Edades U-Pb en zircones de tobas de la Fm. Piedra Clavada, pcia. de Santa Cruz, Argentina: un marcador albiano tardio para la evolución tectónica y biológica de la Cuenca Austral.

POIRÉ, DANIEL G.; IGLESIAS, ARI; VARELA, AUGUSTO; RICHIANO, SEBASTIÁN; MEJIA IBAÑEZ, MAURICIO; STROEMBERG,CAROLINE

Tucumán

Congreso; XX Congreso Geológico Argentino; 2017

Asociación Geológica Argentina

The Piedra Clavada Formation (= Kachaike Fm.) is a very significant lithostratigraphic unit (306 m thick) in the Cretaceous sedimentary record of the Austral Basin in southern Patagonia, Argentina, due to represents the final part of a rift stage forming a large passive-margin delta system, before the developing of a foreland basin stage. In the same way, this unit bears one of the most diverse marine and littoral fauna and flora of the region. However, the precise age of the Piedra Clavada Formation was unknown and just approximately estimated from its fossil content ranging from the Upper Aptian to the Cenomanian, from different authors. The aim of this contribution is point out the U-Pb age of this unit taken from zircons of two tuffs levels from the upper part of the Piedra Clavada Formation. By the way, the obtained age (100-101 Ma) coincides with the oceanic anoxic event 1d (OAE1d), which generates black euxinic shales in the oceanic bottoms and great biological proliferation in coastal and continental areas, as Piedra Clavada Fm. palaeoenvironment.