Foraminíferos planctônicos e bentônicos cretáceos da Ilha de Quiepe, Formação Algodões, Bacia de Camamu, Bahia, Brasil

Abstract

A sampling program from Camamu Bay and its neighborhood were undertaken to microfossils appraisal of the Algodoes Formation outcrops, Camamu Basin. Among the basins of the Brazilian eastern margin, the Camamu Basin is the least known. This study aimed to identify planktonic and benthonic foraminifera of the Algodoes Formation, Camamu Basin, and to make biostratigraphic, paleoecological and paleobiogeographic inferences based on the microfauna. The sampling points were located at the Boipeba Island (Boipeba and Tassimirim beaches), and at the Camamu Bay (Barra Grande and Taipus de Fora beaches; Quiepe and Cangaiba islands). In total, 50 rock samples were collected, constituted in great part of calcarenites, besides dolomites, calcilutites and calcareous shale. All the material was subjected to a three laboratory techniques, applied to recover or observe carbonate microfossils: thin section, acetolysis and hydrogen peroxide methods. Only five samples from Quiepe Island showed results. Planktonic foraminifera, belonging to the genus Whiteinella (W. aff. aprica, W. archaeocretacea, W. baltica and Whiteinella sp. 1) were identified, besides scarce specimens assigned to Hedbergella (Hedbergella ? sp.1). The paleoecological studies, based on the benthonic foraminifera, revealed predominance of calcareous specimens (Bolivinidae ?), followed by agglutinated taxa (Spiroplectamminidae ? and Textulariidae ?). The occurrence of W. aff. aprica, W. archaeocretacea and W. baltica in the planktonic assemblage suggests a upper Cenomanian to upper Turonian age for the studied section of the Algodoes Formation. However, the correlation with ammonites data (Mammites, Kamerunoceras, Romaniceras and Neoptychites) allows to a better biostratigraphic resolution, indicating strata of early-middle Turonian age. The benthonic foraminifera observed (Bolivinidae ?, Spiroplectamminidae ? and Textulariidae?) indicated the predominance of infaunal organisms that lived on substrates constituted by calcareous mud preferably, and probably occupied the middle-deep neritic paleobathymetric range. The finding of Whiteinella (W. aff. aprica, W. archaeocretacea, W. baltica, Whiteinella sp. 1), besides the ostracod specimens of the Sapucariella ex gr. sapucariensis are important biogeographical records in the upper Cretaceous of South America and Africa.