Geoarchaeology and paleoecology of the deeply stratified Richard Beene site, Medina River valley, South-Central Texas, USA

摘要

AbstractA geoarchaeological investigation that included soil-stratigraphic and paleoecological analyses was conducted at Richard Beene, a deeply stratified open-air site associated with an alluvial terrace of the Medina River in south-central Texas. The sequence of cultural and alluvial deposits at the site is one of the most complete records of Holocene human occupation and sedimentation documented in North America, and is very important to the interpretation of the cultural history of the Inner Gulf Coastal Plain and adjacent areas of the Southern Plains. The most salient ecological characteristics of the site are its riparian setting and location in the ecotone between North America's western grasslands and eastern woodlands. The cultural record spans the past 10,000 years and is buried in 14 m of fine-grained flood deposits with multiple buried paleosols. Excavations totaling 730 m2sampled 20 stratigraphically distinct archaeological components in valley fill beneath the Applewhite terrace, yielding more than 80,000 artifacts, including flakes, tools, bones, mussel shells, and fire-cracked rocks left by Archaic and Late Pre-Columbian hunter-gatherers. Seven primary stratigraphic units and five laterally traceable buried paleosols were identified at the site. The oldest stratigraphic unit consists of coarse-grained channel deposits that accumulated soon before 33,00014C yr B.P. Most of the units, however, consist of fine-grained alluvium that accumulated between ca. 10,000 and 100014C yr B.P. The δ13C values of organic matter from the site's soil-stratigraphic sequence indicate increased C4production during the Younger Dryas (11,000–10,00014C yr B.P.), and C4productivity generally increased throughout the Holocene, culminating in peak warm intervals at ca. 5000 and 200014C yr B.P. Although during relatively dry periods grasses expanded at the expense of trees, a mosaic of trees and grasses (i.e., a savannah) typical of a grassland-forest ecotone prevailed at the site throughout the Holocene. Such a food-rich environment characterized by an abundance of deer and geophytes, as well as mussels from the Medina River accounts for repetitive human occupation spanning at least 10,000 years.