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General Facts about the Gulf of Mexico
From: Gore, 1992; Darnell and Defenbaugh, 1990; unless otherwise noted.
LOCATION AND SIZE
ORIGINS AND GEOLOGIC HISTORY
From: Gore, 1992; Donnelly, 1975; Martin, 1975; Uchupi, 1975 After Salvador, 1991
The Gulf of Mexico basin is a relatively simple, roughly circular structural basin approximately 1,500 km in diameter, filled in its deeper part with 10 to 15 km of sedimentary rocks that range in age from Late Triassic to Holocene (approximately 230 m.y. to present). Little is known about the geologic history of the Gulf of Mexico Basin before Late Triassic time. Since pre-Triassic rocks are known from only a few widely separated outcrop areas and wells, much of the geologic history of the basin during Paleozoic time needs to be inferred from the study of neighboring areas. Some authors have postulated the presence of a basin in the area during most of Paleozoic time, but most evidence seems to indicate that Paleozoic rocks do not underlie most of the Gulf of Mexico basin and that the area was, at the end of Paleozoic time, part of the large supercontinent of Pangea, the result of the collision of several continental plates. The present Gulf of Mexico basin, in any case, is believed to have had its origin in Late Triassic time as the result of rifting within the North American Plate at the time it began to crack and drift away from the African and South American plates. Rifting probably continued through Early and Middle Jurassic time with the formation of "stretched" or "transitional" continental crust throughout the central part of the basin. Intermittent advance of the sea into the continental area from the west during late Middle Jurassic time resulted in the formation of the extensive salt deposits known today in the Gulf of Mexico basin. It appears that the main drifting episode, during which the Yucatan block moved southward and separated from the North American Plate and true oceanic crust formed in the central part of the basin, took place during the early Late Jurassic, after the formation of the salt deposits.
Since Late Jurassic time, the basin has been a stable geologic province characterized by the persistent subsidence of its central part, probably due at first to thermal cooling and later to sediment loading as the basin filled with thick prograding clastic wedges along its northwestern and northern margins, particularly during the Cenozoic. To the east, the stable Florida platform was not covered by the sea until the latest Jurassic or the beginning of Cretaceous time. The Yucatan platform was emergent until the mid-Cretaceous. After both platforms were submerged, the formation of carbonates and evaporites has characterized the geologic history of these two stable areas. Most of the basin was rimmed during the Early Cretaceous by carbonate platforms, and its western flank was involved during the latest Cretaceous and early Tertiary in a compressive deformation episode, the Laramide Orogeny, which created the Sierra Madre Oriental of eastern Mexico.
Today, the Gulf of Mexico is a small oceanic basin surrounded by continental land masses. Due to their physical structure, the Gulf and the Caribbean Sea are sometimes combined and referred to as the 'American Mediterranean'. Uchupi (1975) divides the Gulf into two distinct geographical provinces (Terrigenous and Carbonate) while Antoine (1972) recognizes seven. The scheme proposed by Antoine is presented here, with additional information derived from other sources.
1) Gulf of Mexico Basin
2) Northeast Gulf of Mexico
3) South Florida Continental Shelf and Slope
4) Campeche Bank
5) Bay of Campeche
6) Eastern Mexico Continental Shelf and Slope
7) Northern Gulf of Mexico
CIRCULATION AND CURRENTS
Water enters the Gulf through the Yucatan Strait, circulates as the Loop Current, and exits through the Florida Strait eventually forming the Gulf Stream. Portions of the Loop Current often break away forming eddies or 'gyres' which affect regional current patterns. Smaller wind driven and tidal currents are created in nearshore environments.
Drainage into the Gulf of Mexico is extensive and includes 20 major river systems (>150 rivers) covering over 3.8 million square kilometers of the continental United States (Moody, 1967). Annual freshwater inflow to the Gulf is approximately 10.6x1011 m3 per year (280 trillion gallons). 85% of this flow comes from the United States, with 64% originating from the Mississippi River alone. Additional freshwater inputs originate in Mexico, the Yucatan Peninsula, and Cuba.
The Gulf of Mexico ecosystem provides a wide array of valuable resources to the nations on its shores. Brief summaries of petroleum and fisheries resources can be found below.
Physical / Mineral
It is estimated that 1.4-7.2x108 barrels of petroleum and 4.4-22.3x1010 cubic meters of natural gas are present beneath the seafloor in the northern Gulf (Darnell and Defenbaugh, 1990). According to the Minerals Management Service, offshore operations in the Gulf produce a quarter of the U.S. domestic natural gas and one-eighth of its oil. In addition, the offshore petroleum industry employs over 55,000 U.S. workers in the Gulf (MMS, 2002). In Mexico, the Secretariat of Energy (Secretaria de Energia - SENER) estimated that the daily crude oil and natural gas production from Gulf of Mexico offshore operations in the years 2000 to 2005 ranged from 2.293 to 2.839 million barrels and 41.4 to 44.8 million cubic meters, respectively (SENER 2006).
Gulf fisheries are some of the most productive in the world. In 2000, the commercial fish and shellfish harvest from the five U.S. Gulf states was estimated to be 1.7 billion pounds (approximately 772 million kg), which represents almost 1/5 (19.4%) of the total domestic landings in the United States. In the same year, commercial catches in the Gulf represented approximately 25% of the total U.S. domestic commercial fishing revenue and were valued at over $900 million. The Gulf also supports a productive recreational fishery. Excluding Texas, U.S. Gulf states accounted for over 40% (>104,000 lbs or >47,000 kg) of the U.S. recreational finfish harvest in 2000 (O'Bannon, 2001).
