Indian Ocean Summer Monsoon (IOSM)-dynamics within the past 4 ka recorded in the sediments of Lake Nam Co, central Tibetan Plateau (China)

Kasper, Thomas; Haberzettl, Torsten; Doberschütz, Stefan; Daut, Gerhard; Wang, Junbo; Zhu, Liping; Nowaczyk, Norbert; Mäusbacher, Roland

doi:10.1016/j.quascirev.2012.02.011

Cited by 107 publications

(92 citation statements)

References 81 publications

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“…4). At Nam Co it constitutes the main mode of the multimodal rEM sediment (Kasper et al, 2012). It was absent in the small TT lake, but could be integrated in Targo Xian rEM 4 (Figs.…”

Section: Remote Dustmentioning

confidence: 98%

“…2) and was absent in the deeper position. It may have contributed to the broader clay mode that dominated the lowermost lithological unit in the record of lake Nam Co, which was deposited during times of a higher lake level (Kasper et al, 2012). At Targo Xian it was part of a broad clay end member with a mode between 0.7 and 5 µm (maximum at 1.7 µm).…”

Section: Fluvial Claymentioning

confidence: 99%

“…Only lake Donggi Cona has an outflow since ca. 4 cal ka BP (Opitz Wrozyna et al (2010), Kasper et al (2012Kasper et al ( , 2013) * See Fig. 1 for location.…”

Section: Study Sitesmentioning

confidence: 99%

“…Grain-size distributions with the secondary mode (rEM 2, Fig. 2b) were interpreted as representative for a lake level rise (Kasper et al, 2012).…”

Section: Remote Dustmentioning

confidence: 99%

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Sediment transport processes across the Tibetan Plateau inferred from robust grain-size end members in lake sediments

et al. 2014

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Abstract. Grain-size distributions offer powerful proxies of past environmental conditions that are related to sediment sorting processes. However, they are often of multimodal character because sediments can get mixed during deposition. To facilitate the use of grain size as palaeoenvironmental proxy, this study aims to distinguish the main detrital processes that contribute to lacustrine sedimentation across the Tibetan Plateau using grain-size end-member modelling analysis. Between three and five robust grain-size end-member subpopulations were distinguished at different sites from similarly-likely end-member model runs. Their main modes were grouped and linked to common sediment transport and depositional processes that can be associated with contemporary Tibetan climate (precipitation patterns and lake ice phenology, gridded wind and shear stress data from the High Asia Reanalysis) and local catchment configurations. The coarse sands and clays with grain-size modes > 250 µm and < 2 µm were probably transported by fluvial processes. Aeolian sands (∼ 200 µm) and coarse local dust (∼ 60 µm), transported by saltation and in near-surface suspension clouds, are probably related to occasional westerly storms in winter and spring. Coarse regional dust with modes ∼ 25 µm may derive from near-by sources that keep in longer term suspension. The continuous background dust is differentiated into two robust end members (modes: 5-10 and 2-5 µm) that may represent different sources, wind directions and/or sediment trapping dynamics from long-range, upperlevel westerly and episodic northerly wind transport. According to this study grain-size end members of only fluvial origin contribute small amounts to mean Tibetan lake sedimentation (19 ± 5 %), whereas local to regional aeolian transport and background dust deposition dominate the clastic sedimentation in Tibetan lakes (contributions: 42 ± 14 % and 51 ± 11 %). However, fluvial and alluvial reworking of aeolian material from nearby slopes during summer seems to limit end-member interpretation and should be crosschecked with other proxy information. If not considered as a stand-alone proxy, a high transferability to other regions and sediment archives allows helpful reconstructions of past sedimentation history.

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“…4). At Nam Co it constitutes the main mode of the multimodal rEM sediment (Kasper et al, 2012). It was absent in the small TT lake, but could be integrated in Targo Xian rEM 4 (Figs.…”

Section: Remote Dustmentioning

confidence: 98%

Section: Fluvial Claymentioning

confidence: 99%

“…Only lake Donggi Cona has an outflow since ca. 4 cal ka BP (Opitz Wrozyna et al (2010), Kasper et al (2012Kasper et al ( , 2013) * See Fig. 1 for location.…”

Section: Study Sitesmentioning

confidence: 99%

“…Grain-size distributions with the secondary mode (rEM 2, Fig. 2b) were interpreted as representative for a lake level rise (Kasper et al, 2012).…”

Section: Remote Dustmentioning

confidence: 99%

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Sediment transport processes across the Tibetan Plateau inferred from robust grain-size end members in lake sediments

et al. 2014

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“…Accordingly, the age-depth curves of core NC 08/01 is established based on 9 reliable dates (Figure 2(j), from [19,23]). …”

Section: Sediment Dating and Depth-age Curvementioning

confidence: 99%

Mechanism of variations in environmental magnetic proxies of lake sediments from Nam Co, Tibet during the Holocene

Gao

Liu

et al. 2013

Chin. Sci. Bull.

