Lithofacies, palaeoecology and palaeoenvironments of the Agrio Formation, Lower Cretaceous of the Neuquén Basin, Argentina

LAZO, D.G., CICHOWOLSKI, M., RODRÍGUEZ, D.L. & AGUIRRE-URRETA, M.B.

The Neuquén Basin: A Case Study in Sequence Stratigraphy and Basin Dynamics

Geological Society of London

Lugar: Londres; Año: 2005; p. 295 - 315

The lithofacies and macrofossil guilds of the Agrio Formation (Upper Valanginian–Lower Barremian) have been analysed using evidence from sedimentological, taphonomic and palaeoecological studies. The study area is Agua de la Mula and adjacent regions in central Neuque´n. Seven lithofacies have been recognized in the field, which indicate that the Agrio Formation was deposited in an open-marine, ramp depositional system under storm influence. Lithofacies indicate conditions that range from low-energy basin to high-energy inner ramp. Outer and mid-ramp deposits are the most abundant. Macrofossils have been grouped into 16 guilds based on tiering, life habit and feeding category. The guilds indicate normal benthic oxygen level, normal salinity, and soft–firm muddy and sandy bottoms. Suspension-feeders are more common than deposit-feeders suggesting the predominance of suspended food particles over deposited food resources. A low input of siliciclastics and, possibly, other palaeoceanographic conditions allowed the development of oolitic facies in the inner ramp and coral patch reefs in the upper mid-ramp for a limited period of time. limited period of time. limited period of time.