Recent High Resolution Seismic, Magnetic and Gravity Data Throws New Light on the Early Development of the Gulf of Mexico

Abstract

186,500 km of long (12 km) offset 2D marine seismic data, processed in time and depth, along with gravity and magnetic shipborne data (standard corrections applied) were acquired during 2015-16, covering the entire Mexican Gulf of Mexico (MGoM). These data tie into similar datasets in US waters and enable a better understanding of the deep structure of the entire GoM. The high resolution of the seismic data has allowed: 1. a correction of the GoM oceanic spreading transform fault locations, previously only diffusely identifiable on a Vertical Derivative version of the Sandwell Free Air Anomaly Map; 2. a study of transform zone width and angle of sediment wedges within the transform zone; and finally, 3. a refinement of existing models of the extinct Jurassic-early Cretaceous GoM spreading ridge locations by coupling the above with gravity and magnetic grids (themselves constructed using the transform faults as constraints) and profile plots of seismic depth (real and isostatically balanced) of top oceanic crust vs distance. The shipborne magnetic and gravity data were acquired in a direction slightly oblique to the transform ridges. However, the transform fault constrained magnetic anomaly and gravity maps have a broader frequency content than public magnetic and gravity (largely satellite derived) data. Because of thick sediment (up to 13 km) overlying the oceanic crust in the GoM, the magnetic anomaly signal and therefore the spreading anomaly pattern are more difficult to identify than those in younger and wider oceanic basins. Nonetheless, the location of the magnetic isochrons are readily identifiable by forward modelling of transform parallel transects within each spreading segment, and we are able to review existing models of oceanic opening time, rotation poles and spreading rates. Finally we review spreading ages and bathymetry in a similarly small, but younger, oceanic spreading segment, the Gulf of Aden. This analysis leads us to conclude that, at the end of spreading, new GoM oceanic crust would have been some 1000 meters shallower than if standard age vs depth models (mostly based on wide spreading basins, such as the NW Pacific) were applied. This has important implications for salt deposition models in the entire GoM basin in the mid Jurassic.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017