Testing the model for linking grain-size component to lake level status of modern clastic lakes

Abstract

A model was proposed recently for linking grain-size component to lake level status based on investigations of Daihai Lake in Inner Mongolia. To test this model, grain-size components of the surface sediments of Dali Lake, 500 km northeast of Daihai Lake, were partitioned and their relationships with the lake level status were examined in this study. The data show that modern clastic sediments of Dali Lake contain five distinct grain-size components representing specific depositional processes and sedimentary environments within the lake in common with Daihai Lake. These components are specified as long-term suspension clay, offshore-suspension fine silt, offshore-suspension medium-to-coarse silt, nearshore-suspension fine sand and nearshore-saltation medium sand. In Dali Lake, by contrast, the offshore-suspension components are lacking in more samples from the nearshore zone; the nearshore-suspension and saltation components occur in more samples from the offshore and transitional zone, respectively; and two adjacent components are well separated. These differences would result from higher-energy hydraulics of Dali Lake generated by stronger and more frequent winds occurring in the lake region. Under this hydraulic condition, clastic materials entering the lake and the resultant components would be reworked more seriously during transportation within the lake, leading to further basin-ward transportations of the major components and better separations of two adjacent components. Percentage of the nearshore components is negatively related to water depth, suggesting the grain-size component–lake level status model for the lake. This model was applied to a sediment core from the lake, showing that high percentages of the nearshore components in the core coincide with low precipitations reconstructed on the pollen profile of the same core. The coincidence of two independent proxies demonstrates the wide applicability of the grain-size component–lake level status model to lake's paleohydrological reconstruction.