Sutikno Bronto
Centre for Geological Survey, Geological Agency, Jln. Diponegoro No. 57 Bandung

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Journal : Jurnal Geologi dan Sumberdaya Mineral (Journal of Geology and Mineral Resources)

Geologi Gunung Padang dan Sekitarnya, Kabupaten Cianjur – Jawa Barat Bronto, Sutikno; Langi, Billy B.
Jurnal Geologi dan Sumberdaya Mineral Vol 17, No 1 (2016): Jurnal Geologi dan Sumberdaya Mineral
Publisher : Pusat Survei Geologi

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Abstract

Permasalahan arkeologi Gunung Padang mengemuka apakah sebagai punden berundak di atas batuan bentukan alam atau seluruhnya merupakan bangunan sebuah piramida buatan manusia. Untuk membantu menyelesaikan persoalan itu dilakukan penelitian geologi di daerah Gunung Padang dan sekitarnya. Berhubung daerah ini tersusun oleh batuan gunung api, maka metoda penelitian di dasarkan pada pemahaman geologi gunung api purba dan sejarah geologinya lebih memperhatikan perkembangan volkanisme setempat. Daerah Gunung Padang dan sekitarnya merupakan  perbukitan berketinggian 800 – 1200 m dml., terletak pada perpotongan sesar Cimandiri (WNW – ENE) dengan sesar Gede-Cikondang (NNW – SSE). Batuan penyusun dibagi menjadi enam satuan, yakni Breksi gunung api, Argilik-kuarsa-pirit,  Silisifikasi-urat kuarsa-limonitik, Intrusi andesit gunung Padang, Intrusi andesit pasir Pogor, dan aluvium. Satuan pertama merupakan batuan sisa kerucut komposit Gunung api purba Karyamukti. Kedua satuan batuan ubahan hidrotermal tersebar di dalam fasies pusat dan mewakili batuan terobosan dangkal tua. Satuan intrusi andesit Gunung Padang merupakan hasil erupsi termuda, membentuk leher gunung api yang ke permukaan menjadi sumbat/kubah lava berstruktur kekar kolom. Di sebelah utara Gunung api purba Karyamukti diterobos oleh andesit Pasir Pogor. Sebagai akibat proses geologi endogen dan eksogen sangat lama kekar kolom Gunung Padang semakin lama semakin renggang akhirnya batu kolom roboh berserakan. Oleh manusia masa lalu batu kolom itu kemudian ditata sebagai punden berundak untuk upacara pemujaan, yang sekarang dinamakan Situs Megalitik Gunung Padang. Kata kunci: gunung padang, gunung api purba, karyamukti, kekar kolom
IDENTIFIKASI GUNUNG API PURBA PENDUL DI PERBUKITAN JIWO, KECAMATAN BAYAT, KABUPATEN KLATEN – JAWA TENGAH Bronto, Sutikno
Jurnal Geologi dan Sumberdaya Mineral Vol 20, No 1 (2010): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

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Abstract

According to previous workers, Mount Pendul were considered as micro gabbro intrusive rocks. However, in the present quarry area pillow basaltic lava flows are exposed in the eastern slope of the hill. The lava was erupted through a paleoconduit below deep sea water, having massive to autoclastic breccias, obsidian in the glassy rims and gradually changes to apanetic texture in the inner part. Microscopically, the obsidian is devitrified to become spherulites, while to the inner part the basaltic rock gradually changes from vitrophyric to hypocrystallin porphyritic textures. On the basis of the volcanic geology idea, the association of those basic intrusive and extrusive rocks is believed to be a remnant of Pendul Paleovolcano that has been eroded through the time. The age of volcanisms, particularly in Bayat area and regionally in the Southern Mountains, can be divided into four periods, e.g. Paleocene, Late Eocene - Early Oligocene, Early Miocene and Middle Miocene. However, based on the range of radiometric ages and predominant volcanic rocks in the Southern Mountains, it is suggested that volcanisms had been continued from Late Eocene to Early Miocene. The oldest (Paleocene) and the youngest (Middle Miocene) radiometric ages should be verified in order to develop researchs on volcanism and tectonics in the Southern Mountains, Java.Keywords: bayat, java, jiwo, paleovolcano, pendul, southern mountains
Gunung Api Lumpur di Daerah Cengklik dan Sekitarnya, Kabupaten Boyolali Provinsi Jawa Tengah Bronto, Sutikno; Asmoro, Pudjo; Efendi, Mutiara
Jurnal Geologi dan Sumberdaya Mineral Vol 18, No 3 (2017): Jurnal Geologi dan Sumberdaya Mineral
Publisher : Pusat Survei Geologi

