Crustal Structure of the Salton Trough: Integration of Receiver Functions, Gravity, and Magnetic Data

We have constructed new crustal scale models of a unique basin, the Salton Trough of southwestern California, which is inferred to be an incipient ocean basin. The Salton Trough is a polyphase basin with significant extension in addition to dextral shear. To further explore the origin and evolution of this basin, we have integrated receiver functions, gravity, and aeromagnetic data to create subsurface crustal scale models. Gravity data analyses show that lower crust is the source of the anomalies in the Salton Trough area. Receiver function data suggests the Moho is 22 km deep to the south of the Salton Sea and deepens to 32 km in the region east of the Salton Trough. Gravity modeling shows that the density of the lower crust is 2950 kg/m3, which is an indication for gabbroic composition, while the density of the upper crust varies from 2650 kg/m3 to 2450 kg/m3 and the depth of sedimentary and meta-sedimentary rocks appears to be 8-10 km. Most of magnetic anomalies show shallow relief and are low amplitude with some exceptions in the marginal areas, which suggests the absence of shallow buried mafic intrusions and deep basement. Slab window model fails to explain the low gravity, low magnetic anomalies along the coastal margin of the Salton Trough because of 1) the steep lateral decrease in the heat flow from the Coastal Ranges to the Great Valley, and 2) the source of the anomalies is in the crust; instead we refer these anomalies to the isostatic effect of the Peninsular Ranges. Gravity data filtering revealed an anomaly that crosses the Salton Trough in E-W direction and extends from the Pacific Ocean to Arizona. We tested several scenarios to explain this anomaly; we suggest that this anomaly represents a Jurassic rift flank.

Keyword(s): 
crustal structure
receiver function
gravity
magnetic
Research Effort: