Tectonic and climatic forcing of chemical weathering intensity in the northeastern Tibetan Plateau since the middle Miocene

The thick and continuous Cenozoic successions in the Qaidam Basin provide an excellent paleoclimate archive. Here, we focus on the ostracod fauna, stable isotope records, and paleoweathering indices from a well-dated Cenozoic sedimentary section in the Qaidam Basin, to develop an understanding of Middle Miocene aridification in central Asia. Microfossil analyses suggest that the ostracod species diversity decreased suddenly after 13.3 Ma, and that the dominant ostracod genus shifted from Ilyocypris to Cyprideis. Stable isotope data from ostracod valves have displayed abrupt positive shifts of 3.75‰ in δ18O values and 5.28‰ in δ13C values since 13.3 Ma. The chemical index of weathering (CIW) and K2O/Na2O ratios decrease markedly after 13.3 Ma, reflecting a significant decrease in chemical weathering intensity. These combined and consistent observations suggest that the Qaidam Basin has experienced increased aridification since 13.3 Ma. The dating was obtained directly from previous magnetostratigraphic studies and can be correlated accurately with global climate evolution and regional tectonic events. A comparison of these results with global paleoclimatic records and previous geologic studies of the Tibetan Plateau revealed that global cooling, rather than uplift of the Tibetan Plateau, played a key role in the drying of the Qaidam Basin at approximately 13 Ma.

Download Full-text

Lithium isotopes and implications on chemical weathering in the catchment of Lake Donggi Cona, northeastern Tibetan Plateau

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2017.06.026 ◽

2017 ◽

Vol 213 ◽

pp. 155-177 ◽

Cited By ~ 11

Author(s):

Marc Weynell ◽

Uwe Wiechert ◽

Jan A. Schuessler

Keyword(s):

Tibetan Plateau ◽

Chemical Weathering ◽

Lithium Isotopes ◽

Northeastern Tibetan Plateau

Download Full-text

Role of late glacial to mid-Holocene climate in catchment weathering in the central Tibetan Plateau

Quaternary Research ◽

10.1016/j.yqres.2004.09.012 ◽

2005 ◽

Vol 63 (2) ◽

pp. 161-170 ◽

Cited By ~ 32

Author(s):

Zhang-Dong Jin ◽

Yanhong Wu ◽

Xiaohui Zhang ◽

Sumin Wang

Keyword(s):

Tibetan Plateau ◽

Chemical Weathering ◽

Late Glacial ◽

High Elevation ◽

Climatic Conditions ◽

Central Plateau ◽

The Holocene ◽

Physical Weathering ◽

Central Tibetan Plateau ◽

Weathering Intensity

The lightness (L*) and concentrations of Rb, Sr and organic carbon (Corg) have been measured in the age-constrained lake sediment cores recovered from Co Ngoin in the central Tibetan Plateau. Dissolved Sr flux is a dominant control on the variation of Rb/Sr ratios in the sediments. Variations in color and geochemical proxies of Co Ngoin sediments display a continuous history of late glacial to mid-Holocene chemical versus physical weathering intensity in response to past climatic changes between approximately 13,500 and 4500 cal yr B.P. A lower chemical weathering under a late glacial climate was followed by a higher weathering during the Holocene Optimum. Weathering intensity in the central Tibetan Plateau catchment also responds to well-known climatic events, such as the Younger Dryas (YD), and possibly the Holocene Event 5 (HE-5). Although there are differences in time or duration of the climatic events, many of the well-known late glacial to mid-Holocene events occurred in high-elevation Co Ngoin where atmospheric circulation might play a hemispherical role in climatic forcing. The sediment hiatus since c. 4200 14C yr B.P. in the Co Ngoin indicates a period of desiccation that was probably associated with a sharp decrease in summer monsoon strength. Our lascustrine results not only imply catchment weathering variations in response to late glacial to mid-Holocene climatic conditions in the central plateau, but also provide further evidence for global connections between regional climates.

Download Full-text