First Radioisotope (Potassium-Argon) Age of Marine Neogene Rionegro Beds in Northeastern Patagonia, Argentina

Abstract

An average age of 9.41 million years was obtained from radioisotope (potassium-argon) age determinations of three glass concentrates of a tuff from the upper part of the marine Rionegrense at Punta Cracker in Golfo Nuevo, Argentina. This age correlates with the Tortonian marine stage of Europe and the Chasicoan Land Mammal Age of South America.

Age, distribution, tectonics, and eustatic controls of the Paranense and Caribbean marine transgressions in southern Bolivia and Argentina

“…The top of the marine section of the Puerto Madryn Formation in Bahía Cracker (Zinsmeister et al, 1981) and Península Valdés (Scasso et al, 2001) yields ages of 10-9 Ma. Magnetostratigraphic studies of marine strata near Río Paraná led Bidegain (1993) to propose a Pliocene age.…”

Early history of Asteraceae in Patagonia: Evidence from fossil pollen grains

“…They come from San Julián, Monte León (Austral basin), Chenque (San Jorge basin), and Puerto Madryn (Valdés basin) formations. The ages of the formations are well constrained based on fossil evidence (e.g., dinoflagellate) and absolute (radiometric) data (Zinsmeister et al 1981;Feagle et al 1995;Palamarczuck & Barreda 1998;Scasso et al 2001;Parras & Casadío 2006). Fossils are housed in MACN: BA PAL.…”

The southernmost record of a Neuryurini Hoffstetter, 1958 (Mammalia, Xenarthra, Glyptodontidae)

“…This specimen comes from the upper levels of the Puerto Madryn Formation exposed in Península Valdés (specifically from Rincón Chico near Punta Delgada, northeastern Chubut Province); associated fossil vertebrates indicate the Huayquerian SALMA (late Miocene) for these sediments. 40 K/ 39 Ar dates were obtained from a tuff in the upper part of the marine Rionegran, in Bahía Cracker (Chubut Province), with an age averaging 9.41 Ma (Zinsmeister et al 1981). Recently Scasso et al (2001) presented several dates obtained by 87 Sr/ 86 Sr from bivalves, giving an average age of 10.1 Ma.…”