GEOARCHEOLOGICAL FRAMEWORK FOR DEEPLY STRATIFIED ARCHAIC TERRACE SITES IN THE UPPER OHIO RIVER BASIN

Low terraces on large rivers in the upper Ohio River basin have yielded many deeply stratified Archaic sites. Early Archaic artifacts are particularly well represented, but Middle and Late Archaic components also may be preserved and stratigraphically discrete. Post-Archaic artifacts and features generally are limited to the upper meter of sediment, often with poor stratigraphic context. Paleoindian points are widely reported but rare in excavation; these artifacts typically have been retrieved from eroding river-banks with little stratigraphic context.

The late Quaternary stratigraphic and geomorphological framework of these terrace sites is essential to understanding regional archeology. About 1/4 of its basin was glaciated, and the Upper Ohio River experienced significant incision while it evolved from an aggrading outwash stream to a predominantly single-channel system after Laurentide ice retreated out of the basin; unglaciated tributaries incised as a consequence of lowered local base levels. The transition in stream type appears to have taken several millennia, with channel profiles approaching equilibrium around 10,000 C-14 yr B.P. Many new terraces began to form soon thereafter, possibly in response to a decrease in channel width required to convey relatively small Holocene floods.

Although cultural factors must be acknowledged, the well-developed deeply stratified Archaic sites common in the upper Ohio River basin may represent the outcome of high sedimentation rates and excellent preservation potential in the early stages of terrace formation. Subsequent cultural assemblages are less likely to be deeply stratified because river plan form and hydraulic geometry were relatively stable, so few sites saw high sedimentation rates during the late Holocene, until the advent of navigational lock and dams. Stratified sites with significant in-situ Paleoindian components may be limited to special circumstances, such as upper reaches of tributaries somewhat removed from the influence of base level controls exerted by the Ohio River.