BDP Cores 96-1/-2

Baikal Drilling Programme BDP Cores 96-1/-2 (http://icdp.gfz-potsdam.de) Late Pliocene climate variation in the Lake Baikal region: How do they relate to N-Hemisphere onset of glaciation

From a palaeomagnetically dated Late Pliocene sediment core high climatic variability is recorded between 3.6-2.35 Ma. A major climate change occurred in the Lake Baikal area at about 2.75-2.65 Ma. Enhanced physical weathering in the catchment, mirrored in the illite to smectite ratio, and temporarily reduced bioproduction in the lake, reflected by the diatom abundance, evidence a change towards a colder and more arid climate, probably associated with an intensification of the Siberian High. Fluctuations like the Zr/Al ratio are traced back to changes in the aeolian input, with high values in warmer, more humid phases due to a weaker Siberian High. Expansion of steppe and boreo-alpine vegetation occurred as early as 3.48 to 3.39 Ma. Peak records of non-arboreal pollen types and spores, including subarctic-boreo-alpine Selaginella selaginoides , evidencing advances of open vegetation, can be correlated to cool-glacial marine oxygen isotope stages. Around 3-2.9 Ma the climate oscillated with steadily increasing amplitudes between cold-dry and warm-moist conditions. Cooling strengthened after 2.89 Ma and severely restricting Tsuga development. Due to decreasing precipitation extensive areas with open steppe and rock-steppe vegetation permanently established after 2.62 Ma. Dryness became a dominant environmental factor in the Baikal region, coeval in time to the Red Clay-Loess shift in northern China. This climatic transition can be explained as a consequence of major intensification of Northern Hemisphere Glaciation around 2.75 Ma evidenced by marine records of ice-rafted debris. Assuming that the sand content in the sediment reflects tectonic pulses, the Lake Baikal area was tectonically active during the entire investigated period, but in particular around 2.65 Ma. Tectonic movements have likely led to a gradual catchment change since about 3.15 Ma from the western towards the eastern lake surroundings, as indicated in the geochemistry and clay mineralogy of the sediments. The strong coincidence between tectonic and climatic changes in the Baikal area hints at the Himalayan uplift being one of the triggers for the Northern Hemisphere Glaciation.

Partner: Johannes Müller, Dieter Demske, Carsten Eckert, Barbara Mohr, Hans Hubberten (AWI Potsdam)