Print this pageAbstract: Late Cretaceous Turbidite Sedimentation and Submarine-Fan Facies of Great Valley Sequence, Northern and Central California
The Late Cretaceous part of the Great Valley sequence (GVS) provides a unique opportunity to study deep-marine sedimentation within an arc-trench gap. Fan models and turbidite facies of Mutti and Ricci Luchi allow reconstruction of the following depositional environments: basin plain, outer fan, midfan, inner fan, and slope. The basin plain is characterized by hemipelagic mudstone with randomly interbedded thin sandstones exhibiting distal turbidite characteristics. The outer fan is characterized by regularly interbedded sandstone and mudstone, and commonly exhibits thickening-upward (negative) cycles that constitute depositional lobes. The sandstone is present as proximal to distal turbidites without channeling. The midfan is characterized by the predominance of coarse-g ained, thick, channelized sandstone beds that often are amalgamated. Thinning-upward (positive) cycles and braided channelization are common. The inner fan is characterized by major channel-fill complexes (conglomerate, pebbly sandstone, pebbly mudstone) enclosed in mudstone and siltstone. Much of the fine-grained material consists of levee (overbank) deposits that are characterized by rhythmically interbedded thin mudstone and irregular sandstone beds with climbing and starved ripples. The slope is characterized by mudstone with little interbedded sandstone. Slumping and contortion of bedding are common.
Progressions of fan associations can be described as receding and prograding suites that correspond, respectively, to onlapping and offlapping relations in the basin. The paleoenvironments, fan associations, and tectonic setting of the Late Cretaceous fore-arc basin are similar to those of modern arc-trench systems.
Geometries of fan components may aid the search for hydrocarbons by outlining possible migration paths from fine-grained source beds on fan fringes through coarse-grained fan assemblages and into major-channel complexes. Mid- and outer-fan patterns in the outcrop belt of the GVS suggest possible channel locations in the subsurface on the east.
AAPG Search and Discovery Article #90976©1976 AAPG-SEPM-SEG Pacific Section Meeting, San Francisco, California