Evidence for Thick Sedimentary Sequences Trapped Against Old Strike-Slip Faults--Santa Maria Valley, California
F. C. Monastero
The Santa Maria Valley onshore California has undergone at least two distinct periods of intense deformation, one of which involved primarily thrust faulting and the other of which involved primarily strike-slip movement. The overprint of the thrust faulting has in many places in the valley obscured basement structure and the related role of strike-slip tectonics in basin formation. Recent reflection seismic data acquired with techniques that focus on subthrust structure consistently show coherent reflectors at depths of 3.2 sec two-way travel time (20,000 ft) and as deep as 4.0 sec (26,000 ft). These deep reflectors are located beneath major thrust fault zones and are coincident with negative anomalies in the potential field data. It is believed that these features represent small slivers of pre-Miocene sedimentary rocks which were trapped against the old strike-slip faults during lateral movement. These sedimentary sequences may represent a new play in the Santa Maria Valley.
AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.