Tuf Banten (Qpvb) adalah endapan piroklastik hasil erupsi eksplosif gunung api di sekitar Selat Sunda pada zaman Kuarter yang tersebar luas di Banten. Penelitian skripsi dilakukan di daerah Kecamatan Kragilan dan Sekitarnya, Kabupaten Serang, Provinsi Banten. Daerah penelitian termasuk dalam Peta Geologi Lembar Serang oleh Rusmana dkk. (1991). Secara keseluruhan penelitian ini menggunakan metode analisis foto udara, kegiatan lapangan, analisis distribusi ukuran butir, analisis komponen, dan petrografi. Luaran dari penelitian ini adalah karakteristik fisik Tuf Banten dan mekanisme erupsinya. Berdasarkan hasil penelitian yang telah dilakukan, terdapat 7 litofasies yang dikelompokkan berdasarkan karakteristik endapan, yaitu T29, LT20, LT26, T24, A29, A24, dan LA20. Orientasi kemiringan (dipping) dari singkapan menunjukkan ke arah barat daya dan singkapan di barat daya juga cenderung lebih tak terkonsolidasi. Hasil analisis distribusi ukuran butir berupa diagram plotting median diameter (φ scale) dan standar deviasi (φ scale) yang digunakan untuk menentukan mekanisme erupsi dan berkaitan dengan sortasi endapan. Dari distribusi nilai puncak ukuran butir, litofasies T29, LT26, A29, dan A24 memiliki sebaran nilai puncak unimodal dan litofasies LA20 adalah polimodal. Hasil analisis komponen dan petrografi menunjukkan dominasi batuapung dengan kehadiran rata-rata 90%. Berdasarkan dominasi batuapung tersebut dapat diinterpretasikan erupsi yang terjadi di daerah penelitian adalah tipe magmatik. Sejarah pada daerah penelitian terbagi menjadi 3 episode erupsi, yaitu episode 1 ditandai oleh terjadinya erupsi magmatik pertama dengan mekanisme piroklastik jatuhan, aliran, dan surge. Selanjutnya episode 2 ditandai oleh terjadiya erupsi magmatik kedua dengan mekanisme piroklastik jatuhan, dan episode 3 ditandai oleh terjadinya erupsi magmatik ketiga dengan mekanisme piroklastik jatuhan, aliran, dan surge.
Banten Tuff (Qpvb) is a pyroclastic deposit from an explosive volcanic eruption around the Sunda Strait during the Quaternary period which is widespread in Banten. This research was held in the Kragilan District and its surroundings, Serang Regency, Banten Province. The research area is included in the Geological Map of Lembar Serang by Rusmana et al. (1991). The methods used are imagery analysis, field work, grain-size distribution analysis, component analysis, and petrography. The output of this research is the characteristics of the Banten Tuff and its eruption mechanism. Based on the results that has been carried out, there are 7 lithofacies based on the characteristics of the deposits, namely T29, LT20, LT26, T24, A29, A24, and LA20. The dipping orientation shows to the southwest and the outcrop in the southwest also tends to be unconsolidated. The results of the grain-size distribution analysis are plotting diagrams of the median diameter (φ scale) and deviation standard (φ scale) which are used to determine the eruption mechanism and relate to pyroclast sorting. From the distribution of grain size peak values, lithofacies T29, LT26, A29, and A24 had a unimodal peak value distribution and lithofacies LA20 were polymodal. The results of component analysis and petrography show the dominance of pumice with an average presence of 90%. Based on the dominance of the pumice, it can be interpreted that the eruption that occurred in the study area was magmatic type. The history of the study area is divided into 3 eruption episodes, namely episode 1 marked by the occurrence of the first magmatic eruption with pyroclastic fall, flow, and surge mechanism. Furthermore, episode 2 is marked by the occurrence of a second magmatic eruption with a pyroclastic fall mechanism, and episode 3 is marked by the occurrence of a third magmatic eruption with pyroclastic fall, flow, and surge mechanism. |
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