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Abstract
Slope-instability processes caused by salt movements in a complex deep-water environment, Bryant Canyon area, northwest Gulf of Mexico
Efthymios K. Tripsanas,1 William R. Bryant,2 Brett A. Phaneuf3
1Texas A
M University, Department of Oceanography, College Station, Texas 77845; [email protected]
2Texas AM University (TAMU), Department of Oceanography, College Station, Texas 77845-3146; [email protected]
3Texas AM University, Department of Oceanography, College Station, Texas 77845
AUTHORS
Efthymios Tripsanas is currently working as a postdoc at Bedford Institute of Oceanography in Dartmouth, Nova Scotia, with David Piper, Dave Mosher, and Kimberley Jenner. He is originally from Delphi, Greece, where he received his bachelor's degree in geology. He obtained his Ph.D. at Texas AM University, College Station, Texas, with William Bryant. Efthymios has worked on sediment facies and slope instability associated with active salt tectonics on the Gulf of Mexico slope. His current research is focused on the understanding of sediment instability on the continental margin east of Newfoundland, particularly Orphan basin.
William Bryant is a professor of oceanography. He received an M.S. degree and a Ph.D. at the University of Chicago. He has spent the last 40 years at TAMU teaching and doing research in marine geology, high-resolution marine geophysics, and marine geotechnology. He was head of the Department of Oceanography from 1998 to 2000. He has worked in the Gulf of Mexico, Caribbean, west Africa, the Arctic and Antarctic, and sailed all five of the Russian polar seas. He is the author of more than 300 papers, co-editor of 1 book, and advisor of more than 100 M.S. and Ph.D. graduates. He was co-chief scientist on Deep-Sea Drilling Program Leg 10, and scientist on Leg 96 and Oil Drilling Program Legs 113 and 121.
Brett Phaneuf is a graduate student in the Department of Oceanography. His research focuses primarily on high-resolution applications to deep-sea imaging. Phaneuf works extensively with the U.S. Navy, particularly aboard the U.S. Nuclear Research Submarine, NR-1, and also has been working with the Deep-Tow Research Group at Texas AM for eight years.
ACKNOWLEDGMENTS
This project was sponsored by a National Science Foundation grant to Texas AM (no. BES-9530370) with supplemental support from Amoco, Chevron, Mobil, Texaco, Phillips, Marathon, Marsco, Inc., and Geotek, Ltd. We acknowledge the following people for their significant assistance in this project: Armand Silva and Dan Bean for their contribution in collecting the Jumbo piston cores during the Knorr cruise, 1998; Arnold Bouma, David Prior, and Hans Nelson for their help on the development of the above ideas. Tripsanas acknowledges the State Scholarships Foundation Institution of the Republic of Greece for funding work on his Ph.D.
ABSTRACT
Halokinetic and slope-instability processes have sculpted numerous morphological features on the flanks of the intraslope basins in the Bryant Canyon area. High-resolution geophysical data and long sediment cores (as much as 20 m [66 ft] long) were used to define the time and spatial evolution of sediment failures and their relationship to halokinetic processes. Two episodes of increased salt-tectonic activity are defined: (1) The first acted at the beginning of interglacial oxygen isotope stage 5 as salt adjusted to the abandoned environments of the Bryant and Eastern Canyon systems, and (2) the second occurred during the last glacial period and is characterized by the seaward propagation of salt masses. Three types of slopes are recognized in the intraslope basins: (1) highly inclined slopes with low-relief morphologic features resulting from shallow, translational slump complexes, (2) highly inclined slopes with high-relief morphologic features resulting from deep, rotational slump complexes, and (3) highly inclined slopes dissected by high-relief canyonlike landslide troughs resulting from channelized rotational slumps. The first two slope types occur mainly on the northern flanks of the basins, whereas the third type occurs on the southern flanks. We propose that the slump complexes on types 1 and 2 slopes were triggered by the oversteepening of the flanks by the seaward mobilization of underlying salt masses. The channelized rotational slumps on type 3 slopes are interpreted to result from the development of salt diapir bulges that lead to locally increased gradients on the basin flanks. Most of the sediment failures have been transformed into debris flows and led to the most recent phase of infilling of the basin floors.
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