Stratigraphic record of Pliocene-Pleistocene basin evolution and deformation within the Southern San Andreas Fault Zone, Mecca Hills, California

• Published in: Tectonophysics 2017-11, Vol.719-720, p.66-85
• Main Authors: McNabb, James C., Dorsey, Rebecca J., Housen, Bernard A., Dimitroff, Cassidy W., Messé, Graham T.
• Format: Article
• Language: English
• Subjects: Active control; Cenozoic; Conglomerates; Deformation; Deformation mechanisms; Evolution; Fault lines; Fault zones; Faults; Geologic mapping; Geological faults; Geological mapping; Gulf of California; Hills; Kinematics; Magnetostratigraphy; Mecca Hills; Palaeomagnetism; Paleomagnetism; Pleistocene; Pliocene; San Andreas Fault; Sedimentary rocks; Sedimentation; Sedimentology; Slip; Spring; Stratigraphic analysis; Stratigraphy; Strike-slip basins; Studies; Tectonostratigraphy; Terrestrial environments; Unconformity; Uplift; Valleys
• ISSN: 0040-1951; 1879-3266
• DOI: 10.1016/j.tecto.2017.03.021

A thick section of Pliocene-Pleistocene nonmarine sedimentary rocks exposed in the Mecca Hills, California, provides a record of fault-zone evolution along the Coachella Valley segment of the San Andreas fault (SAF). Geologic mapping, measured sections, detailed sedimentology, and paleomagnetic data document a 3–5Myr history of deformation and sedimentation in this area. SW-side down offset on the Painted Canyon fault (PCF) starting ~3.7Ma resulted in deposition of the Mecca Conglomerate southwest of the fault. The lower member of the Palm Spring Formation accumulated across the PCF from ~3.0 to 2.6Ma during regional subsidence. SW-side up slip on the PCF and related transpressive deformation from ~2.6 to 2.3Ma created a time-transgressive angular unconformity between the lower and upper members of the Palm Spring Formation. The upper member accumulated in discrete fault-bounded depocenters until initiation of modern deformation, uplift, and basin inversion starting at ~0.7Ma. Some spatially restricted deposits can be attributed to the evolution of fault-zone geometric complexities. However, the deformation events at ca. 2.6Ma and 0.7Ma are recorded regionally along ~80km of the SAF through Coachella Valley, covering an area much larger than mapped fault-zone irregularities, and thus require regional explanations. We therefore conclude that late Cenozoic deformation and sedimentation along the SAF in Coachella Valley has been controlled by a combination of regional tectonic drivers and local deformation due to dextral slip through fault-zone complexities. We further propose a kinematic link between the ~2.6–2.3Ma angular unconformity and a previously documented but poorly dated reorganization of plate-boundary faults in the northern Gulf of California at ~3.3–2.0Ma. This analysis highlights the potential for high-precision chronologies in deformed terrestrial deposits to provide improved understanding of local- to regional-scale structural controls on basin formation and deformation along an active transform margin. •We interpret a 3–5Myr history of deformation and sedimentation in the Mecca Hills.•We use magnetostratigraphic analysis and the 0.76Ma Bishop Ash to constrain ages.•Sedimentary rocks in the Mecca Hills record regional tectonic reorganizations.•Deformation events at ~2.6Ma and ~0.7Ma were controlled by regional tectonics.•Vertical slip on the Painted Canyon fault controlled local sedimentation.