GEOLOGICAL CONTEXT OF THE PALEOINDIAN FLOODPLAIN SITE (28WA528), NEW JERSEY: INSIGHTS FROM 800 MHZ GEORADAR IMAGING

High-resolution 800 MHz ground-penetrating radar (GPR) images were collected along the east bank of the Delaware River to reconstruct the geological context of the Snyder Site, New Jersey. Surveys across a low terrace revealed a depression (depth: ~ 2 m; width: >25 m) separated from the present river channel by a topographic high. This trough is interpreted as a secondary channel accentuated by coarse basal gravel lag and filled with fine-grained sediment. The paleo-topographic high between the Delaware River and paleo-depression includes a complex sequence of Paleoindian (latest Pleistocene), Archaic, and Woodland occupation surfaces with artifacts. Georadar signal penetrated the upper heavily ploughed horizon (up to 0.5 m), which produces a characteristic chaotic signal return. Lack of signal attenuation within radargrams suggests low clay content, which was confirmed by groundtruthing. Multiple hand augers and the dig site aided in correlating key bounding surfaces with fluvial/aeolian lithostratigraphic interfaces. Scattered gravel clasts and artifacts are manifested as isolated hyperbolic diffractions, with basal lag represented by a continuous band of diffractions. Our research indicates that GPR not only helps identify potential cultural remains as point-source reflections, but also helps reconstruct the antecedent topography and stratigraphic architecture of a floodplain site formation sequence.