Life at the continental–marine interface: palaeoenvironments and biota of the Alcobaça Formation (Late Jurassic, Central Portugal), with a formal definition of the unit appended

Abstract The Kimmeridgian Alcobaça Formation of the Lusitanian Basin forms a mixed carbonate–siliciclastic unit between basinal deposits Abadia Formation, and fluvial–terrestrial strata Lourinhã Formation. This study presents >2.5 km detailed logs nine outcrop sections in its type region. Eight these encircle Caldas da Rainha Diapir, which was prominent, emergent, passive salt diapir during time deposition. Palaeoenvironments form complex mosaic low- to high-energy, carbonate- or siliciclastic-dominated shallow shelf settings; coastal embayments lagoons; plains with rivers, lakes playas. In strata, abundant microfauna is often joined by rich macrofauna, usually dominated bivalves. Locally, corals, calcareous sponges oysters meadows patch reefs. These autochthonous parautochthonous remnants former communities are assigned 35 benthic macrofaunal associations. integration palaeoecological analysis associations microfaunal sedimentological data provides constraint on their salinity ranges, range from slightly hypersaline freshwater. Frequent temporal spatial fluctuations attributed variations relative sea-level, tectonics climate. NNE-trending Diapir induced pronounced facies differentiation. Predominantly, non-marine siliciclastic northwest carbonate siliciclastic, marine brackish southwest contrasted shallow-marine east diapir. Comprehensive exposure well-preserved fossils make an excellent showcase demonstrate how biofacies can help disentangle interplay climate changes, sea-level tectonics. Based improved characterisation unit, formally defined, seven members established.