Short Papers of Commission members

Late Quaternary Paleosols And Environmental Change In The Huand-Huai-Hai Plain

LIU LIANG-WU, Institute of Soil Science, Academia Sinica, P.O. Box 821, Nanjing 210008, P.R.China

Paleosols in the Huang-Huai-Hai Plain consist of 3 horizons: topsoil horizon of warp soil horizon, black soil horizon and calcareous concretion loess horizon. Based on the soil properties and ages, as well as soil-forming environment, author thinks that the soils aren't the product formed during modern environmental conditions, and are a superimposed paleosols developed on polygenetic sediment during different geologic periods.

Calcareous concretions are an important characteristic of the loess horizon, which accumulated in layers within the profile, a single layer, or interrupted layers, or even successive layers. They are rich in carbonate, from 290 g/kg to 720 g/kg. Of the carbonate in the concretions 97% is calcium carbonate. In the Plain, the hydraulic gradient is normally 1/3500 - 1/6000, and there are several layers of confined void groundwater. Moreover, shallow buried depth of the groundwater with only 0.5-2 m, slow runoff and high evaporation through vertical evaporation is the predominant mode of drainage. All these favorite the formation of the concretions. In addition, the groundwater is characterized by Ca2+, Mg2+ and HCO3-1, which supplies abundant material source in the formation of calcareous concretions. Radiocarbon dating, spore-pollen analysis and chemical analysis of the calcareous concretion loess horizon, as well as geological information demonstrate that the loess horizon of ancient fluvial deposit formed in the landscape of conifer - dominated conifer - broad leaf mixed forest-steppe, with a fairly dry cool-temperate climate during 15750 a B.P.

Black soil horizon with the thickness of 30 cm is generally located under plowpan, black (dry, 10YR 3/1 - 10YR 5/1, wet, 10YR 1/3) in color, with a relatively low content of organic carbon (7-14.5 g/kg). Pollen analysis and zoolite discovered from this stratum show a landscape with marsh meadow. Unfortunately, the development degree of the black soil horizon on fluvial and lacustrine deposit is still rather weak from the point of view of pedogenesis. The black soil horizon at the bottom of depression in relief are dated at ca. 1800 a B.P., whereas the horizons at the highland in microrelief have older ages, ranging from 4130 to 4865 years.

The black soil horizon gas affected by human activities for thousands of years, of which a part has already differentiated into topsoil horizon. Of course, the topsoil horizon is also effected by recent fluvial flood material, which results in brown red in color and riches in carbonate. The carbonate in warp soil horizon can increase to 120 g/kg from 15 g/kg of original topsoil.

From here we see that the soils of the Huang-Huai-Hai Plain have undergone 3 cycles of deposition- soil formation during different geological periods. And the 3 soil horizons are considered as a kind of paleosol, a superimposed paleosol, showing environment change of late Quaternary.