O ALINHAMENTO DE ROCHAS ALCALINAS POÇOS DE CALDAS-CABO FRIO (RJ) E SUA CONTINUIDADE NA CADEIA VITÓRIA-TRINDADE

Abstract

Geologic, geomorphologic and geochronologic evidences indicate that the WNW-ESE alignment of alkaline rocks between Poços de Caldas and Cabo Frio, in the State of Rio de Janeiro, emplaced during the displacement of the South American plate over a hot spot. During the Eocene, the hot spot probably arrived at the eastem limit (coast of Rio de Janeiro State) of the South American continent, and resulted in important tectonic and magmatic events. Associated to these events, occurred a relative displacement of the hot spot to the alignment of volcanic rocks of the Cadeia Vitória-Trindade along the oceanic zone. As a consequence the following events took place: (a) intense eocenic volcanism of the Plataforma de Cabo Frio and Arquipelago de Abrolhos; (b) opening of the tapnrogenic basins in the Brazilian Southeast (Taubaté, Resende, Volta Redonda, and others), about 40 Ma ago; and (c) formation of eocenic unconformities and/or the contemporaneous volcanism in the sedimentary sequences of the marginal Brazilian basins of Pelotas, Santos, Campos, Espírito Santo, Cumuruxatiba and Jequitinhonha. Two important mprphologic features can be observed in the sense of reinforcing this intepretation. One is the pronounced inflection, to southwest, of the west Umit of the Cadeia Vitória-Trindade, in contrast to its preferential east-west direction along the oceanic zone. The other is the northeast alignment of the oil fields of the Campos Basin, the most important oil production Brazilian basin, that is in agreement with the proposed path of the hot spot.