Near-shore sand thickness and stratigraphy mapping with a submerged GPR antenna system; southeast Lake Michigan

Conference · Fri Apr 01 00:00:00 EST 1994 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:6949512

Sauck, W A; Seng, D L ^[1]

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1. Western Michigan Univ., Kalamazoo, MI (United States)

Twenty-one shore perpendicular profiles, spaced at nominal 5 km intervals, have been surveyed with a bottom-sled mounted Ground Penetrating Radar (GPR) antenna system between Benton Harbor, MI, and Gary, IN. Either a commercial 500 MHz or a custom 145 MHz antenna were used. The bottom sled also carried an upward looking SONAR transducer to give concurrent water depth, and was towed from the beach out to water depths of 6 meters or more, usually ending about 500 meters from shore. Bedding structures and details are clearly visible on the GPR sections within the sand bars and sand blankets. Bottom morphology and the nature of the sand bodies change markedly from the NE to the SW limits of the survey area. At the NE profiles there are multiple, pronounced (or high amplitude) offshore bars, with the substrate (glacial clay, shale, or silty sand) exposed or nearly exposed between bars. Internal structure is generally foreset or cross bedding in the bars. Sand was thin or missing immediately to the Sw of several other jetty structures in addition to the one at St. Joseph. In general the sand bars became much less pronounced to the SW, and internal structures were dominated by parallel bedding and subtle angular unconformities. Near St. Joseph, the exposed substrate is almost certainly being eroded, even to water depths as great as 6 meters. Thus, the equilibrium bottom profile continues to deepen shoreward, causing the continued threat of bluff erosion in spite of annual beach nourishment efforts at this site.

• OSTI ID: 6949512
• Report Number(s): CONF-9404217-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 26:5; Conference: 27. annual conference of the North-Central Section of the Geological Society of America (GSA), Kalamazoo, MI (United States), 28-29 Apr 1994; ISSN 0016-7592
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
47 OTHER INSTRUMENTATION
GEOLOGIC DEPOSITS
MAPPING
STRATIGRAPHY
LAKE MICHIGAN
RADAR
PERFORMANCE
SONAR
ELECTRONIC EQUIPMENT
SEDIMENTS
EQUIPMENT
GEOLOGY
GREAT LAKES
LAKES
MEASURING INSTRUMENTS
RANGE FINDERS
SURFACE WATERS
580000* - Geosciences
440700 - Geophysical & Meteorological Instrumentation- (1990-)