Estimated Emplacement Temperatures for a Pyroclastic Deposits From the Sundoro Volcano, Indonesia, Using Charcoal Reflectance Analyses

DOI: 10.17014/ijog.5.1.1-11This study applies the charcoalification measurement method to infer the emplacement temperature of pyroclastic flow deposits erupted from the Sundoro Volcano, Indonesia. This pyroclastic flow partially covered the Liyangan archeological site, a site where Hindu temples were constructed approximately 1,000 years ago. Five samples of charcoal collected from this area were analyzed for reflectance and elemental composition. Charcoalification temperatures were determined based on mean random optical reflectance values (Ro) plotted on published Ro-Temperature curves. Charcoalification temperatures were also estimated using a published formula based on the charcoal\u27s hydrogen to carbon (H/C) ratio. These two methods for determining pyroclastic flow deposition temperatures indicated that the pyroclastic deposits that entombed the Liyangan archeological site ranged from 295° to 487°C when they were deposited. This study used very simple, rapid, precise, and low-cost methods of charcoalification temperature measurement to infer the emplacement temperature of a pyroclastic deposit. This estimation procedure could be applied widely to predict emplacement temperatures in volcanic area in Indonesia to enhance volcanic hazard mitigation

Estimated Emplacement Temperatures for a Pyroclastic Deposits From the Sundoro Volcano, Indonesia, Using Charcoal Reflectance Analyses

DOI: 10.17014/ijog.5.1.1-11This study applies the charcoalification measurement method to infer the emplacement temperature of pyroclastic flow deposits erupted from the Sundoro Volcano, Indonesia. This pyroclastic flow partially covered the Liyangan archeological site, a site where Hindu temples were constructed approximately 1,000 years ago. Five samples of charcoal collected from this area were analyzed for reflectance and elemental composition. Charcoalification temperatures were determined based on mean random optical reflectance values (Ro) plotted on published Ro-Temperature curves. Charcoalification temperatures were also estimated using a published formula based on the charcoal\u27s hydrogen to carbon (H/C) ratio. These two methods for determining pyroclastic flow deposition temperatures indicated that the pyroclastic deposits that entombed the Liyangan archeological site ranged from 295° to 487°C when they were deposited. This study used very simple, rapid, precise, and low-cost methods of charcoalification temperature measurement to infer the emplacement temperature of a pyroclastic deposit. This estimation procedure could be applied widely to predict emplacement temperatures in volcanic area in Indonesia to enhance volcanic hazard mitigation

PENGELOMPOKAN GEOKIMIA MINYAK BUMI MENGGGUNAKAN METODE CHEMOMETRIC DI CEKUNGAN JAWA TIMUR UTARA

Penelitian dilakukan di Cekungan Jawa Timur Utara menggunakan 43 sumur yang terletak di onshore maupun offshore. Cekungan Jawa Timur Utara membentang dengan arah Barat hingga Timur dan merupakan cekungan yang terbukti menghasilkan minyak bumi. Minyak bumi pada cekungan ini sangat menarik untuk dipelajari untuk mengetahui karakter geokimia batuan induknya. Tujuan penelitian ini adalah untuk mengelompokan minyak bumi berdasarkan data geokimia menggunakan Metode Chemometric. Metode Chemometric dapat menganalisis data geokimia dalam jumlah yang banyak, sehingga sangat efisien dalam hal pengelompokan minyak bumi. Selain itu, analisis pengisian nilai kosong dengan metode Markov Chain Monte Carlo (MCMC) juga dilakukan karena keterbatasan data geokimia. Data geokimia yang digunakan adalah API gravity, sulfur, pristane, phytane, Tm/Ts, sterol, Ro, karbon senyawa jenuh, dan karbon senyawa aromatik. Berdasarkan analisis chemometric, kelompok minyak bumi pada daerah penelitian terbagi menjadi lima kelompok, yang terdiri dari Group 1, Group 2, Group 3, Group 4 dan Group 5. Group 1 memiliki berat jenis minyak berupa medium oil yang batuan induknya diendapkan pada lingkungan fluvio-deltaic; Group 2 memiliki berat jenis minyak berupa medium oil yang batuan induknya diendapkan pada lingkungan fluvio-deltaic; Group 3 memiliki berat jenis minyak berupa light oil yang batuan induknya diendapkan pada lingkungan fluvio-deltaic; Group 4 memiliki berat jenis minyak berupa heavy oil yang batuan induknya diendapkan pada lingkungan marine dan Group 5 memiliki berat jenis minyak berupa light oil yang batuan induknya diendapkan pada lingkungan fluvio-deltaic. Minyak bumi pada penelitian ini berasal dari batuan induk yang diendapkan pada lingkungan fluvio-deltaic hingga marine. Kata kunci: Geokimia, Minyak Bumi, Chemometric, Jawa Timur Utara