Evaluating Elemental and Petrophysical Data From Scientific Ocean Drilling for Sedimentary CaCO 3 Reconstruction and Application to Cenozoic Deep‐Sea Carbonate Burial
Rongting Zheng, Jiuyuan Wang, Yi Wang, Xin Tong, Quanyou Liu, Ellen Thomas, Yixin DongAbstract
The variation in calcium carbonate (CaCO 3 ) content with water depth in deep‐sea sediments is critical for reconstructing paleo‐oceanic events, global carbon cycling, and climate change. High‐resolution (e.g., centimeter‐scale) CaCO 3 measurements in Cenozoic marine sediments remain limited, and proxy‐based estimates have not been sufficiently validated. This study evaluates CaCO 3 conversion models using proxies in sediments recovered by scientific ocean drilling. Elemental data obtained through Inductively Coupled Plasma Atomic/Optical Emission Spectrometry (ICP‐AES/OES) and Scanning X‐ray Fluorescence Spectroscopy (XRF), along with petrophysical data from Natural Gamma Radiation (NGR) and Gamma Ray Attenuation Bulk Density (GRA) measurements, are statistically compared to coulometrically measured CaCO 3 values, and CaCO 3 wt% is estimated through correlation. Using 116 International Ocean Discovery Program/Ocean Drilling Program sites with records most suitable for our purpose, we identify optimal models to estimate CaCO 3 wt% from proxies for different sediment types: the elemental data‐based method provides the best overall estimates, NGR performs best for clay‐carbonate binary systems, and GRA is suitable for biogenic silica‐carbonate mixtures. These optimized regressions enable higher‐resolution CaCO 3 reconstructions than chemical analyses alone, and allow estimates in data‐limited intervals and regions. Building on these method evaluations, we applied the optimized framework to a method‐screened set of records to reconstruct Cenozoic deep‐sea CaCO 3 burial patterns as an example of its potential paleoceanographic applications. The reconstructed burial record captures the distinct responses of deep‐sea carbonate burial to major Cenozoic climate transitions. We thus establish a practical framework for selecting and applying proxy‐based CaCO 3 reconstruction methods and demonstrate its potential for investigating long‐term changes in marine carbonate burial.