Pleistocene-Holocene Sediments Interpreted by Seismic Refraction and Wash-Bore Sampling,Plum Island-Castle Neck,Massachusetts.

摘要

The wash-bore method of soil sampling was found to be an excellent technique for subsurface study in coastal areas. Phenomena to be considered when interpreting seismic refraction records include (a) the 'blind zone', (b) the non-zero time intercept, (c) time gaps in the time-distance photo over buried peat,and (d) variable thicknesses of dry sand layers. The seismic method successfully located Pleistocene and bedrock topography. However, glaciomarine clay did not show a seismic contrast with respect to sandy,water-soaked sediments. Topography exposed during lower sea level has a dominant influence on modern coastal geology. Barrier islands became anchored on Pleistocene features as the sea level rose and deposition occurred in the estuaries behind the barrier beaches. Major channels of the estuaries migrated landward with the sea-level rise. (Modified author abstract)