image: Figure 1 The land-sea distribution of Asia and the location map showing clay minerals records mentioned in this study. view more
Credit: ©Science China Press
As the second largest dust source on the globe, the tectonic and climatic evolution of continental Asia has an important impact on regional and global climate change and has been of interest to scientists. Clay minerals, as an important detrital component of sediments in the West Pacific, are fine-grained weathering products of continental rocks and are thus influenced by multiple factors, including parent rock lithology, tectonic setting, and climatic conditions. Generally, relative higher content of illite and chlorite implies weaker chemical weathering degree or stronger physical erosion rate. Therefore, clay minerals compositions and crystallographic characteristics are widely used in provenance tracing and paleoclimate reconstruction. However, the overall evolutionary tendency and response mechanism of clay mineral assemblages over large spatial and long timescales across Asia remains unclear as there are very few long-term records extending to the Oligocene–early Miocene, which is a critical period with major uplift of the Tibetan Plateau. Here, continuous, long-term, and high-resolution clay mineral records are reconstructed using sediments from Deep Sea Drilling Project (DSDP) Sites 292 and 296 in the West Pacific (Figure 1). The clay mineral compositions and eolian fractions are used to reconstruct the aridification history of the Asian interior since the late Oligocene. Furthermore, the driving mechanisms in clay mineral evolution since 30 Ma are further explored by comparing clay mineral records from broad regions.
The relative contents of illite and chlorite in eolian sediments in the West Pacific show an overall increase, which indicates progressive aridification of the Asian interior since the late Oligocene and strengthened aridification at approximately 20, 14, 7, and 3 Ma (Figure 2). Combining published clay mineral records from the continent and marginal seas of Asia with those from other regions of the world, it appears that illite and chlorite in Asia increased more dramatically than in other regions since ~20 Ma, followed by a consistent rapid increase over the globe after ~3 Ma (Figure 3). By comparing climatic records and tectonic events of the Tibetan Plateau, it is demonstrated that the illite and chlorite in Asian clay mineral records increased during 20–3 Ma in response to the uplift of the Himalayan-Tibetan Plateau and the Central Asian Orogenic Belt, whereas their increase after 3 Ma was driven by global cooling and the expansion of the Arctic ice sheet.
This study reported new long-term records of the drying history of the Asian interior since the Oligocene, and, for the first time, summarizes and compares the tectonic time-scale clay mineral records in Asia, which highlights the significance of Tibetan uplift in strengthening continental weathering and erosion in Asia at the Cenozoic.
See the article:
Tang Y, Wan S, Zhao D, Yu Z, Xu Z, Zhang J, Song Z, Li M, Jin H, Jiao W, Dong H, Li A. 2023. Evolution of Asian drying since 30 Ma revealed by clay minerals record in the West Pacific and its tectonic-climatic forcing. Science China Earth Sciences, 66(6): 1365–1382, https://doi.org/10.1007/s11430-022-1075-0
Journal
Science China Earth Sciences