Geologie Mexického zálivu

V souvislosti s katastrofální ekologickou havárií v Mexickém zálivu, podívejme se trochu na geologii oblasti.

Little is known about the geologic history of the Gulf of Mexico Basin before Late Triassic time. Some authors  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 is believed to have had its origin in Late Triassic time as the result of rifting within the North American Plate as 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 such as the Louann Salt. 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. ^[3]

In 2002 the geologist Michael Stanton published a speculative essay suggesting an impact origin for the Gulf of Mexico at the close of the Permian, which could have caused the Permian-Triassic extinction event.

Since Late Jurassic time, the basin has been a stable geologic province characterized by the persistent subsidence of its central part, which probably came about first because of thermal cooling and later because of 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, there are 7 main areas of the gulf:

• Gulf of Mexico Basin, which contains the Sigsbee Deep and can be further divided into the continental rise, the Sigsbee Abyssal Plain, and the Mississippi Cone.

• Northeast Gulf of Mexico, which extends from just east of the Mississippi Delta near Biloxi to the eastern side of Apalachee Bay.

• South Florida Continental Shelf and Slope, which extends along the coast from Apalachee Bay to the Straits of Florida and includes the Florida Keys and Dry Tortugas.

• Campeche Bank, which extends from the Yucatan Straits in the east to the Tabasco-Campeche Basin in the west and includes Arrecife Alacran.

• Bay of Campeche, which is an isthmian embayment extending from the western edge of Campeche Bank to the offshore regions just east of the port of Veracruz.

• Western Gulf of Mexico, which is located between Veracruz to the south and the Rio Grande to the north.

More on: http://www.gulfbase.org/facts.php

ZDROJ: www.wapedia.mobi