IDENTIFICATION OF THE CHARACTERISTICS OF PALEOTSUNAMI DEPOSITS IN THE LUMAJANG AND SURROUNDING AREAS, EAST JAVA PROVINCE

• Main Author: PAMUNGKAS , GILANG
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/27527
• Institution: Institut Teknologi Bandung

<p align="justify">Indonesia is a country that has active volcanism and seismic activities, so that Indonesia is vulnerable to natural disasters. The southern Java region has at least two areas which are thought to be seismic gaps, which makes the south Java region an area that has the potential to cause a tsunami. The Lumajang and surrounding areas are the areas that near by the subduction zone and has a low and flat relief, so that Lumajang and surrounding areas are a good location to preserve paleotsunami deposits. Paleotsunami research is needed to find out the seismic history and the occurrence of tsunamis that have occurred in the south of Java. The research was carried out by taking the 200 cm depth sediments samples in the field and continued with laboratory analysis in the form of granulometry analysis, XRF (X-Ray Fluoresence) analysis, micropaleontology analysis, and palinology analysis. <br /> <br /> Two candidate of paleotsunami layers were archived in sediments on the swale morphology. The layer lie on the interval of 100 cm - 127 cm and 71 cm - 87 cm with the discovery of rip-up clast and erosional contact with the paleosoil layer at the bottom. Grain size analysis showed that the Paleotsunami A layer has a thickness of 17 cm with coarse silt - very fine sand grain size range, very poorly sorted, fine skewed - coarse skewed, kurtosis in platykurtic types, and bimodal frequency distribution curves. While the Paleotsunami B layer has a thickness of 16 cm with grain size of rough silt - fine sand, very poorly sorted, very fine skewed - symmetrical, kurtosis on platykurtic - leptokurtic types, and bimodal frequency distribution curves. XRF analysis shows that the paleotsunami layers A and B have increased elements of Ca and Sr which are the marine environment elements. Bentonic foraminifera (Bulimina sp.) and shell fragments were found in the paleotsunami A layer. While in the paleotsunami B layer found planktonic foraminifera (Globigerinoides ruber, Globigerinoides trilobus, Neogloboquadrina dutertei), bentonic foraminifera (Bolivina sp., Spiroloculina sp., Triloculina sp.), radiolaria, and shell fragments. The abundance of pollen and spores in paleotsunami deposits have a significant decline in number and the discovery of marine palinomorphs (Dinoflagellata cyst) in these deposits.<p align="justify">