jurassic paleogeography and biogeography of west central pangaea some preliminary notes l.
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Jurassic paleogeography and biogeography of west-central Pangaea: Some preliminary notes. Section 1 Plate Tectonics: Pre break-up fit of western Pangaea and the early opening of the Caribbean M. Iturralde-Vinent

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Section 1 Plate Tectonics: Pre break-up fit of western Pangaea and the early opening of the Caribbean

M. Iturralde-Vinent

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

Section 3 Biogeography of the Jurassic Marine Animals M. Iturralde-Vinent and Zulma Gasparini

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Section 1

Plate Tectonics:

Pre break-up fit of western

Pangaea and the early opening

of the Caribbean

M. Iturralde-Vinent

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Understanding the west-central Pangaean fit and the break-up of the continents leading to the formation of the Caribbean sea requires a plate tectonic framework as a starting point. Here is chosen the pre-break-up fit of Mann (1999), with some modifications, in order to find a place within Pangaea for the Cuban Southwestern Terrains (Guaniguanico, Pinos and Escambray), as well as for the North Cuban allochthonous belts. Finding a place for these terrains is very important because they encompass some of the only places within the Caribbean realm where the Jurassic continental margin sections outcrop.

The following slides provide some geological data about the Cuban Southwestern Terrains, the North Cuban belts, and the age of the ocean crust, useful to understand the early opening of the Caribbean.

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Present-day position of the Cuban Southwestern

terrains (CSW) and the North Cuba allochthonous belts

(Ophiolites and Placetas belts)

PROTO CARIBBEAN CRUST AND MARGINS

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Tithonian reconstruction of the Caribbean

Jurasic marine basalts found in Siquisique (Bajocian), Guaniguanico terrain (Oxfordian) and Camaján (Tthonian) are indications of extension of the continental margin and the coeval formation of oceanic crust within the Caribbean (Iturralde-Vinent, 1988, 1994, 1998).

Guaniguanico’s

Oxfordian marine

basalts

Camajan’sTithonian

marine basalts

Siquisique’s Bajocian

marine basalts

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Palinspastic cross-sections of the Tithonian Caribbean

PreCallovian

siliciclastics

Tithonian

basalts

Kimmerid-Tith

Carbonate platform

Bathonian-Bajocian

marine rocks

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The age of the ocean crust

in the Gulf of Mexico

The age of the ocean crust in the Gulf of Mexico has been identified as Late Jurassic Oxfordian (Sawyer et al., 1991; Marton and Buffler, 1999), post-dating the evaporite beds deposited in the area.

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The age of the ocean crust within the Caribbean

Dating the Caribbean crust is a complicated matter, as it is considered allochthonous by many authors (Pindell, 1994). Consequently, the occurrence of Jurassic radiolarian cherts associated with basalts in Dominican Republic (Late Jurassic), Puerto Rico (Pliensbachian, Kimmeridgian-Tithonian) and La Desirade (Tithonian) (Montgomery et al., 1994) is currently interpreted as a probe of the allochthony of the Caribbean crust, because these antique crustal elements “pre-date” the opening of the Caribbean (Pindell 1994).

Therefore, the safest way to identify the age of the original ocean crust in the Caribbean would be the occurrence of marine basalts intercalated within the continental margin sections of the area.

Marine basalts are known from Bajocian-Bathonian age (Andean terrains: Siquisique, Venezuela), Oxfordian-early Kimmeridgian age (Guaniguanico terrain, Cuba), and early Tithonian age (Camaján hills, North Cuban foldbelts). As Siquisique may be part of the Pacific ocean crust, the 400 m thick Oxfordian-early Kimmeridgian basalts in Guaniguanico are the oldest best indication of the possible occurrence of in situ oceanic crust in the Caribbean (Iturralde-Vinent, 1988, 1994). This also suggests that oceanic crustal formation may have started somewhat earlier.

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Conclusions of Section 1

1. The pre break-up fit of Pangaea must be kept loose in order to open a space between Maya Block (Yucatan) and South America (SOAM) for the Cuban Southwestern terrains.

2. The presence of marine basalts within the continental margin sections of NOAM and SOAM suggest that the Caribbean may have been partially opened since the Bathonian-Bajocian, but certainly since the Oxfordian.