IDENTIFIKASI DAN REKONSTRUKSI FASIES GUNUNG MERAPI
PROVINSI DAERAH ISTIMEWA YOGYAKARTA
IDENTIFICATION AND RECONSTRUCTION
OF THE PROVINCE YOGYAKARTA OF MOUNTAIN MERAPI FACIES
Muhammad Adam, Ulva Ria Irfan, Irzal Nur
Jurusan Geologi, Fakultas Teknik, Universitas Hasanuddin
Alamat Korespondensi:
Jalan Toddopuli VII Stp 3 No.69 Makassar
Muhammad Adam
HP: 0813 4242 9074
ABSTRAK
Material hasil letusan gunungapi merupakan informasi yang sangat berharga untuk mengetahui fasies dan urutan proses kejadian gunungapi. Penelitian ini bertujuan mengindentifikasi dan merekonstruksi fasies Gunung
Merapi di Provinsi Daerah Istimewa Yogyakarta. Metode yang digunakan adalah pendekatan yang
mengkombinasikan antara penelitian kualitatif dan kuantitatif. Metode penelitian yang diterapkan adalah metode induktif, dengan memadukan hasil-hasil kajian pustaka, penelitian terdahulu, data lapangan, serta hasil-hasil penelitian laboratorium, yang keseluruhannya dikaji, dianalisis, dan disintesis secara komprehensif untuk mendefinisikan kesimpulan tentang fasies Gunung Merapi di Provinsi Daerah Istimewa Yogyakarta. Hasil penelitian menunjukkan bahwa fasies Gunung Merapi terbagi atas 4 fasies, yaitu fasies sentral, fasies proksimal, fasies medial, dan fasies distal. Pada zona sentral, sebagian penciri utama fasies sentral dijumpai, seperti topografi yang terjal yang mengindikasikan zona kubah lava, basal porfiri yang diinterpretasi sebagai anggota batuan intrusi dangkal, serta orientasi kedudukan perlapisan batuan yang mencirikan struktur vulkanik; fasies ini berjarak 1 km dari pusat erupsi. Fasies proksimal dicirikan dengan breksi vulkanik, tufa dan lahar, topografi yang terjal, dip perlapisan 30°-35°, dan struktur vulkanik; berjarak 6 km dari batas selatan fasies sentral. Fasies medial dicirikan dengan lapili dan tufa kasar, topografi pedataran bergelombang, dip perlapisan 15°-20°, dan struktur vulkanik; berjarak 16,86 km dari batas selatan fasies proksimal. Fasies distal dicirikan dengan tufa halus, tufa kasar, lava basal, breksi vulkanik, dan batugamping kristalin, topografi relatif datar, dip perlapisan 5°-10°, dan intensifnya struktur tektonik; berjarak 20,56 km dari batas selatan fasies medial.
Kata kunci: identifikasi, rekonstruksi, fasies volkanik, Gunung Merapi
ABSTRACT
Results of volcanic materials were the important information to known facies and series itself. The objectives of this study are to identify and reconstruct volcanic facies of the Merapi Volcanic (Gunung Merapi) in the Special Province of Yogyakarta. Methods applied is an approach that combines qualitative and quantitative research. This is an inductive method which covers literature review, previous studies, field data, and laboratory work results, which were comprehensively reviewed, analyzed, and synthesized to define a conclusion about volcanic facies of Gunung Merapi in the Special Province of Yogyakarta. The study indicates that volcanic facies of
Gunung Merapi can be divided in four facieses, namely central facies, proximal facies, medial facies, and distal fasies. In the central zone, some of typical characteristics of central facies were identified, such as steeply topography which is indicates a lava dome, pophyritic basalt which were interpreted as a member of hypabisal intrusion, and orientations of the volcanic rocks which indicate a volcanic-related structure; this facies entends about 1 km from the eruption centre. Proximal facies is characterized by volcanic breccia, tuff and lahar, steeply topography, dip range of 30°-35°, and indication of volcanic-related structure; extends about 6 km from south end of the central facies. Medial facies is characterized by lapilli and coarse-grained tuff, topografi pedataran bergelombang wavy flat topography, dip range of 15°-20°, and volcanic-related structure; extends about 16,86 km from south end of the proximal facies. Distal facies is characterized by fine-grained tuff, coarse-grained tuff, basalt lava, volcanic breccia, and crystalline limestone, nearly-flat topography, dip range of 5°-10°, and an intensity of tectonic-related structure; extends about 20,56 km from south end of the medial facies.