Chapter 17: Atlantic and Gulf of Mexico continental margins

Abstract

The U.S. Atlantic and Gulf of Mexico continental margins are thickly sedimented passive margins that formed when Pangea split apart during Middle Jurassic time to create the Atlantic Ocean and Gulf of Mexico. Keys to understanding the process of continental breakup and its relation to preexisting structure are found in the structure of the crust beneath the sediment-filled basins and adjacent platforms and embayments that outline the margins. Because of the great thickness of post-rift sedimentary rock in the basins and the presence of massive reef carbonates and salt layers and diapirs, the crustal structure beneath the basins in the region of the transition between oceanic and continental crust is poorly known at present. Recent advances in seismic reflection and refraction data collection techniques (both sources and receivers), however, are just beginning to yield new data to look at the crustal structure in this important region. One of the most important results on the deep structure of continental margins obtained in recent years is recognition of a thick, high-velocity (7.2 to 7.5 km/sec) layer at the base of the crust beneath the U.S. Atlantic continental margin as well as beneath several other margins worldwide. This layer is observed beneath both extended continental crust and early oceanic crust and has been interpreted to indicate that extensive intrusive magmatism was associated with the late stage of rifting and early sea-floor spreading. Only a weak suggestion of such a layer has been observed beneath the Gulf of Mexico margin, although this may be in part due to the difficulty of observing lower crustal arrivals because of the extensive presence of salt in the shallow section.

Jurassic Reconstruction of the Gulf of Mexico Basin

“…Geological and geophysical aspects of the Central Atlantic opening and the evolution of its margins have been reviewed in many excellent papers (including Manspeizer, 1981;Sheridan, 1989;Trehu et al, 1989) and the plate tectonic aspects have been summarized in Olivet et al (1984) and Klitgord and Schouten (1986). The plate kinematic framework advanced in the latter publication, including rotation parameters and spreading rates, have been used without any revision in the present study.…”

Coastal Subsidence Due to Faults: Insights from Elevation Profiles of Vehicular Bridges, Southeastern Louisiana, U.S.A.

“…Three of the five faults investigated here are considered to be an eastward extension of the TBRFZ (Figures 2 and 3). The en echelon geometry of this fault zone follows the underlying Lower Cretaceous carbonate shelf edge margin and south flank of the Wiggins Arch (Montgomery, 2000;Tréhu et al, 1989). The margin (and the fault zone) separates two regional Gulf Coast provinces.…”

Crustal structure of the eastern Piedmont and Atlantic coastal plain in North Carolina and Virginia, eastern North American margin

“…1960;Hales et al 1968;James et al 1968). During the 1970s, the US Geological Survey conducted seismic reflection surveys along the US Atlantic continental margin (summarized in Pakiser and Mooney 1989) to determine the crustal structure and tectonic framework along the margin (Klitgord et al 1988;Trehu et al 1989;Glover and Klitgord 1995). Cook et al (1979Cook et al ( , 1981 interpret seismic reflection profiles in terms of thin-skinned tectonics in the southern Appalachian Mountains.…”