Palynostratigraphy of the Paleogene Huitrera Formation in N-W Patagonia, Argentina

713-Melendi,3.12. 24.04.2003 11:25 Uhr Seite 205 (Schwarz Bogen)

N. Jb. Geol. Paläont. Abh. 228 (2) 205 – 273 Stuttgart, Mai 2003

Daniel L. Melendi, Laura H. Scafati, Buenos Aires, and Wolfgang Volkheimer, Mendoza With 16 figures and 1 table

MELENDI, D. L., SCAFATI, L. H. & VOLKHEIMER, W. (2003): Palynostratigraphy of the Paleogene Huitrera Formation in N-W Patagonia, Argentina. – N. Jb. Geol. Paläont. Abh., 228: 205– 273; Stuttgart.

Abstract: Palynological assemblages of the Huitrera Formation from two localities of the Río Negro and Neuquén provinces, are analysed. 1) At Nahuel Huapí Este locality the microflora contains forms with records starting during the Early Eocene (Periporopollenites demarcatus) and forms whose records end with the Early Eocene (Plicatopollis wodehousei). The form-genus Nothofagidites is absent from this association. The corresponding microfloras would be of Early Eocene age. - 2). At the Confluencia locality appears, at higher stratigraphic levels of the same Huitrera Formation, a microflora of Middle to Late Eocene age with Rhoipites sphaerica (with records beginning with the Middle Eocene) and Tricolporites valvatus (known from the Middle Eocene), together with Tricolpites (Psilatricolpites) lumbrerensis (whose youngest register is of Middle Eocene age) and Matonisporites ornamentalis (whose known records begin with the Late Eocene). Tuberculatosporites parvus, Tricolpites anguloluminosus and Triatriopollenites bertelsii end their records in the Late Eocene. The microflora of Confluencia is dominated by Nothofagidites (brassii and fusca groups). - Thus, both microfloras correspond to sediments of the eastern- most volcanic arc (of Paleocene to Eocene age) of northwestern extra-Andean Patagonia, constituted by the rocks of Huitrera Formation and not to the western arc (of Oligocene to Miocene age). - The incoming of Nothofagidites during the emplacement of the volcanic arc and the large frequency of this genus are evidence of an important climatic change from warm to cool-temperate conditions.