Abstract

LAZO, Darío G.. Taphonomy, time-averaging and lateral transport of the macrofossils of the Pilmatué Member of the Agrio formation, lower cretaceous, neuquén basin, argentina. Ameghiniana [online]. 2006, vol.43, n.2, pp.311-326. ISSN 1851-8044.

A taphonomic and sedimentary facies analysis of the Pilmatué Member of the Agrio Formation in central Neuquén basin is presented to determine the time-averaging and degree of lateral transport of its macrofauna. The Pilmatué Member is characterized by abundant fossil concentrations dominated by benthic organisms such as corals, serpulids, bivalves and gastropods. Stratigraphic occurrence of benthic elements was accurately dated by a refined ammonite zonation of the Agrio Formation. Three sections were studied between Chos Malal and Zapala (Neuquén) situated on a north-south line of 44.2 km. Five litofacies and nine taphofacies were defined. The depositonal system is interpreted as a storm influenced homoclinal shoreface to shelf environment. Taphonomic analysis showed that most macrofaunistic associations are autochthonous or slightly parautochthonous with no significant lateral transport. Census, within-habitat time-averaged and environmentally condensed assemblages were identified. Time scales of fossil accumulation span from days-years up to 0.5 My. Nearshore assemblages are less time-averaged than shelf assemblages as in modern settings.

Keywords : Valanginian-Hauterivian; Storm influenced shoreface-shelf; Macrofauna; Taphonomy.