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Pedosedimentary Development and Paleoenvironmental Significance of the S1 Paleosol on the Northeastern Margin of the Qinqhai-Xizang (Tibetan) Plateau, China
Rob A. KEMP, Edward DeRBYSHIRE, Department of Geography, Royal Holloway, University of London, Egham, United Kingdom.
CHEN Fahu & MA Haizhou, Department of Geography, Lanzhou University, Gansu, People's Republic of China
The S1 pedocomplex, correlated to oxygen isotope stage 5 of the ocean cores, has been traced west of the Loess Plateau per se onto the extreme northeastern margin of the Quinghay-Hizang (Tibetan) in China. Detailed micromorphological analysis of closely-spaced thin sections from the pedocomplex at this site provides the basis for reconstruction of the sequence of pedosedimentary processes and associated paleoenviromental changes occurring during this time interval. The six identified pedosedimentary stages are interpreted in terms of temporal variations in depositional rates, size or particles transported and availability of moisture for pedogenic alteration as determined by changing balance in dominance of winter and summer monsoonal forces. Two main "soil-forming intervals" are isolated: the more extensive of the two reflects pedogenic alteration as a relatively "stable" landsurface under a semiarid climate during the later part of pedosedimentary stage 2. The other main period corresponds to pedosedimentary stage 4 and 5 when leaching and bioturbation processes were active at aggrading surfaces leading to development of an accretionary unit without clear differentiation of horizons. Pedosedimentary stages 1, 3 and 6 were mainly characterised by rapid rates of coarse loess accumulation with synsedimentary modification restricted to surface slaking and crust formation, and minor localised redistribution of calcite.
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