Regional correlation of the Sonsela Member (Upper Triassic Chinle Formation) and detrital U-Pb zircon data from the Sonsela Sandstone bed near the Sonsela Buttes, northeastern Arizona, USA, support the presence of a distributive fluvial system

Abstract

AbstractThe Sonsela Sandstone bed was first named as an informal unit in the lower part of the Chinle Formation in northern Arizona, USA, and it was later assigned a type section near the Sonsela Buttes, where it is composed of two prominent sandstone units separated by a predominately siltstone unit. The Sonsela Sandstone bed has been correlated to a number of specific sandstones within the thicker, formal Sonsela Member at Petrified Forest National Park in northern Arizona. Here, we present the first detrital U-Pb zircon data for the Sonsela Sandstone bed at the Sonsela Buttes to hypothesize the maximum deposition age of that unit (216.6 ± 0.3 Ma) that are consistent with the proposed lithostratigraphic correlation with the fossiliferous Jasper Forest bed of the lower part of the Sonsela Member at the Park. These results are corroborated by previous high-resolution U-Pb dates and detrital zircon provenance studies from Petrified Forest National Park and similar sections in northern Arizona and western New Mexico, USA. The hypothesized chronostratigraphic correlation of these sandstones throughout northern Arizona permits the recognition of diachronous facies distributions in the lower part of the Chinle Formation as these coarse sediments prograded from the southwest into a continental basin already receiving finer-grained fluvial sediments from the southeast. The new age data corroborate the Norian age designation for the Sonsela Member (and the Sonsela Sandstone bed) and suggest that the Sonsela Sandstone bed at the Sonsela Buttes is within the Adamanian land vertebrate estimated holochronozone.