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Fractional abundances of branched glycerol dialkyl glycerol tetraethers (brGDGT) from the Arid Central Asian Data Base (ACADB) for surface brGDGT samples

Climate parameters of the Arid Central Asian Data Base (ACADB) for surface brGDGT samples

Environmental parameters of the Arid Central Asian Data Base (ACADB) for surface brGDGT samples

Global soil and peat branched GDGT compilation dataset

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.

BrGDGT-based temperature evolution through an Eocene hyperthermal event

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) from maar sediments were analyzed in order to reconstruct continental air temperatures across a middle Eocene (47.2 Ma) hyperthermal event. Additionally, carbon isotopes of total organic carbon (δ13C TOC) were measured from the same samples to reconstruct changes in global and local carbon cycle. Measurements for both, brGDGTs and carbon isotopes, were carried out between beginning of 2021 and end of 2022. Based on the current age model the temporal resolution of the samples is millennial to sub-millennial. Sediment samples (organic-rich pelites) are from the FB2001 drill core, recovered from the Messel Fossil Site located in the vicinity of Frankfurt, Germany. The brGDGTs were solvent extracted by Soxhlet apparatus and further analyzed by high-performance liquid chromatography (HPLC-) - atmospheric pressure chemical ionization (APLCI-) - mass spectrometry (MS). Aliquots for total organic carbon isotope measurements were decalcified with HCl (10%) prior analyses on a Flash Elemental Analyzer.

Estimated adjusted depth of CO2 of FB2001 drill core from Messel

This table contains atmospheric CO2-estimates based on stomata retrieved in the Messel fossil pit (Grein 2010, Grein et al., 2011). It lists the original out-crop depth relative to marker beds, the depth (m) projected onto the FB2001 drill core, the age (Ma) as well as mean, maximum and minimum of the CO2 estimates. The respective plant species is indicated as well.

XRF Fe/TI and K/Ti ratios of FB2001 drill core from Messel

The data contains Fe/Ti and K/Ti ratios obtained via XRF core scanning of drill core FB2001 from the Messel fossil pit versus core depth and age. Scanning was performed at the Institute of Institute of Earth Sciences, Heidelberg University (Germany).

Recurrence times of siderite layers of FB2001 drill core from Messel

Statistically computed recurrence times of Fe/Ti peaks in the XRF scanning record of FB2001, reflecting siderite layers that are interpreted to reflect strong precipitation events. Upper and lower boundaries are calculated based on bootstrapping.

Mean Annual Air Temperatures of FB2001 drill core from Messel

This table contains Mean Annual Temperatures (MAT) reconstructed using branched GDGTs obtained on core FB2001 from Messel, relative to the core depth and age. The error given reflects the calibration error. Measurements were performed at the the Senckenberg Biodiversity and Climate Centre, Frankfurt (Germany) and at the RWTH Aachen (Germany).

brGDGT distributions and environmental parameters of lake sediments from the Eastern Canadian Arctic and Iceland, 2003-2019

This dataset contains fractional abundances of the 15 commonly-measured branched glycerol dialkyl glycerol tetraether (brGDGT) lipids in 43 lake surface sediments. It also contains 5 air temperature variables (mean annual temperature (MAT); mean air temperature of months above freezing (MAF); warmest month temperature (WMT); mean summer temperature (MST); summer warmth index (SWI)), mean lake water conductivity, pH, and dissolved oxygen, and minimum dissolved oxygen. Finally, it contains basic lake parameters, including coordinates, maximum lake water depth, and approximate surface area.

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