SPOROPOLINIC ANALYSIS OF THE RÍO TURBIO FORMATION (EOCENE OF SANTA CRUZ PROVINCE) AND ITS RELATION WITH GLOBAL PALEOCLIMATIC CHANGES: MIXED PALEOFLORA EVOLUTION.

FERNÁNDEZ, D. A.; BARREDA, V. D.; TELLERÍA, M. C.; PALAZZESI, L.

Simposio; XVII Simposio Argentino de Paleobotánica y Palinología; 2018

The palynomorph content recovered from marine deposits exposed along Río Turbio, in Santa Cruz Province, assigned to the homonymous formation is described. The palynomorph assemblages are rich and diverse. In general they are dominated by species of Nothofagidites, Podocarpidites and Myrtaceidites. A total of 22.805 sporomorphs and 9.486 microplankton specimens were counted. The sporomorphswere grouped into 116 morphospecies, of which 77 were recognized for the first time in the unit, four represent the first record for South America and one thefirst record for Argentina. Samples from the two members of the Río Turbio Formation (RTF) were distinguished based on their palynomoph content by performing a cluster analysis. At the top of the sequence, a third group of samples was recognized that yielded a specific association, containing forms indicative of warm climate and high diversity, which could be Oligocene in age. A diversity analysis for the RTF was performed for the first time, by means ofrarefaction curves and standing diversity. The entire unit is characterized by high levels of floristic diversity and the presence of warm climate forms. However, the latter are more abundant and the diversity is slightly higher inthe Lower Member. This suggests that the period represented by the Eocene samples of the RTF would correspond to a decrease in the mean annual temperature, consistent with previous models based on oxygen isotopes, with asignificant deterioration of floristic diversity in samples from the top of the sequence, probably belonging to the Oligocene.