Microfossil turnover across the uppermost Danian at Caravaca, Spain: Paleoenvironmental inferences and identification of the latest Danian event

Abstract

The Latest Danian Event (LDE) or Top Chron C27n hyperthermal event has been identified in the Caravaca section (Southern Spain) by means of calcareous nannofossil biozones (Subzone NTp7b) and the recognition of a prominent, negative ~0.6 per mille carbon isotope excursion measured in benthic foraminiferal tests. This is the first time that this Danian hyperthermal event has been identified in a deep-water, middle to lower bathyal setting from the Western Tethyan realm.The analysis of benthic foraminiferal assemblages shows gradual changes in the assemblages prior to the onset of the LDE and an increase in food supply to the seafloor during the LDE, in agreement with results from shallower Southern Tethyan settings. The benthic assemblage changes across the LDE at Caravaca share some characteristics with other hyperthermal events, including the negative carbon isotope excursion, the increased abundance of buliminids, or the common occurrence of A. aragonensis, an opportunistic species that proliferated during other Paleogene hyperthermal events. In addition, the increased abundance of Nuttallides truempyi, a dissolution-resistant form that thrived during the Paleocene Eocene Thermal Maximum, and the abundance of calcareous infaunal morphogroups, which calcify in less carbonate-undersaturated pore waters, indicate slightly CaCO3-corrosive bottom waters during the LDE.Turnover of calcareous plankton across the LDE is similar to other sites globally distributed, including the evolution of photosymbiotic foraminiferal lineages and the radiation of the nannofossil “fasciculiths group”. The occurrence of innovative morphostructures (Diantholitha and Lithoptychius) towards the base of the LDE may indicate a more efficient biological pump. This hypothesis is supported by increased percentages of benthic infaunal morphogroups and a decrease in the abundance of oligotrophic species.A reworked interval has been identified immediately above the LDE. Higher up in the section, benthic and planktic assemblages from the post-LDE interval point to the recovery of the environmental conditions, including a decrease in the food supply to the seafloor.