Mineralogy, geochemistry, and genesis of glauconite mineral from paleotsunami deposit in Lebak, Banten, Indonesia

Abstract

Bagedur coast in Lebak regency, Banten province, Indonesia is part of lowland-swampy swale area that consist of various sediment deposit. Based on its sediment characteristics and geomorphology profile, Bagedur coast is assumed as depositional environment of paleotsunami deposit. Hand Auger drilling method is used to collecting loose sediment sample from eight observation stations. The depth of hand drilling in BG 01 station to BG 08 station is consecutively as follows: 115 cm, 100 cm, 80 cm, 700 cm, 400 cm, 450 cm, 160 cm, and 143 cm. This research is carried out to understand the diagenetic process of glauconite mineral in presumption paleotsunami deposit. The diagenetic process of glauconite mineral is identified based on its mineralogical and geochemical characteristics by petrography and X-Ray Fluorescence (XRF) methods. Observation samples is taken from green sand sediment bed in hand drilling core. Petrographic analysis under polarized microscope shows various glauconite mineral which recognized as matrix, oval pellets, replacement of precursor mineral, and bioclastic shell infillings. XRF analysis result show that glauconite in observation site are classified as glauconitic-illite type. The diagenetic stage is interpreted as early stage of diagenetic (nascent) which characterized by low Fe2O3 and K2O content relative to Al2O3 content.