Tectonostratigraphy of Cretaceous Carbonate Platform and Slope in the Santaren Channel, Bahamas

Abstract

In the GOM/Caribbean area, aggrading to prograding Albian platforms are well known whereas Cenomanian platforms have not been widely recognized below the well-known Mid Cretaceous Unconformity. Based on an extensive 3D seismic dataset in the Santaren Channel area of the Bahamas, we investigate the development and demise of an Albian and a Cenomanian platforms in an active compressional tectonic setting. The initiation and development of the Albian platform corresponds to the onset of breakup of the Early Cretaceous Megabank with clear shelf-to-basin differentiation within Late Albian. The top of the Albian platform is characterized by a karst event followed by the drowning of the Albian platform and the backstepping of the platform margin 15 to 25 km back its location in the Albian. The continuing post Albian overall relative sea-level increase leads to the development of an a 1000 m high aggrading Early Cenomanian platform. This steep-sided platform has spectacular margin faulting, collapse and rotation during Cenomanian time along margin parallel faults (or slides) plane. The steep sided Cenomanian platform has a by-pass slope with a thick sediment wedge onlaping the steep slope that contain high amplitude and slightly incoherent seismic reflection that are interpreted as a debris flow related to margin collapse. High amplitude, wavy and contorted reflections mark the top of the platform corresponds to the regionally recognized MCU exposure event. The subsequent drowning of the MCU platform is characterized by the development of numerous up to pinnacles. Tectonic loading and tilting of the platform produces normal faults and large slumps of the drowning sediments. The Cenomanian Platform morphology has lasting influence on the Tertiary deposits, potentially up to the sea floor. Tertiary pelagic sediment onlap that topography and differential compaction between the area of the Cenomanian platform and the more basinal area create a margin parallel fault that almost reach the seafloor. The massive Cenomanian Platform seems to have a strong control on the shape of the folds associate with the Cuban orogeny. Compression caused preferential deformation of the Albian and post-Albian pelagic sediment but seems to just have tilted the MCU platform while leaving it unfolded. As the deformation front propagated eastward, detachment occurs and thrust faults initiated on a deep ductile layer, a decollement potentially mediated by salt.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017