TY - JOUR

T1 - Salinity-controlled isomerization of lacustrine brGDGTs impacts the associated MBT5ME' terrestrial temperature index

AU - Wang, Huanye

AU - Liu, Weiguo

AU - He, Yuxin

AU - Zhou, Aifeng

AU - Zhao, Hui

AU - Liu, Hu

AU - Cao, Yunning

AU - Hu, Jing

AU - Meng, Bowen

AU - Jiang, Jiawei

AU - Kolpakova, Marina

AU - Krivonogov, Sergey

AU - Liu, Zhonghui

N1 - Funding Information: Three anonymous reviewers and the editor are thanked for their constructive comments. This research was supported by the Chinese Academy of Sciences (XDB40000000, XDA2007020202), Hong Kong Research Grants Council (17325516), the Second Tibetan Plateau Scientific Expedition and Research (STEP) program (2019QZKK0101), West Light Foundation of the Chinese Academy of Sciences (XAB2019A03), and the Youth Innovation Promotion Association, CAS (2019403). Lake investigations in southern Siberia and Mongolia were supported by RSF (17-77-10086), RFBR (21-55-53037, 19-05-00403 a, 19-29-05085, 18-35-00072 mol_a, 18-33-20038 mol_a), and the State assignment of the Institute of Geology and Mineralogy SB RAS. Publisher Copyright: © 2021 Elsevier Ltd

PY - 2021/7/15

Y1 - 2021/7/15

N2 - Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are microbial molecular fossils ubiquitous in natural environments. The correlation between the Methylation Index of brGDGTs (the MBT5ME' paleothermometer) and temperature offers an important tool for reconstructing past terrestrial temperatures. However, factors other than temperature could also affect the distribution of brGDGTs in lacustrine systems, hampering the quantitative application of this paleothermometer. Here we investigated brGDGT distributions in contemporary sediments collected from 52 lakes in mid-latitude Asia. Combined with published brGDGT data from other lakes across the globe, we have found a strong salinity control on the relative abundance of 5-methyl brGDGTs versus their late-eluting isomers (including 6-methyl, 7-methyl, and unknown isomers). This allows the development of novel indices based on the isomerization of brGDGTs for tracing past lake water salinity. We also demonstrate that salinity-controlled isomerization of pentamethylated and hexamethylated brGDGTs can significantly impact the MBT5ME' paleothermometer, potentially leading to an overestimation of past temperature, but the temperature signal can be extracted out of the MBT5ME' index after correcting the salinity effect. As demonstrated in application to a Lake Qinghai (China) sediment core spanning the last 18 kyr, our finding could facilitate the simultaneous retrieval of reliable temperature and salinity records using brGDGTs in lacustrine settings, in particular for lakes that have experienced large salinity changes during the geological past.

AB - Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are microbial molecular fossils ubiquitous in natural environments. The correlation between the Methylation Index of brGDGTs (the MBT5ME' paleothermometer) and temperature offers an important tool for reconstructing past terrestrial temperatures. However, factors other than temperature could also affect the distribution of brGDGTs in lacustrine systems, hampering the quantitative application of this paleothermometer. Here we investigated brGDGT distributions in contemporary sediments collected from 52 lakes in mid-latitude Asia. Combined with published brGDGT data from other lakes across the globe, we have found a strong salinity control on the relative abundance of 5-methyl brGDGTs versus their late-eluting isomers (including 6-methyl, 7-methyl, and unknown isomers). This allows the development of novel indices based on the isomerization of brGDGTs for tracing past lake water salinity. We also demonstrate that salinity-controlled isomerization of pentamethylated and hexamethylated brGDGTs can significantly impact the MBT5ME' paleothermometer, potentially leading to an overestimation of past temperature, but the temperature signal can be extracted out of the MBT5ME' index after correcting the salinity effect. As demonstrated in application to a Lake Qinghai (China) sediment core spanning the last 18 kyr, our finding could facilitate the simultaneous retrieval of reliable temperature and salinity records using brGDGTs in lacustrine settings, in particular for lakes that have experienced large salinity changes during the geological past.

KW - brGDGTs

KW - Isomerization

KW - MBT

KW - Salinity

KW - Temperature

UR - http://www.scopus.com/inward/record.url?scp=85110414681&partnerID=8YFLogxK

U2 - 10.1016/j.gca.2021.05.004

DO - 10.1016/j.gca.2021.05.004

M3 - Article

AN - SCOPUS:85110414681

VL - 305

SP - 33

EP - 48

JO - Geochmica et Cosmochimica Acta

JF - Geochmica et Cosmochimica Acta

SN - 0016-7037

ER -