Integrated Analysis of Seismic Data and Potential Fields in Southeastern Gulf of Mexico With Implications to Pre-Salt Sediments and Crustal Architecture

Abstract

The pre-salt sediments in the Gulf of Mexico are imaged in seismic along the western margin of the Yucatan Peninsula. The characterization of this section from seismic alone is challenging, as the base of the pre-salt layer is not always imaged confidently. In this project, we combine seismic data with gravity and magnetics to study the pre-salt sediments and the overall crustal architecture of the southeastern Gulf of Mexico.

For our analysis we have develop a series of integrated geophysical models throughout the western Yucatan margin to characterize the pre-salt sediments and crustal structures. We then correlated those with lineaments in potential fields to outline key tectonic elements in our study area, namely the pre-salt basin, the region with SDRs in the upper crust, two drastically different crustal zones in continental domain, and the Ocean- Continent boundary (OCB).

As a result of our combined analysis, we drew the following conclusions: 1) The pre-salt basin extends along the entire western margin of the Yucatan; it narrows down to the north and eventually pinches out at the northernmost tip of the peninsula. The pre-salt basin appears to be compartmentalized with the width of individual segments up to 150 km; the thickness of the pre-salt section is up to 3 km. 2) The SDR province is located in the northern part of the study area; it is up to 350 km long and about 50 km wide. It requires higher magnetic susceptibilities in the upper crust to fit the magnetic signal. The SDR region bounds the pre-salt basin under the Yucatan salt province from the south. Our analysis does not support any SDRs along the Campeche margin. 3) Two distinct crustal zones were identified in the continental domain. The first one is under the pre-salt basin; it has stretched and intruded crust with a total thickness of about 10 km.The crust of the second zone is up to 35 km thick. The boundary between them is roughly coincident with the SDRs in the north and with the Campeche magnetic anomaly in the south. The latter is modeled as an intrusive body in the lower crust. 4) Several highly magnetic intrusions in the lower crust are required to fit the observed magnetic signature; some of the intrusions are of the reversed magnetic polarity. This is similar to the observations from the northern GOM.

The results of this study are important for tectonic reconstruction of the Gulf of Mexico, as the pre-salt basins and SDR provinces should be aligned on conjugate margins. The integrative approach in data analysis led to more confident results as the derived subsurface structures and outlined tectonic regions honor multiple geophysical datasets.

AAPG Datapages/Search and Discovery Article #90350 © 2019 AAPG Annual Convention and Exhibition, San Antonio, Texas, May 19-22, 2019