New Mexico Geological Society Annual Spring Meeting — Abstracts

Strata traditionally assigned to the Abo and Yeso formations comprise most of the Lower Permian stratigraphic section in central New Mexico. In 2005, we revised Abo-Yeso lithostratigraphy (NMMNH Bulletin 31). The Abo Formation is now divided into two formal members, a lower, Scholle Member and an upper, Cañon de Espinoso Member. Thick mudstone slopes and troughcrossbedded, channelform sandstone bodies, conglomeratic sandstone and conglomerate characterize the Scholle Member, whereas siltstone and thin sheets of fine-grained sandstone with ripple and climbing-ripple laminations characterize the Cañon de Espinoso Member. The Yeso Formation has been raised to group rank, and the term Meseta Blanca Member has been abandoned as an unnecessary synonym of the De Chelly Sandstone. Strata in south-central New Mexico equivalent to, but lithologically distinct from, the De Chelly Sandstone (and formerly termed Meseta Blanca Member) have been named the Arroyo de Alamillo Formation. In central New Mexico, the Yeso Group thus consists of the De Chelly and San Ysidro formations (Jemez Mountains and northern Sandia Mountains, Sandoval County), the De Chelly and Los Vallos formations (Lucero uplift, Valencia County) and the Arroyo de Alamillo and Los Vallos formations (southern Manzano Mountains, Torrance County and Joyita Hills-Cerros de Amado, Socorro County). In Socorro County, the Los Vallos Formation consists of three members (ascending), Torres, Cañas and Joyita. The Torres and Cañas members show a pattern of transgressive-regressive cycles in which carbonate horizons mark transgressive events. A revised Abo-Yeso lithostratigraphy better reflects current lithostratigraphic understanding of these units and provides a more precise framework for analysis of regional correlations, depositional systems and paleogeography.