Geoarchaeological investigations of the upper Lampasas River, Texas

Abstract

Three terraces and a modern floodplain were identified along a segment of the upper Lampasas River in Bell County, Texas. The oldest terrace, T3, is composed of one major depositional unit (I), and is capped by a well-developed soil (Sl) believed to be Pleistocene in age. Terrace 2 (T2) is also composed of a single depositional unit (II) which ranges in age from about 1000 B.P. to at least 6000 B.P., and is capped by a soil (S2). The first terrace (Tl) is underlain by two stratigraphic units (III and IV). Unit III was deposited between about 1000 B.P. and 700 B.P., and is capped by the Lovelady Paleosol (S3). Unit IV overlies Unit III, is about 600 years old, and is capped by a soil (S4). The modern floodplain consists of fairly recent sediment (Unit V), that in some places has incipient soil development (S5). Based on this geochronology a predictive site location model is given. Pre-Clovis sites, if any should exist, will only be found in unit I or on the T3 surface. Paleo-Indian sites could only be found deeply buried in unit II alluvium, or on the T3 surface. Early and Middle Archaic sites (of which several are known in the valley) exist in the unit II alluvium and on the T3 surface. Late Archaic sites exist in the unit III alluvium or on the T2 and T3 surfaces. Late Prehistoric sites exist in unit IV alluvium and on the Tl, T2, and T3 surfaces. Historic or Proto-Historic sites can only exist in unit V alluvium or on any terrace surface. Because all but the T3 surface are occasionally inundated, many sites which might otherwise be directly on a terrace surface may be in a shallow buried context.