The outer domain of the southern Gulf of Mexico margin: along-strike variations in the continent-ocean transition and salt distribution

Abstract

The Middle Jurassic Campeche salt was deposited during late stages of crustal rifting and prior to the onset of steady-state oceanic spreading. Its early spatial and thickness distribution in the outer domain was therefore controlled by ongoing lithospheric extension and the geometry of breakup. Published interpretations have suggested that the outer domain is: (1) characterized everywhere by an outer trough below the level of oceanic crust, (2) separated by a basement high into the Yucatan subbasin, with an outer trough, and the Campeche subbasin, with an outer high, or (3) more variable, with outer troughs along ridge segments of the margin and outer highs along transform segments. Depth-migrated 2-D seismic data are used to test these ideas and map the outer domain along much of the Yucatan and northern Campeche portions of the margin. The results are illustrated by a single surface representing the combined base of autochthonous salt and the top oceanic crust along with three boundaries: the inner edge of the outer trough, the limit of oceanic crust (LOC), and the frontal edge of the early salt nappe extending out over oceanic crust. The Yucatan margin is dominated by outer troughs with short offsets, whereas the Campeche margin is dominated by outer highs with short intervening outer troughs. In both areas, the salt nappe extends farther basinward from the outer troughs than from the outer highs, and is thus more widespread off northern Yucatan. The findings are compatible with model (3) above, where the relationship of salt to underlying crust switched back and forth along strike, occurring in outer troughs along ridge segments but perched above the level of subsequent oceanic crust along transform segments.

AAPG Datapages/Search and Discovery Article #90369 © 2020 AAPG Hedberg Conference, Geology and Hydrocarbon Potential of the Circum-Gulf of Mexico Pre-salt Section, Mexico City, Mexico, February 4-6, 2020