ALBERT

Description: A high-resolution carbonate C-isotope (δ13Ccarb) stratigraphy for the Aptian is presented for the Cau core from Alicante, Spain. The studied succession, lower to upper Aptian, embraces the record of the Early Aptian OAE 1a. The data provided includes δ13Ccarb, δ18O isotopes, Total Organic Carbon (TOC) and CaCO3. Four overlapping cores (D1 to D4) were drilled with an almost 100% recovery of a total (corrected for dip) thickness of 143 m. The cores were split in two parts. One half was described, photographed and scanned, and then sampled with a drill to obtain powdered samples for geochemical analyses. Also, small solid samples were taken from the drill for biostratigraphic characterization of the nannofossil and planktonic foraminifera associations. Second half was stored for archive and future research.

Description: This is the archaeal biomarker dataset for global peatlands. The first dataset contains biomarker data for each individual sample as for many peatlands we analysed more than one sample. The second dataset contains the averaged data for isoGDGT isomers in all sites that contains both associated pH and temperature measurements.

Description: This is the archaeal GDGT dataset for global peatlands. The first dataset contains biomarker data for each individual sample as for many peatlands we analysed more than one sample. The second dataset contains the averaged data for isoGDGT isomers in all sites that contains both associated pH and temperature measurements. Other biomarker data for these samples can be found here: https://doi.pangaea.de/10.1594/PANGAEA.883763

Description: Sphagnum moss is the dominant plant type in modern boreal and (sub)arctic ombrotrophic bogs and is of particular interest due to its sensitivity to climate and its important role in wetland biogeochemistry. Here we reconstruct the occurrence of Sphagnum moss - and associated biogeochemical change - within a thermally immature, early Paleogene (~55 Ma) lignite from Schöningen, NW Germany using a high-resolution, multi-proxy approach. Changes in the abundance of Sphagnum-type spores and the C23/C31n-alkane ratio indicate the expansion of Sphagnum moss within the top of the lignite seam. This Sphagnum moss expansion is associated with the development of waterlogged conditions, analogous to what has been observed within modern ombrotrophic bogs. The similarity between biomarkers and palynology also indicates that the C23/C31n-alkane ratio may be a reliable chemotaxonomic indicator for Sphagnum during the early Paleogene. The d13C value of bacterial hopanes and mid-chain n-alkanes indicates that a rise in water table is not associated with a substantial increase in aerobic methanotrophy. The absence of very low d13C values within the top of the seam could reflect either less methanogenesis or less efficient methane oxidation under waterlogged sulphate-rich conditions.

Description: The Cenomanian/Turonian (C/T) intervals at DSDP Sites 105 and 603B from the northern part of the proto-North Atlantic show high amplitude, short-term cyclic variations in total organic carbon (TOC) content. The more pronounced changes in TOC are also reflected by changes in lithology from green claystones (TOC〈1%) to black claystones (TOC〉1%). Although their depositional history was different, the individual TOC cycles at Sites 105 and 603B can be correlated using stable carbon isotope stratigraphy. Sedimentation rates obtained from the isotope stratigraphy and spectral analyses indicate that these cycles were predominately precession controlled. The coinciding variations in HI, OI, delta13Corg and the abundance of marine relative to terrestrial biomarkers, as well as the low abundance of lignin pyrolysis products generated from the kerogen of the black claystones, indicate that these cyclic variations reflect changes in the contribution of marine organic matter (OM). The cooccurrence of lamination, enrichment of redox-sensitive trace metals and presence of molecular fossils of pigments from green sulfur bacteria indicate that the northern proto-North Atlantic Ocean water column was periodically euxinic from the bottom to at least the base of the photic zone (〈150 m) during the deposition of the black claystones. In contrast, the green claystones are bioturbated, are enriched in Mn, do not show enrichments in redox-sensitive trace metals and show biomarker distributions indicative of long oxygen exposure times, indicating more oxic water conditions. At the same time, there is evidence (e.g., abundance of biogenic silica and significant 13C-enrichment for OC of phytoplanktic origin) for enhanced primary productivity during the deposition of the black claystones. We propose that increased primary productivity periodically overwhelmed the oxic OM remineralisation potential of the bottom waters resulting in the deposition of OM-rich black claystones. Because the amount of oxygen used for OM remineralisation exceeded the amount supplied by diffusion and deep-water circulation, the northern proto-North Atlantic became euxinic during these periods. Both Sites 105 and 603B show trends of continually increasing TOC contents and HI values of the black claystones up section, which most likely resulted from both enhanced preservation due to increased anoxia and increased production of marine OM during oceanic anoxic event 2 (OAE2).

Description: The stable carbon isotopic compositions of free and sulfur (S)-bound biomarkers derived from algae, (cyano)bacteria, archaea and higher plants and total organic carbon (TOC) during the first phase of the late Cenomanian/Turonian oceanic anoxic event (OAE) were measured in black shales deposited in the southern proto-Atlantic Ocean in the Cape Verde basin (DSDP Site 367) to determine the response of these organisms to this major perturbation of the global carbon cycle resulting from widespread burial of marine organic matter. The average positive isotope excursions of TOC and biomarkers varied from 5.1 per mil to 8.3 per mil. The d13C values were cross correlated to infer potential common sources of biomarkers. This revealed common sources for C31 and C32 hopanes but no 1:1 relationship for pristane and phytane. The correlation of d13CTOC with the d13C value of sulfur (S)-bound phytane is the strongest. This is because S-bound phytane is derived from phytol that originates from all marine primary producers (algae and cyanobacteria) and thus represents a weighted average of their carbon isotopic compositions. The d13C values of S-bound phytane and C35 hopane were also used to estimate pCO2 levels. Before the OAE burial event, pCO2 levels are estimated to be ca. 1300 ppmv using both biomarkers and the independent maximum Rubisco fractionation factors. At times of maximum organic carbon burial rates during the OAE, reconstructed pCO2 levels are estimated to be ca. 700 ppmv. However, compared to other C/T OAE sections the positive isotope excursion of S-bound phytane is also affected by an increased production during the OAE. When we compensate for this, we arrive at pCO2 levels around 1000 ppmv, a reduction of ca. 25%. This indicates that burial of organic matter can have a large effect on atmospheric CO2 levels.