GEOMORPHIC CONTEXT OF ARCHAEOLOGY SITES ON THE CUMBERLAND RIVER AND SITE DISTURBANCE BY SEISMICITY

Geomorphology investigations for two archaeology surveys (5 km apart) provide evidence to interpret the geomorphic history of the T1 terrace along the Cumberland River near Clarkesville, TN. Twenty-five trenches were excavated to interpret site stratigraphy prior to the archaeology work at the northern site. The depositional history of the terrace is reconstructed from the ridge and swale morphology and relative dating of soil profiles. T1a is oldest ridge and is interpreted as a Late Pleistocene landform. Repeated channel migration followed by stabilization deposited two younger ridges. The early Holocene T1b contains lithic debitage in a buried A-horizon. Three Ab-horizons were recorded in the T1c, which was deposited since the mid-Holocene. Artifacts were recorded in two of these buried soils. The third buried soil was described in Geoprobe cores at a depth of 280 cm. A sandy crevasse splay deposit fills the upstream end of an adjacent paleochannel (flood chute). Ceramic artifacts and clay pipe stems indicate that this younger sand deposit dates to the Woodland period, between 1ka and 3ka. These crevasse splay sands have been documented in flood chutes of other drainage basins in the southeast.

Investigations at the southern site were limited to the T1c terrace where archaeologists were excavating site 40MT911. This T1 terrace has a similar geomorphology. Archaeology excavations encountered truncated strata and areas where the buried A-horizon was missing. This disturbance is attributed to liquefaction features that truncated site stratigraphy. Cultural deposits in the Ab-horizons and C14 dates indicate that these liquefaction features are less than about 2ka old. The seismic disturbance complicates the archaeologist’s interpretation of this stratified archaeology site. The site is 150 km east of the New Madrid seismic zone, but USGS maps do not show earthquake epicenters in the Clarkesville area. Therefore, these liquefaction features are attributed to a distal, high magnitude seismic event. Sand blows from earlier New Madrid earthquakes have been dated to 1450 A.D., 900 A.D. and 2350 B.C. Geomorphology investigations identified buried cultural deposits within the different landforms and interpreted post-depositional modifications to sites along the Cumberland River.