INCORPORATION OF NEW DATA TO REFINE THE TECTONIC HISTORY OF THE GULF OF MEXICO 230 MA - 180 MA

The break-up of Pangea and the separation of Laurentia from Gondwana began almost 230 million years ago. While the large scale plate motions have been generally well understood, the initial positions of the smaller blocks and exact timing of rifting and breakup between them remains controversial. We focused on the tectonic evolution of the Yucatan and Florida blocks in an attempt to reconcile interpreted tectonic elements on both margins, namely seaward dipping reflectors and pre-salt basins, to pre-existing tectonic models of the Gulf of Mexico.

Most existing models for the Yucatan begin at 200 Ma or even later. We believe that the reconstruction should start earlier, at 230 Ma when the extension between the Yucatan and Florida blocks began. We used integrated analysis of potential fields and seismic data to determine the extent of the pre-salt basins and the seaward dipping reflector provinces on both conjugate margins. We also used fracture data and extension estimates of rift basins to further constrain the original position of both blocks. The motion of the Yucatan from 230 Ma to the onset of sea-floor spreading was then modeled using stress models based on deformation of the continental lithosphere. Stress changes and their possible effects were modeled using finite element programs coupled with maps of pre-existing features to ensure that the motion predicted would adequately explain the observed deformation. Initial models suggest that the Central Atlantic Magmatic Province (CAMP), emplaced at 200 Ma, coincides with the change in major stresses acting on eastern North America. CAMP resulted from the change from the Yucatan’s and possibly South America’s motion dominating from 230 Ma to 200 Ma to Africa’s motion dominating from 200 Ma to 180 Ma.