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Summary for Field Activity Number 1974-012-FA

Alternate Leg ID: KNKE BLM-Leg Alpha; CORPUS 22/28

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

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

Information to be derived: Samples and chemical analysis

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.

USGS Project Number: STEX-OCS

Contact: Chuck Holmes ()

Map for Area of Operations :

Map of field activity boundary.

Platform Info:
photo of KANA KEOKI
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