Ichnology and sedimentology of Miocene Hyperpycnites of the Austral foreland basin (Tierra del Fuego, Argentina): trace fossil distribution and paleoecological implications

Combined ichnologic and sedimentologic analysis of Miocene deep-marine hyperpycnites in the Austral foreland basin, Tierra del Fuego, Argentina, allows recognition and characterization of different trace fossil assemblages from proximal to distal within this depositional system. In proximal and middle settings, hyperpycnal channel and inner levee deposits contain trace fossils in climbing-ripple and parallel-laminated sandstone facies; dwelling structures of suspension-feeding organisms (e.g., Diplocraterion) dominate. In outer levee deposits, fine-grained heterolithic intervals display a suite of trace fossils related to op-portunistic producers composed of concentrically laminated burrows of detritus or deposit feeders and also locomotion and grazing traces (e.g., Protovirgularia, Gordia). The general low intensity of bioturbation and the dominance of structures pro-duced by opportunistic organisms suggest a stressful environment probably be-cause of episodes with high sedimentation rates and fluctuating salinity. In addition, in the middle slope setting, escape structures of imported bivalves occur in isolated sandstone bodies that accumulated at the base of the depositional slope.