Elsevier

CATENA

Volume 137, February 2016, Pages 203-218
CATENA

Spatio-temporal pattern of detrital clay-mineral supply to a lake system on the north-eastern Tibetan Plateau, and its relationship to late Quaternary paleoenvironmental changes

https://doi.org/10.1016/j.catena.2015.09.003Get rights and content

Highlights

  • Provenance analyses from Lake Donggi Cona, Tibetan Plateau

  • Clay-mineral fingerprints from modern and fossil lake sediments

  • Spatio-temporal variability of detrital sediment supplies since the late Glacial

  • Water-level fluctuations control transport paths of detrital sediments

  • Reduced detrital input during the Holocene because of enhanced summer monsoon

Abstract

Clay-mineral fingerprints from modern and fossil lake sediments from Lake Donggi Cona, situated on the north-eastern Tibetan Plateau were studied to determine changes in sediment provenance and environmental development since the late Glacial. To infer the source areas of the lake sediments, characteristic facies units (cover sediments and soils) from the catchment of the lake were studied concerning their clay-mineral compositions and through statistical analyses using the Fuzzy C-Means algorithm.

Sediment contributions from the various geological provinces in the catchment of the lake are reflected in a systematic spatial pattern of variable clay-mineral assemblages, which is most pronounced in modern fluvial and lake sediments. Downcore changes in the clay-mineral fingerprints of lake sediments provide information on the spatio-temporal variability of detrital sediment supplies, related to climate-influenced changes in environmental boundary conditions.

Since the late Glacial, water-level fluctuations driven by glacier melt appear to have exerted the greatest control over the transport paths of detrital sediments. Probably glacial melt-waters carried mainly illitic rich pre-Cenozoic debris into the lake from the northern and north-western catchment areas. During the Holocene the detrital clay mineral supply was mainly controlled from pre-Cenozoic and Neogene sources. However, because of the increased summer monsoon precipitation the lake level rose dramatically to at least modern levels, resulting in a relative increase in the supply from pedogenic karstic weathering sources mainly from the east, which during the Holocene was possibly flooded more widely than today. During the late Holocene a decreasing input of smectite suggests a relative reduction in the supply of far-traveled aquatic suspensions into the lake. In contrast, during the same interval kaolinite concentrations increased, which suggests a relatively strong sediment supply from the east, possibly triggered by a current flowing from east to west.

Introduction

The north-eastern Tibetan Plateau represents a key region for the recognition of climate processes as it represents one of earth's most vulnerable regions in respect to global warming and environmental changes. Its extreme setting at high altitude at the intersection between the climate regimes of the summer and winter monsoon and the westerly wind system gave rise to the establishment of a complex and sensitive geo-ecosystem since the late Pleistocene. In this context sedimentary archives give evidence of the pronounced effects of natural climate variability on environmental changes. Especially lake sediments provide valuable archives for the reconstruction of climatic and environmental conditions. However, to gain deeper insights into the lake system and its complex depositional history within the context of a geologically heterogeneous catchment area, it is important to determine the source areas of the different sediment deposits.

Our current understanding of the environmental history of the Tibetan Plateau and its relationship to climate change is largely derived from investigations of terrestrial records (Sun et al., 2007) and lake sediments (Mischke et al., 2010a, Mischke et al., 2010c). Recent investigations have integrated catchment area studies with lake research (Dietze et al., 2010, Dietze et al., 2012, Lehmkuhl and Haselein, 2000, Wünnemann et al., 2008, Stauch et al., 2014). Depending on the geomorphology and geology of the catchment area, the climatic signals preserved in sediments can be altered both during and after deposition. Physical processes such as weathering and relocation, and biological processes such as pedogenesis and vegetation changes, can therefore leave a multidimensional fingerprint on the sediments (Baumann et al., 2014, Chamley, 1989).

Clay-mineral assemblages have previously been used as proxies for regional paleoenvironmental reconstructions, and also for provenance analyses in marine (Diekmann and Kuhn, 1999), fluvial and lacustrine environments (Fagel et al., 2003, Popp et al., 2007, Yuretich et al., 1998). In tropical environments with efficient chemical weathering, clay minerals are widely used as paleoclimate proxies, but in cold temperate areas such as the Tibetan Plateau, with arid to semi-arid climatic conditions similar to those in polar regions, clay minerals are useful as source indicators (Chamley, 1989, Gao et al., 2002).

The objective of our research was to improve the understanding of the provenance of late Glacial and Holocene sediments in the complex depositional history of Lake Donggi Cona, in the north-eastern part of the Tibetan Plateau, using clay-mineralogy to investigate both terrestrial sediments and the modern and fossil lake sediments within a pilot study. To infer the source areas of the lake sediments, characteristic facies units (cover sediments and soils) from the catchment of the lake were studied concerning their clay-mineral compositions and through statistical analyses using the Fuzzy C-Means algorithm.

Section snippets

Lake Donggi Cona and its regional setting

Lake Donggi Cona (35°18′N, 98°32′E) is located in the north-eastern part of the Tibetan Plateau within the Kunlun Mountain Range, at an altitude of 4090 m above sea level (a.s.l.) (Fig. 1). The lake and its catchment area fall in the Qinghai Province of the People's Republic of China. The mountainous terrain of the A'nyêmaqên and Burhan Budai ranges surrounds Lake Donggi Cona. The basin of the lake is a pull-apart basin within the active Kunlun Fault zone (van der Woerd et al., 2002). The 60 × 30 

Surface sediment samples

To obtain information on clay-mineral assemblages 94 samples of lake sediment surface samples (DCS) were collected across the lake during the summers of 2003, 2006 and 2009, using a Hydro-Bios-Ekman grab. To trace the origins of the clay minerals 64 terrestrial surface reference samples (DC) were collected from characteristic facies units in the Donggi Cona catchment area (Fig. 2).

