Original paper

Dating of lacustrine sediments from the tropical maar Ranu Klindungan, East Java (Indonesia)

Pirrung, Michael; Büchel, Georg; Schulte-Vieting, Ulrich; Scharf, Burkhard W.; Treutler, Hanns-Christian

Abstract

Ranu Klindungan is a 126 m deep maar lake near Pasuruan, East Java, Indonesia. Profundal sediments down to 1.06 m sediment depth consist of calcareous diatom gyttja with frequent turbidites. Distinct seasonal climatic variations are reflected by high magnetic susceptibility of terrigenic layers deposited during the rain season (November–April) and by low magnetic susceptibility of diatom gyttja layers with thin distal turbidites, deposited during the dry season (May–October). Within the diatom gyttja, sublayers of diatom valves and calcite crystals represent episodic algal blooms after partial mixis events and not annual laminae (varves). The linear sedimentation rate (5 cm/yr) determined by correlation of cores taken in 1998 and 2003 is unusually high for maar lake sediments. This results from the connection to a large catchment area on the northern slope of the Tengger Massif via an artificial inflow. Since 1986, when a dam controlling the lake level was raised by one meter, the terrigenic content strongly decreased while diatom valves increased. This is a consequence of increasing eutrophication by fish farming in the lake and of less suspension input through the artificial inflow. During rain seasons with a lake level highstand the hydraulic gradient between lake level and artificial inlet is lower than before 1986.

Keywords

maar lake sedimentsmagnetic susceptibilitysedimentation rateeast java