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Section 2 Stratigraphy of the Circum Caribbean Realm and the Gulf of Mexico M. Iturralde-Vinent

Section 2 Stratigraphy of the Circum Caribbean Realm and the Gulf of Mexico M. Iturralde-Vinent. Stratigraphic framework

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Section 2 Stratigraphy of the Circum Caribbean Realm and the Gulf of Mexico M. Iturralde-Vinent

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  1. Section 2 Stratigraphy of the Circum Caribbean Realm and the Gulf of Mexico M. Iturralde-Vinent

  2. Stratigraphic framework In order to understand how and when marine animals disperse across Caribbean-Gulf of Mexico area during the Jurassic, a series of columnar-environmental sections have to be elaborated for the area. The next slide is a tectonostratigraphic map of the Caribbean and its surroundings, showing those tectonic terrains that were active during the formation and early evolution of the Gulf of Mexico and the Caribbean. The numbers on the map are the middle position of the regions for which stratigraphic-environmental columnar sections are presented in the later-on slide.

  3. Tectonic units and terrains related to the Jurassic paleogeography of western Pangaea Numbers on the map are the location of the stratigraphic-environmental columnar sections presented in the next slide

  4. Stratigraphic-environmental columns of west-central Pangaea

  5. The stratigraphic sections suggest that west central Pangaea evolved as several distinct areas in terms of the presence of Jurassic marine rocks. These are: A. The Mexican terrains, Gulf of Mexico and South America which yield marine rocks since at least the Lower Jurassic and specially the first two present many stratigraphic similarities B. The Guaniguanico terrain (CSW terrains) and Cuba North-Bahamas which yield marine rocks at least since the Middle Jurassic C. The Chortis Block, Maya Block and Florida Block which yield generally Late Jurassic and younger marine sections The following slide provide a general interpretation of marine environments in the area, taking as a framework the sea level curves.

  6. Evolution of the marine environments This graphic illustrates the fact that, during the Latest Triassic and Jurassic, the sea level curve clearly suggest growing possibilities of incursions of marine environments into the continental margins. In this process about Bajocian times the possibilities of transgressions are larger, and this had a clear reflect in the sedimentary facies of the Caribbean realm and its surroundings. Marine transgressions are recorded in the Bajocian-Bathonian, Oxfordian and Tithonian within the Gulf of Mexico and the Caribbean margins. This diagram also suggest that the Caribbean seaway opened as such much later than the Central Atlantic and the Gulf of Mexico.

  7. The previous slide suggest that permanent marine inundation of the Caribbean took place only since the Oxfordian, but short time incursions may have taken place since the Bathonian. For biogeography purposes, it is important to be precise as when the Caribbean marine pathway opened, or in other words, when and how western Laurasia and western Gondwana became isolated as individual landmasses. The answer to this problem can be explored from two sources of non-biological, but stratigraphic evidences within the Caribbean realm: 1. The first source is the age of the oldest ocean crust in the Caribbean, which is Oxfordian, or probably older 2. The second source can be the oldest marine rocks within the latest Triassic-Jurassic time interval in the Caribbean In the following slides will evaluate this second matter

  8. The oldest marine sediments in the Caribbean realm The oldest Mesozoic marine sediments known from the Caribbean realm crops out in the Cuban Guaniguanico terrain and belong to the pre mid-Oxfordian San Cayetano and equivalent Formations. This formation is a coastal siliciclastic complex with shallow marine Bajocian-Bathonian shales and early Oxfordian marine sandstones and limestones as well as marine basalts. The possibility of the occurrence of older marine sediments in this unit requires more investigation. Outcrop of San Cayetano Formation

  9. SEISMIC SECTION FROM FLORIDA TO BLAKE BAHAMAS Florida Strait Providence channnel Blake Bahamas Basin Upper Jurassic Latest Triassic Upper Jurassic Lower to Middle Jurassic Continental crust Oceaniccrust Pre Late Jurassic rift basins This seismic section display pre-Upper Jurassic rocks filling rift basins, but it is not known if these deposits contain marine strata, neither its precise age, which according to some authors is not older than Callovian or the best Bajocian. Drilling of these Mesozoic strata is important in order to identify the oldest marine rocks.

  10. Conclusions of Section 2 The stratigraphic data discussed in this section illustrate the following facts: 1. The Mexican terrains and the Gulf of Mexico were inundated by marine water since the Early Jurassic 2. The Caribbean area, represented by the continental margin sections in the Guaniguanico terrain (CSW) and the North Cuba-Bahamas area, were inundated by marine water since the Middle Jurassic (Bajocian-Bathonian), but more research of the San Cayetano Formation and the sediments filling of the Florida-Bahamas rift basins is needed.

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