C and O Isotope Chemostratigraphy and Bulk Chemistry of Reef Limestones of the Tambaba Formation, Paraíba Basin, Northeastern Brazil

Abstract

This work focuses on the behavior of the C and O isotopes and major and trace element chemistry of the carbonate rocks of the Tambaba Formation, Paraíba Basin, Northeastern Brazil. Thirteen carbonate samples collected from three vertical profiles located perpendicular to the bedding along the coast of the state of Paraíba were analyzed. The δ13C values ranged from 1.6 to 2.8‰ VPDB while the δ18O values ranged from -1.2 to 1.8‰ VPDB, thus suggest a restricted shallow-platform depositional environment. X-ray fluorescence analyses suggested diagenetic changes, such as the replacement of dolomite by calcite (Mn/Sr ratios from 0.6 to 28) and dolomitization, which was identified by high Mg/Ca ratios (0.5 to 0.6). The very low SiO2 and Al2O3 content attested to the low terrigenous material influx. The carbon isotope values suggest that the carbonate rocks were deposited after the Paleocene-Eocene Thermal Maximum (PETM) event.