1980 Volume 30 Issue 164 Pages 363-371
The northern part of Sierra Madre Oriental is composed mainly of calcareous and clastic sediments of Upper Jurassic to Upper Cretaceous age. The initial transgression had started in Divesian-Kimmeridgian stage, and thick layers of evaporites were accumulated under sublittoral condition. Coahuila Peninsula and Tamaulipas Island were still emerged at the begining of Neocomian stage. Paleozoic basement was then covered unconformably by Lower Cretaceous sediments. Early Cretaceous transgression spread over almost all the area, and deep and/or shallow depositional environments persisted until Albian stage according to the various evolutional stages of Mexican Geosyncline. Upper Cretaceous sedimentation was regressive, and the area was totally uplifted at the end of this age. The Mesozoic sediments were strongly folded and faulted, accompanied by Tertiary volcanics and intrusives during Laramide Orogeny, and the saline residues appeared to have played an essential role in this deformation. Recent geochronological data supplied from a cooperative survey between Metal Mining Agency of Japan and Consejo de Recursos Minerales indicate that the principal folding period was in 45-35 m.y. and the main igneous activities were also in Paleogene. However, some plutonic rocks are dated as Miocene-Pliocene.
