SUB-SURFACE STRATIGRAPHY AND DEPOSITIONAL ENVIRONMENTS OF PENNSYLVANIAN STRATA OF THE RAINSVILLE TROUGH IN NORTHERN NEW MEXICO

The Taos-Rainsville Trough (also known as Rowe-Mora basin), located in northern New Mexico was one of several tectonically active basins associated with the late Paleozoic ancestral Rocky Mountains. The intra-basinal high El-Oro Rincon divided the basin into western (Taos trough) and eastern (Rainsville trough) halves. The western portion of the Taos-Rainsville trough was uplifted by the Cenozoic deformation as part of the Sangre de Cristo Mountains, however, late Paleozoic strata of the Rainsville trough are mostly subsurface. Numerous wells penetrated through the Permo-Pennsylvanian strata that provides data to interpret subsurface stratigraphy, correlating lithofacies, and interpreting depositional environment using available petrophysical well log data.

Lithological cross-sections and isopach maps demonstrate the distribution of electrofacies (lithofacies from logs) across the basin. Pennsylvanian strata usually thin towards eastern and southern parts of the basin suggesting roughly north-south trending basin depocenter located close to the El-Oro-Rincon uplift to the west. Cylindrical and funnel shapes of gamma ray curves of Early Pennsylvanian Sandia Formation represent coarsening upward sequences of probably prograding fan-delta deposits. Deposition of thin coal beds indicate existence of marsh conditions during Morrowan-Atokan. Carbonate flooding during the middle part of the Desmoinesian indicates marine transgression inundated across the area. Variations in relative sea level periodically restricted the basin resulting Desmoinesian-aged anhydrite beds. Dominantly, irregular shapes of gamma ray indicate alternating mudstone-sandstone sequences of fluvial floodplain deposits during the Late Pennsylvanian.