KARAKTERISTIK BATUAN VULKANIK BERDASARKAN ANALISIS PETROGRAFI DAERAH TANGKIT SERDANG, TANGGAMUS, LAMPUNG

Abstract

ABSTRAK: Secara Administratif daerah penelitian berada di daerah Tangkit Serdang, Kabupaten Tanggamus, Provinsi Lampung. Daerah penelitian didominasi oleh endapan vulkanik yang terdiri dari, Satuan Breksi Vulkanik, Sataun Tuff dan satuan lava andesit. Hal inilah yang mendasari dilakukannya penelitian mengenai karakteristik batuan vulkanik yang terdapat di daerah penelitian. Metode penelitian berupa pengumpulan data lapangan serta untuk mengetahui karakteristik batuan vulkanik pada daerah penelitian, dilakukan analisa petrografi di bawah mikroskop sehingga didapatkan struktur, tekstur dan komposisi pada batuan. Dari hasil data lapangan ini didapatkan sebanyak 7 sampel batuan diambil secara acak yang mewakili luasan daerah penelitian, terdiri dari 4 sampel batuan breksi vulkanik, 2 sampel batuan tuff dan 1 sampel batuan lava andesit. Hasil analisis petrografi ini menunjukkan bahwa batuan vulkanik di daerah penelitian, pada foto mikrograph memperlihatkan struktur vesicular glass dengan tekstur Pilotaxitic yang mengindikasikan bahwa material vulkanik kuarter di daerah penelitian berasal dari erupsi lelehan yang mengeluarkan material klastika yang kemudian terendapkan secara aliran (flow). Hal ini didukung oleh morfologi daerah penelitian yang dikontrol oleh lereng perbukitan dengan pola aliran yang cenderung paralel. Dengan didukung beberapa aspek seperti litologi, geomorfologi dan interpretasi penyebaran material vulkanik dari pusat erupsi, didapatkan bahwa daerah penelitian diperkirakan masuk ke dalam fasies proksimal – fasies medial.

Kata Kunci: Tanggamus, karakteristik, batuan vulkanik, petrografi

ABSTRACT: Administratively the research area is located in the Serdang Tangkit area, Tanggamus Regency, Lampung Province. The research area is dominated by volcanic deposits consisting of, Volcanic Breccia Unit, Sataun Tuff and andesite lava units. This is what underlies the study of the characteristics of volcanic rocks found in the study area. Research methods in the form of field data collection and to determine the characteristics of volcanic rocks in the study area, petrographic analysis was carried out under a microscope so that the structure, texture and composition of the rocks were obtained. From the results of this field data, 7 rock samples were taken at random representing the area of the study area, consisting of 4 volcanic breccia rock samples, 2 tuff rock samples and 1 andesite lava rock sample. The results of this petrographic analysis show that volcanic rocks in the study area, on photo micrographs show a vesicular glass structure with Pilotaxitic texture which indicates that the quarterly volcanic material in the study area originates from melted eruptions which release clastic material which then is deposited by flow. This is supported by the morphology of the study area which is controlled by hilly slopes with parallel flow patterns. With the support of several aspects such as lithology, geomorphology and interpretation of the spread of volcanic material from the eruption center, it was found that the study area was estimated to enter into the proximal facies - medial facies.

Keywords: Tanggamus, characteristics, volcanic rocks, petrography