The Permian system at Abo Pass, central New Mexico (USA)

The Permian stratigraphic section at Abo Pass at the southern tip of the Manzano Mountains (Torrance, Valencia and Socorro Counties, New Mexico) is ~800 m thick and is assigned to the (ascending order): Bursum Formation (Red Tanks Member), Abo Formation (Scholle and Cañon de Espinoso members), Yeso Group (Arroyo del Alamillo Formation and overlying Los Vallos Formation divided into Torres, Cañas and Joyita members), Glorieta Sandstone and San Andres Formation. The Bursum Formation is ~35-40 m thick and consists of interbedded red-bed siliciclastics (mudstone, sandstone and conglomerate) and marine limestones. The Abo Formation is ~310 m thick and consists of siliciclastic red beds divided into the Scholle Member (~140 m of mudstone with channelized beds of crossbedded sandstone and conglomerate) overlain by the Cañon de Espinoso Member (~170 m of mudstone, siltstone and many thin beds of sandstone that display climbing ripple lamination). The lower formation of the Yeso Group, the Arroyo de Alamillo Formation, consisting of ~80 m of red-bed sandstone (mostly ripple and laminar with some gypsiferous beds) and very minor dolomite. The overlying Torres Member of the Los Vallos Formation is ~180 m thick and consists of mostly gypsiferous siltstone, claystone, gypsum and a few prominent beds of dolomite and gypsiferous sandstone. The overlying Cañas Member is 16-52 m thick, consisting mostly of gypsum and includes a few beds of gypsiferous siltstone and dolomite. The Joyita Member is ~21 m thick and consists of red-bed sandstone that is crossbedded, ripple laminated and, in some beds, gypsiferous. The Glorieta Sandstone is ~78 m thick and consists of crossbedded, laminar and ripple laminar quartzose sandstone. In the Abo Pass area, the upper part of the San Andres Formation has been eroded, leaving up to 91 m of mostly limestone (lime mudstone). It is overlain by Triassic strata east of the Abo Pass area. Bursum deposition took place in a mixture of nonmarine fluvial and shallow marine depositional environments in a tectonically active, mostly coastal setting. Rivers that deposited the Abo Formation formed extensive muddy floodplains traversed by incised rivers early in Abo deposition that later gave way to extensive sheetflooding. Yeso sedimentation began with dominantly eolian deposition on an arid coastal plain (Arroyo de Alamillo Formation) followed by deposits of coastal sabkhas, dunes and restricted marine embayments (Torres and Cañas members of Los Vallos Formation). Yeso sedimentation ended with the Joyita Member of the Los Vallos Formation, which formed by eolian and fluvial processes during lowered sea level. The Glorieta Sandstone is mostly of eolian origin, and the San Andres Formation represents shallow marine deposits. Fusulinids from the Bursum Formation at Abo Pass indicate it is early Wolfcampian in age. The Abo Formation at Abo Pass yields fossil plants, tetrapod tracks and other trace fossils, as well as vertebrate fossils of Coyotean age. Microfossils from the Yeso Group, Glorieta Sandstone and San Andres Formation encompass two new species named here, Velebitella americana and Calcitornella interpsammica. Local paleontological data coupled with regional correlations indicate that the Abo Formation is middle Wolfcampian to early Leonardian and the Glorieta and San Andres formations are late Leonardian in age. 313