Barra de Tabatinga and Touros Formations: evidence of pleistocene hich sea-level stillstands of the Rio Grande do Norte coast

KENITIRO SUGUIO, ALCINA MAGNÓLIA FRANCA BARRETO, FRANCISCO HILÁRIO REGO BEZERRA

Resumo


The Barra de Tabatinga Formation corresponds to the previous informally named Barra de Tabatinga unit, after a homonymous beach name. These marine terrace deposits occur along the present shoreline in patches between Natal and Barra de Sagi (ca. 80km). The summit of those deposits is about 7.5m above m.s.l. at Natal. They are composed of very friable clayey sandstones and conglomerates, exhibiting more-or-less conspicuous hydrodynamic sedimentary structures. The Touros Formation, after a homonymous town name, corresponds to the previous Tertiary Guamaré Formation, found by Petrobras only in subsurface. These marine terrace deposits extend, frequently as steep sea-cliffs along the present shoreline, between São Bento and Zumbi (ca. 120 km). The summit of these deposits reaches to a maximum of 20m above m.s.l., 2km to the N of Zumbi. Deposits are made-up of medium to coarse-grained sanstones, frequently well-cemented due to partial dissolution of biodetrital components. Hydrodynamic sedimentary structures, and trace fossils of Ophiomorpha nodosa, are very conspicuous. Both marine terraces, recently dated by TL and/or OSL methods, indicated Upper Pleistocene ages, and overlie unconformably the Neogene Barreiras Formation. Finally, as they fulfill all the requirements of the Brazilian Stratigraphic Nomenclature Code, as demonstrated in this paper, two new formations are formally proposed here.

 


Palavras-chave


Pleistocene; Marine terrace deposits; Sea-leve change.

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DOI: https://doi.org/10.22456/1807-9806.20264

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