Geology of the Lucea Inlier, Western Jamaica

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Grippi, Jack
Lucea Inlier; petrology; tectonics; Geology; Sedimentology; Tectonics and Structure
thesis / dissertation description
The Lucea Inlier exposes a Santonian to Campanian 4 km + thick sequence of shale-siltstone, resedimented volcaniclastics, lenses of shallow-water limestone, micritic limestone, pebbly mudstone and sandy pebble to boulder conglomerate. Clastics were deposited by a variety of gravity flow mechanisms. Petrographically sandstones are lithic or feldspathic arenites and contain only very small amounts of detrital quartz. Structurally the inlier is characterized by simple, open, east-west trending folds. A spaced, vertical axial-planar cleavage is developed in shales and fine siltstones. Two major east-west trending left-lateral fault zones, the Fat Hog Quarter and Maryland faults, cut the inlier into three blocks, northern, central and southern. The basal part of the sequence has been subjected to a prehnite-pumpellyite metamorphism. The rocks of the Lucea Inlier are interpreted to represent a shelf to basin sequence within an upper slope basin of a Cretaceous intraoceanic arc trench system. Detritus shed from the arc was funneled down submarine canyons feeding a submarine fan complex. Between canyon heads, shoal areas fringing volcanic islands locally accumulated bioclastic, reef-type limestone. The geology of the northern Caribbean plate boundary records a complex array of Cretaceous to Eocene arc-trench systems that has been modified by Cenozoic left-lateral slip along the Oriente and Swan transforms. Ridge related north-south lineated topography of the Cayman Trough suggests that a minimum of 720 km of left-lateral movement has occurred between the North American and Caribbean plate since approximately Oligocene times. Presently active northwest, northeast and east-west trending structures within Jamaica are interpreted as being of compressional, extensional and strike-slip origin, respectively, and are thought to be related to Recent left-lateral slip along the northern Caribbean plate boundary.