a stratified rockshelter in Presidio County, Texas with archaeological components dating from 6250 cal BP to the Modern period. Also, San Esteban contains a sedimentary record as old as 20,000 cal BP. Furthermore, 6250-year-old atlatl foreshafts represent the oldest in situ archaeological component in a rockshelter or cave in the Big Bend region of West Texas. Hence, San Esteban presents a rare opportunity to explore questions of past lifeways in the Big Bend, and is a potential source of paleoenvironmental data. That opportunity depends on a thorough understanding of site stratigraphy, formation processes, and geochronology. Geoarchaeological investigation at San Esteban co-occurred with archaeological excavation in the summers of 2019, 2020, and 2021. Stratigraphic analyses revealed a set of seven primary stratigraphic units, and a total of 13 sedimentary units across the site. Before 1800 cal BP, natural processes mostly drove site formation at San Esteban. After that time, however, anthropogenic activities became important site formation process, and over the past century, illicit collection became a significant process destroying some of the archaeological record. Despite the effects of looting, much of the archaeological record remains intact in areas that were difficult to access. Also, the configuration of the rockshelter prevented rainwater infiltration in the southern portions of the rockshelter, resulting in remarkable preservation of perishable materials. A total of 43 radiocarbon ages and one optically stimulated luminescence age were used in Bayesian modeling to understand the history of sedimentation and human occupation at San Esteban. The earliest sedimentary deposits recorded during the 2019-2021 excavations pre-date 17,000 years ago. Sedimentation was continuous throughout the terminal Pleistocene but appears to have paused during the Pleistocene-Holocene transition, perhaps because of bioclimatic change. Sedimentation was underway again by ca. 8800 cal BP, and while middle Holocene deposits have not been found at the site, they may occur in untested portions of the rockshelter. Occupation modeling indicates early use of San Esteban was likely brief, but by 2000 cal BP, human occupation intensified, resulting in longer and repeated use of the site.
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Date
2022-12-31
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University of Kansas
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Keywords
Archaeology, bayesian modeling, Big Bend, geoarchaeology, rockshelters, site formation processes, stratigraphy