Integration With Non-Seismic Methods: An Example From the Northern Gulf of Mexico

Abstract

Seismic imaging in the northern part of the Gulf of Mexico (GOM) is particularly challenging due to presence of thick and complex salt bodies located at multiple levels within over than 15 km thick sedimentary section. Those salt bodies obscure the image not only of sedimentary structures, but also of the crust. That is why the tectonic settings and the crustal distribution in the northern GOM is still being debated. The two contradicting tectonic models have been published for the northwestern GOM - volcanic-rich passive continental margin versus a volcanic – poor rift resulted in exhumed mantle. In the central GOM, the difference between published ocean-continent boundaries (OCB) reaches 140 km (87 mi). This study aims to integrate multiple geophysical datasets from public domains – gravity, magnetics, both reflection and refraction seismic and well data – in order to test different hypotheses for the crustal architecture in the northern Gulf of Mexico.

The set of 2-dimentional subsurface models was developed along several seismic lines; the framework for this study was built on the refraction profiles from GUMBO experiment. The densities and magnetic susceptibilities of the model’s layers were assigned based on published sources. The gravity and magnetic responses were computed and compared with the observed ones; the detected mismatches guided the adjustment of the model in such a way that the model remains geologically reasonable and honors all of the data.

The integrative analysis of seismic, gravity and magnetic data allowed for testing different tectonic hypotheses in the northern GOM and various OCB locations in the central GOM. The result of this study undoubtedly shows that the hyperextended margin with mantle exhumation in the northwestern part of the basin is not supported by both gravity and magnetics, while the hypothesis of volcanic–rich rifted margin is preferable as it agrees better with all the geophysical data used in the study. In the central GOM, the preferred model supports the OCB near the Sigsbee Escarpment; however, the other OCB locations cannot be totally ruled out. Overall, this study illustrates how integrative approach in geophysical data analysis can be used to validate different geological scenarios.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018