Correlation of Middle to Upper Eocene Units from High Latitude Southwestern Atlantic Sites

Abstract

The Palaeogene was a time of important climatic and palaeoceanographic changes. To understand these modifications in the Southern Hemisphere, and especially those related to the opening of the Drake Passage (DP), is essential to correlate the lithostratigraphic units of Eocene age in areas adjacent to this passage, such as those from the Austral-Magallanes Basin (to the north of the DP) and James Ross Basin (to the south of the DP). For many years, there was no correlation between these units due to the absence of reliable chronostratigraphic and biostratigraphic information. Recently, other authors published new detrital zircon U/Pb data for the Austral-Magallanes Basin and introduced important modifications to the previous stratigraphic scheme. Subsequently, due to the reinterpretation of the new available isotope data together with additional U/Pb ages from Chilean sections, the recent chronostratigraphic model was modified again, including not only the Austral-Magallanes Basin units but also those from the James Ross Basin. In the light of an updated quantitative dinoflagellate cyst dataset from southern South America and northern Antarctic Peninsula we performed a compositional Principal Component Analysis to evaluate and discuss the different age models proposed for the studied sections. We also compare our results with other assemblages from southern Chilean sections, Malvinas (Falkland) Plateau, and the South Orkney sites. We conclude that this analysis comparing different Eocene units from areas adjacent to the DP shows a high correlation between the dinoflagellate cyst assemblages considered to be Bartonian in age in the last proposed stratigraphic scheme.