Environmental Changes Deduced from Grainsize Characteristics of the Sediments from Hongjiannao Lake, Shaanxi Province

Key words: 
• Hongjiannao Lake /
• lacustrine sediment /
• grainsize /
• paleosandstorm characteristics /
• lake evolution history

Abstract: On the basis of analyzing grainsize proxies, the evolution history of Hongjiannao Lake for the past 80 yrs. is discussed in this article. Grainsize distribution of the samples from the lower part of the sedimentary core is characterized by the “doublepeak” feature, which enables us to distinguish the aeolian materials from the lacustrine sediments. It's revealed that Hongjiannao Lake formed in about 1928 A.D. and in its initial stage sandstorms were prevalent with three extremes took place in 1936 A.D., 1939 A.D. and 1941 A.D.. During 1952~1960 A.D., the lake expanded greatly, due to the sharp increase of inflow waters to the lake as a result of the channelledoff water from the around swamp caused by human beings. Hongjiannao Lake has remained a higher water level since 1960s and the frequency and intensity of sandstorms have reduced a lot with the “doublepeak” feature of the grainsize frequency curve changing into the “singlepeak” feature. The water level of Hongjiannao Lake has been holding a dropping trend since 1950s. The lake evolution history as well as the paleosandstorm characteristics and the anthropogenic activities are perfectly inferred from the study of grainsize proxies.