Primer registro en superficie de sedimentitas continentales del Cretácico Superior en la cuenca del Colorado, sureste de La Pampa

CASADÍO, S.; MANERA, T.; PARRAS, A.

Revista de la Asociación Geológica Argentina

Asociación Geológica Argentina

Año: 2000 vol. 55 p. 129 - 133

First record at the surface of continental Upper Cretaceous deposits in the Colorado Basin, Southeast of La Pampa. Outcrops of continental Cretaceous deposits on the west edge of Colorado Basin, southeast of La Pampa Province, are described. The outcrops are small and restricted to two localities; however, based on the information obtained from them and from subsurface data, it is possible to establish that the Cretaceous deposits are in a graben, which is bounded by northwest - southeast normal faults, and wedging out to the northeast. The sedimentary rocks rest on the crystalline basement, but the contact is not visible at the surface. Only the upper part of the section, which is formed by 3 m of medium to conglomerate sandstones and conglomerates in coarsening-up facies is expose. The facies association documents environments of mid to distal alluvial fans. The sedimentary rocks studied here are assigned to the Colorado Formation and, because of the presence of eggshells and crushed eggs tentatively recognized as of titanosaus, a Campanian-Maastrichtian age is suggested. The presence of coarsening-up fluvial deposits at the top of the studied section suggests active tectonism in the graben during the Upper Cretaceous.