Correlation of Mississippian Shelf-to-Basin Strata, Eastern California

Abstract

Mississippian rocks in eastern California comprise two distinct facies: a siliceous clastic facies to the northwest and a carbonate facies to the southeast, separated by a transition zone within which the two facies apparently interfinger (Fig. 1). Carbonate-facies rocks of the Cordilleran miogeocline represent shelf-margin and platform deposits (Rose, 1976; Gutschick and others, 1980), whereas clastic-facies rocks have been inferred to have been deposited in a foredeep basin located along the southeast margin of the mid-Paleozoic Antler orogenic belt (Poole, 1974; Poole and Sandberg, 1977). Through most of Mississippian time, the axis of this foredeep basin must have been located northwest of the area shown in Figure 1 (Stevens and Ridley, 1974). Although studies by Pelton (1966) and Randall (1975) clarified many aspects of the Mississippian stratigraphy in this region, only a somewhat generalized correlation of units across the transition zone has been developed (Fig. 2). Analysis and interpretation of platform, shelf-margin, and basin relationships of the type carried out by Rose (1976) in areas farther northeast have not been possible in eastern California because of abrupt lateral changes in lithology and thickness, scarcity of age-diagnostic fossils, and paucity of complete Mississippian sections in the transition zone. The Lee Flat Limestone, defined by Hall and MacKevett (1958) for exposures in the southern Santa Rosa Hills (Fig. 1), has been especially difficult to correlate with other formations. As defined, this formation poses two stratigraphic problems. First, the depositional top of the Lee Flat Limestone is not exposed in the type area, nor at other exposures of this unit mapped by Hall and MacKevett (1962), and no age-diagnostic fossils were recovered. Thus, the age and relationships to other Mississippian units (Rest Spring Shale and Perdido Formation) proposed by Hall and MacKevett (1962; Fig. 2A) have remained in doubt. Second, the lithology of the Lee Flat Limestone in the type area (thin-bedded, medium to dark gray, silty limestone) is distinctly different from the very light gray, massive-appearing, crinoidal limestone or marble mapped by Stadler (1968), Hall (1971), Johnson (1971), Randall (1975), Holden (1976), and Moore (1976) as Lee Flat Limestone in the carbonate facies region to the east and southeast. This latter lithology was identified as Lee Flat Limestone by these workers on the basis of its stratigraphic position between the Perdido and Keeler Canyon Formations, a position similar to that assumed by Hall and MacKevett (1958) for the Lee Flat Limestone at its type locality.