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High-resolution environmental records from the Tibetan Plateau are essential to understand past global climatic and environmental changes. Magnetic minerals in lake sediments are important proxies to reconstruct environmental and climatic changes. Nam Co (lake) is a typical great lake in the transitional region of southwest monsoon in the Tibetan Plateau. Previous studies have extensively focused on geochemistry, microfossils, sedimentology and biochemistry analysis of Nam Co, which provides sound interpretation of paleoclimatic and paleoenvironmental changes. However, up to now, no systematic environmental magnetic studies have been carried out. Therefore, high-resolution and systematic magnetic studies combined with geochemical parameters were carried on lake sediments of core NC 08/01 from Nam Co for the Holocene period (11.3 cal ka BP) in order to explore how magnetic properties of the sediments respond to climatic changes. Based on variations of magnetic proxies, the sequence can be separated into 3 units. Unit 1 (236-199 cm, 11.3-7.8 cal ka BP) contains dominantly coarse-grained magnetite with homogeneous grain size. A positive correlation between magnetite and Ti strongly suggests that these coarse-grained detrital magnetites reflect detrital input signals due to insignificant effects of postdepositional dissolution processes on these coarse-grained magnetite particles. For Unit 2 (198-102 cm, 7.8-2.1 cal ka BP), magnetic grain size is finer and the corresponding concentration of magnetite is also reduced. This is mainly due to significant dissolution of these fine-grained detrital magnetite particles, which were transported under reduced water flow conditions during this period. For Unit 3 (101-0 cm, 2.1-0 cal ka BP), the bulk magnetic properties are dominated by a mixture of single domain biogenic magnetite and detrital magnetite. The concentration of magnetic minerals is not correlated with the Ti content. In conclusion, the preservation of magnetic minerals in the lake sediment and thus the corresponding magnetic properties are related to the initial grain size. Combination of magnetic properties (including variation of grain size and concentration) and other proxies of detrital inputs (e.g. Ti) can be used to infer the variation of redox conditions in Nam Co. These results provide a viable framework for reconstructing the paleoenvironmental changes of this lake. lake sediment, rock magnetism, Nam Co, Tibetan Plateau, Holocene Citation:Su Y L, Gao X, Liu Q S, et al. Mechanism of variations in environmental magnetic proxies of lake sediments from Nam Co, Tibet during the Holocene.

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High‐resolution paleomagnetic and sedimentological investigations on the Tibetan Plateau for the past 16 ka cal B.P.—The Tangra Yumco record

Henkel

Haberzettl

St‐Onge

et al. 2016

Geochem Geophys Geosyst

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The spatial distribution of paleomagnetic secular variation (PSV) records on the Tibetan Plateau and adjacent areas covering the Holocene and Late Glacial is sparse. In order to reconstruct PSV in this area, a piston core covering the past 17.5 ka cal B.P. retrieved from Lake Tangra Yumco, southern‐central Tibetan Plateau, was analyzed. In the laminated sediments, several event layers are intercalated. Those were identified by sedimentological analysis and excluded for age‐depth modeling and interpretation. Paleomagnetic measurements on u‐channels reveal two contrasting core sections. The lower section (dated to 17.5–15.9 ka cal B.P.) is very coarse grained (up to 220 µm) and characterized by low intensities (0.8 mA m−1) and high maximum angular deviation values (mean 25°), making it unsuitable for PSV reconstruction. In contrast, the upper unit (dated to <15.9 ka cal B.P.) yields ideal properties with a well‐defined magnetization carried by low‐coercivity minerals in the pseudo single domain state making those younger sediments a proper record for PSV studies. The robustness of the PSV reconstruction for the past 3000 years is highlighted by a comparable inclination and declination pattern of three short sediment cores (2 m) from Tangra Yumco. On a regional scale, the obtained inclination signal for the past 15.9 ka cal B.P. is in good agreement with the Lake Baikal record (3000 km to the North), PSV stack for East Asia, as well as with predictions of geomagnetic field models. This study is a step forward in constructing a PSV reference curve for central Asia.

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Indian Ocean Summer Monsoon (IOSM)-dynamics within the past 4 ka recorded in the sediments of Lake Nam Co, central Tibetan Plateau (China)

Cited by 107 publications

References 81 publications

Sediment transport processes across the Tibetan Plateau inferred from robust grain-size end members in lake sediments

Sediment transport processes across the Tibetan Plateau inferred from robust grain-size end members in lake sediments

Mechanism of variations in environmental magnetic proxies of lake sediments from Nam Co, Tibet during the Holocene

High‐resolution paleomagnetic and sedimentological investigations on the Tibetan Plateau for the past 16 ka cal B.P.—The Tangra Yumco record

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