High-precision U-Pb geochronology and a new chronostratigraphy for the Cañadón Asfalto Basin, Chubut, central Patagonia: implications for terrestrial faunal and floral evolution in Jurassic.

CUNEO, R., RAMEZANI, J., SCASSO, R., POL, D., ESCAPA, I.

GONDWANA RESEARCH

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2013 vol. 24 p. 1267 - 1275

1342-937X

The Cañadón Asfalto rift basin in the Chubut province of Argentina includes an important thickness of Jurassic volcaniclastic deposits that lack of a confident geochronological framework capable of offering better calibrated correlations for the many geological and paleontological events represented in the region. U-Pb radiometric datings were preliminary performed on four key areas involving different basinal depocenters of the Cañadón Asfalto and Cañadón Calcáreo formations. Obtained concordia ages based on ID-TIMS methodology indicate that the Cañadón Asfalto formation begun its deposition by the late Early Jurassic along its different depocenters, and extended up to the early Middle Jurassic; while the Cañadón Calcáreo Fm. was mainly deposited during the early Late Jurassic. On this ground, several geological and paleontological connotations are now more clearly established, including an extended time span of no deposition during the late Middle Jurassic. Additionally, the underlying Lonco Trapial Fm. is now interpreted as fully deposited during the late Early Jurassic most likely during a short period. From a paleontological viewpoint, plant-animal events related to each of the Jurassic stages are now clearly seen, which envisages novel implications in terms of their evolutionary behavior.