A field study on river-induced currents - An intermountain lake, Lake Okotanpe, Hokkaido.

Abstract

In an intermountain lake, Lake Okotanpe, Hokkaido,

Sedimentation in an intermountain lake, Lake Okotanpe, Hokkaido. II Sedimentation rate and its sedimentary processes introduced from the 1977 Usu volcanic ash layer of sediment core.

“…The fine sand was composed of plagioclase, hypersthene and augite. The mineral composition coincided with that of the phenocryst of andesitic rocks in the drainage area of Lake Okotanpe (CHIKITA et al, 1985). Thus, the increase of hypersthene and augite for the 42-43 cm core sediment is due to a concentration of the debris produced from the andesitic phenocryst, into the coarsest grains of lake sediments.…”

“…The dissipation process is extensive turbulent entrainment for the turbidity currents which is exalted by convective currents induced persistently in the river -lake system (CHIKITA et al ., 1985 ;CHIKITA, 1986).…”

“…This shows that the lake sediments are mostly supplied from the western lake shore through sediment discharge of the influent rivers, especially the III river. From the observation of river induced density currents by CHIKITA et al (1985), the lake sedimentation is considered to be induced by river -induced turbidity currents during the torrential runoffs (CHIKITA, 1986). from off the IIriver mouth, the confluent turbidity currents are seen to flow down toward the maximum -depth region of lake with the concentration of suspended matters decreased by their deposition.…”