Driving factors of interglacial paleosol formation on the Chinese loess plateau and the effect of precession and ice sheets

Abstract

The loess-paleosol sequences in the Chinese Loess Plateau (CLP) are an important terrestrial paleoclimate record. However, quantitative understanding of the response of paleosol development to various climate and environmental factors remains poor. Based on simulations with combined soil-climate models (SoilGen2-LOVECLIM1.3), this study investigates the sensitivity of paleosol development to different soil forming factors as well as the influence of ice sheets and astronomical forcing during the interglacials of the past 500 ka. Sensitivity analyses show that precipitation, dust addition and evapotranspiration are the dominant factors controlling the interglacial paleosol formation, but their relative importance varies between intergalcials and for different soil properties such as calcite and clay contents. Our results show that the simulated S1, S2, S3, S5-1 paleosols, which correspond to MIS 5, 7, 9 and 13 respectively, exhibit strong relationship with precession through its control on precipitation, whereas the precession signal is weak in the simulated S4 paleosol, in line with the weak precession variation during MIS 11. The results also show variable length of lags between different soil properties and precession and also in different interglacials. The lag between the simulated calcite and precession is shorter than that of clay. Moreover, clay content also shows strong relation with temperature during MIS 5 and MIS 13. Large ice sheets in the early and late phases of the interglacials have substantial impact on both temperature and precipitation in the CLP and thus on carbonate leaching and clay migration. Therefore, the simulated paleosols result mainly from the joint effect of precession and ice sheets via their control on local climate, and they show qualitative agreement with observations.