Marine influence in the Barreiras Formation, State of Alagoas, northeastern Brazil

Anais da Academia Brasileira de Ciências

Dilce F. Rossetti²  Ana M. Góes¹ 

[1] ,Instituto Nacional de Pesquisas EspaciaisSão José dos Campos SP ,Brasil

关键词: Miocene;    marine transgression;    tidal currents;    sedimentary structures;    northeastern Brazil;    Mioceno;    transgressão marinha;    correntes de maré;    estruturas sedimentares;    nordeste do Brasil;   

DOI  :  10.1590/S0001-37652009000400012

来源: SciELO

【 摘 要 】

Tidal processes were important for deposition of the Barreiras Formation located in northern Brazil, while correlatable deposits in northeastern Brazil have been traditionally related to continental environments. Facies analysis in southern Alagoas revealed that the Barreiras Formation consists of cross-stratified conglomerates and sandstones (facies Sx and Cgx), compound cross-stratified sandstones (facies Cx), and heterolithic beddings (facies H). A significant portion of these deposits occurs within channel morphologies displaying fining and thinning upward successions. An abundance of sedimentary features is comparable to those from the northern Brazilian counterpart. These include: tidal bundles; herringbone cross-stratification; heterolithic beddings with sandstone and mudstone beds in sharp contacts; and ichnofossils mostly consisting of Ophiomorpha nodosa, Skolithos and Planolites. Altogether, these features point to a marginal marine depositional setting dominated by tidal processes, which are related to an estuarine system, an interpretation also provided for the Barreiras Formation in northern Brazil. The widespread occurrence of deposits with unambiguous evidence of tidal processes in the Barreiras Formation of northern Brazil, and now in the State of Alagoas, leads to argue that the early/middle Miocene worldwide marine transgression might have left a much more widespread sedimentary record along the Brazilian coast than currently regarded.

【 授权许可】

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