Upper Paleozoic strata in the Sierra Madre Oriental near Victoria, Tamaulipas, Mexico: Outcrop analogs of an underexplored potential petroleum system

Abstract

Upper Paleozoic strata constitute an underexplored potential petroleum system that may underlie much of the onshore and offshore parts of the southern Gulf of Mexico. These deposits form one of the most promising frontier exploration targets in the southern sector of the Gulf. One thousand six hundred meters of middle and upper Paleozoic strata are exposed in the Sierra Madre Oriental directly west of Ciudad Victoria, Tamaulipas. These exposures are rare outcrop analogs of correlative, possibly petroleum-bearing, Paleozoic deposits in the subsurface to the east. Upper Paleozoic strata were first recognized in Cañón de la Peregrina 13 km west of Ciudad Victoria almost one hundred years ago (Girty, 1926). There and in neighboring canyons, the Paleozoic succession consists of the following units from bottom to top (Stewart et al., 1999). (1) Silurian Cañón de Caballeros Formation: shallow marine conglomerate, sandstone, siltstone, and minor limestone. (2) Lowest Carboniferous Vicente Guerrero Formation: shallow marine sandstone, siltstone, and shale. (3) Lower Carboniferous El Aserradero Rhyolite: zircon U/Pb age of 334 +/- 39 Ma. (4) Upper Carboniferous Del Monte Formation: turbiditic grainstone and sandstone, minor siltstone. (5) Lower Permian Guacamaya Formation: marine turbiditic sandstone and siltstone, intermediate water depth. Little is known about these Paleozoic strata beyond lithology, depositional environment, and depositional age (from fossils), leaving key aspects of the petroleum system undetermined. Major outstanding questions surround fundamental geological aspects of these rocks including sediment provenance, tectonic setting during deposition, the original extents and thicknesses of the deposits, the geochemistry of potential petroleum source rocks, petrophysical characteristics, and types and intensities of deformation that affected the strata. These topics are the subjects of our ongoing research in the División de Geociencias Aplicadas at IPICYT. For example, our new detrital zircon U-Pb ages and point counting results from stratigraphically overlying Jurassic sandstone indicate only local sediment sources and provide context for understanding the results of future provenance studies of the Paleozoic deposits. Similarly, our new structural and petrophysical data from stratigraphically overlying Cretaceous limestone emphasize the importance of microporosity and fracture permeability in these rocks and likewise provide a framework for interpreting future structural and petrophysical measurements from the Paleozoic strata. Such studies of the exposed Paleozoic strata will be essential for petroleum exploration in correlative sub-surface deposits to the east, both onshore and offshore.

AAPG Datapages/Search and Discovery Article #90369 © 2020 AAPG Hedberg Conference, Geology and Hydrocarbon Potential of the Circum-Gulf of Mexico Pre-salt Section, Mexico City, Mexico, February 4-6, 2020