Late Holocene soil formation in the valley of the River Yenisei, Central Siberia

Alluvial sod soil sequences from the 9 m terrace in the valley of the River Yenisei were used to reconstruct the paleoecological history and paleohydrological regime of the river. The terrace consists of an Early Holocene (5000–>6000 BP) sequence of alluvial sands and loamy sands and a Late Holocene sequence which has been transformed by soil development. Analyses of organic matter extracted from buried soils in two sections and comparisons with pollen assemblages suggest that the ratio of carbon in humic acids to that in fulvic acids and particular fractions of the humic or fulvic acids (termed `typical fractionsʹ) record changing conditions of regional environment.