Paleogeography of Late Cretaceous clastic shelf deposits, northeastern Sacramento Valley, California
The Chico Formation of the northeastern Sacramento Valley, California, is a thick sand-dominated sequence of late Coniacian to early Campanian age that deepens upward from fluvial and deltaic or shelf conditions, reflecting Late Cretaceous transgression and subsidence. During maximum marine conditions in the late Santonian and early Campanian, the shoreline was located near the southern end of the Chico outcrop area, and sedimentary environments deepened to the northwest. The southernmost exposures of the Chico Formation, represented by the Pentz Road member, consist of cross-stratified sandstone with minor shale and lenses of metamorphic pebbles. These strata are of estuarine origin, and they contain a brackish to marine fauna that includes species transported from the rocky intertidal zone. Inner shelf conditions are represented to the north at Butte Creek and Big Chico Creek, where the Ten Mile member consists of erosively based beds of fine-grained, hummocky cross-stratified sandstone. Bioturbation is common in the Ten Mile Member, and basal shell lags of storm-surge origin contain a diverse marine fauna. Farther north, at Mill Creek and Antelope Creek, an outer shelf environment is represented by the Kingsley Cave member, which consists of parallel-laminated to highly bioturbated mudstone and siltstone with an inoceramid-dominated fauna. Similar mudstones at Tuscan Springs, at the northern end of the Chico outcrop area, include slope-related interbeds of parallel-laminated sandstone and matrix-supported, intrabasinal conglomerate. The outer shelf area between Mill Creek and Tuscan Springs extended an unknown distance to the north-northeast, where Upper Cretaceous deposits are completely covered by Tertiary volcanics.
- Research Organization:
- Univ. of California, Davis
- OSTI ID:
- 6886473
- Report Number(s):
- CONF-8604187-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 70:4; ISSN AAPGB
- Country of Publication:
- United States
- Language:
- English
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