Rapid seismic reflection imaging at the Clovis period Gault site in central Texas

Hildebrand, JA, Wiggins SM, Driver JL, Waters MR.  2007.  Rapid seismic reflection imaging at the Clovis period Gault site in central Texas. Archaeological Prospection. 14:245-260.

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Clovis, data-acquisition, electromagnetic induction, geophones, land-streamer, Palaeoindian, seismic reflection, stratigraphy


Using a modified seismic reflection imaging system with rapid translation of receivers, stratigraphic profiles were collected at the Gault site in central Texas. For rapid data collection, spikeless geophone receivers were placed in sand-filled bags at tight spacing, and these receivers were rapidly pulled along the ground surface between shots. Shots were produced by a small hammer strike to a vertical pipe at 20-cm intervals. High quality ultrashallow seismic reflection profiles were collected at a rate of 25 m h(-1), significantly faster than what is possible with conventional seismic reflection imaging using individually planted geophones. Ground-penetrating radar was attempted, but abandoned owing to the poor penetration of the radar signals in the clay soils present at the Gault site. Electromagnetic induction grids were collected surrounding each seismic reflection profile, and provided information on near-surface ground water. Seismic reflection images of Gault site stratigraphy provided greater depth penetration than accessible from backhoe trenching and coring, and helped to better outline the site geological context. Seismic images reveal coherent reflections at shallow depths (0-2.5 m), and extensive scattering at deeper levels (2.5-8 m), underlain by reflection-free zones. These data are interpreted as clay and gravel layers overlaying palaeostream channels carved into the limestone bedrock. Where comparative data were available, the geophysical findings were corroborated by observations of site stratigraphy in archaeological excavation units, backhoe trenches and cores. Seismic reflection studies at the Gault site revealed a palaeochannel filled with pre-Clovis age sediments. Pre-Clovis age sediments are not known to occur at other locations within the Gault site. They provide a unique opportunity to test for cultural remains of great antiquity. Copyright (C) 2007 John Wiley & Sons, Ltd.