论文部分内容阅读
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_2, Al_2O_3 and TiO_2 decrease 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.
Paleosols in the Huang-Huai-Hai Plain occur mainly in the Huaibei, Xuhuai, Yischuhe and Jiaolai areas. They each result from the 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 the con-cretions, compared this with that of that of the enclosing soil horizons, and draws some environmentalconclusions. Three kinds occur: embryonic calcareous concretions, mature calcareous concretions, and calcareous hardpans (petrocalcic horizons). The embryonic concretions formed during themid-Holocene (6780 ± 130 yr. BP), mature calcareous concretions during the late-Pleistocene (weighted average of 31 samples = 15670 ± 370 yr. BP), and calcareous hardpans (petrocalcichorizons) 16 to 40 ka BP The calcium carbonate content increases from 412 g / kg in the embryonic concretions, to 551 g / kg in the mature concretions, and to 691 g / kg in the hardpan, while contents of SiO 2, Al 2 O 3 and TiO 2 decrease accordingly. Spore pollen analysis shows that late-Pleistocene there was dry and cool, where the mid-Holocene was warm and humid and lakes were more extensive than today.