TECTONIC-SEDIMENTARY HISTORY OF SOUTHEASTERN JAMAICA

The late Miocene change from a transtensional to transpressional stress regime along the sinistral, strike-slip, northern-boundary of the Caribbean Plate north of Jamaica profoundly affected the sedimentary architecture of the White Limestone and Coastal Groups. The Miocene to Recent succession can be divided into five mixed clastic-carbonate sedimentary packages (A to E) separated by angular unconformities, major hiatuses and/or dramatic facies changes. The Miocene (-?Lower Pliocene) succession (Pelleu Island and ?August Town Formations, package A) consists of deep-water chalks with abundant planktic foraminifers that pass upwards into shallow-water bioclastic carbonates with abundant larger benthic foraminifers. Some sections consist of grainstones with meniscus cements that are interpreted as beachrock deposits. The succession records the rapid uplift of eastern Jamaica associated with NE-SW directed transpression. The Upper Pliocene (Buff Bay and Bowden Formations, package B) is represented by deep-water planktic-foraminifer-bearing marls interbedded with sediment gravity flows containing reworked igneous pebbles, cobbles and boulders. The succession shows rapid subsidence which we relate to the propagation of the Plantain Garden Fault that separated the rapidly uplifting Blue Mountains Block from the subsiding southern St. Thomas Belt. The Early Pleistocene (Manchioneal Formation, package C) is represented by shelf sandstones with HCS, gutter casts and abundant hermatypic corals. The succession consists of an offlapping sequence set, with the sequences of probable glacial-eustatic origin. We attribute this phase of uplift to the development of a fault to the south of Jamaica that now forms the island-shelf break. Late Pleistocene successions (un-named formation and Port Morant Formation, packages D and E) are formed by fan-delta successions with mixed marine-clastic sedimentary successions. Each succession was constructed on the southern margin of the St. Thomas Belt, and has a basal angular unconformity indicating an important episode of tectonic deformation. We suggest that the tectonic events separating packages A to E record the successive accretion of the Blue Mountains Block and Southern St. Thomas Belt onto the Gonvae Microplate as stresses propagated to the south-west.