Sedimentological evolution of the Cretaceous carbonate platform of Chiapas(Mexico)

The Cretaceous epicontinental carbonate platform of Chiapas (south-east of Mexico) extends along a 200 km NW-SE narrow strip, north of the Sierra Madr e basement, from Ocozocoautla to Comitan. In the western and central domain , three stratigraphic sections of the Sierra Madre Formation (late Aptian t o early Senonian) display well exposed facies sequences enabling broad faci es correlations about: (1) The successive transgressive-regressive stages, (2) the different subsidence rates controlling the outer to inner platform environmental evolution, (3) the conditions of tectonically controlled part ial platform drowning during Campanian-Maastrichtian. Three other sections through the eastern Maastrichtian carbonate platform area record the change s from limestone to dolomite during the Angostura Maastrichtian platform st age. This evolution of thickness and facies in the occidental domain of Pie dra Parada and in the central domain of Guadalupe Victoria and Julian Graja les illustrates the settlement process of the carbonate platform and the ge neral decreasing of the thickness of the Sierra Madre Formation from west t o east. The eastern platform domain (Comitan) crops out extensively and ena bles new correlations along a south-north transect. The Sierra Madre Format ion and Angostura Formation documents continuous carbonate platform sedimen tation with foraminifers, rudists and dasy-cladacean algae during Campanian and Maastrichtian. These sections permit palaeogeographical comparisons of depositional conditions of the Mexican margin of the Maya block. (C) 1998 Elsevier Science Ltd. All rights reserved.