TRENDS IN CARBONATE PRESERVATION AND SURFACE PRODUCTIVITY ACROSS DANIAN–SELANDIAN FROM THE SÃO PAULO PLATEAU

Sedimentary sections from the Brazilian margin were scarce during the Danian and Selandian intervals. Among the few sections recovered are the Poty Quarry (Pernambuco Parnaíba Basin) and some Deep-Sea Drilling sites (Rio Grande Rise and São Paulo Plateau). The Site 356, which was recovered from the São Paulo Plateau, provides a continuous record from Danian to Selandian strata, as determined through the biostratigraphy of planktic foraminifera. This study uses elemental ratios to present a trend in dissolution and oceanic carbonate productivity, and to evaluate carbonate preservation patterns in the central South Atlantic. A total of 68 sediment samples were collected from DSDP Site 356 analysed by X-ray fluorescence (XRF) owing to determine their geochemical composition. XRF analyses were performed on these samples for this purpose (you can remove this sentence). During the Danian interval, we observed an increasing trend in carbonate content (e.g., Ca/terrigenous ratio and CaCO₃%),  and paleoproductivity (e.g., Ba/element ratio). The increase in carbonate content, which is associated with the increase in primary productivity in the São Paulo Plateau, appears to be a associated with the progressive recovery of calcifying organisms that were greatly affected by the K-Pg boundary event. During the Selandian interval, a gradual decline in carbonate content is observed, while primary productivity appears to remain relatively constant in part of this section, suggesting a progressive increase in dissolution (high lysocline and/or carbonate compensation depth). A slight decrease in productivity associated with a carbonate drop is recognized in the upper portion of the Selandian (Planktonic Foraminiferal Biozone P4). This can be attributed to the combined effects of productivity and dissolution. The observed carbonate cycle dynamics detected at Site 356 appeared to be related to improved pelagic conditions (e.g., increased productivity) during the Danian period. However, during the Selandian interval, a slight decrease in carbonate content was followed by a subsequent drop in paleoproductivity and dissolution in the upper Selandian.