Geology of the Quebrada Honda, basin of Lago La Plata, Chubut

Abstract

The quebrada Honda is situated in the Lago La Plata-Fontana basin in Chubut. The stratigraphy of the area begins in the Upper Jurassic with the calc-alkaline intermediate to acidic Lago La Plata Formation rocks. The Neocomian Coyhaique Group, which includes the Tres Lagunas and Katterfeld Formations, is the sedimentary filling of the intraarc basin that was developed by that time. These units are included in a paleoenviromental model as a shelf-margin system tract followed by a transgressive system tract. The discovery of Favrella americana in the Katterfeld Formation constrains to the Early Hauterivian the age of these sequences. The hypabissal calc-alkaline Quebrada Honda Gabbro is related to extension as well as the more evolved Late Neocomian Don Rueda Formation volcanism. This subaerial magmatic event shows evidences of interaction with aqueous bodies that indicate the concomitance with the last sedimentary Coyhaique Group filling of the basin. A maximum age of 80 My is assigned to the tectonic inversion observed in the area.