Antoine, J.W. 1972. Structure of the Gulf of Mexico. In: Rezak, R. and V.J. Henry (eds.) Texas A&M University Oceanographic Studies, Volume 3: Contributions on the geological and geophysical oceanography of the Gulf of Mexico. Gulf Publishing Company, Houston. 303 p.
Antoine, J.W. and Ewing, J.I. 1963. Seismic refraction measurements on the margins of the Gulf of Mexico. J. Geophys. Res. 68:1975-1996.
Bornhauser, M. 1958. Gulf Coast tectonics. Am. Assoc. Petroleum Geologists Bull. 42:339-370.
Bryant, W.R., Antoine, J.W., Ewing, M. and Jones, B. 1968. Structure of Mexican continental shelf and slope, Gulf of Mexico. Am. Assoc. Petroleum Geologists Bull. 52:1204-1228.
Darnell, R.M. and R.E. Defenbaugh. 1990. Gulf of Mexico: Environmental Overview and History of Environmental Research. American Zoologist 30:3-6.
Donnelly, T.W. 1975. The geological evolution of the Caribbean and Gulf of Mexico, some critical problems and areas. Chapter 3, The age of the Gulf of Mexico. In: Nairn, A.E.M., and Stehli, F.G. (eds.). The ocean basins and margins, vol. 3: The Gulf of Mexico and the Caribbean. Plenum Press, NY, p. 666-668.
Ewing, M., Ericson, D.B. and B.C. Heezen. 1958. Sediments and topography of the Gulf of Mexico. In: E. Weeks (ed.) Habitat of Oil. Am. Assoc. Petroleum Geologists, Tulsa, p. 995-1053.
Ewing, J.I., Ewing, M. and Leyden, R. 1966. Seismic profiler survey of Blake Plateau. Am. Assoc. Petroleum Geologists Bull. 50:1948-1971.
Gore, R.H. 1992. The Gulf of Mexico. Pineapple Press, Inc. Sarasota Florida. 384 p.
Halbouty, M.T. 1967. Salt domes, Gulf region-United States and Mexico. Gulf Publishing, Houston, 425 p.
Hardin, G. 1962. Notes of Cenozoic sedimentation in the Gulf Coast Geosyncline, USA. In: E.H. Rainwater and R.P. Zingula (eds.) Geology of the Gulf Coast and central Texas and guidebook to excursions. Houston Geol. Soc., Houston, p. 1-15.
Martin, R.G. 1975. Geophysical studies in the Gulf of Mexico. Chapt. 5, Origin of the Gulf of Mexico. In: Nairn, A.E.M. and Stehli, F.G. (eds.). The ocean basins and margins, vol. 3: The Gulf of Mexico and the Caribbean. Plenum Press, NY, pp. 97-99.
Meyerhoff, A.A. 1968. Geology of natural gas in south Louisiana. Lafayette and New Orleans Geological Soc. In: B.W. Beebe and B.F. Curtis (eds.) Natural gases of North America. Am. Assoc. Petroleum Geologists Mem. 9, Tulsa, p. 376-581.
Minerals Management Service (MMS), 2002. Summary of offshore petroleum operations in the Gulf of Mexico OCS Region. Located at: http://www.gomr.mms.gov/homepg/whoismms/aboutmms.html
Moody, C.L. 1967. Gulf of Mexico distributive province. AAPG Bulletin, 51(2):179-199.
Murray, G.E. 1961. Geology of the Atlantic and Gulf coastal province of North America. New York: Harper and Bros.
Nowlin, W.D. 1971. Water masses and general circulation of the Gulf of Mexico. Oceanology 5(2):28-33.
O'Bannon, B.K. 2001. Fisheries of the United States 2000. National Marine Fisheries Service, Office of Science and Technology, Fisheries Statistics and Economics Division. U.S. Dept. Commerce. Silver Spring, MD.
Oglesby, W.R. 1965. Folio of South Flordia basin, a preliminary study. Map series No. 19, State Division of Geology, Florida Geological Survey, Tallahassee.
Ordonez, E. 1936. Principal physiogeographic provinces of Mexico. Am. Assoc. Petroleum Geologists Bull. 20:1277-1307.
Salvador, A. 1991. Introduction. In: Salvador, A. (ed.) The Gulf of Mexico Basin. Geological Society of America, The Geology of North America, Boulder, Colorado.
SENER [Secretaria de Energia]. Sistema de Informacion Energetica: Informacion Estadistica. http://sie.energia.gob.mx/, accessed on July 25, 2006.
Sheridan, R.E., Drake, C.L., Nafe, J.E. and Hennion, J. 1966. Seismic refraction study of continental margin east of Florida. Am. Assoc. Petroleum Geologists Bull. 50:1972-1991.
Turner, R.E. 1999. Inputs and outputs of the Gulf of Mexico. Chapt. 4, In: Kumpf, H., Steidinger, K. and Sherman, K. (eds.) The Gulf of Mexico large marine ecosystem; assessment, sustainability and management. Blackwell Science, Inc. 704 pp.
Uchupi, E. 1975. Physiography of the Gulf of Mexico and Caribbean Sea. In: Nairn, A.E.M. and Stehli, F.G. (eds.) The ocean basins and margins, vol. 3: The Gulf of Mexico and the Caribbean. Plenum Press, NY. 706 p.
Uchupi, E. and Emery, K.O. 1968. Structure of continental margin off Gulf Coast of United States. Am. Assoc. Petroleum Geologists Bull. 52:1162-1193.
Worzel, J.L., Leyden, R. and Ewing, M. 1968. Newly discovered diapirs in Gulf of Mexico. Am. Asso. Petroleum Geologists Bull. 52:1194-1203.
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