Eocene basin development and sedimentation patterns in central and western Jamaica

Abstract

Previous palaeogeographic reconstructions of the mid Paleogene to early Neogene of Jamaica were based on microfacies analyses of the White Limestone, with the Clarendon Block (CB) characterized by shallow-water facies dominated by larger benthic foraminifers (LBF) and the North Coast Belt (NCB) characterized by deep-water chalks. The boundary between these units was placed close to the Duanvale Fault Zone, a rather defuse zone of E-W lineaments some 10 km inland from the north coast. Extensive geological mapping, carbonate facies analysis, biostratigraphy and tectonic studies have been undertaken in the last ten years to understand the character of this boundary. Three tectonostratigraphic intervals (conveniently matching lithostratigraphic units) are recognized: (1) early to middle Eocene Yellow Limestone; (2) late Eocene to early Miocene White Limestone; and (3) Coastal Group. In the early (late Ypresian) to middle Eocene (Bartonian), the platform had a ramp-style morphology with a gradual northward deepening from the edge of the CB into the NCB. The CB has four shallow-water clastic-carbonate depositional cycles arranged in a broadly retrogradational set. The NCB has a deepening upward succession passing from clastics (late Ypresian) to shallow-water limestones (early Lutetian) to deep-water marlstones (mid Lutetian to Bartonian). Active tectonics is indicated by NNW-SSE and E-W trending faults at this time, which locally uplifted early Cretaceous limestones and volcaniclastics. Subsequently (beginning in the Priabonian), White Limestone deposition shows a significant basinward shift of facies with fenestral micrites and LBF grainstones extending some 5 km further north than the platform break in Yellow Limestone time, a facies pattern that persists until the early Miocene. The platform margin has markedly changed, and is now steep (maybe a 1 km steep slope) and controlled by a thrust (not the non-existent Duanvale Fault, which is a series of uplift terraces). Significant thrust movements are associated with unconformities on the CB, the tectonic shedding of turbidites into the chalks of the NCB, and also correlate with regressive phases in global transgressive-regressive cycles (demonstrating a likely plate tectonic control on these cycles). In the mid Miocene, the platform margin migrates northwards again, the CB and NCB were uplifted, exposed, and karstified, and the rocks of the Coastal Group were deposited. North-south compression across the CB-NCB, which drives the thrusting, was likely caused by 500 km of convergence between North America and South America from the mid Eocene to present. The new model explains facies patterns exposed across the CB and NCB during the Cenozoic.

AAPG Datapages/Search and Discovery Article #90330©2018 AAPG Hedberg: Geology of Middle America – the Gulf of Mexico, Yucatan, Caribbean, Grenada and Tobago Basins and Their Margins “Integration of the geology of the area from the southern onshore of North America to the northern onshore of South America”, Siguenza, Guadalajara, Spain, July 2-5, 2018