--> ABSTRACT: Tectonic Controls on Pliocene Evaporite Facies, Enriquillo Basin, Dominican Republic, by Michael E. Lamar and Paul Mann; #91022 (1989)

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Tectonic Controls on Pliocene Evaporite Facies, Enriquillo Basin, Dominican Republic

Michael E. Lamar, Paul Mann

Well, seismic stratigraphic, and outcrop observations from the Enriquillo basin, Dominican Republic, are used to reconstruct Pliocene evaporite environments in a complex strike-slip basin. The 2,000-km2 floor of the Enriquillo basin is presently bounded by strike-slip, reverse, and thrust faults which form part of a 200 to 250-km wide zone of left-lateral, strike-slip motion between the North American and Caribbean plates. Convergent strike-slip displacement of bounding mountain blocks over the last 5 m.y. has depressed certain areas of the present valley floor to 80 m below sea level. In the deepest part of the basin, middle Miocene carbonate basement is overlain by up to 5 km of upper Miocene to Holocene clastic and evaporitic sedimentary rocks.

Surface and subsurface data indicate important tectonic controls on two distinct groups of Pliocene evaporite facies. (1) A shallow-water evaporite group occupies a 50-km2 anticlinal high defining the northern edge of the post-middle Miocene basin. This shallow-water group consists of four 1 to 9 m-thick gypsum horizons within an 860-m thick, coarsening-upward section of sandstone, siltstones, and conglomerate. Gypsum facies include nodular alabastrine gypsum, finely crystalline laminated gypsum, cavoli-type selenite with blades up to 40 cm in length, and gypsrudites. (2) A deep-water evaporite group occupies a 150-km2 synclinal low in the subsurface immediately to the south of the exposed shallow-water group. This deep-water group consists of approximately 1,700 m of 0.3 to 2-m thick beds of halite, gypsum, and anhydrite interbedded with euxinic black mudstones and siltstones. We interpret the deep-water evaporite group as forming within an actively subsiding synclinal axis, while the shallow-water evaporite group formed 10-20 km to the north on an actively growing anticline. This anticlinal high acted to shield the deep-water evaporite group from coarse clastic input.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.