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Abstract

District of Boyolali and surrounding area have manifestation of an old mud volcano deposits which is locally exposed in E-W direction, about 20 km length and 3-5 km wide, start from Cengklik Lake until western side of Solo River. The mud volcano deposits have clay-silt size and sand-gravel of scoriaceous basaltic andesite in Gununglondo village. Materials below the mud deposits are composed by dike or sills-like rocks which penetrate within the sediment layer and fill the fracture formed a diapiric and mud ball structure, whereas the loss materials tend to leave diatremal traces and surficial deposits. Data showed in this research illustrate the mud movement from subsurface to the earth surface which is comparable with volcanic eruptions. After reaching the surface, mud deposits form layers with some slight folded and faulted structure. Cengklik Lake depression is presumed to be paleo mud volcano crater. Cengklik and surrounding areas are rapidly develop due to the existence of Adisumarmo international airport and construction of Solo-Semarang–Surabaya toll road. Considering the geological condition below Cengklik and surrounding area, which is composed by mud volcano deposits and experienced many fracture, they assumed to be a weak zone. The main potential geological hazard is the surface deformation along the toll road because of its low capability to endure the road construction and vehicle weight. Other potential hazards are groundwater pollution, earthquake, and mud volcano reactivation. Therefore, sustainable research and geological hazard mitigation of Cengklik and surrounding areas are necessary to do. keywords: mud volcano, Cengklik, Boyolali, geological hazards, mitigation 
LONGSORAN RAKSASA GUNUNG API MERAPI YOGYAKARTA – JAWA TENGAH Bronto, Sutikno; Ratdomopurbo, Antonius; Asmoro, Pudjo; Adityarani, Malia
Jurnal Geologi dan Sumberdaya Mineral Vol 15, No 4 (2014): Jurnal Geologi dan Sumberdaya Mineral
Publisher : Pusat Survei Geologi

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Abstract

Longsoran raksasa merupakan longsoran sangat besar kerucut gunung api komposit ke arah tertentu sehingga membentuk kawah bukaan tapal kuda, yang dihadapannya terlampar endapan berbentuk topografi gumuk. Penyelidikan lapangan di daerah Godean dan sekitarnya, Kabupaten Sleman Yogyakarta telah menemukan endapan longsoran raksasa dari G. Merapi, yang membentuk topografi gumuk di tepi utara perbukitan batuan gunung api purba Godean. Sebaran sisa endapan longsoran Merapi itu menutupi area berukuran 2 km x 2 km dan ketinggian gumuk kurang dari 30 m di atas dataran di sekitarnya. Endapan longsoran masih sangat lepas, berupa fasies bongkah berlapis, yang tersusun oleh endapan piroklastika, aliran lava dan endapan rombakan. Seluruh endapan mengalami frakturasi sangat kuat, membentuk rekahan gergaji dan sesar minor sebagai akibat gerakan longsor. Endapan longsoran ini dapat terawetkan karena membentur dan tertahan oleh perbukitan batuan Tersier Godean. Dari G. Merapi sampai Godean endapan longsoran itu bergerak sejauh 30 – 35 km dengan volume mencapai 10 km3 dan daerah terlanda mencapai 300 km2. Ke arah selatan, material longsoran berubah menjadi aliran lahar, yang melanda daerah Bantul sampai di wilayah Pandak, berjarak 50 km dari G. Merapi. Di bagian barat lahar mengalir melalui K.Progo dan di sebelah timur mengikuti K. Bedog. Di bagian tengah endapan lahar tertahan oleh perbukitan batuan Formasi Sentolo sehingga menyisakan banyak bongkah besar andesit di wilayah Sedayu. Untuk mengantisipasi terulangnya bencana katastrofik longsoran G. Merapi pada masa mendatang diperlukan mitigasi yang lebih seksama.Kata kunci: Godean, longsoran raksasa, lahar, Merapi, Yogyakarta
Volkanostratigrafi Inderaan Jauh Kompleks Gunungapi Gede dan Sekitarnya, Jawa Barat, Indonesia Agustin, Fitriani; Bronto, Sutikno
Jurnal Geologi dan Sumberdaya Mineral Vol 20, No 1 (2019): Jurnal Geologi dan Sumberdaya Mineral
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (196.166 KB) | DOI: 10.33332/jgsm.geologi.20.1.9-16

Abstract

Remote sensing technology greatly helps to identify the various of volcano features, including active, old and ancient volcanoes. The aim of this  paper is intended to introduce various volcanic features in the Gede Volcano Complexs (GVC) and souronding area; compose volcanostratigraphy; and estimate the history of the volcanoes. The method used is a visual interpretation 9 meters spatial resolution of Digital Elevation Model (DEM) TerraSar-x image. Indonesian Stratigraphy Nomenclature Guide 1996 was implemented in vocanostratigraphy unit classification, involving Arc, Super Brigate, Brigate, Crown and Hummockly. Based on the interpretation the DEM image, volcanostratigraphic unit the Gede Volcano Complex consists of Bregade Masigit (Br. M.), which consists of Joklok (Gm.J.) and Gegerbentang (Gm.G.) Hummocs; Crown Lingkung (Kh.L.) consisting of Pangrango (Gm.P.), Situ Gunung (Gm Sg.), Cikahuripan (Gm.Ck.), Pasir Prahu (Gm.Ph) Hummocs; Gege Crown (Kh.G.), which is located in the east of Lingkung Crown. The Gede Crown consists of Gumuruh humock (Gm.Gh.), Gunung Gede lava flows (LG 1,2,3,4,5), and giant debrise avalances (gv-G). The geological mapping based volcanostratigraphy is very useful for exploration of mineral and energy resources, as well as geological hazards.Keywords : volcanostratigraphy, DEM TerraSar-x image, Gunung Gede Complexs.DOI: 10.33332/jgsm.2019.v20.1.9-16