Temperature changes reconstructed from branched GDGTs on the central Loess Plateau during the past 130–5 ka
Introduction
Loess-paleosol sequences (LPS) on the Chinese Loess Plateau (CLP) are important terrestrial archives of the evolution of past climate changes since the Neogene (Heller and Liu, 1982; Porter and An, 1995; Guo et al., 1998, 2002; Liu and Ding, 1998; Hao et al., 2012). Quantitative reconstruction of the temperature variations recorded in LPS on the CLP is crucial for understanding the mechanism of past climate change in Northwest China. During the last two decades, magnetic susceptibility (Lu et al., 1994; Han et al., 1996) and phytoliths (Lu et al., 2007) have been used as proxies of paleotemperature to quantitatively reconstruct the air temperature history recorded in LPS on the CLP. However, different proxies often produce distinct temperature variations, perhaps due to their complicated sensitivity to air temperature change.
Archaeal and bacterial tetraether membrane lipids, i.e. GDGTs (glycerol dialkyl glycerol tetraethers), are recognized to being sensitive to ambient temperature change (Wuchter et al., 2004; Weijers et al., 2007; Yang et al., 2014; Ding et al., 2015). Therefore, GDGT distributions can be applied to reconstruct past temperature variations on the CLP (Peterse et al., 2011, 2014; Gao et al., 2012; Jia et al., 2013; Lu et al., 2016; Tang et al., 2017).
The branched GDGTs (brGDGTs) occur widely in soils and are considered to be of bacterial origin (Weijers et al., 2007). The MBT (methylation index of branched tetraethers) and CBT (cyclisation ratio of branched tetraethers) proxies were defined based on brGDGTs in surface soils (Weijers et al., 2007). The MBT proxy in brGDGTs has been proven to have a strong linear correlation with mean annual air temperature (MAT) and soil pH, while the CBT proxy is primarily related to soil pH (Weijers et al., 2007). Thus, the MBT-CBT proxies have been applied to reconstruct MAT variation in terrestrial settings (Peterse et al., 2011).
Global transfer functions (Weijers et al., 2007; Peterse et al., 2012) and a Chinese transfer function (Yang et al., 2014) have been established to reconstruct ancient MAT by MBT-CBT proxies. Up to now, GDGT compositions in the LPS at Mangshan (Peterse et al., 2011, 2014) on the eastern CLP, at Lantian (Gao et al., 2012) and Weinan (Yang et al., 2014; Tang et al., 2017) on the southern CLP, and at Yuanbao (Jia et al., 2013) on the western CLP have been studied. Although the temperature histories on the eastern, southern and western CLP are reconstructed by the application of brGDGT indices, these studies are inadequate to provide comprehensive information of the spatial-temporal temperature variations with regard to the whole CLP because of the lack of the GDGT composition of LPS on the central CLP. In addition, the previously reported MAT variations estimated by brGDGT indices are higher than the current MAT value at Mangshan and Lantian sections (Peterse et al., 2011; Gao et al., 2012) during the Last Glacial Maximum (LGM), while the MAT variations calculated by global MBT-CBT indices (Weijers et al., 2007) are lower than the current MAT during the LGM at Yuanbao on the western CLP (Jia et al., 2013).
Investigation of the GDGT composition of the LPS on the central CLP is significant for quantitative reconstruction of the MAT variations on the whole CLP. This study determined the GDGT composition of the LPS in Xifeng section on the central CLP. The aims of this study are to (1) quantitatively reconstruct the past air temperature changes at Xifeng during the past 130–5 ka, and (2) compare the temperature variations at Xifeng on the central CLP with those at other sites on the eastern and western CLP.
Section snippets
Sampling
The well-defined LPS is deposited at Xifeng on the central CLP. The mean annual precipitation and MAT at Xifeng are 513.5 mm and 8.5 °C, respectively; the average air temperature in July at Xifeng was 21.0 °C from 1951–2001 AD (Wang et al., 2006).
