CHARACTERIZATION OF CALDERA LAKE’S SEDIMENTS THROUGH ROCK MAGNETISM AND GEOCHEMICAL ANALYSES CASE STUDY: LAKES BUYAN AND TAMBLINGAN ON THE ISLAND OF BALI

• Main Author: Komang Tri Suandayani, Ni
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/79440
• Institution: Institut Teknologi Bandung

Industrial and agricultural activities, as well as settlements, have changed much of the lake's environment, as recorded in lake sediments. In this study, concentrations of trace metals and rare earth elements (REE) as well as low frequency mass specific magnetic susceptibility ( ???????????? ) are used to explain the anthropogenic components associated with religious activities in Lake Buyan and Tamblingan on the island of Bali. Balinese residents, who are predominantly Hindu, hold various religious activities in temples, around the lake. There are 8 temples on Lake Tamblingan and 3 on Lake Buyan. Measurement of surface sediment at 20 points in Lake Buyan and 16 points in Lake Tamblingan. From magnetic analysis, it shows that the value of ( ???????????? ) and the concentration of trace metals and REE in Lake Tamblingan is higher than in Lake Buyan, using susceptibility Frequency dependent magnetic (?FD%) sediment characteristics in both lakes are almost the same, with the presence of superparamagnetic (SP) grain concentrations in the range of 2–10% classified as a mixture of SP and non SP grains, indicated that the magnetic minerals in the sediments in both lakes originate from diagenetic processes controlled by natural factors (lithogenic) and anthropogenic factors such as religious activities. Meanwhile, the results of geochemical analysis show that all elements are high in Lake Tamblingan, except for the content of the element Gadolinium (Gd), which is higher in Lake Buyan. Magnetic susceptibility ( ???????????? ) in both lakes is well correlated with all elements except for Silicon (Si) which is very weakly inversely correlated in Lake Buyan. But in Lake Tamblingan, Silicon (Si) and Yttrium (Y) are weakly correlated. The undetectable presence of Cu and Zn in rocks from the mountains around the lake implies that the surface sediments of Buyan and Tamblingan Lakes record anthropogenic activities, especially religious activities observed close to the temple. The content of Cu and Zn elements is dominant in Lake Tamblingan compared to Lake Buyan because there are more temples, so the intensity of religious activities is greater. Meanwhile, in Lake Buyan, the Gadolinium (Gd) element is more dominantly related to anthropogenic emissions such as residential emissions, agriculture and the ( ???????????? ) value of rock samples is high, which is igneous rock which contributes to surface sediments in both lakes. The water in both lakes is peripheral water.