Lithostratigraphy of the State 2–14 Borehole: Salton Sea Scientific Drilling Project

Abstract

Sedimentary rocks from the (California) State 2–14 research borehole of the Salton Sea Scientific Drilling Project, located in the Imperial Valley of southern California, were deposited in the continental basin of the Salton Trough. Lacustrine shale and siltstone are the dominant lithologies. Sandstones were deposited in lake margin, meander channel fill, and lacustrine delta environments. Framework modal clast compositions of the sandstones indicate a dominant Colorado River provenance. Rare pebbly mudstones were deposited as storm‐induced debris flows. Primary depositional structures in the sediments are commonly disrupted by seismic disturbances. Nonmarine gastropods and ostrocods are relatively uncommon, and occurrences of stratabound sulfides suggest periods of brackish water conditions. Bedded anhydrite and centimeter‐scale mudcracks record intervals of dessication. The State 2–14 sedimentary rocks are interpreted as the basinward facies of the Borrego and Brawley formations which range from Pliocene to Pleistocene in age.

Sedimentation and crustal recycling along an active oblique-rift margin: Salton Trough and northern Gulf of California

“…A 10-12-km-deep basin fi lled since 5.3 Ma would require an average sediment accumulation rate of 1.9-2.3 km/m.y. (1.9-2.3 mm/yr), consistent with measured rates of 2-3 mm/yr in Pleistocene and Holocene deposits (Van Andel, 1964;Herzig et al, 1988).…”

“…Subsidence continued beneath the axial Salton Trough and produced a sedimentary basin as deep as 10-12 km, where Colorado River sediment is intruded by young mafi c and silicic sills (Elders et al, 1972;Fuis et al, 1984;Schmitt and Vazquez, 2006). Sediment accumulation rates of 2.2-2.3 mm/yr are indicated by presence of the 760 ka Bishop Tuff 1.7 km below the surface (Herzig et al, 1988).…”

Crustal-scale tilting of the central Salton block, southern California

“…10). If the accumulation rate is similar to that documented nearby in rapidly subsiding depocenters of the Salton Trough (1-2 mm/yr; Herzig et al, 1988;Schmitt and Hulen, 2008;Dorsey et al, 2011;McNabb, 2013), we would predict a depth of ~1.2-2.4 km to the contact between predetachment and postdetachment deposits in the subsurface. Combining the asymmetric morphology of the Santa Rosa Mountains, wedge-shaped basin geometry beneath the southern Coachella Valley, and possible range of depth to the base of postdetachment deposits (Fig.…”

“…The WSDF is a regional structure bounding a large supra detachment basin that is well mapped where the basin has been inverted by young uplift, and is inferred to be present beneath deep modern basins in the western Salton Trough and Coachella Valley where inversion has not occurred (Axen and Fletcher, 1998;Janecke et al, 2010). Regional extension and lithospheric rupture across the plate boundary have continued to the present day, resulting in rapid subsidence and accumulation of Colorado River-derived sediment in basins as much as 10-12 km deep (Fuis et al, 1984;Elders and Sass, 1988;Herzig et al, 1988;Schmitt and Vazquez, 2006;Schmitt and Hulen, 2008;Dorsey, 2010).…”

Temporal Changes in Decay-Series Isotope Concentrations in Response to Flow Conditions in the Sssdp Well, Salton Sea, California

“…The geothermal system is situated within sedimentary Pliocene-Pleistocene rocks that were deposited in the continental basin of the Salton Trough [3] and is well characterized, both geologically and geophysically [4]. Studies of radionuclide behavior in the SSGF [1,2] have shown that radium and lead isotopes are present in high concentrations due to the formation of complexes with Cl-, the high salinity of the brines, and the low abundance of available adsorption sites.…”