Non-depositional and erosional “offshore” bioeroded hardgrounds from the Lower Cretaceous of the Neuquén Basin, Argentina: Insights into their sequence-stratigraphic implications and controls

摘要: Abstract Hardgrounds are important surfaces for basin analysis and oil exploration, representing in some cases significant markers of the sedimentary fill. In Neuquen Basin, bioerosion structures common on shell benthic organisms, but bioeroded hardgrounds comparatively uncommon. Pilmatue Member Lower Cretaceous Agrio Formation (Valanginian-Hauterivian) two examples described detail, allowing to recognize contrasting palaeoenvironmental sequence-stratigraphic contexts, turn, discussing potential major controlling factors each example. both Trypanites isp. Gastrochaenolites described, interpreted as belonging a ichnofacies. The developed different environmental conditions: one non-depositional offshore conditions at top parasequence (i.e., transgressive surface); other erosional settings with omission surface located an intra-parasequence position, no obvious connotation. These marked differences palaeonvironmental (non-depositional vs erosive) context (inter occurrence) these example allowed us propose related generation hardgrounds. Despite differences, namely long periods non deposition low-energy shorter time high-energy (erosive) conditions, ichnofacies is developed, aspect be considered characterization evolution based surfaces.