Giant Submarine Fans in a Greenhouse World—The Paleogene of the Gulf of Mexico

During the Paleogene of North America, Laramide uplift; a warm, humid climate; very large rivers; long-lived submarine canyons and relatively stable sea level created the most favorable conditions of the Cenozoic in North America for the development of submarine fans. These conditions are recorded by the Paleogene Wilcox Group. A century of outcrop and subsurface mapping and a robust subsurface database make the Wilcox Group a unique laboratory to explore the controls on a continent-scale depositional system in a Greenhouse climate.

The Wilcox Group spans about 18 million years of the Paleocene and Eocene. During this time 800,000 km3 of sediment were deposited in the northern Gulf of Mexico Basin. Sixty-four percent of this sediment was deposited in deep-water depositional environments. Strikingly 44% of the total sand deposited in the northern Gulf of Mexico Basin was deposited in deep-water, a significantly higher volume than seen later in the Cenozoic. Wells drilled into these submarine fans have encountered impressive thicknesses of sandstone. For example, the Leopard well (Alaminos Canyon 691) encountered 2500 m of Wilcox Group deposits half of which is sandstone.

While growth faulting at the shelf edge acted to conservation sediment in deltas, several other factors favored efficient routing of sediment, especially sand, to deep water. These factors included: long-live submarine canyons associated with deltaic depocenters and a relatively narrow continental shelf, about 50 km wide. When combined with lower amplitude of sea-level fluctuations these allowed for continuous input of sediment to deep water.