Miocene climate change on the Chinese Loess Plateau: Possible links to the growth of the northern Tibetan Plateau and global cooling

Abstract

The evolution of the Asian monsoon-arid environmental system during the Cenozoic was closely related to the growth of the Himalayan-Tibetan Plateau and global climate change. However, due to inconsistencies in paleoclimatic reconstructions and to various constraints on the timing of the growth of the Tibetan Plateau, the relative impacts of regional uplift and global cooling on Asian climate change remain controversial. Here we investigate the mineralogical composition of a Miocene Red Clay deposit on the western Chinese Loess Plateau in order to infer changes in chemical weathering and monsoon intensity. Variations of four mineralogical ratios (chlorite/quartz, illite/quartz, calcite/quartz, and protodolomite/quartz) reveal that the summer monsoon intensity was relatively strong during the early Miocene (23.5-18.5 Ma), weakened gradually until 9.5 Ma, and strengthened again in the late Miocene. We synthesized previously published thermochronological data from the northeastern Tibetan Plateau and surrounding mountains, and the results suggest that two phases of the rapid growth of northern Tibet occurred around 24-17 and 13-7 Ma. Comparison of paleoclimatic proxies and thermochronological data suggests that the gradual weakening of the summer monsoon intensity from 18.5 to 9.5 Ma paralleled global cooling, whereas two intervals of strengthened monsoon in the early and late Miocene were possibly related to the rapid growth of northern Tibet. Our combination of paleoenvironmental proxies and thermochronological data reveals possible links between Miocene Asian monsoon evolution, phased growth of the Tibetan Plateau, and global climate change, and confirms the interconnection of geodynamic and atmospheric processes in the geological past.

Checklist for the use of potassium concentrations in siliciclastic sediments as paleoenvironmental archives

“…Most climate reconstructions of the Cenozoic period are based on marine sediments with major biogenic components (Zachos et al, 2001;De Vleeschouver et al, 2017;Miller et al, 2017), while continental siliciclastic (detrital) sedimentary archives have been used less frequently (Abels et al, 2010;, Valero et al, 2014, Sun et al, 2015. Currently, continental archives seem underrepresented in climate reconstructions, although they could overcome a problem like a widespread hiatus in marine sediments from the periods tightly preceding the Miocene Climatic Optimum (MCO) (Miller et al, 2017), which hinders correlation of existing sedimentary records, dating of the MCO triggers, and their identification.…”

End-member modeling of the grain-size record of Sikouzi fine sediments in Ningxia (China) and implications for temperature control of Neogene evolution of East Asian winter monsoon

“…Dust has extensively deposited in the Chinese Loess Plateau (CLP) at least since the Late Oligocene [1–4]. Most loess deposits are generally underlain by Miocene to Pliocene red clay [4–10].…”

“…Most loess deposits are generally underlain by Miocene to Pliocene red clay [4–10]. Both loess and red clay are dominated by silt particles.…”

Continental drift and plateau uplift control origination and evolution of Asian and Australian monsoons

“…The elevated CO 2 levels during the late Eocene may have caused increased precipitation in the mid-latitudes, but our results suggest that there did not exist a typical summer monsoon circulation over mainland East Asia during this time. Although our simulations suggest the enhancement and expansion of the East Asian summer monsoon under the condition when only the plate movement and plateau uplift are considered from LO to LM, some geological records113233 show that the intensity of the East Asian summer monsoon decreased on the whole in the Miocene. Thus, other forcing factors, such as atmospheric CO 2 concentration323334, should also be considered in order to fully understand the long-term evolution of the Asian monsoons.…”