Abstract

Based on core description and log analysis, the McKee sandstone in the Teague field was deposited in an estuarine to deltaic environment. The descriptive analysis of two cored wells combined with well log data in Teague Field, Lea County New Mexico serve as the basis of this study to better understand the lithology, depositional environment and cyclicity of the Simpson Group in southeastern New Mexico. The cored intervals from the Baylus Cade Federal #6 and the E.C. Hill Federal “B” #13 were determined to be from the McKee sandstone, the basal sandstone unit of the Tulip Creek Formation. The McKee is composed of clean, high-quartz content sandstones with abundant shales. Comparison with well log data confirmed the distribution of lithologies field-wide. Thin sections were used to determine the petrologic characteristics of the cored interval: rock texture, grain distribution, sorting and rounding of the abundance of quartz grains, as well as sandstone classification and identification of marine fossils. Porosity estimations were made from the thin sections. The findings from both the core, and from thin section analysis, consist of: significant bioturbation, vertical/subvertical burrows, shaley intervals, minor limestone and cross-bedded sandstones. Although the sedimentary structures are typical of a fluvial environment, the presence of a diverse community of organisms suggest brackish to marine salinities in a deltaic/estuarine depositional system.

The Middle Ordovician Simpson Group sandstones of West Texas and New Mexico are classified as transitional marine to marine sediments deposited in the ancestral Tobosa Basin. The Teague Field is located at the northern end of the basin, proximal to sources of sand in the Pedernal Uplift area. The formation of an accurate depositional model for the Simpson Group units in New Mexico will prove useful in any comparative study to further understand the sequence stratigraphy and complex lithology of important productive units within the Simpson Group.