The Xifeng section (35°46.04′ N,107°38.10′ E) lies on the central CLP (Fig. 1). A vertical outcrop of LPS exposed by road work was sampled. The top 0.2 m was not sampled because it had been disturbed by human cultivation. The sampled depth of the
Age model of the Xifeng section
Climate on the CLP is governed by the East Asian monsoon system. The LPS in different parts of the CLP can be temporally well correlated (Liu and Ding, 1998). Thus, the age model of an undated loess section can be established by correlating it to a loess section that has been dated with radiocarbon and/or optically stimulated luminescence (OSL) ages (Zeng et al., 2011; Gao et al., 2012).
The Weinan loess section (34°25′38.8″N, 109°34′37.4″E) has been dated by a high-resolution OSL dating method,
Conclusions
- (1)
The variation of MAT at Xifeng on the central CLP during the past 130–5 ka has been reconstructed from MBT-CBT proxies of brGDGTs. Comparison of the MAT record at Xifeng on the central CLP with other MAT records on the eastern and western CLP shows a decrease from southeast to northwest, consistent with the modern MAT pattern.
- (2)
Different transfer functions of the MBT (MBT′)-CBT index produce distinct MAT variations at Xifeng. Nearly all MAT values during the past 130–5 ka (including the Last
Acknowledgements
We thank Professor Shucheng Xie, Xianyu Huang, Guoqiao Xiao, Zhixiang Wang, Zeyang Zhu, Wenfeng Zhou, Xinyue Dang, Weihua Ding for laboratory experiments, and Xiangjun Liu for field work. We thank Dr. Shugang Kang for providing data of Weinan section, and Fei Wang for providing original meteorological data at Xifeng. We thank professor Qingzhen Hao for helpful discussions, and three anonymous reviewers for constructive comments. We are grateful to Professor Philip A. Meyers for his invaluable
References (36)
- et al.
Magnetic susceptibility evidence of monsoon variation on the Loess Plateau of Central China during the last 130,000 years
Quat. Res.
(1991) - et al.
The importance of solar insolation on the temperature variations for the past 110 kyr on the Chinese Loess Plateau
Palaeogeogr. Palaeoclimatol. Palaeoecol.
(2012) - et al.
Climate extremes in loess of China coupled with the strength of deep-water formation in the North Atlantic
Glob. Planet. Change
(1998) - et al.
An improved method to determine the absolute abundance of glycerol dibiphytanyl glycerol tetraether lipids
Org. Geochem.
(2006) - et al.
Closely-spaced recuperated OSL dating of the last interglacial paleosol in the southeastern margin of the Chinese Loess Plateau
Quat. Geochronol.
(2011) - et al.
Variation in 6-methyl branched glycerol dialkyl glycerol tetraethers in Lantian loess–paleosol sequence and effect on paleotemperature reconstruction
Org. Geochem.
(2016) - et al.
Phytoliths as quantitative indicators for the reconstruction of past environmental conditions in China II: palaeoenvironmental reconstruction in the Loess Plateau
Quat. Sci. Rev.
(2007) - et al.
Molecular records of continental air temperature and monsoon precipitation variability in East Asia spanning the past 130,000 years
Quat. Sci. Rev.
(2014) - et al.
Revised calibration of the MBT-CBT paleotemperature proxy based on branched tetraether membrane lipids in surface soils
Geochim Cosmochim Acta
(2012) - et al.
Decoupled warming and monsoon precipitation in East Asia over the last deglaciation
Earth Planet. Sci. Lett.
(2011)
Quantitative relationships between magnetic enhancement of modern soils and climatic variables over the Chinese Loess Plateau
Quat. Int.
Provenance of loess material and formation of loess deposits on the Chinese Loess Plateau
Earth Planet. Sci. Lett.
Environmental controls on bacterial tetraether membrane lipid distribution in soils
Geochim Cosmochim Acta
Climate reconstruction based on GDGT-based proxies in a paleosol sequence in Japan: postdepositional effect on the estimation of air temperature
Quat. Int.
Correlations between microbial tetraether lipids and environmental variables in Chinese soils: optimizing the paleo-reconstructions in semi-arid and arid regions
Geochim Cosmochim Acta
Branched glycerol dialkyl glycerol tetraethers in Pleistocene loess-paleosol sequences: three case studies
Org. Geochem.
The last glacial maximum
Science
Distributions of glycerol dialkyl glycerol tetraethers in surface soils of Qinghai–Tibetan Plateau: implications of GDGT-based proxies in cold and dry regions
Biogeosci. Discuss.
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