Rock Magnetism and Geochemical Analysis of Paleoenvironmental Sediment in Kabuh and Pucangan Formations: Sangiran, Central Java, Indonesia Muhammad Irfan Nawawi (a), Shandiyano Putra (a), Budi Legowo (a), Wiwit Suryanto (b), and Budi Purnama (a*)
a) Physics Department, Universitas Sebelas Maret, Jawa Tengah 57126, Indonesia
*bpurnama[at]mipa.uns.ac.id
b) Physics Department, Universitas Gadjah Mada, Daerah Istimewa Yogyakarta 55281, Indonesia
Abstract
Research on the characteristics of paleoenvironmental sediments in Sangiran is very important. Sangiran is located north of the Solo zone and south of the Kendeng zone, which is the center of the Java Basin, where rapid sediment deposition occurred during the Miocene to Pleistocene epochs. This indicates that the depositional environment in Sangiran is very complex. The aim of this study is to identify the characteristics of the sedimentary environment in Sangiran using its magnetic properties. Magnetic properties stored in sediments and rocks have specific characteristics as fingerprints of ancient volcanic activity. The rock magnetism method combined with geochemical analysis was applied in this study. The results of this study indicate positive magnetic susceptibility values, ranging from 6.42\times10^{-3} to 122\times10^{-3} SI in the Pucangan formation, and 12.63\times10^{-3} to 142.67\times10^{-3} SI in the Kabuh formation. XRF analysis of samples with the highest magnetic susceptibility values shows that the dominant elements in both outcrops are Fe (33.6 percent in Pucangan, 26.6 percent in Kabuh) and Si (37.18 percent in Pucangan, 42.36 percent in Kabuh). XRD analysis shows the presence of magnetite and hematite minerals in both samples. The \chi_{fd} value from MS2B analysis is 0.1 to 0.86 percent which indicates the presence of magnetic multidomains. The Kabuh Formation reflects a dynamic river depositional environment and is strongly influenced by volcanic activity, while the Pucangan Formation depicts a quieter depositional environment, most likely a lake, with more limited volcanic influence.
Keywords: Rock Magnetism- Geochemical Analysis- Sangiran- Paleoenvironmental
