Preliminary tight-fit Neogene paleoreconstruction of Baja California Peninsula, Mexico

Abstract

A preliminary paleoreconstruction of the relative position of Baja California peninsula with respect to mainland Mexico prior to the opening of the Gulf of California is obtained by a geometric-based computational method. The reconstruction restores the Gulf rifting and the proto-Gulf extension, thus resulting in a tight fit of the peninsula against northwestern Mexico. No major modifications of the margins have occurred since proto-Gulf crustal extension and attenuation, break-~p and Gulf opening, particularly not in the form of coast-parallel transport of margin slivers or trans-peninsular faulting. Major gap areas correspond to the Wagner, Delfin and Sal Si Puedes basins in the northern section, and La Paz Bay in the southern section. Block rotations and strike-slip motion within the extensional zone can accommodate part of the gap areas. The major overlap area corresponds to Los Mochis region of Sinaloa over the Loreto region in the peninsula. The long-term rotation parameters for the past 16 Ma of the Baja California peninsula and the North American plate are found for a best-fitting rotation pole at 32.0°N, 107.5°W and a computed angular rate of 2.64° per Ma, which corresponds to an average half-spreading rate of about 3 cm/yr at the East Pacific rise at the mouth of the Gulf. These values integrate the early crustal extension phase of the proto-Gulf and the subsequent seafloor spreading process, with the recent plate reorganization phases.