Ancient Coastlines in the Continental Shelf of the State of Ceará, Northeast Brazil: Evidence from Sediment Chemistry and Stable Isotopes

• Published in: International geology review 2008-12, Vol.50 (12), p.1141-1156
• Main Authors: Marques, Wanessa Sousa, Sial, Alcides Nobrega, de Albuquerque Menor, Eldemar, Ferreira, Valderez Pinto, Sá Freire, George Satander, de Albuquerque Medeiros Lima, Enjolras, Belo de Souza, Roberto Lúcio
• Format: Article
• Language: English
• Subjects: Amphistegina; Foraminifera; Peneroplis planatus
• ISSN: 0020-6814; 1938-2839
• DOI: 10.2747/0020-6814.50.12.1141

Continental shelf sediments from the state of Ceará, northeastern Brazil, have been studied to investigate meteoric diagenesis of marine sediments of previously defined ancient coastal lines. Major elements for 131 samples of carbonate sediments and C and O isotopes for 51 carapace samples of benthonic foraminifers of the Amphistegina radiata and Peneroplis planatus species were analyzed. Geochemical signatures of δ 13 C, δ 18 O, SiO 2 (stoichiometrically calculated as quartz %), Sr and Mn, and XRD document the impact of meteoric diagenesis on relict sediments from current depths of 25-30 m, 45 m, and 80 m. Morphologies of the marine shelf at these depths, interpreted from previous bathymetric profiles, correspond to holocenic marine terraces. Despite a recent sedimentary cover, it was possible to confirm that these terraces possess relict detrital, biogenic, and continental material, that resulted from erosional reworking of ancient coastlines during the Flandrian transgression.