An 8.6 million year reconstruction of paleotemperatures and paleovegetation from Lake Baikal, Russia, derived from Baikal Drilling Project core materials. This dataset also includes compiled paleovegetation data from the Late Pliocene and Early Pleistocene from boreal regions and a new global mean surface temperature stack derived from published sea surface temperature records. Paleotemperatures were estimated from the methylation of branched glycerol dialkyl glycerol tetraethers. Paleovegetation was reconstructed from plant wax n-alkane distributions and published pollen data. Paleovegetation data were compiled from published studies.

Methods:All sediments analyzed for biomarkers were freeze dried and weighed prior to homogenization. Lipids were extracted by an accelerated solvent extractor (ASE) 350 using 2:1 dichloromethane: methanol (c.f. Auderset et al., 2020; Powers et al., 2010). Oven temperature was set to 100°C, rinse volume to 150%, purge time to 120 seconds, heating time to 5 minutes, and with 4 10-minute static cycles. Total lipid extracts were spiked with 100 µL of a general recovery standard (20.5 ng/µL 5α-androstane, 20.5 ng/µL stearyl stearate, 20.5 ng/µL 1,1'-binapthyl, 20.5 ng/µL cis-11-eicosenoic acid, 20.5 ng/µL 19-methyleicosenoic acid, 20.5 ng/µL C20:1 Δ11-eicosenol, and 20.5 ng/µL 5α-androstan-3β-ol), desulfurized by sequential addition of activated copper wire, and evaporated under N2 prior to elution on a 0.5 g dry-packed LC-NH2 column to separate neutral (4 mL 2:1 dichloromethane: isopropanol), acid (4 mL 4% acetic acid in diethyl ether), and polar (4 mL methanol) fractions. Neutral and polar fractions were recombined and again dried under N2 prior to elution on a wet-packed silica gel (0.5 g, 60 Å, 70–230 mesh, Millipore) column with 3 mL hexanes (apolar / aliphatic), 4 mL dichloromethane (semi-polar / aromatic), and 4 mL methanol (polar / alcohols). The apolar / aliphatic fraction containing n-alkanes were quantified by gas chromatography-mass spectrometry (GC-MS) at the University of California, Santa Cruz, on an Agilent 7890A GC 5975B MS with split/splitless injector and HP-5 column (30 m length, 250 µm i.d., 0.25 µm phase thickness). 1 µL of sample was injected at an inlet temperature of 320°C and oven temperature of 60°C. Oven temperature was held at 60°C for 1.5 minutes, ramped to 150°C at 15°C/min and then to 320°C at 4°C/min and held for 10 minutes. The MSD ion source was held at 350°C with an electron energy of 70 eV and quadrupole temperature at 150°C. Samples were analyzed in fill scan mode, scanning from 50–550 dalton cycling at ~3 scans/s. Peaks were integrated on the Agilent Chemstation software by extracting ion peak areas for the n-alkanes (m/z 57) and the 5α-androstane (m/z 245) internal recovery standard. n-alkane concentrations were determined via external calibration of n-alkane response factors relative to the recovery standard 5α-androstane every 10 sample injections. Further funding information: PR 1414/1-1 Deutsche Forchungsgemeinshaft Priority Program "ICDP" 1006 Geological Society of America Continental Drilling Science Division Graduate Student Grant 13282-21* Sigma Xi Grants in Aid of Research G20211001-101