Paleosols of sandy lands and environmental changes in the western part of northeast plain of China western during holocene

Abstract

Two-three paleosol layers were formed in the western part of the Northeast Plain. China during Holocene. These paleosol layers interlaid with eolian fine sand layers. Dated by¹⁴C dating, archeology and TL and analyzed by statistics, the formation periods of paleosols are divided from the results. The periods are 11,000–7000 5500–4500, 3500–2800 and 1400–1000 a B. P. respectively.

According to the spore-pollen compositions in more than ten sand dune paleosol profiles, it is discovered that there is little spore-pollen in the sand layers and a little spore-pollen in the paleosol layers. The spore-pollen compositions in the paleosols are simple, mainlyArtemisia (50%–70%) and Chenopodiaceae. In the paleosols of 11,000 – 7000 a B. P., the spore-pollen composition isArtemisia-Rubiaceae-chenopodiaceae. The contents ofEphedra pollen in the lower and upper parts of the layer are less than that in the middle part. In the paleosols of 5500–4500 a B. P., the spore-pollen composition isArtemisia-Chenopodiaceae-Melilotus. There is someSalix sp. andBetula sp. pollen in the lower part of the layer and someEphedra pollen in the upper part. In the paleosols of 3500–2800 a B. P., the spore-pollen composition isArtemisia-Chenopodiaceae—Rubiaceae. There are someKochia and Baryaceae. In the paleosols of 1400–1000 a B.P., the spore-pollen composition is alsoArtemisia-Chjenopodiaceae-Rubiaceae. There is a little pine pollen.

The grain size of paleosol is relatively coarse, but still finer than that of eolian sand and becomes coarser from the bottom to the top of the profile. This fact reflects that the weathering environments during the paleosol formation periods were wetter than that during the eolian periods and became dryer from middle to late Holocene.