Cretaceous geology and tectonic assembly of Jamaica

Abstract

AbstractThis paper provides new data on the Cretaceous geology together with existing data to define four terranes for the Cretaceous of Jamaica. The Northeast Blue Mountain Terrane (NEBMT) contains a shallow-water pile of Campanian basaltic and andesitic lavas interbedded with shallow-water, rudist-bearing limestones. The Southeast Blue Mountain Terrane (SEBMT) contains plume-related basalts attributed to the Caribbean Large Igneous Province (CLIP) of Turonian–Coniacian age overlain by interbedded cherts, limestones and basalts with CLIP affinity of Coniacian–Campanian age; the overlying succession is provisionally attributed to the late Campanian to Maastrichtian. The Western Blue Mountain Terrane (WBMT) contains a suite of Campanian arc rocks intruded by granodiorites which have tectonic contacts with metamorphic rocks (high pressure–low temperate blueschists, amphibolites and greenschists). The Western Jamaica Terrane (WJT) contains a suite of volcanic arc rocks in the Valanginian–Hauterivian, Barremian, Turonian, Santonian to Campanian, and Maastrichtian to Paleocene. These rocks are interbedded with thick to very thick (up to several kilometres) sedimentary sequences which occur at outcrop and in hydrocarbon exploration wells. Three major unconformities are present in the WJT, at the bases of the Crofts Synthem (earliest Campanian), Kellits Synthem (late Campanian to early Maastrichtian) and Yellow Limestone (late Paleocene to early Eocene). The NEBMT and SEBMT are separated from the WBMT and WJT by a NE–SW, left-lateral transform fault that defined the edge of the Caribbean Plate from the early(?) Cretaceous to the mid Eocene and allowed the Cuban oceanic arc and eastern Jamaican terranes to be emplaced between the Americas. Metamorphism in the WBMT indicates the existence of a northeasterly dipping subduction zone which allowed the subduction of CLIP lithosphere in the Campanian. Rudist bivalves suggest an affinity between Jamaica and the Siuna (Chortis) and Guerrero (Mexico) terranes in the Lower Cretaceous, suggesting that these arcs were close together. Subsequently, the three unconformities record interactions between the Jamaican arc segment and the Chortis Block and finally the collision with the Jamaican arc segment with the Maya Block in the Paleocene. The petroleum geology of each Cretaceous terrane is reviewed in the context of source and reservoir rocks. Possible source rocks exist in the Jurassic under northern Jamaica, the Albian to Turonian interval, which is associated with oceanic anoxic events, and the Maastrichtian, which contains thin units of organic-rich shales. Reservoirs are largely confined to limestones which preserve porosity in the body chambers of rudist bivalves and which have also been locally dolomitized and fractured (increasing both porosity and permeability). Oil-associated gas seeps present at outcrop, and oil shows of Jurassic and Cretaceous age from exploration wells indicate the existence of active petroleum systems, but not necessarily of economic hydrocarbon accumulations.