Radiocarbon Dating of Interdune Paleo-Wetland Deposits to Constrain the Age of Mid-to-Late Holocene Microlithic Artifacts from the Zhongba site, Southwestern Qinghai-Tibet Plateau

摘要

Microlithic artifacts, some found in situ, are abundant in the Zhongba archaeological site in southwestern Tibet. The site environment consists of extant wetlands and paleo-wetland deposits found in depressions between sand dunes derived from the Yarlung Tsangpo floodplain. Constraining ~(14)C dates from wetland vegetation and shell from one site fall between ca. 6600-2600 cal. yr B.P., while a second site is dated 3400-1200 cal. yr B.P. A significant and variable ~(14)C reservoir effect—up to 1400 ~(14)C yr—limits these ranges to terminus post quem constraints. The in situ artifacts are supplemented by surface collections fully characterizing raw material and typological variability for each site. Raw material found at Zhongba is chert and chalcedony likely sourced from Cretaceous bedrock near the site. Typologically, microblades are nongeometric and are derived from conical and wedge-shaped cores similar to those identified in the Qinghai Lake Basin and the Chang Tang Nature Reserve of similar or greater age. The later occupation period at Zhongba is broadly contemporaneous with sites on the Qinghai-Tibet Plateau containing bronze and iron artifacts, indicating microlithic technology remained an important tool-making strategy in western Tibet late into the protohistoric period.