Novak, Joseph B; Prokopenko, Alexander A; Tarasov, Pavel E; Russell, James M; Lindemuth, Emma; Shichi, Koji; Kashiwaya, Kenji; Peck, John A; Vachula, Richard; Swann, George E A; Polissar, Pratigya J: Lake Baikal paleotemperature record derived from the methylation of brGDGTs [dataset]. PANGAEA, https://doi.pangaea.de/10.1594/PANGAEA.983538 (dataset in review), In: Novak, JB et al.: Paleotemperature and Vegetation Records from Lake Baikal, Russia, Over the Last 8.6 Million Years [dataset bundled publication]. PANGAEA, https://doi.pangaea.de/10.1594/PANGAEA.986603 (dataset in review)
Abstract:
An 8.6-million-year record of paleotemperature change from Lake Baikal, Russia, derived from the methylation of sedimentary brGDGTs. Paleotemperatures were estimated from MBT'5Me using the global lakes regression of for lake samples with IR6Me values ≤ 0.4 (Novak et al. 2025, doi:10.1029/2024GC012069). Samples with IR6Me values > 0.4 were rejected for paleotemperature estimation due to possible non-thermal effects on brGDGT methylation (see Novak et al. 2025). We note that all samples older than 50 thousand years old have IR6ME values ≤ 0.4.
Keyword(s):
References:
Auderset, Alexandra; Schmitt, Mareike; Martínez-García, Alfredo (2020): Simultaneous extraction and chromatographic separation of n-alkanes and alkenones from glycerol dialkyl glycerol tetraethers via selective Accelerated Solvent Extraction. Organic Geochemistry, 143, 103979, https://doi.org/10.1016/j.orggeochem.2020.103979
Hopmans, Ellen C; Schouten, Stefan; Sinninghe Damsté, Jaap S (2016): The effect of improved chromatography on GDGT-based palaeoproxies. Organic Geochemistry, 93, 1-6, https://doi.org/10.1016/j.orggeochem.2015.12.006
Huguet, Carme; Kim, Jung-Hyun; de Lange, Gert J; Sinninghe Damsté, Jaap S; Schouten, Stefan (2009): Effects of long term oxic degradation on the , TEX86 and BIT organic proxies. Organic Geochemistry, 40(12), 1188-1194, https://doi.org/10.1016/j.orggeochem.2009.09.003
Novak, Joseph B; Russell, James M; Lindemuth, Emma; Prokopenko, Alexander A; Pérez-Angel, Lina C; Zhao, Boyang; Swann, George E A; Polissar, Pratigya J (2025): The Branched GDGT Isomer Ratio Refines Lacustrine Paleotemperature Estimates. Geochemistry, Geophysics, Geosystems, 26(3), e2024GC012069, https://doi.org/10.1029/2024GC012069
Powers, Lindsay; Werne, Josef P; Vanderwoude, Andrea J; Sinninghe Damsté, Jaap S; Hopmans, Ellen C; Schouten, Stefan (2010): Applicability and calibration of the TEX86 paleothermometer in lakes. Organic Geochemistry, 41(4), 404-413, https://doi.org/10.1016/j.orggeochem.2009.11.009
Funding:
National Science Foundation (NSF), grant/award no. NNA 22-02918: Rainfall, Ecosystems, and Fire in Warm Late Neogene Climates of the Lake Baikal Region
Coverage:
Median Latitude: 53.601587 * Median Longitude: 108.298086 * South-bound Latitude: 53.444800 * West-bound Longitude: 108.155800 * North-bound Latitude: 53.667170 * East-bound Longitude: 108.361000
Date/Time Start: 1991-08-02T00:00:00 * Date/Time End: 1992-07-28T00:00:00
Minimum Elevation: -333.0 m * Maximum Elevation: -280.0 m
Event(s):
333-PC2 * Latitude: 53.653000 * Longitude: 108.155800 * Lake water depth: 390 m * Location: Lake Baikal/Academician Ridge * Method/Device: Piston corer (PC)
Comment:
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).
