Geologic map of the northwestern Caliente Range, San Luis Obispo County, California

Abstract

The map area lies in the southern Coast Ranges of California, north of the Transverse Ranges and west of the southern San Joaquin Valley. This region is part of the Salinia-Tujunga composite terrane that is bounded on the northeast by the San Andreas fault (fig. 1) and on the southwest by the Nacimiento fault zone (Vedder and others, 1983). The Chimineas fault of this map is inferred to be the boundary between the Salinia and the Tujunga terranes (Ross, 1972; Vedder and others, 1983). Geologic mapping in the region of the California Coast Ranges that includes the area of this map has been largely the work of T.W. Dibblee, Jr. Compilations of geologic mapping at a scale of 1:125,000 (Dibblee, 1962, 1973a) provide the regional setting for this map, the northeast border of which lies about 6 to 7 km southwest of the San Andreas fault. Ross (1972) mapped the crystalline basement rocks in the vicinity of Barrett Creek, along the northeast side of the Chimineas fault ("Barrett Ridge" of Ross, 1972). Recent 1:24,000-scale mapping in the La Panza Range (fig. 1) (Vedder and others 1986a,b) overlaps onto the southwest edge of this map and provides useful information about the older rocks, mostly southwest of San Juan Creek. Stratigraphic knowledge of the area, which lies in the northern part of the middle Tertiary Cuyama basin, has evolved over a period of years beginning with the molluscan biostratigraphic work of Anderson and Martin (1914) and Loel and Corey (1932). Hill and others (1958) described the Tertiary stratigraphy of the region and proposed stratigraphic names. This stratigraphy was discussed further by Dibblee (1973b), and his revised nomenclature is used here. Stratigraphic studies in the southeastern Caliente Range (fig. 1) (Repenning and Vedder, 1961; Vedder, 1973) provided valuable information on the interrelations of continental, shallow-marine, and deeper marine facies in the southern part of the Cuyama basin, which have basinwide application. More recent stratigraphic studies by Lagoe (1984, 1985, 1987, 1988) further elaborate on aspects of Miocene basin history and paleogeography. Contributions to the tectonic history of the area have been made by Schwade and others (1958), on the basis of oil exploration in the Cuyama Valley area (fig. 1) in the 1940's and 1950's; by Bartow (1974), as part of a regional stratigraphic study; by Ballance and others (1983), on the basis of a study of Oligocene and early Miocene sedimentation; and most recently by Davis and others (1988) and Yeats and others (1988), who utilized a variety of new data from seismic reflection and from stratigraphic and structural studies. Field work for this map was done mostly in 1969-73 as part of a regional study of the Simmler and Vaqueros Formations (Bartow, 1974). Detailed field mapping was, therefore, concentrated on those units; other parts of the area were mapped by geologic reconnaissance and air-photo interpretation that were supplemented by data from published maps (Dibblee, 1973a; Vedder and others, 1986a,h). Mapping of the crystalline basement rocks at "Barrett Ridge" is from Ross (1972, plate 1). The structural style depicted in the accompanying cross sections favors the thrust belt concepts of Davis and others (1988) over the older interpretations of Dibblee (1962) or Cross (1962).