Calcifying marine organisms provide a valuable means to access high-resolution historical records of the marine environment captured within their skeletal geochemistry. These records are essential for comprehending the effects of human-induced climate change and reducing uncertainties in future projections. Integrating investigations across various taxa, depths, and geographic locations can help identify universal environmental proxies and serve as a basis for targeted studies in the future. Here, we provide a comprehensive georeferenced database of measured values of Li/Mg, Mg/Ca, Sr/Ca, Ba/Ca, U/Ca and Sr-U in coral and coralline algae compiled from the scientific literature (1950-2021; http://www.webofknowledge.com, accessed 2022-09-30) for the purpose of interrogating and refining global, mineralogy specific and/or taxon-specific proxies for seawater temperature and barium. We include metadata relating to the source, timing and location of each study, the methodology used, and environmental and experimental information. The dataset presents an opportunity to quantify uncertainty and test the robustness of trace and minor element proxies for past environmental conditions, of which will be of value within the fields of geochemistry, ecology, climate, and palaeobiology. Full methodology and additional information provided in Williams et al. (2024).
Accurate temperature records for the deep geological past are a vital component of paleoclimate research. Distributional changes of branched glycerol dialkyl glycerol tetraether (brGDGT) lipids in geological archives including paleosoils are a promising indicators to infer past continental air temperatures. However, the 'orphan' status of the brGDGTs, the potential effect of temperature-independent parameters on their relative distribution, and the uneven geographical distribution of the soils used for calibration contribute to the high uncertainty of brGDGT-based transfer functions (root mean squared error, RMSE: ± 5 °C). Here, we expand the soil dataset from the previous calibration(s) with new and published soil data. We use Bayesian statistics to calibrate the relationship of the 5-methyl brGDGTs (MBT'5Me) and mean annual air temperature (MAAT). The addition of soils from warm (>28 °C) environments from India substantially increases the upper limit of the Bayesian calibration (BayMBT) from 25 to 29 °C, aiding in the generation of temperature records for past greenhouse climates, such as the Eocene. The BayMBT model also effectively minimizes the structured MAAT residuals prevalent in previous calibrations, therefore giving the opportunity to explore confounding factors on the calibration. We formulate a set of alternative calibration models to test the effect of specific environmental parameters and show that soils at mid-latitudes with temperature seasonalities >20 °C are not well described by the BayMBT model. We find that the MBT'5Me index is best correlated to the average temperature of all months >0 °C, called the BayMBT0 model. This finding supports the hypothesis that brGDGT production ceases or slows down in the winter months. However, a persistent feature of the BayMBT model and previous calibrations is the significant scatter at mid-latitudes, which is speculatively linked with a possible increase in diversity of microbial brGDGT-producing communities in these locations.
Here, we compile an extensive global surface sediment dataset of OH-isoGDGTs as well as regular isoprenoid GDGTs (isoGDGTs), with both data generated at NIOZ and previously published data from other laboratories. We explore recently developed temperature proxies based on hydroxylated isoprenoid Glycerol Dialkyl Glycerol Tetraethers (OH-isoGDGTs), such as %OH, RI-OH, RI-OH' and OHC for their potential for reconstructing past temperature changes. The data contains surface sediment data from the global ocean used in the study 'Evaluating isoprenoidal hydroxylated GDGT-based temperature proxies in surface sediments from the global ocean'. The excel sheet contains information regarding the surface sediments, their location, enivironmental parameters from each location extracted from WOA database, peak area of iso-GDGTs and OH-isoGDGTs, proxy indices discussed in the study and references for previously published data.