Analysis of bioerosion in clasts from a Miocene rocky-shore, Concepción Formation, Veracruz, México

摘要: Abstract Study of bioerosion traces in the geologic record rocky shores is can establish location ancient shorelines and aid understanding evolution marine communities marginal environments. As an example, ichnologic associated with cobbles conglomerate that crops out along east side Neovolcanic Ridge, near Plan del Rio village Veracruz State, south-central Mexico described explained. The corresponds to upper part Concepcion Formation, deposited during Miocene. bivalves gastropods included sandy matrix, presence oysters bryozoans on surfaces clasts, allowed interpretation this as shore. present work deals recorded clasts. Six ichnogenera ten ichnospecies were determined, corresponding activity polychaetes and/or sipunculids ( Caulostrepsis taeniola , Maeandropolydora sulcans Trypanites weisei ), echinoids Circolites isp.), clionaid sponges Entobia cateniformis E. geometrica ovula boring Gastrochaenolites cluniformis G. lapidicus torpedo ). relative abundance organisms allows these biota be placed within ichnofacies, which characteristic hard substrates deep bioerosion. diversity ichnoassociations studied indicate a shallow environment low sedimentation rate, including episodes removal or rolling This process inferred from clast roundness most surfaces. On other hand, complete eroded borings same shows different Results allow for genetic history conglomerate, confirming its deposition shore palaeoenvironment indicating shoreline west margin Gulf