Sequence Sratigraphic Framework of the Southwestern Part of the Actopan Carbonate Platform, Lower Cretaceous, Hidalgo State, Mexico

Abstract

Abstract

The superb outcrops of a Lower Cretaceous mixed terrigenous-carbonate sedimentary succession in the southwestern region of the Actopan Platform, Hidalgo State, allowed to build its sequence stratigraphy framework. This stratigraphic package represents the oldest sedimentary facies in this platform and is at least 700 m thick. The oldest unit, partially exposed, corresponds to the “Santuario” Formation and the youngest unit is part of the El Abra Formation. The Santuario Formation is a, 324 m-thick, terrigenous-carbonate sedimentary package and consists of interbedded fluvial and deltaic terrigenous facies systems and shallow subtidal lagoonal carbonate facies. A layer of vitro-crystalline tuff occurs at the base of the section. El Abra Formation is a calcareous succession and 376 m of it were studied in detail. This unit consists of typical inner platform facies deposited from lagoonal to supratidal environments. Their fossil contents of this formations and U-Pb zircon ages (127 ± 1 Ma) from the tuff horizon suggest an age from the upper Barremian to the lower Aptian for the whole studied stratigraphic section.

Based on the chronostratigraphic framework and assuming a constant sedimentation rate, the analyzed facies stack forming parasequences or fifth-order cycles whose thickness varies from 1 to 13 m. Likewise, the parasquences stack forming fourth-order high frequency sequences whose thicknesses range from 15 to 71 m. The fourth-order sequences also stack forming third-order depositional sequences whose thicknesses range from 176 to 323 m. Three depositional sequences (SD) were identified, named, from the oldest to the youngest, informally: SD-1, SD-2, and SD-3. The SD-1 and SD-2 are possibly correlated with youngest eustatic cycles identified for the Barremian-Aptian and the two oldest depositional sequences proposed for the Cupido Formation in northeastern Mexico. The stratigraphic architecture of the Actopan Platform during late Barremian-early Aptian time was essentially controlled by the accommodation space, in turn controlled by the eustasy, and the sedimentation rate. The stratigraphic architecture stablished for the Lower Cretaceous in this part of the Actopan Platform represent an excellent outcrop analog that can be utilized in petroleum exploration activities of similar sedimentary systems. Additionally, the fluvial deposits correspond to incised fluvial-valleys within a carbonate systems documented for the first time in this part of Mexico.

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