Stratigraphic/Sedimentological Analysis of Two Major Marine Transgressions During Cretaceous Time in the Actopan Platform, Hidalgo State, Mexico

Abstract

Abstract

The Actopan Platform cropping out nearby Actopan, Hidalgo State, is part of a system of carbonate platforms developed extensively in Mexico during Cretaceous time. A detailed stratigraphic-sedimentologic analysis of two diachronic sections named Tordillo and La Flor was conducted. The Tordillo Section, 345 m thick, is located in the southwestern part of the Actopan Platform. The lower part of this section consists of 198 m of the El Abra Formation and is represented by a sedimentary succession of shallow-water carbonate facies. Their fossiliferous content allowed to define a Barremian to Aptian age at this location. The El Abra Formation is overlaid gradually by a deep-water marine carbonate sedimentary succession whose microfossils indicate a late Aptian age, documented by the first time in the Actopan Platform. This unit passes normally upward to fine- and very coarse-grained carbonate sediments composed by pelagic facies, carbonate turbidites, and gravity-driven calcareous breccias. Fossil content in this deep-water deposits indicates an early-middle Albian age.

The La Flor Section, 45 m thick, is located in the northeastern part of the Actopan Platform. The lower part of the section corresponds to 28 m of shallow-water skeletal grainstones that represent a platform-margin carbonate sand shoal of El Abra Formation. This unit is overlain normally by 17 m of transgressive thin carbonate beds of the Agua Nueva Formation. The well-preserved lamination in these facies, their dark gray color, and pelagic micropaleontologic content suggest a deep-water marine setting developed during late Cenomanian time.

The detailed study of these sections allowed to document two important transgressive events that affected the Actopan Platform. The first event corresponds to the late Aptian and has not been reported in this platform, previously. It coincides in time with the OAE1a anoxic event, documented in northern Mexico wich allows to presume that the marine transgression was of global scale. However, the Actopan Platform was not completely drowned and was reestablished during the Albian having its major productivity during the Albian-Cenomanian. The second transgressive event that affected the Actopan Platform and practically drowned it occurred during the late Cenomanian and coincides with the OAE2, this event is represented by the facies of the Agua Nueva Formation in the La Flor Section.

AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016