Part II: Notes on the Geology of the Region of Placer de Guadalupe and Plomosas, Chihuahua

Abstract

 The Placer de Guadalupe and Plomosas area constitutes the northwestern part of the Sierra de La Monilla, to the north and northwest of the Conchos River, in the northeastern part of the State of Chihuahua. Recent studies conducted by Bridges (1964) revealed for the first time in this part of Mexico the presence of Paleozoic sedimentary rocks predating the Carboniferous.
A critical evaluation of the results obtained by Bridges, supported by field observations made by the author and regional geological data, indicates that the Paleozoic stratigraphic sequence was severely deformed during the early Permian (Marathon Orogenic Epoch), resulting in thrusting from the northeast to the southwest, and during the Late Permian-Early Triassic (Coahuilian Orogeny), with thrusting from the east. The Mesozoic rocks show the development of folds with an NNW-SSE orientation during the Hidalgoan Orogeny (Early Eocene), which also affected rocks and structures formed prior to the Mesozoic. Faulting in blocks during the rest of the Tertiary, accompanied by continental sedimentation and volcanism, has been the most recent geological event responsible for the development of this geologically complex area.