Comment on Zepeda et al. (2018) A major provenance change in sandstones from the Tezoatlán basin, southern Mexico, controlled by Jurassic, sinistral normal motion along the Salado River fault: Implications for the reconstruction of Pangea https://doi.org/10.1016/j.jsames.2018.07.008

Abstract

Zepeda et al. (2018) present the sandstone petrography of Lower-Middle Jurassic sedimentary rocks of the Tezoatlán basin, in Oaxaca, southern Mexico. These data are for a well-known locality, historically know for its plant and ammonite fossil content. They also present detrital zircon geochronology for two samples in a measured section about 200 m thick. Additional data include heavy mineral and paleocurrent data. Their data show a transition from volcanic rich conglomerates and sandstones, to metamorphic clast rich sandstone. Using this information, and a recently published age for micas in the Salado River Fault, they conclude that this WNW trending fault was active in the Jurassic and somehow influenced sedimentation in the Tezoatlán basin. They also conclude that fault activity is related to rupture of Pangea. We believe these data are over-interpreted and supported by an incomplete interpretation of depositional environments. The change in sediment provenance can be explained by gradual erosion of the volcanic cover of the local basement. Moreover, this section is part of a well recognized extensional system with continental rift characteristics. The Salado River fault appears to be a fault of complex geometry, perhaps a scissor fault, connecting two basins of a continental rift. There is no indication of a continental scale, crustal scale, left lateral strike slip fault linked to rupture of Pangea.