Structure and Kinematic Implications of the Western Gulf of Mexico Transform Margin, and the Oxfordian Pre-Drift Reconstruction of Yucatán

Abstract

Abstract

New seismic data from the Mexican Gulf of Mexico (GoM) provide unprecedented insights into the basin's crustal and depositional architecture. The entire basin, including the northern and southern rifted margins, the western transform margin, and the near-pole Florida Straits rift axis and East Yucatán margin are examined using integrated, depth-imaged data. Following a prolonged synrift history and period of salt deposition during outer marginal collapse, seafloor spreading began at a rectilinear ridge system within hyperextended continental crust and/or exhumed sub-continental mantle between the US and Yucatán margins. The initial position of this spreading system is visible in aeromagnetic data and in maps of basement using seismic data. The westernmost spreading segment trended E-W and initially abutted the East Mexican margin at about 23.8N, at the north end of today's eastern Mexico transform margin. Spreading ceased after the ridge had migrated southward to a position east of southern Tuxpan. By then, the boundary had become a continent-ocean fracture zone behind it to the north, but was left as a dead continent-ocean transform to the south. The margin today is narrow, steep and locally inverted (Laramide), and passes southward into Veracruz Basin (which is now subaerial) and Tehuantepec. Oceanic crust outboard from the transform displays a clear top, internal dike sets, normal faults, layer 2/3 boundaries, Moho, and the former spreading ridge. Western GoM ocean crust rises toward the transform COT due to the buoying effect on subsidence of eastern Mexico's coupled continental crust. Beneath the Burgos Basin shelf, an abrupt NW trending southward rise in basement marks the “Burgos marginal offset”, which carried continental Mexico into the “Colombian overlap position” in Pangean reconstructions. This lineament appears to have a displaced continuation in Chiapas on Yucatán Block that provides an offset marker for an Oxfordian reconstruction. There is no salt along the fracture zone-transform margin, as it post-dates salt deposition. The Oxfordian reconstruction predicts that the Perdido area's conjugate margin is the Salinas Basin and trends between the Chiapas Massif and Los Tuxtlas volcanoes. We show the position of the Huayacocotla Basin relative to the Oxfordian reconstruction, whose Callovian Tepexic limes and shales suggest that the seawater for GoM salt probably is west derived.

AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016