The conchostracans of the São José do Belmonte Basin, Lower Cretaceous, Northeastern Brazil

Abstract

The São José do Belmonte Basin, comprises an area of 610 km2 in the São José do Belmonte, Serrote de Cima, Verdejante and São Tomé counties, Pernambuco State, Brazil. The basin is limited by normal faults in an east- west direction, controlled by the Pre-Cambrian regional lineaments of Paraíba and Pernambuco. The lithologies are conglomerates, coarse sandstones, medium-fine sandstones, siltstones and shales. The coarse clastic sediments are distributed in the basin borders, while in the central-south region of the São José do Belmonte Basin dominate fine-grained sediments. These are yellowish and reddish shales and mudstones interbeded with siltstones and carbonate levels. In this study are analyzed the conchostracans from the shales of Lagoa da Areia. These are cyzicids identified as Cyzicus brauni, a common species in other sedimentary basins of Northeast Brazil (Jatobá, Sousa, Uiraúna, Iguatu, Malhada Vermelha, Rio Nazaré, Padre Marcos and Araripe) and also with great anatomical similarities with species from African basins, such as Cyzicus anomala, Cyzicus kitariensis and Cyzicus anchietae. The presence of Cyzicus brauni occur mainly in Neocomian rocks (Rio da Serra – Aratu Stages), and its palaeoecological context is related to temporary freshwater lakes, with well oxygenated alkaline water, in a hot climate. Their living environment are controlled by the local rainy conditions and the temporary presence of water is not adequate to a diversified freshwater biota.