AAPG Bulletin; June 2007; v. 91; no. 6;
p. 823-833; DOI: 10.1306/12180606049
© 2007 American Association of Petroleum Geologists (AAPG)
Brine volume and salt dissolution rates in Orca Basin, northeast Gulf of Mexico
Robin S. Pilcher1 and
Raleigh D. Blumstein2
1 Hess Corporation, One Allen Center, 500 Dallas Street, Houston, Texas 77002; robin.pilcher{at}hess.com
2 Hess Corporation, One Allen Center, 500 Dallas Street, Houston, Texas 77002; rblumstein{at}hess.com
Robin is a senior exploration geologist specializing in structural geology and salt tectonics for Hess Corporation. He received his B.Sc. degree from Durham University, an M.Sc. degree in applied structural geology from Imperial College, London, and his Ph.D. on the structural and tectonic evolution of the Huqf uplift of Oman from the University of London.
Raleigh D. Blumstein is a geologist working in the South America and West Africa Exploration Group for Hess Corporation. He worked for 2 years as a geologist with Baker Atlas, specializing in structural and stratigraphic interpretation of image logs. He received a B.S. degree (2000) in petroleum geology and an M.S. degree (2003) in geology from the University of Oklahoma.
The Orca Basin, on the northern Gulf of Mexico continental slope, is unique among the many intraslope basins of the area, in that it contains a large brine lake at the base of the water column. The brine lake is of scientific significance on many levels: as an unusual hypersaline marine habitat; a laboratory for study of the preservation of organic and inorganic matter in anoxic environments; an anomalous geophysical phenomenon; and a closed system where the dissolution of rock salt in the submarine environment can be investigated. The latter two subjects are the focus of this article. The brine lake occupies an area of approximately 123 km2 (47.5 mi2) in the base of the Orca Basin and is up to 220 m (721 ft) deep in places. High-resolution multifold three-dimensional seismic reflection data enable this unique feature to be mapped and described quantitatively for the first time. An updated physiographic description of the Orca Basin and a calculation of the volume of the brine lake is presented. At 13.3 km3 (3.2 mi3), the volume of brine represents the dissolution of about 3.62 billion t of Jurassic Louann Salt in seawater. We calculate the time-averaged addition of salt to the Orca Basin through the dissolution of exposed salt at nearly 0.5 million t/yr.
Copyright © 2009 by American Association of Petroleum Geologists (AAPG)
