Professor SUN Jimin and his team present high-resolution carbon isotope time series of both organic matter and bulk carbonates, covering the past 2.58 Ma, derived from the loessesoil successions on the southern Chinese Loess Plateau.

They conclude that such tectonic time scale C4 plant expansions are controlled by enhanced seasonality of precipitation (relatively more precipitation in the warm growing season) as well as regional aridity, and this long-term fluctuation superimposes on the orbital scale variations of C4 plants, while the latter appears phase-locked with cyclical changes of summer monsoon circulations.

Fig. 1. The records of both organic matter and bulk carbonates during the Quaternary. (Image by SUN)

Sun et al. Stepwise expansions of C4 biomass and enhanced seasonal precipitation and regional aridity during the Quaternary on the southern Chinese Loess Plateau. Quaternary Science Reviews. 2012, 34: 57-65 (Download Here)