Sedimentology, sandstone petrofacies, and tectonic setting of the Late Mesozoic Bisbee Basin, southeastern Arizona.

Abstract

The Late Mesozoic Bisbee basin of southeastern Arizona was an intracratonic back-arc rift basin. Extension was coupled with seafloor spreading in the Gulf of Mexico and back-arc extension behind a magmatic arc along the convergent Pacific continental margin. Tectonostratigraphic evolution of the basin occurred in three phases. Initial mid-Jurassic rifting of the basin, marked by eruption of the Canelo Hills Volcanics, may have been complicated by sinistral strike-slip motion along the Mojave-Sonora megashear. During continued rifting, from latest Jurassic to Early Cretaceous time, the Glance Conglomerate was deposited by alluvial fans and braided streams in grabens, half-grabens, and caldera-related depressions; locally interbedded volcanic rocks represent waning rift-related back-arc magmatism. The upper Bisbee Group was deposited during Early to earliest Late Cretaceous passive thermotectonic subsidence. The Bisbee Group and correlative strata occur in most mountain ranges in southeastern Arizona, and are subdivided into southeastern, northwestern, northern, and western facies. Southeastern facies were deposited in alluvial fan, meandering fluvial, estuarine, marginal marine and subtidal shelf environments as a transgressive-regressive sequence including a marine interval that was continuous with Gulf Coast assemblages during Aptian-Albian marine transgression. Northern facies were deposited in alluvial fan and braided stream environments along the northern rift shoulder of the basin. Southeastern and northern facies sandstones are dominantly quartzose, and were derived mainly from cratonic sources to the north. Subordinate volcaniclastic sandstones in the southeastern facies become more abundant to the west, proximal to eroding Jurassic and Cretaceous volcanic arcs. Basal northwestern facies arkosic strata deposited in alluvial fan, braided stream and lacustrine environments were derived from local basement uplifts, and were ponded in a northwestern depocenter by rift-related topography. A thin estuarine interval within overlying dominantly fluvial facies indicates integration of regional drainage networks by the time of maximum transgression. Transition upward to quartzose sandstone compositions reflects wearing down of local basement uplifts and increasing abundance of craton-derived sediment in the northwestern part of the basin. Western facies alluvial fan, braided stream and lacustrine intramontane deposits are composed of locally-derived arkose and lithic arkose.