Cenozoic Deformation along the Little Pine Fault Zone, and Implications for the Tectonic History of the Santa Maria Basin, California

In the Santa Maria Basin (SMB), which lies along the northern boundary of the Western Transverse Ranges (WTR) block, basin inversion has resulted in deformation of petroleum-rich, Cenozoic sedimentary rocks. This basin inversion has been caused by the rotation of the WTR block about a vertical axis. Vertical-axis rotation is common to many tectonic environments, but is often overlooked when evaluating active basin inversion. The Little Pine Fault Zone (LPFZ) defines the northeast boundary of the SMB. To date, no studies have been performed that utilize kinematic indicators, fault-slip data, or fold pattern analysis to support previous interpretations of the faults history.

The primary goal of this study is to obtain an understanding of the patterns and kinematics of structures linked to rotational basin inversion, and to better understand the role that the Little Pine Fault Zone has had in formation of the complex regional geology of the SMB. Types of slip that characterize the LPFZ have been described through analysis of slip plane data, and fold patterns were digitized and analyzed to elucidate the faults movement history. For this study, the LPFZ was broken into five segments, each with an approximated average strike.

Fault data for all locations indicate right-lateral, oblique-slip. Data for the Happy Canyon, Santa Cruz Creek, and Southeastern segments of the LPFZ also yielded p-axis solutions that would indicate a separate episode of sinistral slip. Preliminary analysis suggests that the fold patterns describe 3 separate domains that may point to a new interpretation of the structural framework of the eastern part of the basin: (1) A northwestern domain (Foxen Canyon segment)characterized by right lateral strike-slip, and reverse-oblique slip, (2) A central domain (Zaca and Happy Canyon segments) characterized by reverse-oblique slip, with a right lateral component, and (3) A southeastern domain (Santa Cruz Creek and Southeastern segments) characterized by reverse-oblique slip (RL), as well as a separate phase of sinistral slip. Kinematic data confirm earlier ideas that the Little Pine Fault has experienced a combination of reverse and strike-slip motion. Further work is underway to determine the timing relationship between these two modes of faulting, as well as the temporal relationship between faulting and folding within the basin.
 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California