New Mexico Geological Society Annual Spring Meeting — Abstracts

Outcroppingsof the Abo Formation in the Lucero region of west central New Mexico are limited to the Zuni Mountains, Joyita Hills, Sierra Lucero-Lucero Mesa areas, and east of socorro. Analysis of drill cutting and geophysical logs provide a stratigraphic framework between surface exposures. Subsurface data correlate with complete Abo sections near Lucero Mesa and east of Socorro.

In the Lucero region, the Abo Formation overlies precambrian rocks, Pennsylvanian limestones, rocks assigned to the Bursum Formation, and is overlain by the Meseta Blanca Member of the Yeso Formation. Thickness of the Abo Formation varies from 450 feet over the Zuni uplift to 820 feet near Mesa Lucero.

The Abo Formation consists of very fine to medium grained sandstones, siltstones and mudstones, with coarser sandstones and conglomerates locally occurring over the Zuni uplift, Joyita Hills, and in exposures east of Socorro. In the western portion of the study area sandstones and siltstones dominate the Abo stratigraphic section by almost 4 to 1 over mudstones. Mudstones become more prevalent to the east with sandstone plus siltstone to mudstone ratios as low as 1:4.

High percentages of sandstones and siltstones suggest alluvial fan and braided stream environments prevailed in the western portion of the Lucero region. To the east, an abundance of mudstones suggests a meandering fluvial environment of deposition.

Initial analysis of well-log curve shapes to determine grain size trends appears compatible with the above interpretations, however this type of analysis was found to be more difficult than expected.