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Extreme Evaporative Drawdown of the Gulf of Mexico at the Paleocene-Eocene Boundary*

By

Joshua H. Rosenfeld1 and Jon F. Blickwede2

 

Search and Discovery Article #30042 (2006)

Posted July 21, 2006

 

*Oral presentation at AAPG Annual Convention, Houston, Texas, April 9-12, 2006

 

Click to view presentation in PDF format (12.4 mb).

 

1Independent, Granbury, TX (jrosenfeld@charter.net)

2Statoil, Houston, Texas (jobli@statoil.com)

 

Abstract 

Deep paleocanyons in the western Gulf of Mexico, thick sands in the deep Gulf, salt in the Veracruz Basin and a major unconformity in deep water near the mouth of the Gulf suggest that sea level dropped significantly during the Late Paleocene-Early Eocene. We relate these features to an evaporative drawdown when the Gulf's connection to the world ocean was blocked by the collision of Cuba with the Yucatán and Florida-Bahamas blocks. Sea level fell as the evaporation rate far exceeded additions from rainfall and fluvial runoff.  

The Upper Paleocene-Lower Eocene Wilcox Formation is a submarine fan complex more than 1.5 km thick that blankets a vast area of the western and central deepwater Gulf. We surmise that this anomalously thick, relatively uniform sand accumulation contains recycled Lower Wilcox shelf sands deposited in the deep basin during the lowstand.  

We explain the unconformity between Yucatán and Florida, represented by Pleistocene sediments overlying Cenomanian limestones at DSDP Site 535, as the result of erosion when the oceanic connection was re-established.  

A variety of local explanations have been invoked to explain these and other manifestations of the proposed drawdown; however, a single mechanism linked to a widely accepted plate tectonic model (the Cuba-Bahamas collision) can account for this variety of hitherto unrelated geological phenomena.

 

Selected Figures 

Anomalous areas at Paleocene-Eocene boundary in Gulf of Mexico region.

Isolation mechanism.

 

Cross section of Yoakum paleochannel (after Hoyt, 1959).

Veracruz basin separated from Gulf of Mexico by transform ridge (from Bird et al., 2005).

Log of salt-bearing section below gray Eocene shale, Pemex Mataespino-101B, Veracruz basin (with permission of Pemex: thanks to Alfredo Guzmán and Rosalio Razo).

Bathymetric map of Florida slope, with sinkholes (from Jordan, 1954). A. Part of Florida Keys, Florida reef, and Florida slope. B. Detail of Florida slope.

 

References 

Bird, Dale, E., Kevin Burke, Stuart A. Hall, and John F. Casey, 2005, Gulf of Mexico tectonic history: Hotspot tracks, crustal boundaries, and early salt distribution: AAPG Bulletin, v. 89, p. 311-328.

Galloway, W.E., W.F. Dingus, and R.E. Paige, 1991, Seismic and depositional facies of Paleocene–Eocene Wilcox group submarine canyon fills, northwest Gulf coast, U.S.A., in P. Weimer and M.H. Link, eds., Seismic facies and sedimentary processes of submarine fans and turbidite systems: New York, Springer-Verlag, p. 247–271.

Galloway, W.E.,  Patricia E. Ganey-Curry, Xiang Li, and Richard T. Buffler, 2000, Cenozoic depositional history of the Gulf of Mexico basin: AAPG Bulletin, v. 84, p. 1743–1774.

Hoyt, W.V., 1959, Erosional channel in the Middle Wilcox near Yoakum, Lavaca County, Texas: GCAGS Transactions, v. 9, p. 41-50.

Hutson, F.E., P. Mann, and P.R. Renne, 1998, 40Ar/39Ar dating of single muscovite grains in Jurassic siliciclastic rocks (San Cayetano Formation); constraints on the paleoposition of western Cuba, Geology, v.26, no. 1, p. 83-86.

Jordan, G.F., 1954, Large sink holes in Straits of Florida: AAPG Bulletin, v. 38, p. 1810-1817.

Marton, G., and R.T. Buffler, 1999, Jurassic-Early Cretaceous Tectono-palaeogeographic evolution of the Southeastern Gulf of Mexico Basin, in P. Mann, ed., Caribbean Basin: Sedimentary Basins of the World, 4 (Series ed., K.J., Hsu), Elsevier, p. 63-91.

Rosencrantz, E., 1990, Structure and tectonics of the Yucatan basin, Caribbean Sea, as determined from seismic reflection studies, Tectonics, v. 9, no. 5, p. 1037-1059.