Paleosol evolution and environmental change in the Huang-Huai-Hai Plain, China

Paleosols in the Huang-Huai-Hai Plain occur mainly in the Huaibei, Xuhuai, Yischuheand Jiaolai areas. They result from 3 sedimentation-soil formation cycles since the LatePleistocene. Each cycle left calcareous concretions, a dark soil horizon, and a topsoil horizonand/or a stratified soil horizon all derived from loess. This paper examines the composition of theconcretions, compares this with that of the enclosing soil horizons, and draws some environmentalconclusions. Three types occur: embryonic calcareous concretions, mature calcareous concretions,and calcareous hardpans (petrocalcic horizons). The embryonic concretions formed during themid-Holocene (6780±130 yr. B.P.), mature calcareous concretions during the late-Pleistocene(weighted average of 31 samples = 15670±370 yr. B.P.), and calcareous hardpans (petrocalcichorizons) from 16 to 40 ka B.P. The calcium carbonate content increases from 412 g/kg in theembryonic concretions, to 551 g/kg in the mature concretions, and to 691 g/kg in the hardpan,whereas contents of SiO, AlOand TiOdecrease accordingly. Spore pollen analysis shows thatthe late-Pleistocene there was dry and cool, whereas the mid-Holocene was warm and humid andlakes were more extensive than today.