Abstract

Geophysical investigations provide new data concerning the tectonic and sedimentary history of the southeastern Santa Barbara Channel region. Structure consists generally of a gently folded east-trending Tertiary synclinorium bordered on the north by a regional thrust fault and on the south by a steep asymmetrical anticlinal ridge. Most structures indicate north-south compression that appears to have occurred during early Pleistocene time. Two generations of faults have been observed in seismic reflection profiles. Faults of the older set are not distinct on the profiles; they trend northwest-southeast and are probably pre-late Miocene. The younger set of faults is well defined; they strike generally east-west and are most likely post-Pliocene. These contrasting trends suggest a possible reorientation of the stress field sometime between middle Miocene and early Pliocene time. Three well-defined unconformities appear to represent widespread erosion in late Miocene, early to middle Pleistocene, and late Pleistocene times. The boundaries of Miocene, Pliocene, and lower Pleistocene strata seem to continue uninterrupted eastward along the southern part of Santa Barbara basin to Hueneme Canyon, where they turn northeast and can be traced to the coast near Port Hueneme. These limits probably represent the south edge of the Santa Barbara basin during Pliocene and Pleistocene time. The continuity of these limits suggests that faulting has not been active since Pliocene time in the southeast corner of the Santa Barbara basin and that the western extension of the Malibu coast fault either extends south of Anacapa Island, or is buried beneath Pliocene sediments between the island and the mainland.