Niels Meijer, MSc.



Paleogene history of monsoonal climate and aridification in Central Asia
My research aims to extend the stratigraphic records from the Xining Basin in Central China (Fig. 1) to the Early Paleogene, in order to record the paleoclimate during this critical period of high CO2 concentrations and temperatures. The lithologies in the Xining basin consist of red mudstones deposited in dry mudflats and gypsum beds deposited in saline lakes (Fig. 2). The mudstones are suitable for magnetostratigraphy and will be used for age determination.
Previous research (Licht et al., 2014) showed that the grain surfaces of the mudstones indicate a windblown origin (Fig 3a-c). Additionally, the grainsize distribution is similar to that of modern windblown dust on the Chinese Loess Plateau (Fig. 3d). The loess is deposited by winter monsoon dust storms and the similarities with the Eocene mudstones indicate that these dust storms, and therefore the monsoons, have been active up to 40 Myr ago.
By using similar methods of grainsize analysis, SEM quartz grain surface analysis and XRF I will extend the records of these ancient monsoons and try to find the onset of monsoonal dust in the Xining Basin. Additionally, I aim to record the aridification in the Early Paleogene and reconstruct the climate, by using sedimentological, pollen and stable isotope data. This will enable us to study the behavior of the monsoons as a function of climate.

Also, I will apply the same approach to dated sections in the Tarim Basin (western China) and Tajikistan to record aridification and monsoonal dust.

During the Indo-Asia collision and the resulting transition from a Greenhouse to an Icehouse climate, Central Asia became arid (Fig. 4). The aridification occurred in several steps. Some of these concur with changes in global climate, such as the Middle Eocene Climatic Optimum (MECO) and the Eocene-Oligocene Transition (EOT). Others may be related to the retreat of the Tarim Sea (Fig. 1), and the consequent removal of this moisture source. These changes in moisture source as well as changes in the monsoonal climate are the driving mechanisms behind Asia’s arid interior, but their relative contribution remains unknown. Additionally, the behavior of monsoonal climate in the Early Paleogene, when CO2 concentrations and temperatures were high, has not yet been recorded.

Bijkerk, J. F., Eggenhuisen, J. T., Kane, I. A., Meijer, N., Waters, C. N., Wignall, P. B., & McCaffrey, W. D. (2016). Fluvio-marine sediment partitioning as a function of basin water depth. Journal of Sedimentary Research86(3), 217-235.