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Pattern of Growth Folding at Northern Caribbean Plate Boundary North of Western Hispaniola, as Disclosed by Long-Range Side-Scan Sonar

William P. Dillon, Kathryn M. Scanlon, N. Terence Edgar, Lindsay M. Parson

Off northwestern Hispaniola, where the oceanic crust of the Hispaniola-Caicos basin (North American plate) is being subducted diagonally beneath the island of Hispaniola (Caribbean plate), seismic profiles show folds that increase in amplitude both downward and toward the insular margin and that produce ridges on the sea floor. The areal distribution pattern of these growth folds, as disclosed by GLORIA side-scan sonar imagery, is dominated by long ridges that are approximately parallel to the insular margin; there are also some regions of complex crumpling. Valleys between the ridges commonly are narrow, but some broader valleys are present. Some radial patterns of valleys may relate to slumping off the margin, and smaller gulleys on the flanks of ridges seem to suggest hat mass movement occurred on oversteepened slopes that were produced by active folding. Broad, complex channelways across the ridges appear to funnel turbidity currents to the deep basin. The location of the main channelway at a magnetic low suggests deep structural control. Generally, however, sediments of the Hispaniola-Caicos turbidite basin are being scraped off the downgoing slab and crumpled and faulted independently of basement, a conclusion reached because the smooth magnetic field that is observed shows no relationship to the complex folding of the sediments. Because the growth anticlines become elevated by tectonic processes, similar structures on land or in shallow water might be considered targets for petroleum exploration, if seals are not too disrupted by complex faulting.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.