Imaging the Deep Structure of the Central DeathValley Basin Using Receiver Function, Gravity,and Magnetic Data

We use receiver function, gravity, and magnetic data to image the deep structures of central Death Valley. Receiver function analysis suggests the Moho is 24 km deep in the central part of the basin and deepens to 33 km to the east and 31 km to the west. The estimated lower crustal density is 2900 kg/m3, which suggests a gabbroic composition, whereas the upper crustal density, excluding basin sediments, is estimated to average 2690 kg/m3 or approximately a quartzofeldspathic composition. We modeled the magnetic sources as upper crustal to suggest a relatively shallow Curie depth in this region of high heat flow. We developed models to test the hypothesis that a low-density, non-magnetic body (magma or fluid-rich material?) within the lower crust at a depth of 15 km could coincide with the location of the Death Valley bright spot imaged on a deep seismic reflection profile. Those models suggest that if there is a low density region in the mid to lower crust in the area of the bright spot, then the region is also likely to be underplated by mafic or ultramafic materials which may have contributed to heating, uplift, and thinning of the crust during extension.

Crustal Structure of the Salton Trough: Incorporation of Receiver Function, Gravity and Magnetic Data

The Salton Trough of southwestern California is inferred to be an incipient ocean basin, and is a polyphase basin with significant extension in addition to dextral shear. To further explore the origin and evolution of this basin, we have incorporated receiver function, gravity, and aeromagnetic data to construct new subsurface crustal scale models. Receiver function analysis suggests the Moho is 20 km deep to the southwest of the Salton Sea and deepens to 32 km in the region east of the Salton Trough and dome in shape. Crustal modeling shows that the density of the lower crust is 2950 kg/m3, which is an indication for gabbroic com- position, while the density of the upper crust varies from 2500 kg/m3 to 2600 kg/m3 and the depth of sedi- mentary and meta-sedimentary rocks appears to be 8 - 10 km. Most magnetic anomalies show shallow relief and are low amplitude with some exceptions in the marginal areas, suggesting the absence of shallow buried mafic intrusions and deep basement. Our models show a magmatic body to the southwest of the Salton Sea at depth of about 18 km and extend in SW-NE direction for about 90 km, We expect this magmatic body (mix- ture of lower crust and upper mantle material) is responsible for crustal thinning, stretching and rifting, ac- cording to the crustal models this body doesn’t exist in the north region of Salton Trough, thus, no further propagate of the rift is expected in the north.