Nature of the crust in the northern Gulf of California and Salton Trough

Abstract

In the southern Gulf of California, the generation of new oceanic crust has resulted in linear magnetic anomalies and seafloor bathymetry that are characteristic of active seafloor-spreading systems. In the northern Gulf of California and the onshore (southeastern California, USA) Salton Trough region, a thick sedimentary package overlies the crystalline crust, masking its nature, and linear magnetic anomalies are absent. We use potential-field data and a geotherm analysis to constrain the composition of the crust (oceanic or continental) and develop a conceptual model for rifting. Gravity anomalies in the northern Gulf of California and Salton Trough are best fit with crustal densities that correspond to continental crust, and the fit is not as good if densities representative of mafic rocks, i.e., oceanic crust or mafic underplating, are assumed. Because extensive mafic underplated bodies would produce gravity anomalies that are not in agreement with observed gravity data, we propose, following earlier work, that the anomalies might be due to serpentinized peridotite bodies such as found at magma-poor rifted margins. The density and seismic velocities of such serpentinized peridotite bodies are in agreement with observed gravity and seismic velocities. Our conceptual model for the Salton Trough and northern Gulf of California shows that net crustal thinning here is limited because new crust is formed rapidly from sediment deposition. As a result, continental breakup may be delayed.

Oceanic Isostasy: Seafloor Spreading and Rift Localization

“…While the Salton Trough remains a pull-apart basin, it is not wholly clear whether currently submerged northern gulf basins have recently ruptured fully to seafloor spreading or remain in pull-apart mode (Martin-Barajas et al, 2013;van Wijk et al, 2019) as thick sediments obscure…”

Oceanic Isostasy: Seafloor Spreading and Rift Localization

“…While the Salton Trough remains a pull-apart basin, it is not wholly clear whether currently submerged northern gulf basins have recently ruptured fully to seafloor spreading or remain in pull-apart mode (Martin-Barajas et al, 2013;van Wijk et al, 2019) as thick sediments obscure…”

Looking beyond kinematics: 3D thermo-mechanical modelling reveals the dynamics of transform margins

“…Kameyama et al, 1999;Precigout et al, 2007). To consider that change we limit the Drucker-Prager yield stress to a maximum deviatoric stress of 400 MPa according to the findings in Watremez et al (2013). The ductile deformation is modelled with the Arrhenius flow law for dislocation creep:…”