Late Cenozoic stratigraphy and structure of the western margin of the central San Joaquin Valley, California

Abstract

Late Cenozoic Stratigraphy Late Cenozoic deposits in the west-central San Joaquin Valley and adjacent foothills of the Diablo Range consist mainly of unconsolidated, poorly-sorted to well-sorted gravel, sand, silt and clay derived primarily from the Diablo Range and secondarily from the Sierra Nevada. Sedimentary structures.* such as channeled contacts, laminated bedding, cross-stratification and clast-imbrication indicate that most of the deposits were transported and laid down by running water. These deposits are described and their facies relationships are illustrated in the "Late Cenozoic Stratigraphy" section of this report (see Figures 17, and 26, and Table 9). sea. The freshwater character, however, suggests that the lake was probably periodically flushed through an outlet to the sea. Origin of the Corcoran Clay and computation of the deformation and sedimentation rates in the San Joaquin Valley are presented in the "Late Cenozoic Stratigraphy"and "Late Cenozoic Structure" sections of this report. Within the foothills, the principal Quaternary folds include the Panoche Hills, Wisenor Hills, Los Banos Hills and Laguna Seca Hills anticlines and the Little Panoche Valley, San Luis Valley, Carrisalito Flat and Salt Creek synclines. These structures, much smaller than the San Joaquin Valley syncline, typically have northeaster east-trending axes. The Panoche Hills, however, appears to be a simple quaquaversal dome. Evidence for these folds is presented in the section entitled "Late Cenozoic Structure." The Panoche Hills anticline, the largest foothill structure, has risen at a minimum rate of 0.3 to O.M m per millenium during the late Quaternary. Minimum rates of uplift for the smaller Laguna Seca Hills and Wisenor Hills anticlines approximate 0.2 m per millenium. Three northwest-trending fault systems displace Quaternary deposits in the Los Banos area: the Ortigalita Fault system, forming the principal contact between the Franciscan Assemblage of the central Diablo Range and the Great Valley Sequence of the foothills; the San Joaquin Fault system, separating the foothills from the San Joaquin Valley; and the O'Neill Fault System, which consists of numerous small bedding-plane faults between the San Joaquin and Ortigalita Fault systems. Evidence for displacement along these faults is presented in the section entitled "Late Cenozoic Structure". The Ortigalita Fault displaces late Pleistocene alluvium and probably displaces Holocene alluvium. Its linear, en echelon trace and fault-plane solutions of recent tremors suggest a predominance of lateral displacement. Escarpments along the fault, however, typically have a west-southwest aspect suggesting that oblique displacement may have uplifted the foothill belt relative to the central Diablo Range. This Quaternary activity along the Ortigalita Fault is a reactivation of an earlier Tertiary structure along which Taliaferro (19*13), Briggs (1953), Leith (19W and Page (1981) suggests that the central Diablo Range was elevated. The presence of roughly coeval basalt flow...

The Quaternary alluvial sequence of the Antelope Valley, California

“…This relationship can be demonstrated for deposits of late Modesto, early Modesto, and late Riverbank age, where non-glacial alluvium overlies glacial outwash with no evidence of a buried soil. This relationship is also observed by Lettis (1982), who demonstrated that non-glacial alluvium derived from the western San Joaquin Valley post-dates Sierra Nevada derived glacial outwash without evidence of a buried soil. These relationships indicate that an episode of nonglacial alluviation occurred during several glacial to interglacial transitions.…”

Epeirogenic transients related to mantle lithosphere removal in the southern Sierra Nevada region, California: Part II. Implications of rock uplift and basin subsidence relations

“…Propagation of the sympathetic bulge from the Coast Ranges to the central Foothills area during the Quaternary provides a mechanism for the temporary partitioning off of the Great Valley, and the formation of the Corcoran Lake internal basin. The map distribution of Corcoran Lake based on abundant subsurface data from the 710-615 ka Corcoran E-clay (Frink and Kues, 1954;Lettis, 1982Lettis, , 1988 is shown in Figure 6, and its known subsurface distribution is shown in the structure sections in Figures 5 and 8. The northern limit of the lake parallels the broad culmination of the central Foothills swell, and the age of the lake corresponds in time to constraints presented earlier for growth of the Kern arch.…”

Glacially Driven Cycles in Accumulation Space and Sequence Stratigraphy of a Stream-Dominated Alluvial Fan, San Joaquin Valley, California, U.S.A.

“…The release of sediment during these glaciations was responsible for at least five episodes of aggradation and progradation on stream-dominated alluvial fans along the eastern San Joaquin Valley, including the Kings River alluvial fan (Marchand 1977;Huntington 1980;Marchand and Allwardt 1981;Lettis 1982Lettis , 1988. Interglacial periods, similar to the present climate, left the upper alluvial fans exposed to pedogenic alteration and incision (Arkley 1962;Janda 1966;Shlemon 1971;Marchand 1977;Huntington 1980;Marchand and Allwardt 1981;Lettis 1982Lettis , 1988 (Huntington 1980;Arroues and Anderson 1986). The gray borders show the outline of maps shown in Figure 3.…”