Abstract

Muleshoe Mound is a prominent feature as one drives along the highway from Alamogordo, New Mexico to El Paso, Texas. Its southwest cliff face forms part of the escarpment along the boundary between the Tularosa Basin and the Sacramento Mountains. Information from this previously inaccessible cliff has been incorporated into a point-source depositional model for the buildup.

Six microfacies were defined using hand samples and thin sections: (1) crinoid-bryozoan wackestones/packstones; (2) crinoid-bryozoan wackestones/packstones with sheltered voids; (3) crinoid-bryozoan packstones/grainstones with sheltered voids; (4) marine cemented bryozoan grainstones; (5) crinoid wackestones/packstones; and (6) crinoid packstones/grainstones.

A sediment point-source model with gradational stages was developed to interpret the vertical distribution of microfacies in the measured sections. The stages are: (a) the basal wackestones/packstones baffling stage; (b) the spar-rich substrate modification stage; (c) the crinoid-bryozoan framestone stage; and (d) the marine-cemented bryozoan framestone stage.

The bryozoan-radiaxial-spar point-sources developed from a quiet-water stage, (a), to the turbulent-water stage, (d). Grainstones on the flanks of adjacent point sources prograded laterally and eventually coalesced. This resulted in a complex carbonate buildup of spar-cemented crinoidal debris and localized bryozoan mounding facies.

The progression from a quiet-water to a turbulent-water environment can be followed in three or, possibly, four cycles within the upper core of Muleshoe Mound. This indicates repeated, prolonged exposure to a turbulent environment throughout the history of the buildup.