Cerro del Pueblo Fm (Difunta Group, Upper Cretaceous), Parras Basin, southern Coahuila, Mexico: reference sections, age, and correlation

  • David A. Eberth Royal Tyrrell Museum of Palaeontology, Box 7500, Drumheller, AB, T0J 0Y0 Canada.
  • Carlos R. Delgado-de Jesús Coordinación de Paleontología, Secretaría de Educación Pública de Coahuila, 25000 Saltillo, Coahuila, Mexico.
  • John F. Lerbekmo Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, T6G 2E3 Canada.
  • Donald B. Brinkman Royal Tyrrell Museum of Palaeontology, Box 7500, Drumheller, AB, T0J 0Y0 Canada
  • Rubén A. Rodríguez-de la Rosa Museo del Desierto, Laboratorio de Paleontología, Museo del Desierto-S.E.P.C., A.P. 307, 25000 Saltillo, Coahuila, Mexico.
  • Scott D. Sampson Utah Museum of Natural History and Department of Geology and Geophysics,University of Utah 1390 E Presidents Circle, Salt Lake City, UT 84112-0500, USA.
Keywords: stratigraphy, magnetostratigraphy, dinosaurs, Cerro del Pueblo Formation, Cerro Huerta Formation, Difunta Group, Mesozoic, Cretaceous, Coahuila, México.

Abstract

Principal and supplementary reference sections provide data that clarify the stratigraphic relationships and depositional history of the Cerro del Pueblo Formation (CdP) – an important unit in Late Cretaceous paleobiogeographic studies in northeastern Mexico and the Western Interior of North America. At Saltillo, the CdP is 162 m thick, much thinner than previously reported. To the west, however, the CdP thickens to 449 m at Rincón Colorado (35 km west of Saltillo) and 540 m at Porvenir de Jalpa (70 km west of Saltillo). A substantial stratigraphic interval of interbedded grey-green and red beds is present above the CdP throughout the field area; for consistency, it is assigned to the overlying Cerro Huerta Formation (CH).

Westward-thickening of the CdP indicates an increased rate of subsidence and accommodation in that direction, and further suggests that sediment was supplied from the west along a narrow, east–west oriented trough that paralleled the modern Sierra Madre Oriental south of the field area. This trough was likely the location of an embayment in which CdP sediments first aggraded and then slowly prograded to the east and northeast. Overall, the CdP records deposition in very low gradient lower coastal plain and shallow marine (ramp) settings that were influenced by high-frequency changes in relative sea-level and coastal storm events.

Magnetostratigraphic data from 66 samples collected in the Saltillo area indicate that the CdP was deposited in magnetochronozones 32n.3r–32n.2n. This magnetostratigraphic interval falls within the combined Western Interior ammonite biozones of B. reesidei and B. jenseni, and suggests a maximum absolute age of 72.5 Ma for the CdP in the Saltillo area. The Campanian–Maastrichtian boundary (here accepted as 32n–31r) lies 90 m below the top of the overlying CH. A minimum sediment accumulation rate of 55 cm/1,000 yrs is proposed for the CdP.

Published
2018-05-09
Section
Regular Papers