Effect of Large-Scale Shifts of Gulf Stream on Miocene Sedimentation Patterns of Southeastern U.S. Continental Margin: ABSTRACT

Abstract

A broad scour band bordered by zones of nondeposition is present today beneath the high-velocity core of the Gulf Stream; deposition takes place on either side of the scour band where bottom currents are weaker. Because the Gulf Stream serves as a barrier to the seaward dispersal of river-derived detritus, deposits are compositionally zoned; clastic sediment blankets the Florida-Hatteras shelf and slope and carbonate oozes, the Blake Plateau. Similar bands of erosion and nondeposition are observed in buried Cenozoic deposits across the Blake Plateau and under the shelf. The character and areal distribution of these bands suggest earlier Gulf Stream tracks. The vertical and horizontal distribution of these unconformities and their timing coincident with high and low stands of sea level as mapped by Vail suggest that they result from a dynamic response of the Gulf Stream to global sea-level oscillations and that the Gulf Stream axis shifts landward against the Florida-Hatteras slope during high stands of sea level and seaward across the central Blake Plateau during low stands of sea level. As a consequence, a complex sedimentary record is produced in which the scour band and sedimentary facies shift landward with deepening water and seaward with shoaling water. This hypothesis was tested with a sedimentation model based on Vail's sea-level curve for the Miocene. The model successfully predicts the distribution of sedimentary facies, location of depocenters, and disposition of major unconformities within the Miocene section of the region as defined by seismic reflection profiles and drill-hole data from nine well sites. These results suggest that large-scale shifts in the position of the Gulf Stream have exerted the primary control on sedimentation patterns along this sector of the continental margin. End_of_Article - Last_Page 1669------------