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.

Coastal tectonics on the eastern margin of the Pacific Rim: late Quaternary sea-level history and uplift rates, Channel Islands National Park, California, USA

“…In their model, uplift in this region is caused primarily by upwelling beneath the Peninsular Ranges of southern California and the northern Gulf of California (Mexico), due to upper-mantle heating and thinning. The mantle upwelling model proposed by Mueller et al (2009) for southernmost California and northern Baja California may not be applicable to the present study, however, as the Channel Islands are well north of the area for which their model was considered.…”

“…Elsewhere, studies by Ashby et al (1987), Sirkin et al (1990) and Johnson et al (2007) at Mulege, La Paz, Isla Coronados, and Punta Chivato (see Table 2 for U-series data for the latter two localities) indicate just a few meters of uplift of thẽ 120 ka terrace, yielding uplift rates of less than 0.1 m/ka. Thus, although Mueller et al (2009) proposed that there is no Quaternary coastal uplift south of Bahía de Tortugas in Baja California (Figs. 1 and 18), several localities do indicate at least modest amounts of late Quaternary uplift.…”

“…In addition to the mechanisms of uplift described above, Mueller et al (2009) recently proposed an intriguing hypothesis for explaining low rates of marine terrace uplift in southernmost California and northern Baja California. In their model, uplift in this region is caused primarily by upwelling beneath the Peninsular Ranges of southern California and the northern Gulf of California (Mexico), due to upper-mantle heating and thinning.…”

Marine terraces and rates of vertical tectonic motion: The importance of glacio-isostatic adjustment along the Pacific coast of central North America

“…1; Stock and Hodges, 1989;Mueller et al, 2009). In addition to these larger-scale features, smaller faults and folds also occur along the Pacific coast and offshore regions, mostly accommodating the overall crustal motions across the major tectonic boundaries (Kelsey, 1990;Plesch et al, 2007;Gurrola et al, 2014).…”

“…Since that work, several authors have used the difference between the elevation of marine terraces and "global" sea levels to determine uplift rates for tectonic structures across the northern Mexico, California, Oregon, and Washington coasts. These uplift rates have provided important insights into the behavior of major tectonic features, including the Cascadia subduction zone (Muhs et al, 1990;James et al, 2009), the Mendocino triple junction (Merritts and Bull, 1989), the San Andreas fault zone (Anderson and Menking, 1994;Grove et al, 2010), and seafloor spreading centers in the Gulf of California (Mueller et al, 2009), as well as the many local faults and folds along the Pacific coast of central North America ( Fig. 1; Rockwell et al, 1989;Hanson et al, 1992;Kelsey et al, 1996;Grant et al, 1999).…”