Mesozoic carbonate platforms and banks of the eastern North American margin

Abstract

The Jurassic—Lower Cretaceous carbonate platforms and banks form a discontinuous belt extending over distance of 6000 km from the Grand Banks up to the Bahamas. Six types of carbonate buildups are recognized and document the variability of depositional, paleo-oceanographic and tectonic processes on the eastern North American margin. The composition of the carbonates closely resembles the Recent deposits of the western Great Bahama Bank since oolitic shoals were present near to the shelf edge, and skeletal, peloid wackestones and biomicrites were deposited in the inner part of the platform. Coralstromatoporoid and sponge bioherms were only rare constituents of the carbonate banks. The thickness of carbonate buildups progressively increases southward along the margin, attaining a thickness of more than 5 km on the Bahamas. The carbonate platforms also become younger southwards, which is thought to reflect the northward movement of the North American plate of less than 1.5 cm/yr. The carbonate platforms were seeded over the continental basement following the taphrogenic period of plate tectonics. Building of carbonate ramps which characterized the Early Jurassic, has began during the transitional period between continental rifting and early drift. The second stage in construction of the carbonate platforms and offshore banks proceeded mainly after separation of the continental plates.