Facies architecture and provenance of a boulder-conglomerate submarine channel system, Panoche Formation, Great Valley Group: A forearc basin response to middle Cretaceous tectonism in the California convergent margin

Abstract

Tectonic reorganization induced by a rapid increase in plate motion obliquity and rate beginning at ca. 100 Ma affected California's Andean-style convergent margin, with concomitant changes in the accretionary prism of the Franciscan Complex, the Great Valley forearc basin, and the Sierran continental arc. Using facies analysis and a combined provenance approach, we suggest that this ca. 100 Ma tectonic signal is preserved in a Cenomanian (Upper Cretaceous) boulder-conglomerate outcrop along the San Luis Reservoir (SLR) in the southern Great Valley, which represents the thickest and coarsest deep-water deposit ever described in the Great Valley Group (GVG). We document a 1.8-km-thick by 4-km-long depositional-dip profile of an interpreted SE-directed (axial) submarine channel system that is part of a conglomeratic package that stretches 20 km along the east-central Diablo Range. Our facies analysis of the SLR area documents five facies associations within four aggradational channel complex sets, followed by regional abandonment.Sandstone petrography and mudrock geochemical data suggest a dissected continental Sierra Nevadan arc source. Conglomerate clast counts show abundant ophiolitic-type clasts that may be derived from the Coast Range Ophiolite and/or the Western Sierra Nevada Metamorphic Belt. Detrital-zircon geochronology data also indicate western and central Sierra Nevadan sources; however, we interpret an anomalous (relative to other Cenomanian localities) 105-95 Ma zircon population to indicate the initial erosional products from the volcanic carapace associated with the Late Cretaceous magmatic flare-up within the eastern Sierran arc. This flare-up has been linked to an increase in arc-parallel plate motion that induced deformation along shear zones in the eastern Sierra Nevada, allowing for widespread plutonism. Our provenance interpretation makes the SLR area the earliest Upper Cretaceous GVG locality to receive significant detritus from the flare-up, effectively linking tectonic plate motion changes and coarse-grained, deep-water forearc sedimentation.

Tectonically controlled initiation of contemporaneous deep‐water channel systems along a Late Cretaceous continental margin, western British Columbia, Canada

“…Individual channelform surfaces are difficult to delineate within thick successions of amalgamated FA1 deposits. However, highly composite deposits are a common stratigraphic product of large‐scale submarine channel‐systems, as demonstrated in the Panoche Formation (Greene & Surpless, ), Cerro Toro Formation (Beaubouef, ), Rosario Formation (Kane et al ., ) and Puchkirchen Formation (Hubbard et al ., ; Fig. C).…”

“…Both channel margin and channel abandonment deposits share similar characteristics (McHargue et al ., ) and are commonly difficult to distinguish in outcrop (Greene & Surpless, ). Thus, FA2 represents sandstone‐dominated channel fill that could be attributed to either depositional mechanism.…”

“…Tectonic changes in the hinterland are more likely to produce the conditions necessary for widespread, coarse‐grained deep‐water sediment delivery ( cf . Cibin et al ., ; Romans et al ., ; Greene & Surpless, ). Major regional tectonic events are known to have occurred in the North American Cordillera simultaneous with Geoffrey Formation deposition (Sauer et al ., ; Fig.…”

“…orogenesis, regional pluton emplacement and subduction accretion) that regulate basin subsidence and source area uplift could have a more extensive impact on deep‐water sediment dispersal along a margin (e.g. Kimbrough et al ., ; Greene & Surpless, ). Ancient deep‐water deposits from tectonically active settings have the potential to provide critical perspectives on source to sink sediment routing over long time scales (Romans et al ., ).…”

Multi‐scale analysis of a migrating submarine channel system in a tectonically‐confined basin: The Miocene Gorgoglione Flysch Formation, southern Italy

“…The reconstruction of the evolutionary history of an ancient turbidite system is one of the main goals of recent outcrop studies (e.g. Pickering et al ., ; Di Celma et al ., ; Greene & Surpless, ). For this purpose, the accurate interpretation of the stratigraphic record and the analysis of spatial and temporal changes in depositional architectures are of primary importance (e.g.…”