REVISED STRATIGRAPHIC AND TECTONIC EVOLUTION OF THE SAN FRANCISCO RIDGE; AN EMERGING PUSH-UP STRUCTURE IN THE NORTHEAST DOMINICAN REPUBLIC
"The San Francisco Ridge is bounded by left-lateral strike-slip faults associated with the Septentrional Fault System. In this regard, the Septentrional Fault represents a major fracture in the northeast of the Hispaniola Island and separates an uplifted oceanic crust represented by the Cordillera Septentrional, and a “fore arc” basin, corresponding to the Cibao Valley. The San Francisco Ridge is a 50 km long by 11 km wide deformed and faulted asymmetrical anticline, interpreted as a “push-up” structure. It is located in the northeast region of the Hispaniola Island between the Cordillera Septentrional, to the north, and the Cibao Valley, to the south. The stratigraphy of the study area shows a sequence of limestone and dolomite with early Miocene age, calciclastic and siliciclastic mudstones with middle Miocene age and polymictic conglomerates with Pliocene-Pleistocene age that unconformably overlie the older and fined grained sedimentary units. The conglomerates are located in elevated areas of the San Francisco Ridge, especially in the northeast and northwest regions. The conglomerates have clasts of metamorphic and igneous composition, similar to the lithology reported in the Cordillera Septentrional. Topographic location of conglomerates in the San Francisco Ridge, and the origin of its clastic material, suggests that the San Francisco Ridge was in net contact with the Cordillera Septentrional before the late Miocene. Deposition of the conglomerates was associated with rapid uplifting of the San Francisco Ridge and erosion of the older sedimentary units, in response to compression exerted by the North American plate over the northeastern section of the Caribbean plate, occurred from late Miocene up to Early Quaternary. Based on the presence of a transpressive environment associated with an active strike-slip faulting zone, and the folding and tilting of the conglomerates along with the presence of a Quaternary “pull apart” represented by the Nagua valley, we conclude that the northeastern part of the Hispaniola Island is tectonically active and represents a major seismic hazard for the community of the Dominican Republic."
Stratigraphy, Tectonics, Transpressive Environment
City University of New York - City College
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