PALEOTEMPERATURE ESTIMATIONS FOR THE RÍO TURBIO FORMATION (SANTA CRUZ, ARGENTINA): A KEY FOR UNDERSTANDING THE EOCENE CLIMATE DETERIORATION

PANTI, C.

Mendoza

Congreso; 4th International Paleontological Congress; 2014

The Eocene was a time of a great climatic turnover, ranging from the warmest global climates during the early Eocene to cold temperate climates close to the Eocene/Oligocene boundary. Although the analyses of Eocene climates have received great interest during the last years, middle/late Eocene climatic conditions in southern South America are not so well constrained. The study of fossil angiosperm leaves from the Río Turbio Formation shows a strong reduction in diversity from thelower towards the upper levels of the unit (up to 30%), mainly caused by a decline of neotropical elements. This reduction may have been caused by several factors, being climate change one of the most important. In order to support this assumption, we estimated temperature for the Río Turbio Formation on the bases of the analysis of leaf assemblages preserved in this unit. The mean annual temperature (MAT) estimation was performed using univariate (LMA) and multivariate (CLAMP) approaches based in the updated version of the newest climatic-leaf data set knows as CLAMP3SA. The study was carried out at three levels: (1) MAT estimation for the Río Turbio Formation; (2) MAT estimation for the Lower Member and (3) MAT estimation for the Upper Member. Univariate models for the Río Turbio Formation indicate a MAT of 17 (±2.1) ºC value slightly below that the one obtained for the Lower Member (18.5 ±2.1ºC). On the other side, the MAT calculated for the Upper Member show a decrease of about 5ºC (13 ±2.1ºC). Canonical correspondence analysis shows similar tendencies to those obtained from univariate models with barely high values being more pronounced for the Upper member (16ºC). This analysis show a decrease in the MAT values duringthe deposition of the Río Turbio Formation indicating that the climatic conditions became cooler towards the upper levels allowing the development of the subantarctic paleoflora type in this region. These results are also consistent with the observed upwards reduction in diversity, decline of neotropical elements and increase of austral components, mainly represented by Nothofagus.