AAPG Annual Convention and Exhibition

Datapages, Inc.Print this page

Gravity and Geodynamic Modeling of the Gulf of California


The Gulf of California is a young sheared margin that began rifting about 12 million years ago. It is characterized by substantial differences in extensional style and sediment thickness between the northern and southern part, and details of margin structure, the northward extent of oceanic crust, and sediment thickness are debated. We have constructed two-dimensional cross-sections from gravity data to understand the continent-ocean transition, thickness of the sediment layer, and crustal structure beneath the Gulf of California. We used geophysical and geological data from previous studies in the area to constrain our models. The 2D gravity models show the cross-section of the basin and crustal structure of the segments including the new oceanic crust formed in the southern Gulf, highlighting the difference not only between the northern and southern parts of the Gulf but also the dissimilarity of rift widths between adjacent segments. The gravity models differ to some extent from earlier seismic cross sections in terms of margin (a)symmetry, structure and sediment thickness. We propose that rupture of the Gulf of California rapidly followed pull-apart basin formation. 3D geodynamic crustal models of pull-apart basin formation were constructed using the general purpose finite element package Abaqus to demonstrate that a situation favorable for continental breakup develops rapidly when the segments of the strike-slip faults overlap and tensional stresses rotate to become perpendicular to the strike of the master faults. Our numerical models show how the new spreading centers of Gulf of California may have formed within a short period of geologic time. A modified evolutionary model for pull-apart rift formation includes an hour glass-shaped basin that represents an intermediate stage of pull-apart basin development.