From Bureau of Economic Geology, The University of Texas at Austin (www.beg.utexas.edu).
For more information, please contact the author.

Bureau Seminar, October 15, 2004

Structural Setting of Mississippi Canyon and Atwater Valley,
Northeastern Gulf of Mexico

Renaud Bouroullec

Abstract:

This study presents the results of structural analyses of the Mississippi Canyon and Atwater Valley protraction areas, northeastern deep Gulf of Mexico, carried out at the Energy and Minerals Research Center, University of Colorado at Boulder. Analysis included 12,165 km of 2-D and 378 square miles of 3-D seismic data, tied to 150 exploration wells and biostratigraphy. The study area is an active exploration province, including 50 fields and discoveries, such as Thunder Horse field (BP).

Structural analyses were carried out to characterize the geometry and kinematics of (1) basement structures; (2) extensional, contractional, and strike-slip fault systems; and (3) the multilevel allochthonous salt systems from Jurassic to present. This study also investigates the intricate temporal and spatial relationship between these three tectonic systems, in relation to the formation of main structural traps.

Basement structures consist of a series of horsts, grabens, and half-grabens with various orientations. This organization greatly controls the subsequent evolution of the basin. Three successive extensional and contractional systems are present: (1) a regional pre-mid-Oligocene E/W-trending system, (2) a regional post-mid-Oligocene NNW/SSE trending system migrating landward through time, and (3) series of local NNW/SSE-trending upper Miocene systems. Three levels of allochthonous salt systems are present at the top Albian (99 Ma), top Cretaceous (66 Ma) and the Neogene (between 10 and 4 Ma). Four main contrasting styles of allochthonous salt systems have been identified: basement-controlled, counterregional, Roho, and foldbelt-related allochthonous salt systems. Some of these salt systems have been influenced and/or modified by late strike-slip tectonics triggered by differential subsidence along the slope, which is related to the irregular early (autochthonous and early allochthonous) salt distribution.