Composição dos Estromatólitos Estratiformes da Lagoa Salgada, Rio de Janeiro, Brasil

Abstract

Lagoa Salgada is situated in the north coast of State of Rio de Janeiro, between the districts of Campos dosGoitacazes and São João da Barra, some 41o00’30’’ W and 21o54’10’’S. In the margins of the lagoon the presence ofrecent stromatolitic constructions was verifi ed. The stromatolite may be defi ned as lithifying biosedimentary structure,growing through of sediment blade trapping by the carbonate precipitation as result of microbian organism activity.The aim of this study was to characterize the cyanobacteria assemblage in stratiform stromatolites found on the fl oor oflagoa Salgada. Within the stratiform stromatolites 21 species of cyanobacteria were found, Microcoleus chthonoplastes(Thuret) Gomont 1892 and Lyngbya aestuarii (Liebman) Gomont 1892 are frequent in these stromatolites. The presenceof calcite was observed in the stratiform stromatolites. The fi lamentous cyanobacteria are responsible for the union andimprisonment of sediment to form the layers in the stromatolites. The skeleton remains of mollusks, foraminifers andostracod found in the area, work as a source of calcium carbonate and of sediment to structure the stromatolites.

Keywords

• Stratiform stromatolites
• cyanobacteria
• lagoa Salgada