Water temperature reconstructions based on paired Uk'37 and Tex86 records, and paired surface and subsurface Mg/Ca records

This dataset contains the collection of available published paired Uk'37 and Tex86 records spanning multi-millennial to multi-million year time scales, as well as a collection of Mg/Ca-derived temperatures measured in parallel on surface and subsurface dwelling foraminifera, both used in the analyses of Ho and Laepple, Nature Geoscience 2016. As the signal-to-noise ratios of proxy-derived Holocene temperatures are relatively low, we selected records that contain at least the last deglaciation (oldest sample >18kyr BP).

Osmium concentrations and isotope ratios of ODP Hole 207-1260B and the Furlo section

Oceanic anoxic events (OAEs) were episodes of widespread marine anoxia during which large amounts of organic carbon were buried on the ocean floor under oxygen-deficient bottom waters (Schlanger and Jenkyns, 1976; Schlanger et al., 1987). OAE2, occurring at the Cenomanian/Turonian boundary (about 93.5 Myr ago) (Gradstein et al., 2004), is the most widespread and best defined OAE of the mid-Cretaceous. Although the enhanced burial of organic matter can be explained either through increased primary productivity or enhanced preservation scenarios (Schlanger and Jenkyns, 1976; Schlanger et al., 1987). the actual trigger mechanism, corresponding closely to the onset of these episodes of increased carbon sequestration, has not been clearly identified. It has been postulated that large-scale magmatic activity initially triggered OAE2 (Sinton and Duncan, 1997; Kerr, 1998, doi:10.1144/gsjgs.155.4.0619), but a direct proxy of magmatism preserved in the sedimentary record coinciding closely with the onset of OAE2 has not yet been found. Here we report seawater osmium isotope ratios in organic-rich sediments from two distant sites. We find that at both study sites the marine osmium isotope record changes abruptly just at or before the onset of OAE2. Using a simple two-component mixing equation, we calculate that over 97 per cent of the total osmium content in contemporaneous seawater at both sites is magmatic in origin, a ~30-50-fold increase relative to pre-OAE conditions. Furthermore, the magmatic osmium isotope signal appears slightly before the OAE2 -as indicated by carbon isotope ratios- suggesting a time-lag of up to ~23 kyr between magmatism and the onset of significant organic carbon burial, which may reflect the reaction time of the global ocean system. Our marine osmium isotope data are indicative of a widespread magmatic pulse at the onset of OAE2, which may have triggered the subsequent deposition of large amounts of organic matter.