O NEO-ALAGOAS NAS BACIAS DO CEARÁ, ARARIPE E POTIGUAR (BRASIL): CARACTERIZAÇÃO ESTRATIGRÁFICA E PALEOAMBIENTAL

Abstract

The stratigraphic analysis of the Alagoas Stage (local stage) in Ceara Basin allows the investigated interval to be divided into two parts, with distinctive tectono-sedimentary and paleobiological features. The lower part shows non-marine environmental character and the upper part, inforrnally named Aptian-Albian transition, contains marine organisms in certain levels. These records would represent the first phases of a primitive equatorial Atlantic Ocean in the area. The Trairi Beds at the top of the continental section were deposited in an environmental complex which includes a marginal sabkha, reflecting cyclical conditions of extreme aridity or humidity. Similar events have occurred in the Potiguar Basin with the Ponta do Tubarao Beds and in Araripe Basin with the deposition of thinny calcareous and shale layers, here informally named Batateira Beds. These environmental conditions provided an excellent setting for preservation of organic matter due to cyclical anoxic processes. The observation that the organic extracts from shales of all these strata are similar supports the hypothesis of correspondence of these events.