To further isolate GDGTs, the polar/alcohols (methanol) fraction was further eluted over alumina oxide (0.85 g, J.T. Baker, 0537-01) by elution of 4 mL 9:1 hexane: dichloromethane, 4 mL 1:1 dichloromethane: methanol (containing GDGTs), and 4 mL 100% methanol.
The 1:1 dichloromethane: methanol fraction was then dried over N2 and shipped to Brown University, where they were analyzed for GDGTs on an Agilent/Hewlett Packard 1100 series liquid chromatograph mass spectrometer (LC-MS) using two UHPLC columns (BEH HILIC columns, 2.1 x 150 mm, 1.7 μm, Waters) in series using the protocol of Hopmans et al. 2016.
Prior to analysis, samples were passed through a 0.45 μm filter and spiked with a known quantity of a C46 glycerol trialkyl glycerol tetraether (GTGT) internal standard.
Selective ion monitoring was used to measure m/z 1302, 1300, 1298, 1296, 1292, 1050, 1048, 1046, 1036, 1034, 1032, 1022, 1020, 1018, and 744.
Peak areas were quantified manually. Concentrations of individual GDGT molecules are reported in nanograms per gram of sediment (ng/g sed) assuming a 1:1 relationship between the response factor of the C46 GTGT and the individual brGDGTs (Huguet et al, 2006).
While this assumption may not capture the exact response factors of individual brGDGTs, it is sufficient for understanding the relative concentrations of different brGDGTs in this sample set.
Paleotemperatures were estimated from MBT'5Me using the global lakes regression of Novak et al. (2025) for lake samples with IR6Me values ≤ 0.4. The 68% confidence interval for MBT'5Me-derived paleotemperatures is the 2.3°C 1σ error of the regression reported by Novak et al. (2025). Samples with IR6Me values > 0.4 were rejected for paleotemperature estimation due to possible non-thermal effects on the MBT'5Me index (see Novak et al., 2025).
Samples with IR6Me values > 0.4 were rejected for paleotemperature estimation due to possible non-thermal effects on the MBT'5Me index (see Novak et al., in review).
We note that all samples older than 50 thousand years old have IR6ME values ≤ 0.4. Therefore, none of the conclusions drawn in the main text are dependent upon the exclusion of samples based upon IR6Me.
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
Parameter(s):
| # | Name | Short Name | Unit | Principal Investigator | Method/Device | Comment |
|---|---|---|---|---|---|---|
| 1 | Event label | Event | Novak, Joseph B | |||
| 2 | Latitude of event | Latitude | Novak, Joseph B | |||
| 3 | Longitude of event | Longitude | Novak, Joseph B | |||
| 4 | Sample ID | Sample ID | Novak, Joseph B | |||
| 5 | Site | Site | Novak, Joseph B | |||
| 6 | Section | Sect | Novak, Joseph B | |||
| 7 | Depth, section | Depth sect | cm | Novak, Joseph B | From | |
| 8 | Depth, section | Depth sect | cm | Novak, Joseph B | To | |
| 9 | Sample comment | Sample comment | Novak, Joseph B | |||
| 10 | AGE | Age | ka BP | Novak, Joseph B | See description in dataset comment | Geocode |
| 11 | Age | Age | Ma | Novak, Joseph B | See description in dataset comment | |
| 12 | Temperature, air, mean of months, above freezing | MAF | °C | Novak, Joseph B | See description in dataset comment | 16% |
| 13 | Temperature, air, mean of months, above freezing | MAF | °C | Novak, Joseph B | See description in dataset comment | |
| 14 | Temperature, air, mean of months, above freezing | MAF | °C | Novak, Joseph B | See description in dataset comment | 84 % |
License:
Creative Commons Attribution 4.0 International (CC-BY-4.0) (License comes into effect after moratorium ends)
Status:
Curation Level: Enhanced curation (CurationLevelC)
Size:
1723 data points