EXHUMATION AND TECTONIC HISTORY OF THE EL PASO MOUNTAINS, SOUTHERN CALIFORNIA, USING LOW-T THERMOCHRONOLOGY AND STRUCTURAL SYNTHESIS

The El Paso Mountains, located north of the central Garlock fault, are at the confluence of the Basin and Range, Sierra Nevada, and the Mojave Desert in California. This region documents the dynamic interplay of these structural provinces along with the evolution of the southwestern North American plate boundary. This study presents low-temperature apatite (AHe) and zircon thermochronology (ZHe) coupled with structural synthesis to determine the timing of exhumation and tilting events of the basement and overlying sedimentary rocks in the El Paso Mountains. The AHe and ZHe dates cluster in three ages and reveal distinct cooling episodes. Initial zircon dates are Late Cretaceous ages (~75 Ma), aligning with the exhumation of metamorphic and plutonic rocks in the southern Sierra Nevada and concurrent with the flat subduction onset. The second cluster is early Miocene AHe (~19 Ma) and coincides with the northeastward tilting and erosion of the Paleogene-Eocene Goler Formation. This deformation event is a component of the transtensional tectonics of the central and northern Mojave Desert resulting from the northward movement of the triple junction. The third cluster of AHe dates correspond to a late Miocene (~8 Ma) cooling event by the end of sedimentation of the late Miocene Dove Spring Formation, concurrent with the final uplift and exhumation of the range. This late Miocene cooling event closely correlates with the slip on the Garlock fault, westward propagation of the central Basin and Range extension, and regional uplift of the southern Sierra Nevada.