Maastrichtian to Danian Atlantic transgression in the north of Patagonia: A dinoflagellate cyst approach

摘要

The late Maastrichtian to early Paleocene marine successions in northern Patagonia and neighboring southwestern Atlantic Ocean Basins provided a valuable organic-walled dinoflagellate cysts record. Assemblages around the Cretaceous-Paleogene boundary and more pronounced in the Danian compare well with those coevals from lower latitudes sites (e.g. Brazil, Uruguay, Tunisia, Israel). Humid-warm climate prevailing in Patagonia together with counterclockwise oceanic circulation along the southwestern South Atlantic Ocean would have favored the exchange of taxa of the marine biota with lower-latitude basins, and helped to explain the similarities of the marine palynoflora from the southernmost part of South America and those from the widely separated Tethyan domains. Quantitative data of Danian dinoflagellate cyts assemblages from the north of Patagonia were used to infer palaeoecological and paleoenvironmental conditions in terms of nutrient availability, salinity, and coastal proximity, providing refined local paleogeography in an epicontinental context. Consistent with Tethyan sites records, assemblages from northern Patagonia exhibit high abundance or dominance of the presumed heterotrophic dinoflagellate cysts, denoting a globally nutrient - enrichment of the watermasses during the Danian.