Constraining Interpretations of the Crustal Architecture of the Northern Gulf of Mexico

Mark G. Rowan¹, H. Scott Sumner², Holly Huston³, Sujata Venkatraman⁴, and David Dunbar⁴
¹Rowan Consulting, Inc., 850 8th St., Boulder, Colorado 80302
²Dynamic Global Advisors, 9590 Bella Citta St., Las Vegas, Nevada 89178
³Hunter 3-D, 6001 Savoy Dr., Ste. 110, Houston, Texas 77036
⁴Dynamic Global Advisors, One Briar Lake Plaza, Ste. 150, 2000 W. Sam Houston Pkwy. South, Houston, Texas 77042

The crustal architecture of the Gulf of Mexico has been the subject of much debate for several decades. Most researchers invoke paired passive margins caused by counterclockwise rotation of Yucatan from North America (e.g., Pindell and Dewey, 1982; Marton and Buffler, 1994). However, there is significant uncertainty as to: (1) the amount of rotation during opening of the Gulf, ranging from minimal (Salvador, 1987) to over 40° (e.g., Pindell and Kennan, 2009); (2) the nature and fabric of the underlying crust, with various interpretations invoking areas of thinned continental crust, subaerial volcanic crust, true oceanic crust, and exhumed serpentinized mantle; (3) the orientations and positions of rift-related extensional structures and associated fracture/transfer zones; (4) the position and width of the transition between continental and oceanic crust, with a spread in interpretations of up to 250 mi (400 km) in the northern Gulf of Mexico (Bird et al., 2005); and (5) the style of crustal extension and breakup, from traditional symmetric models to asymmetric models in which the northern Gulf of Mexico represents the lower plate (e.g., Pindell and Kennan, 2007), and from volcanic rifted margins (Imbert and Philippe, 2005) to non-volcanic, hyperextended margins (e.g., Pindell and Kennan, 2009).

The ongoing debate and uncertainty is largely due to a lack of sufficient evidence to constrain the models adequately. The few wells that penetrate basement are in proximal locations, existing refraction seismic data do not provide enough control on deep velocities, gravity and magnetic data are subject to multiple interpretations, and deep reflection seismic data are generally poor quality, especially where there is shallow salt. Here, we use new regional 2D seismic data, combined with potential fields data, to place better constraints on the interpretations. The data, from the SuperCache program in the northern Gulf of Mexico, were acquired with long offsets (9.5 mi or 15 km), powerful sources (9100 in³), and deep tow (60 ft or 18 m) of both source and receiver, and were processed using reverse-time migration down to 130,000 ft (40 km). They provide images of deep structure not previously seen on other datasets.

AAPG Search and Discovery Article #90158©2012 GCAGS and GC-SEPM 6nd Annual Convention, Austin, Texas, 21-24 October 2012