ALBERT

Description: During a time of negligible atmospheric pO2, Earth's early sulfur cycle generated a spectacular geological signal seen as the anomalous fractionation of multiple sulfur isotopic ratios. The disappearance of this signal from the geologic record has been hypothesized to constrain the timing of atmospheric oxygenation, though interpretive challenges exist. Asymmetry in existing S isotopic data, for example, suggest that the Archean crust was not mass balanced, with the implication that the loss of S isotope anomalies from the geologic record might lag the rise of atmospheric O2. Here, we present new S isotopic analyses of modern surface and groundwaters that drain Archean terrains in order to independently evaluate Archean S cycle mass balance. Natural waters contain sulfur derived from the underlying bedrock and thus can be used to ascertain its S isotopic composition at scales larger than typical geological samples allow. Analyses of 52 water samples from Canada and South Africa suggest that the Archean crust was mass balanced with an average multiple S isotopic composition equivalent to the bulk Earth. Overall, our work supports the hypothesis that the disappearance of multiple S isotope anomalies from the sedimentary record provides a robust proxy for the timing of the first rise in atmospheric O2.

Description: Electron microprobe microanalysis (EPMA) map of C, Ca, and Si concentrations in a sieved (less than 7 µm) and pelletized sample of river bedload sediment (site LHWS-1). Details on the analysis method and calibration are provided in the associated manuscript.

Description: Electron microprobe microanalysis (EPMA) map of C, Ca, and Si concentrations in a sieved (212 to 500 µm) and pelletized sample of river bedload sediment (site LHWS-6). Details on the analysis method and calibration are provided in the associated manuscript.

Description: Electron microprobe microanalysis (EPMA) map of C, Ca, and Si concentrations in a sieved (7 to 45 µm) and pelletized sample of river bedload sediment (site LHWS-6). Details on the analysis method and calibration are provided in the associated manuscript.

Description: Electron microprobe microanalysis (EPMA) map of C, Ca, and Si concentrations in a sieved (90 to 212 µm) and pelletized sample of river bedload sediment (site LHWS-6). Details on the analysis method and calibration are provided in the associated manuscript.

Description: Electron microprobe microanalysis (EPMA) map of C, Ca, and Si concentrations in a sieved (212 to 500 µm) and pelletized sample of river bedload sediment (site LHWS-1). Details on the analysis method and calibration are provided in the associated manuscript.

Description: Electron microprobe microanalysis (EPMA) map of C, Ca, and Si concentrations in a sieved (45 to 90 µm) and pelletized sample of river bedload sediment (site LHWS-6). Details on the analysis method and calibration are provided in the associated manuscript.

Description: Bulk carbon concentrations, organic carbon stable isotopic ratios, and organic carbon radiocarbon measurements for fluvial deposits, suspended sediments, and a tree fragment from the Efri Haukadalsá river catchment in Iceland (collected in August 2016).

Description: Sulfur K-edge XANES measurements of the relative proportion of reduced sulfur (i.e., S oxidation state less than or equal to zero) in select analysis spots within samples of suspended sediment, sediment deposits, and blank filters. Details on the analysis method and spectral fitting are provided in the associated manuscript.

Description: This dataset contains the calculation process of global organic carbon burial fluxes over the Neogene (23.0-2.6 Ma) period. The calculation involves a series of consecutive steps. First, we screened 1508 sites from the Deep Sea Drilling Program (DSDP, Leg 1-96), Ocean Drilling Program (Leg 100-210), Integrated Ocean Drilling Program (IODP, Exp 301-312), and International Ocean Discovery Program (IODP, Exp 317-363). Out of the 1508 sites, 81 sites were identified with available total organic carbon concentrations (TOC%), dry bulk density, and age model datums covering most of the past 23 million years. The mass accumulation rates (MARs) of organic carbon (OC) were calculated for each site based on sedimentation rate, bulk density, and TOC%, and were used to determine the spatial and temporal variability of OC burial in the Neogene. Given the inherent bias introduced by any such division, we employed three different subdivision strategies and compared the results to assess the uncertainty of our global reconstruction. To evaluate the potential impact of the Sadler Effect on our reconstruction, we compared the averaging interval (duration of time between tie-points in an age model), sedimentation accumulation, and OC burial for each record to determine the potential for spuriously patterns to arise in our global OC burial flux reconstruction. Also, we compare our global OC burial flux reconstruction with existing forward models of Neogene biogeochemical cycles, as well as include our reconstruction as a forcing in new forward and inverse model runs. This model-data comparison was used to test the accuracy of existing numerical models and to provide insights into observed changes in Neogene climate, atmospheric composition (pCO2), and global erosion/sediment burial rates.