Speaker
Description
The Xi'an AMS Center is equipped with a 3 MV accelerator mass spectrometer for multi-nuclides measurements, which provides a background of 10Be/9Be ratio up to 1.56×10-16, giving us favorable conditions to carry out environmental tracing study by using Chinese loess 10Be. Chinese loess-paleosol sequences are considered as one of three pillars for the global change research, along with marine sediments and ice cores. However, paleomagnetic studies showed that geomagnetic polarity reversals recorded in Chinese loess, such as the Matuyama/Gauss (M/G) reversal (a key time marker for Quaternary/Neogene boundary) and Brunhes-Matuyama (B/M) reversal, were found to be asynchronous with those in marine sediments. Such asynchroneities led to a long-standing debate over the uncertainties of the loess time scale and climatic correlation between terrestrial and marine records. To resolve these problems, we developed Residual Trace Approach (RTA) to disentangle the global geomagnetic and climate signals in Chinese loess 10Be, and reinvestigated the M/G and B/M boundaries using 10Be from loess sections. The results showed that the 10Be-traced M/G and B/M reversals were in fact synchronous with the records from marine sediment, settling the long-disputed question of the apparent asynchroneities of the two important geomagnetic reversals between terrestrial and marine sediments. We further reconstructed geomagnetic field variations for the last ~870 kyr and, for the first time, identified 13 consecutive geomagnetic excursions in loess which provide key time markers for Chinese loess-paleosol sequences. As by-product, we also quantitatively reconstructed multi-time scale Asian monsoon (AM) rainfall using loess 10Be. We proposed that the AM rainfall was mainly modulated by the low latitude insolation gradients and the Earth’s eccentricity can modulate the amplitude of the precession signal in AM rainfall.
| Student Submission | No |
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