Early Pleistocene Reorganization of Plate Motion in the Salton-Trough Gulf of California
Document Type
Presentation
Journal/Book Title/Conference
Early Pleistocene Reorganization of Plate Motion in the Salton-Trough Gulf of California
Volume
41
Publication Date
2010
First Page
44
Abstract
Recent studies in the northern Salton Trough document initiation of the San Jacinto, San Felipe, and southern and central (?) Elsinore fault zones within a few hundred thousand years of one another in the early Pleistocene. The Imperial and Cerro Prieto faults probably replaced the paleo-San Andreas fault in the southern Salton Trough at about the same time (Pacheco et al. 2006). Here, we examine whether these shifts signal a previously unrecognized change in the kinematics of the Gulf of California at this time. From bathymetric and magnetic data from the southern Gulf of California, we find evidence for a ~5° CCW change since 3.5 Ma in direction along the Tamayo transform fault and across the Alarcon Rise, in accord with results reported by MacDonald et al. (1979). From well-mapped marine magnetic anomalies adjacent to the Tamayo fracture zone, we estimate that this change occurred between ~1.8 Ma and ~1.2 Ma, when the transforms first evolved to an ocean-ocean geometry (1.8 Ma) or a volcanic ridge began to form along the possibly leaky transform (1.2 Ma). Relatively constant spreading rates of 48±2 mm/yr across the Alarcon rise and northernmost East Pacific rise since ~2.5 Ma appear to exclude a change in seafloor spreading rates as a possible cause of the proposed kinematic reorganization. Evidence documented by Aragon, Martin and other workers for 3-14° coeval CCW rotations of faults in the central and northern Gulf is also consistent with a possible CCW change in the direction of separation across the Gulf of California-Salton Trough during the early Pleistocene. In the central Gulf, fault-strikes rotate as much as 7-14° (Aragon et al, 2005). Rocks adjacent to the Ballenas Transform in the northern Gulf record a 1.8 Ma pulse of heating that probably reflect its initiation (Sieler et al., 2009). This kinematic change affected the entire ~1300 km long Salton-Trough-Gulf of California plate boundary. It was likely synchronous because the reorganization is the same age at the north and south ends of the province, where it is well dated. Contrary evidence includes a small number of transforms faults that exhibit opposite-sense (CW) rotations during this period.
Recommended Citation
JANECKE, S.U., and DEMETS, C., 2010, EARLY PLEISTOCENE REORGANIZATION OF PLATE MOTION IN THE SALTON-TROUGH GULF OF CALIFORNIA: : Geological Society of America Abstracts with Programs, Vol. 41, p. 44.
