Abstract

Thicknesses of Upper Paleozoic stratigraphic sections measured with plane table are as follows: 2400 meters for Sierra de Palomas, 750 for Sierra de Los Chinos and 800 for Sierra de Santa Rita. Those of Sierra de Palomas, on the basis of lithological characteristics, stratigraphic sequence and faunal content are subdivided into nine units that permit correlation with formations of the Big Hatchet Mountains of New Mexico. The 750 meters of Sierra de Los Chinos consist essentially of dolomites of Wolfcamp and Leonard age. And of the 800 meters of Sierra de Santa Rita the upper 600 also consist essentially of dolomites of Leonard age, which, however, might also range into the Word. The remaining or lower 200 meters of this latter Sierra are separated from the foregoing by an 80 meter covered interval, therefore the true stratigraphic relationships are conjectural. From top to bottom these lower sediments consist of 100 meters of predominantly clean quartzose, fine to medium-grained sandstones; 70 meters of thin to medium-bedded, well-stratified dolomites which are probably in fault contact with the basal 30 meters of dominantly massive, clean, medium to coarsegrained sandstones. Interpretation of the sedimentary environments is considered in relation to position within the Pedregosa Basin of Arizona and Southwestern New Mexico. The faulted anticline seen in the Sierra de Los Chinos is a recommendable location for oil and gas exploration. In addition to its importance to local prospects, this much needed and justifiable section measuring program helps to evaluate the petroleum potential of the relatively large Pedregosa Basin which occupies a large part of northern Chihuahua.