Preprints
https://doi.org/10.5194/cp-2021-32
https://doi.org/10.5194/cp-2021-32

  25 Mar 2021

25 Mar 2021

Review status: a revised version of this preprint is currently under review for the journal CP.

Palaeo-environmental evolution of Central Asia during the Cenozoic: New insights from the continental sedimentary archive of the Valley of Lakes (Mongolia)

Andre Baldermann1, Oliver Wasser1, Elshan Abdullayev2,3, Stefano Bernasconi4, Stefan Löhr5, Klaus Wemmer6, Werner E. Piller7, Maxim Rudmin8, and Sylvain Richoz9 Andre Baldermann et al.
  • 1Institute of Applied Geosciences, Graz University of Technology, NAWI Graz Geocenter, Graz, Austria
  • 2Department of Life Sciences, Khazar University, Baku
  • 3Department of Geoscience, French-Azerbaijani University (UFAZ), Baku, Azerbaijan
  • 4Geological Institute, ETH Zurich, Zurich, Switzerland
  • 5Department of Earth and Environmental Sciences, Macquarie University, Sydney, Australia
  • 6Geoscience Centre (GZG), University of Göttingen, Göttingen, Germany
  • 7Institute of Earth Sciences, University of Graz, NAWI Graz Geocenter, Graz, Austria
  • 8Division of Geology, Tomsk Polytechnic University, Tomsk, Russia
  • 9Department of Geology, University of Lund, Lund, Sweden

Abstract. The Valley of Lakes basin (Mongolia) contains a unique continental sedimentary archive, suitable for constraining the influence of tectonics and climate change on the aridification of Central Asia in the Cenozoic. We identify the sedimentary provenance, the (post)depositional environment and the palaeo-climate based on sedimentological, petrographical, mineralogical and (isotope) geochemical signatures recorded in authigenic and detrital silicates as well as soil carbonates in a sedimentary succession spanning ~34 to 21 Ma. The depositional setting was characterized by an ephemeral braided river system draining prograding alluvial fans, with episodes of lake, playa or open steppe sedimentation. Metamorphics from the northern adjacent Neoarchean to late Proterozoic hinterlands provided a continuous influx of silicate detritus to the basin, as indicated by K-Ar ages of detrital muscovite (~798-728 Ma) and discrimination function analysis. The authigenic clay fraction is dominated by illite-smectite and “hairy” illite (K-Ar ages: ~34-25 Ma), which formed during coupled petrogenesis and precipitation from hydrothermal fluids originating from major basalt flow events (~32-29 Ma and ~29-25 Ma). Changes in hydroclimate are recorded in δ18O and δ13C profiles of soil carbonates and in silicate mineral weathering patterns, indicating comparatively humid to semi-arid conditions prevailed in the late(st) Eocene, changing into arid conditions in the Oligocene and back to humid to semi-arid conditions in the early Miocene. Aridification steps are indicated at ~34-33 Ma, ~31 Ma, ~28 Ma and ~23 Ma and coincide with some episodes of high-latitude ice sheet expansion inferred from marine deep-sea sedimentary records. This suggests long-term variations of the ocean/atmosphere circulation patterns due to pCO2 fall, re-configurations of ocean gateways and ice-sheet expansion in Antarctica could have impacted the hydroclimate and weathering regime in the basin. We conclude that the aridification in Central Asia was triggered by reduced moisture influx by westerly winds driven by Cenozoic climate forcing and the exhumation of the Tian Shan and Altai mountains and modulate by global climate events.

Andre Baldermann et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2021-32', Anonymous Referee #1, 23 Apr 2021
    • AC1: 'Reply on RC1', Andre Baldermann, 01 Jul 2021
  • RC2: 'Comment on cp-2021-32', Jeremy Caves Rugenstein, 18 May 2021
    • AC2: 'Reply on RC2', Andre Baldermann, 01 Jul 2021

Andre Baldermann et al.

Andre Baldermann et al.

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Short summary
We identified the provenance, (post)depositional history, weathering conditions and hydroclimate that formed the detrital and authigenic silicate minerals and soil carbonates of the Valley of Lakes sediments in Central Asia during the Cenozoic (~34 to 21 Ma). Aridification pulses in continental Central Asia coincide with marine glaciation events and are caused by Cenozoic climate forcing and the exhumation of the Tian Shan and Altai mountains, which reduced the moisture influx by westerly winds.