INCITAP   20787
INSTITUTO DE CIENCIAS DE LA TIERRA Y AMBIENTALES DE LA PAMPA
Unidad Ejecutora - UE
artículos
Título:
Correlation of marine beds based on Sr- and Ar- date determinations and faunal affinities across the Paleogene/Neogene boundary in southern Patagonia, Argentina
Autor/es:
PARRAS, A.; GRIFFIN, M.; FELDMANN, R.; CASADÍO, S.; SCHWEITZER, C.; MARENSSI, S.
Revista:
JOURNAL OF SOUTH AMERICAN EARTH SCIENCES
Editorial:
Elsevier
Referencias:
Año: 2008 vol. 26 p. 204 - 216
ISSN:
0895-9811
Resumen:
The San Julián and Monte León formations (Patagonian) are exposed along the Atlantic coast of Patagonia,
whereas in the west equivalent rocks are known as Centinela Formation. Sixteen 87Sr/86Sr measurements
on the oyster Crassostrea? hatcheri (Ortmann) from the San Julián and Centinela formations
and an 40Ar/39Ar-date from a whole-rock sample from the Centinela Formation yielded ages that allow
more precise correlation between the two areas. 87Sr/86Sr measurements from the San Julián Formation
yielded ages between 23.83 and 25.93 Ma, while for the Centinela Formation the ages ranged between
21.24 and 26.38 Ma. The 40Ar/39Ar analysis of a sample of the Centinela Formation yielded an age of
20.48 ± 0.27 Ma. The age data suggest a late Oligocene (Chattian) age for the San Julián Formation and
the lowermost beds of the Centinela Formation (northernmost exposures). The Monte León Formation
along the East coast and the entire section of the Centinela Formation in the southern area and the middle
and upper beds of this same unit in the northernmost localities were deposited at the end of the
Oligocene and early Miocene (ChattianBurdigalian). The invertebrate fauna present in these units shows
diverse preservation patterns that makes these fossils, especially the mollusks, not useful at this stage
for correlation purposes.
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