Place of origin of the Salinian Block, California, as based on clast compositions of Upper Cretaceous and lower Tertiary conglomerates

Abstract

More than 250 pebble counts were done on conglomerates from the Salinian block and nearby terrane in California, Baja California, and Arizona. The regional pattern of conglomerate compositions suggests that the Salinian block originated adjacent to the Mojave block and is not an exotic terrane as interpreted from paleomagnetic results. Upper Cretaceous, Paleocene, and Eocene conglomerates in the Salinian block consist of two remotely derived detrital suites. The principal suite is rich in clasts of felsic volcanic rocks with subordinate amounts of granitic rocks and quartz sandstone. Granitic rocks are more abundant in lower Tertiary conglomerates of this suite. The second suite, only found locally near the base of the sequence, is rich in quartz sandstone. Both suites are very poor in chert. Conglomerates of the Salinian block contrast with those in regions which were located to the north and south before San Andreas fault displacement. Cretaceous and lower Tertiary conglomerates in the Diablo and Temblor Ranges to the north and Cretaceous conglomerates in the Peninsular Ranges to the south are richer in chert than are Salinian block conglomerates. Lower Tertiary conglomerates both to the north and south are poorer in granitic rocks than are Salinian conglomerates. Salinian conglomerates are compositionally similar to conglomerates in native North America in areas bordering directly on the western part of the Mojave block. Although there are no remotely derived Upper Cretaceous conglomerates in the western Mojave region instead only locally derived basal conglomerates conglomerates in the overlying and onlapping Paleocene sequence are similar to the principal Cretaceous conglomerate suite of the Salinian block. Paleocene conglomerates in the Tehachapi and El Paso Mountains and in the San Gabriel Mountains are very similar to Paleocene conglomerates of the Salinian block. An Eocene conglomerate in the San Emigdio Mountains, located at the south end of the San Joaquin Valley and near the western Mojave, is similar to Eocene conglomerates in the Salinian block. Jurassic or Cretaceous conglomerates composed of volcanic rocks and chert in the lower half of the McCoy Mountains Formation of southeastern California and adjacent Arizona are very similar to conglomerates in the Winterhaven Formation in extreme southeastern California. This supports other evidence indi-Manuscript approved for publication February 19, 1992. PLACE OF ORIGIN OF THE SALINIAN BLOCK AS BASED ON CLAST COMPOSITIONS OF CONGLOMERATES are found to be compositional mismatches and on this basis should no longer be used as reference points in estimating fault displacements. 122°M ETHODS AND DEFINITIONS 118° 114°1 10°C OLORADO.

Salinia revisited: a crystalline nappe sequence lying above the Nacimiento fault and dispersed along the San Andreas fault system, central California

“…200 NSAF-SG Iversen Basalt and Mindego volcanic rocks 23.8 Ma Iversen and 23.7 Ma Mindego volcanic rocks Clark and Brabb (1978), Brabb et al (1998a), Wentworth et al (1998), and Springer (2002) 175-185 NSAF-PF Anchor Bay (Gualala) and Skyline/Highway 92 Anchor Bay Member, Gualala Formation, and Anchor Bay Conglomerate Seiders and Cox (1992), Loomis and Ingle (1994), Elder et al (1998), McLaughlin et al (2007), and Burnham (2009 Hall et al (1959Hall et al ( , 1995, Tyler (1972, p. 538), Elder and Saul (1993), Brabb et al (1998a), Saul and Squires (2008), Sanquini (2010, p. 11), Jacobson et al (2011, and Ernst et al (2011) Ku ss, sh, cg: Trask (1927, p. 142), Nomland and Schenck (1932), Saul and Popenoe (1962, p. 301), Sutherland (1990, p. 22-32), Hall (1991, p. 12-13 Correlation between PS and C...…”

“…Although Sutherland (1990) and Seiders and Cox (1992) reported 72% rhyodacite, tuff/felsite (Sutherland 1990) and 82% felsic volcanic rock clasts (Seiders and Cox 1992) from Upper Cretaceous rocks at a few localities in the PS and Big Sur region (Sutherland 1990) and conglomerate clasts in the Big Sur area (Seiders and Cox 1992) (Table 3), there is a relatively high percentage (e.g. 76%, Grove 1989) of felsic plutonic-rock clasts in the PSBig Sur region that are not present in the PiP Formation (Tables 2 and 3) near Pescadero and PiP.…”

Mineralogic and textural analyses of drill cuttings from the San Andreas Fault Observatory at Depth (SAFOD) boreholes: Initial interpretations of fault zone composition and constraints on geologic models

“…The lower package also contains laumontite, which is generally absent in the upper package . The depositional setting, age, and tectonic implications of this block of arenites are discussed in Draper (2007), who suggests that this package of rocks represents a proximal portion of a submarine fan or turbidite sequence, perhaps part of a Late Cretaceous to Early Tertiary Salinian cover sequence found west of the San Andreas Fault (Clarke and Nilsen, 1973;Graham et al, 1989;Seiders and Cox, 1992;Grove, 1993;Draper et al, 2005).…”

Kinematics of Transrotational Tectonism in the California Transverse Ranges and Its Contribution to Cumulative Slip Along the San Andreas Transform Fault System

“…The impact of Tehachapi rotation may have extended across the trace of the present San Andreas fault into the now offset part of the Salinian block that once lay adjacent to the western end of the Tehachapi Mountains (Ross, 1984;Seiders and Cox, 1992;Powell, 1993). Restoration of the Salinian block against the Tehachapi tail of the Sierra Nevada block is achieved by bringing the Vergeles-Zayante fault of the former and the Pastoria fault of the latter into alignment and juxtaposition (Fig.…”