Sediment cores

For clay-mineralogy analyses altogether 197 samples were taken at 10 cm intervals from all sediment cores. The lake

Clay-mineral assemblages and FCM cluster analyses

The siliciclastic clay fraction of the lake and catchment sediments investigated includes both clay minerals and non-clay minerals. The non-clay minerals are mainly quartz, plagioclase, and potassium feldspar, which were not considered any further in these investigations. The clay-mineral spectrum is mainly dominated by illite (42–87%) and chlorite (up to 45%), with smaller quantities of smectite (1–13%) and kaolinite (1–24%; Fig. 3). Although clay-mineral variability in the investigated

Discussion

Any interpretation of the clay-mineral composition of lacustrine sediments needs to take into account a variety of environmental factors and sedimentary processes, the significance of which may vary from one lake system to another, as discussed below. To understand the clay mineral fingerprints of the lake sediments first modern processes have to be studied.

Assuming clays are delivered to the lake as detrital components, the geology and substrates of the catchment area are likely to be the

Conclusions

The main conclusions from our pilot study on the clay-mineral assemblages of the modern and late Quaternary sediments of Lake Donggi Cona, and the terrestrial sediments of its catchment area, can be summarized as follows:

  • The clay-mineral assemblages in the lake sediments can be used to infer the sediment sources within the catchment area. The clay-mineral fingerprints are related to the detrital sediment supplies from the rocks, soils, and cover sediments of different geological provinces.

Acknowledgments

Fieldwork was carried out in conjunction with German and Chinese partners, within the German Research Foundation (Deutsche Forschungsgemeinschaft — DFG) priority project entitled ″Tibetan Plateau: Formation–Climate–Ecosystems“ (TiP). We are grateful to our colleagues for their help during the fieldwork and for the fruitful discussions. We would also like to thank two anonymous reviewers for their very valuable comments. The DFG and the Alfred Wegener Institute for Polar and Marine Research (AWI)

References (57)

  • N. Fagel et al.

    Late Quaternary claymineral record in Central Lake Baïkal (Academician Ridge, Siberia)

    Palaeogeogr. Palaeoclimatol. Palaeoecol.

    (2003)
  • N. Fagel et al.

    Mineralogical signatures of Lake Baikal sediments: sources of sediment supplies through Late Quaternary

    Sediment. Geol.

    (2007)
  • B. Fu et al.

    Late Quaternary systematic stream offsets caused by repeated large seismic events along the Kunlun fault, northern Tibet

    Geomorphology

    (2005)
  • F.X. Gingele

    Holocene climatic optimum in Southwest Africa—evidence from the marine clay mineral record

    Palaeogeogr. Palaeoclimatol. Palaeoecol.

    (1996)
  • U. Herzschuh

    Palaeo-moisture evolution at the margins of the Asian monsoon during the last 50 ka

    Quat. Sci. Rev.

    (2006)
  • J. IJmker et al.

    Environmental conditions in the Donggi Cona lake catchment, NE Tibetan Plateau, based on factor analysis of geochemical data

    J. Asian Earth Sci.

    (2012)
  • J. IJmker et al.

    Characterisation of transport processes and sedimentary deposits by statistical end-member mixing analysis of terrestrial sediments in the Donggi Cona lake catchment, NE Tibetan Plateau

    Sediment. Geol.

    (2012)
  • J. IJmker et al.

    Dry periods on the NE Tibetan Plateau during the late Quaternary

    Palaeogeogr. Palaeoclimatol. Palaeoecol.

    (2012)
  • F. Lehmkuhl et al.

    Quaternary paleoenvironmental change on the Tibetan Plateau and adjacent areas (Western china and Western Mongolia)

    Quat. Int.

    (2000)
  • T.D. Li

    The process and mechanism of the rise of the Qinghai–Tibet Plateau

    Tectonophysics

    (1996)
  • S. Mischke et al.

    Ostracods and stable isotopes of a late glacial and Holocene lake record from the NE Tibetan Plateau

    Chem. Geol.

    (2010)
  • S. Opitz et al.

    Late glacial and Holocene development of Lake Donggi Cona, north-eastern Tibetan Plateau, inferred from sedimentological analysis

    Palaeogeogr. Palaeoclimatol. Palaeoecol.

    (2012)
  • S. Opitz et al.

    Holocene lake stages and thermokarst dynamics in a discontinuous permafrost affected region, north-eastern Tibetan Plateau

    J. Asian Earth Sci.

    (2013)
  • S. Opitz et al.

    Climate variability on the south-eastern Tibetan Plateau since the Lateglacial based on a palaeolimnological multiproxy approach from Lake Naleng — comparing pollen and non-pollen signals

    Quat. Sci. Rev.

    (2015)
  • R. Petschick et al.

    Clay mineral distribution in surface sediments of the South Atlantic: sources, transport, and relation to oceanography

    Mar. Geol.

    (1996)
  • E.P. Solotchina et al.

    Climate signals in sediment mineralogy of Lake Baikal and Lake Hovsgol during the LGMHolocene transition and the 1 Ma carbonate record from the HDP-04 drill core

    Quat. Int.

    (2009)
  • G. Stauch et al.

    Interaction of geomorphological processes on the north-eastern Tibetan Plateau during the Holocene, an example from a sub-catchment of Lake Donggi Cona

    Geomorphology

    (2014)
  • G. Stauch et al.

    Aeolian sediments on the north-eastern Tibetan Plateau

    Quat. Sci. Rev.

    (2012)
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