U-Pb geochronology of the Santa Cruz Formation (early Miocene) at the Río Bote and Río Santa Cruz (southernmost Patagonia, Argentina): Implications for the correlation of fossil vertebrate localities

CUITIÑO, JOSÉ IGNACIO; FERNÍCOLA, JUAN CARLOS; KOHN, MATTHEW; TRAYLER, ROBIN; NAIPAUER, MAXIMILIANO; BARGO, M. SUSANA; KAY, RICHARD, F.; VIZCAÍNO, SERGIO F.

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2016 vol. 70 p. 198 - 210

0895-9811

The early Miocene Santa Cruz Formation (SCF) in southern Patagonia hosts the Santacrucian SouthAmerican Land Mammal Age (SALMA), whose age is known mainly from exposures along the Atlanticcoast. Zircon U-Pb ages were obtained from intercalated tuffs from four inland sections of the SCF:17.36 ± 0.63 Ma for the westernmost Río Bote locality, and 17.04 ± 0.55 Mae16.32 ± 0.62 Ma for centralRío Santa Cruz localities. All ages agree with the bounding age of underlying marine units and withequivalent strata in coastal exposures. New ages and available sedimentation rates imply time spans foreach section of ~18.2 to 17.36 Ma for Río Bote and 17.45e15.63 Ma for central Río Santa Cruz (Burdigalian).These estimates support the view that deposition of the SCF began at western localities ~1 Maearlier than at eastern localities, and that the central Río Santa Cruz localities expose the youngest SCF insouthern Santa Cruz Province. Associated vertebrate faunas are consistent with our geochronologicsynthesis, showing older (Notohippidian) taxa in western localities and younger (Santacrucian) taxa incentral localities. The Notohippidian fauna (19.0e18.0 Ma) of the western localities is synchronous withPinturan faunas (19.0e18.0 Ma), but older than Santacrucian faunas of the Río Santa Cruz (17.2e15.6 Ma)and coastal localities (18.0e16.2 Ma). The Santacrucian faunas of the central Río Santa Cruz localitiestemporally overlap Colloncuran (15.7 Ma), Friasian (16.5 Ma), and eastern Santacrucian faunas.