The Role of Ocean Currents on Platform Drowning in the Straits of Florida

Abstract

The breakup of the Florida-Bahamas megabank during the Cretaceous opens up the seaway for ocean currents to flow through the Straits of Florida in the Paleocene. The shallow water carbonate depositional environment persisted until the mid-Cretaceous, when these platforms were not able to re-establish and drowned. The drowning of Florida platform during the Late Cretaceous shows similar seismic geometry as the Middle Miocene platform drowning.

The escarpment margin to the south of the drowned mid-Cretaceous platform is onlapped by continuous seismic reflections of deep-water deposits. However, above the drowning unconformity, a mounded geometry of the deep-water deposits was observed. Mounded geometry that reminiscent drift deposition is also onlapping on the Middle Miocene platforms top. The drowning unconformity is the top of the Miami and Pourtales Terrace. Iron-manganese hardgrounds mantle the top of the Late Middle Miocene strata and produce a high-amplitude reflection. The non-deposition on the two terraces are attributed to the Florida Current, which has swept this part of the drowned platform clean of sediments since the Late Middle Miocene.

The platform drowning also coincides with the onset of the modern Gulf Stream system, which is equivalent to the onset of Florida Current in the Straits of Florida. The coeval occurrence of current intensification and platform drowning is evidence that the two processes are linked. We propose that sweeping of platform margin by currents prevented the shallow water carbonate platform from re-establishing and causing it to drown.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018