William R. Bryant
Continental Slope Innovative Foundations - Geological Oceanography Support
Jia Yuh Liu (PhD student)
It is the aim of this research to determine the exact physiographic and geotechnical nature of three deep water sites, Pigmy Basin, Vaca Basin and the Alaminos Canyon area in the Gulf of Mexico. Multibeam, high-resolution seismic surveys and sediment coring of these areas will supply the physiological and geotechnical parameters necessary for the economic design of deep water production platforms.
This project has supplied the necessary information for the selection of three theme sites and the characterization of those sites. It has and will supply the necessary environmental, physiographic, geological and geotechnical information of the sites to supply the structural and geotechnical engineers the data necessary for the economic design of deep water production platforms in these areas.
The first two years of this project were involved in amassing all data pertaining to the physiography of the continental margin off Texas and Louisiana. The National Ocean Service of NOAA several years ago started but did not complete a detailed multibeam survey of the continental slope off Texas and Louisiana. Using the results of this survey we have established two theme sites, Pigmy and Vaca Basins. Multibeam surveys of Alaminos Canyon, the third theme site, were completed by Texas A&M and detailed bathymetry and physiography of the canyon have been determined. In 1994 on a cruise aboard the R/V Gyre to Pigmy Basin we obtained detailed high-resolution seismic data and fifteen 5 to 10 meter piston cores. The EDO Deep-Tow was transferred from Shell Offshore to OTRC in mid-1995. The system check-out and initial refurbishment was completed in time for the February, 1996 Deep-Tow Survey of Pigmy Basin conducted from the R/V Gyre. The subbottom and side-scan sonar records obtained during this cruise provided corroborating evidence of the mass wasting occurring on the Basin's walls. Furthermore, the records revealed that the sediments surrounding the basin are extensively faulted due to active halokinesis. A second successful Deep-Tow survey was conducted at Alaminos Canyon in April, 1996. In addition to the subbottom and side-scan sonar data acquired, five 8-m piston cores were taken. A Deep-Tow Survey and coring cruise to the third theme site, Vaca Basin, is currently scheduled for September, 1997.
Companies such as Shell Oil have made extensive high-resolution seismic surveys in the deep water portions of the Gulf of Mexico. This data is extensive in coverage and all preparatory with little hope of release within the next decade. The work of GERG at TAMU and LSU on gas seeps, gas hydrates and chemosynthetics on the Texas and Louisiana continental margin supplies a unique environmental and geological data set that will be useful to OTRC goals.
The research resulting from this project combined with others within the OTRC framework as well as the industrial participants will supply the geological and geotechnical parameters and constraints necessary for the economic design of deep water production platforms.
October 1992 to September 1998
We have a Bathymetric data base relating to the northwest continental margin of the Gulf of Mexico that equals or exceeds that of any private or governmental organization. That data base is at the disposal of all members of the OTRC organization. We will transfer this data base, at cost, to all members of the OTRC organization. We will also process requests for specific information, within reason, on any area within the data base. Physiographic diagrams, angle of slope maps and detailed bathymetric maps are available for the three theme sites. Detailed information such as compressional wave velocity, density and other geotechnical properties at 1 cm intervals are available for all piston cores taken in Pigmy Basin and in the future all other areas surveyed. Copies of the deep-tow records to be taken in the future will be available at copy cost to all participants.
Bryant, W.R. and G.R. Simmons. "The Physiography and Engineering Constraints of the Continental Slope in the Northwestern Gulf of Mexico." Civil Engineering in the Oceans, No. 5, pp. 1036-1049, 1993.
Bouma, A.H. and W.R. Bryant. "Physiographic features on the northern Gulf of Mexico continental slope." Geomarine Letters, Vol. 14: 252-263, 1994.
Bryant, W.R., Jia Yuh Liu and J. Ponthier, "The Engineering Constraints of Intraslope Basins and Submarine Canyons of the Northwestern Gulf of Mexico", 1995 GCAGS Transactions, Vol. XLV, pp. 95-101, 1995.