Geology and Paleontology in the Cañadon Asfalto Basin.

SCASSO, R.A.,; ESCAPA, I.; DAMBORENEA, S.; PAGANI, A.,

Field Guide

Museo Egidio Feruglio, V Simposio Argentino del Jurásico,

Lugar: Trelew; Año: 2013; p. 1 - 26

This trip represents a unique opportunity not only to visit this scenically wonderful area but also to observe some impressive Jurassic exposures. During the fieldtrip we will go across the Cañadón Asfalto Basin. The main Mesozoic geological events of Patagonia are recorded in its volcanic and sedimentary succession together with a unique fossil biota including several plant and animal groups. The first day (Fig. 1) we will go from Trelew to the west and our first goal will be the Jurassic igneous rocks (ignimbrites, breccias, tuffs and subvolcanic porphyrites), which are the result of a large magmatic event that affected the southern part of Gondwana. They are also considered the ?technical basement? of the main Jurassic/Cretaceous and Cenozoic basins of Patagonia such as the Cañadón Asfalto and Golfo San Jorge basins. However these volcaniclastic rocks are also part of the filling of extensional rift basins that later evolved to wider sag basins (Uliana et al., 1985). Then we will visit the marine Osta Arena Formation (LowerJurasic) at Pampa de Agnia region. The second day our way goes along the Río Chubut Medio, a sort of oasis in the desertic landscape of central Patagonia with abundant fauna (guanacos, ñandúes, foxes, maras, etc.), visiting localities of geologic and paleontologic interest in the Cañadón Asfalto basin. Exposures of the Lonco Trapial Formation (Early Jurassic), the Cañadón Asfalto Formation (Early-Middle Jurassic) and the Cañadón Calcáreo Formation (Late Jurassic) will be visited. Finally, the third day we will visit the ?Sierra de Taquetren? area, walking around the Lower Jurassic Las Leoneras Formation (Fig. 1).