Southeast Georgia embayment high-resolution seismic-reflection survey

Abstract

A high-resolution seismic survey of the offshore part of the Southeast Georgia Embayment on about a 20 km spacing was completed in 1976. A stratigraphic analyses of the data shows that the largest controlling factor in the depositional history of the shelf has been the Gulf Stream. These currents have shifted back and forth across the shelf, at times incising into shelf sediments, and at all times blocking much of the accumulation of Cenozoic sediments seaward of the Florida-Hatteras Slope. In the southern region the Gulf Stream maintained its present position since Miocene time, blocking the accumulation of Pliocene and younger rocks on the Plateau. Northward, in the middle, region the currents turned slightly to the northeast. The inner portion of the Blake Plateau has been scoured of sediments since the Paleocene in this area, and scouring has also occurred on the shelf from time to time. In the northern part of the survey area a more easterly flow of the Gulf Stream has allowed Eocene and younger rocks to be deposited on the Plateau. Line drawings and a geologic map show the distribution of the various Cretaceous and Cenozoic units. A number of potential environmental hazards or constraints to petroleum development seen in the reflection data are identified. Besides current scour and erosion features, these include gravity faults on the slope, a slump, faulting on the inner Blake Plateau, the shelf edge reef, and deep water reefs on the Blake Plateau.

Analyses of light hydrocarbons from the Florida-Hatteras slope and Blake Plateau

“…The Gulf Stream skirts the edge of the shelf and has affected the development of the'Florida-Hatteras Slope and Blake Plateau (Edsall, 1978). Areas of submarine erosion and scour, probably results of action by the Gulf Stream, were observed on many of the seismic records (Edsall, 1978;Dillon, 1979, 1980a).…”

“…Areas of submarine erosion and scour, probably results of action by the Gulf Stream, were observed on many of the seismic records (Edsall, 1978;Dillon, 1979, 1980a). Profiles along track lines 9 and 15 (from Edsall, 1978) The activity of the Gulf Stream has either removed sediments younger than Paleocene or prevented deposition of the younger sediments in large areas of the southern and middle portions of the survey area of the Florida-Hatteras Slope and Blake Plateau (Edsall, 1978). Site 34960 was located in an area where Edsall (1978) and Paull and Dillon (1979) suggested that Paleocene sediments may be exposed on the sea floor.…”

“…Geology of this region has been summarized by others (1975, 1978), Edsall (1978), and Dillon (1979, 1980a).…”

“…A 600-joule minisparker was used to collect the high-resolution siesmic-reflection data presented by Edsall (1978). The single-channel seismic-reflection profiles reported by Dillon (1979, 1980a) Core sites in this study were selected on the basis of the available seismic data provided by others (1975, 1978), Edsall (1978), and M.M.…”

“…Seismic surveys of the offshore Southeast Georgia Embayment, FloridaHatteras Slope, and western Blake Plateau between latitudes 29°30'N and 33°31'N were conducted by the U.S. Geological Survey during the summer and fall of 1976 (Edsall, 1978;Dillon, 1979, 1980a). A 600-joule minisparker was used to collect the high-resolution siesmic-reflection data presented by Edsall (1978).…”