THE CHARACTERIZATION OF 1968 HISTORICAL TSUNAMI DEPOSIT IN SIRENJA, DONGGALA REGENCY, CENTRAL SULAWESI BASED ON GRANULOMETRY, GEOCHEMISTRY, AND MICROFAUNA ANALYSIS

• Main Author: Yuniar Winangsih, Berliana
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/42144
• Institution: Institut Teknologi Bandung

Sirenja area is a part of Donggala Regency that is situated in coastal area of Central Celebes. This area is affected by some tsunamis that have occurred in Donggala and Palu. One of tsunami that occurred in Sirenja is tsunami in August 14, 1968. The research about 1968 historical tsunami and paleo-tsunami in Sirenja was performed by granulometry, geochemistry (X-ray Fluorescence and Loss on Ignition), and micro-fauna analysis on hand drill sample LBN-11. The research area is a swale environment. Based on field identification, it was found two candidates of tsunami deposits with the youngest deposit was the result of tsunami in August 14, 1968. It was proven by the eyewitness who experienced the tsunami. Both tsunami deposits have lighter colors than another deposit layers. Historical tsunami 1968 deposit has coarse sand grain size with andesite, granite, mica schist, coral and shell fragments with poorly sorted sediments. In Paleotsunami deposit, it has coarse silt – medium sand grain size with poorly sorted sediments and andesite, quarzite, granite and coral fragments. Both tsunami deposit has erosional contact with the layer below. Granulometry analysis results show that both tsunami deposits have sand size matrix that have unimodal, bimodal, and trimodal distribution which characterize as different sources of sediments that brought by tsunami wave. Ca, Sr, K, Zn, Zr as marker to the marine environment in both tsunami deposit increase compared to the layer below meanwhile Fe and Ti as marker to the land environment decrease relatively to layer below. In 1968 historical tsunami deposit carbonate material has higher percentage than organic material that decrease relatively to the layer below. It also found micro-fauna from inner neritic until coastal environment and marine material such as coral fragments that show a transportation material from marine to swale environment, different with 1968 historical tsunami, paleo-tsunami deposit has lower carbonate material than the organic material, but from the graphic the organic material decreases to the layer below. In paleo-tsunami deposit, there is no micro-fauna found, but there still coral fragments which is mean there was marine material transportation to swale environment. Tsunami deposit in core LBN-11 has same criteria with another tsunami deposit that has been observed by previous researcher.