DGS International Group Dinner Meeting
Joshua H. Rosenfeld
Wednesday, April 16, 2014
5:30pm Social Hour
at Brookhaven Country Club
3333 Golfing Green Drive, Dallas, TX 75234
Register today online at www.dgs.org or
By email to Linnea.Castillo@pxd.com
DGS Members $30
No shows will be billed!
Paleocene-Eocene Drawdown and Refill of the Gulf of Mexico – Concept History and Status
Rosenfeld and Pindell (2002, 2003) hypothesized that late Paleocene-early Eocene docking of the northward migrating Caribbean Plate blocked the 200 km strait between the Florida/Bahamans Block and Yucatan, thereby isolating the Gulf of Mexico from the world ocean. Within several thousand years, net evaporation in the Gulf lowered its level by about 2,000 meters and formed a land bridge across the eastern Gulf that encompassed Yucatan, Florida, Cuba, and the Bahamas. Formation of the land bridge was enhanced by isostatic uplift of the basin’s margins as sea level dropped. After about 1 Ma of isolation, reconnection with the world ocean resulted in energetic refill of the basin that cut a deep thalweg between Florida and Cuba. This relatively short duration drawdown explains many phenomena unique to this period of Gulf history, including:
• the excavation of deep canyons across contemporary continental shelves and slopes: e.g., Yoakum, St. Landry, Chicontepec/Bejuco-La Laja paleocanyons, and the many canyons found along the lower continental slopes of Florida and Yucatan (discussed below)
• the sudden deposition, and equally sudden cessation of a widespread, thick, high net sand blanket in the deep Gulf Basin
• salt deposition in the barred Tertiary Veracruz Basin
• an unconformity in the eastern, carbonate-dominated Gulf Basin
The drawdown is coeval with the worldwide Paleocene-Eocene thermal maximum (PETM) possibly triggered by the release of voluminous methane from destabilized hydrates and breached conventional reservoirs of the Gulf at low stand.
The drawdown also profoundly affected the petroleum geology of the Gulf of Mexico, most obviously by deposition of basal Wilcox “Whopper Sand” reservoirs in U.S. and Mexican waters. Further petroleum ramifications include porosity enhancement by fresh water infiltration and leaching of reefal carbonates of the Golden Lane Atoll and deep-water carbonate detritus reservoirs in the Poza Rica Trend and Campeche Sound K/T breccias.
Although a “smoking gun” has not yet been recognized that induces general acceptance of the Paleocene-Eocene Gulf drawdown, convincing evidence may be on the deep-water slopes of western Florida and northeastern Yucatan where sinkholes are present, and steep-walled canyons are observed resembling those along eroded escarpments in preset-day sub-aerial environment .
With increased investigation of the eastern Gulf, the author is confident that definitive evidence will be found that either supports or eliminates the proposed drawdown. Meanwhile, explorers are encouraged to include the idea among their working hypotheses.
Joshua H. Rosenfeld
Josh received his Bachelor’s degree in Geology from the City University of New York in 1960. He taught High School Earth Science for two year before being drafted by the US Army stationed in Guatemala, Central America from 1963 to 1966 as a Terrain Reconnaissance Specialist.
After discharge, he spent another 10 years Guatemala as a Mining Geologist, and eventually as Chief Geologist for the Guatemalan Ministry of Economy. During this time, he also earned his Master’s degree from the University of Miami with thesis work on the 1976 Guatemala earthquake.
Josh returned to the US in 1977 at the State University of N.Y. at Binghamton, earning his doctorate in 1980 on the “Origen and Emplacement of the Santa Cruz Ophiolite in Eastern Guatemala”. He was then hired by Amoco (now BP), working projects around the Gulf of Mexico and on New Ventures in Latin America. He retired from Amoco/BP in 1999 after being the company’s Exploration Manager in Colombia. He then worked on business development in Mexico for Veritas (now CGG) until 2001 before moving to Granbury, Texas where he now ponders geological matters and occasionally consults on international mining and petroleum projects.