Datos preliminares sobre el megabentos de bivalvos del Jurásico Superior - Cretácico basal en el Cañón de San Matías (Zacatecas, México)

Abstract

The present contribution shows the first approach to the interpretation of precise stratigraphic horizons containing megabenthic fossil assemblages made of Upper Jurassic - lowermost Cretaceous bivalves in México. This is a preliminary report focused on the careful analysis of taphonomic features in bivalve assemblages based on the taxonomic identification of bed-by-bed sampled specimens. On a total sample of fifty-one bivalve assemblages, we interpreted their usual character of parautochthonous assemblages deposited on shallow fine-grained to middle-outer shelves. In addition, no cases of taphonomic condensation were recognised, but stratigraphic horizons showing mixing ecological levels, usually, revealed biostratinomic reworking of originally tiered bivalve assemblages