Carlos Rivero¹, John H. Shaw¹

(1) Harvard University, Cambridge, MA

ABSTRACT: Three-Dimensional Modeling of Low-Angle Normal Fault Inversion: A Case Study in the Inner California Borderland, USA

We describe the complex tectonic inversion of a regional low-angle normal system located in offshore southern California. To describe this system, we employ an integrated approach of three-dimensional structural and velocity modeling that incorporates seismic reflection profiles, well control, surface and seafloor geology, and precisely located earthquakes.

The Inner California blind thrust system includes a pair of inverted Miocene extensional detachments that originated during Neogene rifting associated with the formation of the Inner Borderlands. These detachments were reactivated as thrust faults during the Pliocene, when a change to regional transpression inverted the Miocene extensional depocenters, uplifting previously depressed hanging walls. Thrust motions on these detachments also produced several trends of contractional fault-related folds. Growth sediments and regional unconformities record the style and timing of this complex structural inversion.

Our results indicate that the complex geometry of the offshore sedimentary basins in the Inner Borderlands is the result of this tectonic inversion. Moreover, we suggest a genetic correlation between the offshore contractional trends and several coastal and onshore structures that form major oil and gas fields. These results also provide new insights into the sedimentary facies distribution, thermal history, and charge pathways of the offshore hydrocarbon system.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado