EFFECTS OF THE EVOLUTION OF THE CORDILLERAN SYSTEM IN THE CORDOBA PLATFORM REGION, CENTER-SOUTH MEXICO

The geodynamic history of the Cordoba Platform, located on the eastern-central part of Mexico, corresponds to the history of two systems: the eastern system with tethysian influence and the western cordilleran system with pacific afinity.

In the stratigraphic frame, four megasequences are distinguished: *The stage of rift type valley in (Tithonian – Late Aptian); *The stage of platforms installation with carbonated sedimentation (Late Aptian – Cenomanian); *The stage of platforms stabilization (or platform valleys) with carbonated sedimentation (Turonian – Senonian); *The stage of preorogenic valley formation or cordilleran history and flysch sedimentation (Maestrichtian).

In the platform installation stage an important transgression is shown in the Late Aptian, as well as the effect of a generalized subsidence (regional thermo-tectonic subsidence) in the sedimentary valley. During this period the valley experiments its greater extension, going beyond the precedent rift valley limits. The prolongation of the platforms stage is the result of the Turonian transgression, as well as of the high degree of generalized subsidence in the oriental valleys. These two substages formed the sedimentation of megasequences II and III.

In the last stage, the one corresponding to the preorogenic valley, a synorogenic sediment basin was formed by flexural subsidence, where a wide gamut of flysch s. l. sedimentation (Fm Tecamalucan pre-flysch, up to the most delicate Fm. San Felipe flysch or the Fm. Méndez criptoflysch, Megasecuence IV) took place. The materials from this sedimentation came from the uncovering of recent reliefs belonging to the western cordilleran domain. Later, during Paleocene the preorogenic basin migrated towards the East (Paleocene flysch and molasses), because of the advancement of the compressive deformation front over the carbonated sedimentary series of the Cordoba Platform. This way, the carbonated sedimentation comes to an end, and so the Mexico stage of platforms. Particularly, in the whole Sierra Madre Oriental (with tethysian afinity) the pacific cordilleran stage is shown over the series of carbonated platforms. This cordilleran stage closes the Atlantic opening history in the East of Mexico.