First results of study of Lake Baunt bottom sediments (northern Transbaikalia)

Abstract

In March 2014, the Lake Baunt bottom sediments were drilled in the deepest part of the lake basin (33 m). The penetrated interval is 13.7 m thick, with the age of the base being evaluated at 28–30 ka. Lithological study of the penetrated sediments demonstrates the upper part of the section dominated by diatom ooze, whose concentration decreases gradually downward the section, up to the replacement of the ooze by silty clay. The obtained data on variations in petromagnetic parameters, concentration of biogenic silica, and sediment compaction indicate considerable variations of sedimentary environments during the Late Pleistocene and Holocene. Being compared with the previously reconstructed landscape and climate dynamics for the sedimentary succession of Lake Kotokel for this time interval, the above parameters reveal that the Lake Baunt bottom sediments reliably fix the regional paleoclimate signal. For the first time for lakes of the Baikal region, Gothenburg and Mono Lake magnetic excursions are identified in the paleomagnetic record of the Lake Baunt section.

Hydrological (in)stability in Southern Siberia during the Younger Dryas and early Holocene

“…1) and is one of the larger lakes in the Tsipikan-Baunt lake district (Shchetnikov, 2007;Yakhnenko et al, 2008). Located at ~1050 m a.s.l., Baunt has a surface area of 111 km 2 (19 km length on a SW-NE elongation and 9 km width), with an average depth of 17 m and maximum depth of 33 m (Krainov et al, 2017). The catchment predominantly lies to the south, east, and west (Krainov et al, 2017), and is bounded by the Ikat and Tsipikan highlands (Solotchin et al, 2015) (Fig.…”

“…Glaciation in this region is limited to the Kodar range of the Transbaikal mountains (Stokes et al, 2013), and has receded recently due to anthropogenic warming, while extensive mountain glacier coverage existed during the Last Glacial (Margold et al, 2016;Martin and Jansson, 2011;Stokes et al, 2013). Baunt receives water from the Verkhnyaya (Upper) Tsipa and Tsipikan rivers (Krainov et al, 2017), and discharges into the Nizhnyaya (Lower) Tsipa River (Ufimtsev et al, 2009) (Fig. 1).…”

“…The regional geology is predominantly the Barguzin and Vitimkan igneous granitic complexes (part of the Angara-Vitim batholith) (Nenakhov and Nikitin, 2007;Rytsk et al, 2007;Tsygankov et al, 2007). In the lake basin, Neogene-Quaternary sediments including sands, clays and gravels dominate (Bezrukova et al, 2017;Krainov et al, 2017;Shchetnikov, 2007), while Holocene sediments include lacustrine, fluvial and peat deposits (Bezrukova et al, 2017). No carbonate rocks are found within the catchment (Ryabenko et al, 1964), which sits in taiga forest, dominated by Larix gmelinii (Larch) and Pinus sylvestris (Scots Pine).…”

“…1C) was collected in March 2014, while the lake was frozen (maximum ice thickness of ~2 m with limited movements) using a UWITEC gravity corer (Krainov et al, 2017), at the site identified to have the most uniform sedimentation rates. The UWITEC system used hammer action with inner 63 mm PVC liners to extract the 13.66 m core in 8 liners, over 3 days, with a 95% recovery rate (Krainov et al, 2017). The litho-stratigraphy consists of silty clay at the base (1366-1170 cm), followed by a change to silty clay with abundant diatoms (1170-620 cm).…”

“…From 540 cm there is a switch to diatomaceous ooze, which continues to the core top. For full description see Krainov et al (2017) (Fig. 1D).…”