Quaternary rift flank uplift of the Peninsular Ranges in Baja and southern California by removal of mantle lithosphere

Abstract

Regional uplift in southern California, USA, and northern Baja California, Mexico, is interpreted to result from flexure of the elastic lithosphere driven largely by heating and thinning of the upper mantle beneath the Gulf of California and eastern Peninsular Ranges. The geometry and timing of faulting in the Salton Trough and Gulf of California, the history of recent rock uplift along the Pacific coastline, and geophysical data constrain models of lithospheric heating and thinning based on unloading of a continuous elastic plate. High topography that marks the ∼400‐km‐long rift shoulder in northern Baja California mimics the pattern of uplift observed along the Pacific coastline as defined by marine terraces. We interpret this to indicate that recent rock uplift has occurred across the entire width of northern Baja Peninsula and increases from west to east. Pliocene strata deposited at sea level along the Pacific coastline in southern California have not been uplifted significantly above Quaternary marine terrace deposits. This suggests the onset of rock uplift along the Pacific coast here is post‐Pliocene and occurs after Miocene crustal extension in the Salton Trough and Gulf of California. Strong heating of the mantle lid beneath the Peninsular Ranges in northern Baja California thus coincides with crustal extension limited to localized oceanic spreading in the Gulf of California.