Micromorphological Cryogenic Features in Meadow Podbels of Middle-Amur Lowland

Meadow podbels (dark-humus gleyic and gleypodbels in the Classification of soils of Russia) are subject to deep and prolonged freezing in the western part of their area. It is manifested in cryogenic deformations of genetic horizons as well as in thin sections. Micromorphological features of soils on permafrost are well known. and the purpose of this research was to reveal them in three profiles of meadow podbels as related to soil cryological and hydrological regimes. Unlike northern cryogenic soils. the meadow podbels have dark-humus horizons with weak cryogenic manifestations; in eluvial horizons. there are frost-created platy microstructures and numerous iron-organic nodules of any size. Specific microstructures are common in textural BT horizons: these are rounded or ellipsoidal peds with iron-organic nodules in their nuclei. and ooids: rounded aggregates with iron impregnation/segregations in their centres and circular striated b-fabric of the micromass on aggregate peripheries. Typical gley mirofeatures in the lowermost clayey horizons are well expressed. along with illuviation clay coatings. part of them being deformed. The skeleton grains and micromass re-arrangement. as well as concentric orientation of skeleton grains in the groundmass. are weak as compared to cryogenic soils with permafrost.