Estratigrafía de la región de Olinalá-Tecocoyunca, noreste del Estado de Guerrero

Abstract

In the Olinalá-Tecocoyunca region, in the northeastern part of the State of Guerrero, the presence of Upper Permian strata was recognized with the finding of the ammonites Stacheoceras sp. within a 635 m thick sequence of marine sediments the name Los Arcos Formation is proposed for this sequence. This discovery is considered to be important since it confirms stratigraphically the pre-Permian age assignment of the Acatlán Complex. Furthermore, this region is the first one in southern Mexico where the relation between the early Paleozoic metamorphic basement and the overlying upper Paleozoic sedimentary strata is stratigraphic and not tectonic. The insignificant angular unconfurmity that separates the Permian from the Mesozoic sequence, which was deformed only during the early Tertiary, shows the absence of late Paleozoic diastrophism in this region and confirms its cratonic stability from the late Paleazoic until the early Tertiary.