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Abstract

Continuous seismic-reflection profiling (CSP) and ground-penetrating radar (GPR) surveys<br>were conducted by the U.S. Geological Survey in April 1998 over the northern part of<br>John’s Pond, a glacial kettle pond southeast of Otis Air National Guard Base, Cape Cod, Massachusetts.<br>The surveys were conducted to delineate the types and thickness of sedimentary<br>units that may control the infiltration of contaminated groundwater into John’s Pond.<br>Sand-and-gravel deposits, collapse features and recent organic sediments were imaged<br>with the CSP and GPR methods. Hummocky to chaotic reflections were interpreted as sandand-<br>gravel deposits. Slightly wavy, parallel reflections located in depressions in the sand-andgravel<br>deposits were interpreted as filled collapse features. Lower amplitude, horizontal, laminar<br>reflections were interpreted as organic sediments. Entrapped methane gas within some of<br>the organic sediments created a reflection zone that obscured deeper reflections in the CSP<br>records.<br>The CSP and GPR methods provide complementary information over most of the surveyed<br>part of the pond. The methods detect similar interfaces, but a particular interface may<br>produce a stronger reflection in one record than in the other. For example, regions of the pond<br>containing organic sediments with entrapped methane gas, which prevent penetration of the<br>acoustic signal, were penetrated and imaged by GPR. Conversely, regions of the pond containing<br>electrically conductive sediments or deep water, which attenuate the GPR signal, were imaged<br>using CSP. The CSP and GPR data were interpreted to generate a bathymetric map and a<br>map of sediment type and thickness beneath John’s Pond.

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/content/papers/10.3997/2214-4609-pdb.202.1999_041
1999-03-14
2020-09-21
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http://instance.metastore.ingenta.com/content/papers/10.3997/2214-4609-pdb.202.1999_041
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