ABSTRACT: Carbonate Platforms along the Southeast Bahamas-Hispaniola Collision Zone
MULLINS, HENRY
T., Syracuse University, Syracuse, NY, NANCY BREEN, Stanford University, Palo Alto, CA, JAMES DOLAN, California Institute of Technology, Pasadena, CA, ROBERT W. WELLNER, JOHN L. PETRUCCIONE, MARK GAYLORD, and C. BRANNON ANDERSEN, Syracuse University, Syracuse, NY, ALLAN J. MELLILLO and ANITA D. JURGENS, Chevron U.S.A., New Orleans, LA, and DANIEL ORANGE, University of California, Santa Cruz, CA
A SeaMARC II/seismic reflection investigation was conducted along the deep water flanks of Mouchoir Bank, Silver Bank, and Navidad Bank to evaluate the response of these carbonate platforms to active plate tectonic collision. Overall, our data provide evidence of large-scale platform margin retreat, which contrasts sharply with the prograding platform margins in the tectonically passive northwest Bahamas.
North of Silver Bank there is a large, deep water (3000-4000 m) plateau that records the drowning and step-back of an Early Cretaceous carbonate platform margin. Intact (uneroded) segments of this Cretaceous platform margin may occur along the seaward edge of the deep water plateau (Bahama Escarpment) separated by large (20 km across) erosional reentrants. A coalescing system of broad (up to 10 km), shallow (<200 m relief) canyons, akin to mountainous avalanche chutes, funnel debris into the reentrants from the flank of Silver Bank. Drowning and step-back appear to be part of a global response of carbonate platforms to a mid-Cretaceous tectonic pulse of ocean crust formation and relative sea level rise.
The southern margin of Mouchoir Bank has also been drowned and has stepped back. This event occurred during the Late Tertiary prior to the mid-Pliocene and is attributed to tectonic tilting and subsidence resulting from oblique underthrusting of the southeast Bahamas beneath Hispaniola. The southern margin of Mouchoir Bank is also characterized by large amphitheater-shaped "scallops" that expose Tertiary shallow water limestones along their deep water flanks. Seaward of one scallop is a large (25 km wide; 50 km long) mass movement with flow lines preserved on the sea floor. We interpret these scallops as catastrophic collapse structures triggered by large earthquakes generated along the collision zone since the Late Tertiary.
South of Navidad and Silver banks is a series of east-west-oriented down-to-basin normal faults that have caused the platform margin to retreat. Extensional stress along this predominantly transpressive plate boundary may be a consequence of rotation of the nearby Puerto Rico block or lithospheric bending during oblique subduction.
This study provides an initial framework within which to view the actualistic response of carbonate platforms to plate tectonic collision.
AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)