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Summary Information for Field Activity 1974-012-FA

Area of Operations: south Texas continental shelf, Texas, United States, Gulf of Mexico, North America, North Atlantic

Dates: October 27, 1974 to November 08, 1974

Chief scientist: Chuck Holmes

Objectives: The program is designed to establish chemical, biological, and geological baseline on the South Texas Continental Shelf. The focus for the geological program is to establish the nature and amount of the suspended sediment in the water column, to establish the nature and amount of the Holocene sediments on the shelf, and to identify and locate regions of geologic conditions which may be hazardous to OCS operations. Three cruises are planned. The first two cruises are designated as sampling cruises in which grab samples, box cores, and pipe cores will be taken at sites previously designated.

Type of Activity: Sampling; Photography;

Information to be derived:

Summary: 3.5 kHz seismic reflection profiles suggest numerous gas seeps associated with down-to-the-basin faulting along the outer edge of the shelf. Numerous manganese nodules of pebble size were obtained from a topographic high near the outer edge of the shelf in an area of a known high rate of sediment deposition. This is the first report of manganese nodules in the western Gulf. The XBT data showed a mass of warm water over the middle and outer shelf that seems to have become detached from the coast; over the northern part of the survey area the warm water mass was present at the surface, but southward the warm water layer was overlain to progressively greater depths by colder surface water. This is an anomalous and unexpected circumstance that probably reflects a complex water movement pattern on this shelf that is related to an interaction of shelf circulation and wind surface stress. Smith-MacIntyre grabs: 151 (6 subsamples per station); Piston cores: 49 (3-10 feet); Box cores: 5; XBT casts: 67; Bottom photographs: 37; Suspended sediments: 24 (3 at each of 8 stations); Benthic infauna: 156; Drift bottle casts: 43 stations.

Contact: Chuck Holmes ()

InfoBank: uses the identifier K-A-74-GM. Visit this site for more information.

Related Links:

Click to get Google Software - Download 74012.kml to view this field activity in Google Earth

Platform Info:

Publications resulting from these data

Flores, R. M., and Shideler, G. L.,1978, Factors controlling heavy-mineral variations on the South Texas outer continental shelf, Gulf of Mexico: Journal of Sedimentary Research, v. 48, no. 1: p. 269-280. (Also available at

Shideler, Gerald L., and Flores, Romeo M.,1976, Maps showing distribution of heavy minerals on the south Texas outer continental shelf: U.S. Geological Survey Miscellaneous Field Studies Map 841, 1 sheet. (Available as a PDF version)

Shideler, Gerald L.,1988, Heavy-mineral placer potential map of the U.S. continental shelf, western and northern Gulf of Mexico: U.S. Geological Survey Miscellaneous Field Studies Map 2037, 1 sheet. (Available as a PDF version)

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Data Types and Locations:


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