Joint Seminar: Reconstructing post-glacial variations in the Asian monsoon and their impacts on continental environments

The intensity of the Asian monsoon is known to vary after the Last
Glacial Maximum with weak summer rains at that time, intensifying into
the Early Holocene. A variety of climate proxies have been used to argue
that the monsoon reached at a peak around 8 ka and then declined. I have
examined the effects that this variability has had on continental
erosion and weathering. In the Indus basin, monsoon intensification
resulted in intensified erosion of the Lesser Himalaya and a change in
the composition and volume of sediment reaching the ocean. Clay mineral
proxies suggest more chemical weathering into the Holocene, under wetter
conditions, although some of this may also indicate enhanced reworking
in the flood plains, as the rivers incised channels after ~6 ka. On the
South China margin the sediments record the erosion of Taiwan since the
LGM and show a close correspondence between changes in climate and
weathering response. The Early Holocene is marked by increased sediment
flux of clastic materials and a change in hematite/goethite ratios,
indicating short-lived changes of chemical weathering from 12 to 9 ka.
This peak predates the apparent monsoon peak predicted from speleothem
records, but seems to correlate well with salinity records from the
northern South China Sea suggesting that the speleothems may not be so
robust monsoon proxies as previously suggested. That being the case it
is not clear how closely coupled the South and East Asian monsoons are
on millennial timescales.




13:30 Uhr


Bundesstr. 53, room 022/023
Seminar Room 022/023, Ground Floor, Bundesstrasse 53, 20146 Hamburg, Hamburg


Peter Clift, University of Aberdeen


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