LATE QUATERNARY STRATIGRAPHY OF THE UPPER OHIO-ALLEGHENY RIVER BASIN: A DEVELOPING FRAMEWORK FOR GEOARCHAEOLOGICAL INVESTIGATIONS

Site-specific geomorphic and archaeologic investigations throughout the Upper Ohio-Allegheny River basin provide significant insight into the late Quaternary geologic history of the region. This paper presents a selected synthesis of existing data to develop a regional stratigraphic framework for alluvial geoarchaeological investigations in the Upper Ohio-Allegheny River basin.

During glacial and deglacial times, glaciated tributaries routed significant volumes of meltwater and sediment southward through the Upper Ohio-Allegheny River and away from the glacial margin. Existing data indicate glaciers retreated from the basin by 13-14 ka. Streams responded to lower water volumes and sediment supply by incision and a transition from braided to meandering planforms. Both the Allegheny and Upper Ohio rivers are commonly flanked by one to several late Quaternary terraces depending on local geologic and geomorphic conditions. The alluvial landforms hold significant archaeological site potential.

Alluvial terraces along meltwater courses within the basin may contain cultural deposits dating back to the Paleoindian Period in surface and shallow subsurface context. Where present, the oldest Holocene terraces have the potential to contain cultural deposits dating back to the Early Archaic Period. Younger and lower Holocene terraces, and the active floodplain may contain deposits dating to the Middle Archaic and younger depending on specific landform age. Although developed using site-specific data, the stratigraphic framework developed herein should be applicable to meltwater influenced reaches of larger streams in the Upper Ohio-Allegheny River basin, and also provide significant information concerning late Quaternary landscape evolution at the regional scale.