RELACIONES ENTRE LA CUENCA PATAGONICA, LA CUENCA ANDINA Y EL CANAL DE MOZAMBIQUE

Abstract

"Grypbaea balli (Stefanini ) is described for the lowestmost beds of the Coyhaique Formation, in Aysén, Chile. This species, which is known for the Oxfordian-Early Kimmeridgian of the Ethiopian-Indo-Malagasic Faunistic Paleoprovince, developed in this region of the Southern Andes in muddy sea bottoms and in bicarbonates rich waters cooler than those of the region of origin of the referred species. The presence of this species in the eastern region of the Andean Range in Aysén, is an evidence for a Late Jurassic age of the marine ingresion. Cortelations with other regions of the Patagonia and especially with the Magallanes region Southernmost Chile are established on the basis of this determination . The extension of the basin is estimated and from an analysis of the paleogeographic evolution of Patagonia it is demonstrated that the sea retreated gradually towards the south . The migration of Himalayan faunas into the Patagonian Basin was allowed by the conection with the Mozambique Channel, which opened progressively from Northeast to the Southwest. A comparison between the geological evolution of the Geoliminar and Geosincline Sections of the Southern Andes during Mesozoic shows that the Aysén area was transitional between both. A detailed paleontological analysis and the figures of the found specimens is presented."