Palaeoecology and taphonomy of bivalves, mainly Glycymeris insubrica (Brocchi), and bryozoans from the Huelva Sands Fm. (Lower Pliocene, SW Spain).

Abstract

The fossiliferous Huelva Sands Formation belonging to the Upper Neogene complex (Lower Pliocene), that is located at the outfall of Tinto and Odiel rivers, southwestern end of Guadalquivir Basin (SW Spain), consists of fine silty and sandy beds with abundant molluscan faunas. These suffered predation and successive colonisation events during their life span and also after death. Eight bivalve communities are distinguished on the basis of their taxonomic contents and trophic classification. Focussing on the abundant species Glycymeris insubrica (Brocchi), we analysed the borings produced as result of predator-prey interaction, and also the commensalism relationships, and colonisation sequences, both when G. insubrica was still alive and post-mortem. The abundant evidence of encrusting on bivalve shells and also free-living bryozoans, gives a detailed view of the scenario after death of most bivalve faunas. The final skeletal concentrations are described using the nomenclature of Kidwell et al. (1986).