Tectonic Evolution of the Palos Verdes Fault - Lasuen Knoll Segment, Offshore Southern California

Abstract

Seismic mapping indicates that Lasuen Knoll, offshore southern California, is a pop-up structure in a restraining stepover of the Palos Verdes Fault. Dextral shear is apparently transferred southeast through a complex of faults in a linked shear zone to the Carlsbad Ridge and Coronado Bank faults. The Palos Verdes fault along Lasuen Knoll has existed since Delmontian time (before 8 Ma) and thus is more or less as old as the segment of the Palos Verdes fault on San Pedro shelf and adjacent to the Palos Verdes Peninsula. Isochore maps of stratigraphic intervals indicate that extension occurred locally along the Palos Verdes Fault to the south of Lasuen Knoll during the Mohnian stage, and became more widespread during the Delmontian stage. Fanning of dips of Repettian stage strata onlapping Lasuen Knoll indicates that Lasuen Knoll began to form as a pop-up structure by the Early Repettian stage and has been active until Recent. Lasuen Knoll is bounded to the north and south along the Palos Verdes-Carlsbad Ridge-Coronado Bank shear zone by transtensional zones. The transtensional zone north of Lasuen Knoll separates it from the Palos Verdes anticlinorium, the other major uplift along the Palos Verdes fault. Lasuen Knoll and the overall structural high that it is part of is similar in dimension and shape to the Palos Verdes anticlinorium. However, recent models of low-angle ramp faults as major causes of the uplift of Palos Verdes cannot be easily applied to Lasuen Knoll.

AAPG Datapages/Search and Discovery Article #90266 © 2016 AAPG Pacific Section and Rocky Mountain Section Joint Meeting, Las Vegas, Nevada, October 2-5, 2016