Sulawesi was formed during the Oligocene-Miocene collision between the Eurasian Plate and microcontinental fragments detached from the Indian-Australian Plate. The Sengkang Basin situated on the South Sulawesi Province, was formed by a major north northwest-south southeast trending fault system of the Walanae Fault Zone, which was followed by the formation of Late Neogene foreland basin and syn-orogenic deposition. The fault system separated the eastern and western parts of South Sulawesi and influenced the deposition during the Late Miocene to Quaternary. The lower part of the deposition unit consists of small carbonate reefs of the Tacipi Member occupying the East Sengkang Basin, where this shallow marine facies is intercalated within or overlies marine claystones representing the base of the Walanae Formation. The middle sequence is interpreted as a delta foreset consisting of the Samaoling and Beru Members. During the deposition of these two members, the northern part of the Sengkang Basin gradually changed from a tidal and deltaic to fluvial environments. Furthermore, the upper sequence of this sedimentary unit is dominated by fluvial deposits.
This 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's 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.
Formasi batuan pembawa-batubara di daerah Lampung Tengah terletak di tepi batas cekungan atau bagian barat Cekungan Sumatra Selatan, dan secara fisiografi berada di dalam Lajur Palembang yang berbatasan langsung dengan ujung selatan Lajur Barisan.Fasies batuan di bagian bawah adalah konglomerat, batupasir konglomeratan, dan batupasir kuarsa. Di bagian atas terdiri atas perselingan batulanau, serpih, batulempung, batulumpur, batugamping, dan batubara dengan sisipan serpih batubaraan serta batubara serpihan. Satuan fasies batuan pembawa-batubara diyakini merupakan bagian Formasi Talangakar berlingkungan pengendapan mulai dari fluviatil -paralik, yang semakin ke atas berubah menjadi sublitoral, dan berumur Oligo-Miosen. Kondisi lingkungan ini berpengaruh kuat terhadap karakter dan jenis batubara yang terbentuk.Secara stratigrafi, runtunan batuan ini ditindih selaras oleh satuan batugamping berumur Miosen Awal -Tengah, dan diterobos oleh granodiorit berumur Miosen Tengah -Akhir. Batuan dasar runtunan batuan sedimen berumur Tersier ini adalah batuan malihan Kelompok Gunungkasih dan granit berumur Kapur.Sesar normal berarah barat laut -tenggara mengontrol daerah penelitian, dan mempengaruhi kemiringan lapisan batubara ke arah utara -timur, dengan besar sudut kemiringan 15º -23º. Batubara di daerah penelitian terendapkan dalam lingkungan hutan berawa basah, pada saat susut laut dengan tingkat penurunan yang tinggi sampai menengah. Batubara ini termasuk ke dalam peringkat bituminus high volatile sampai low volatile, sementara kematangan termalnya termasuk dalam kategori matang.
Formasi Bobong adalah suatu runtunan batuan sedimen klastika kasar yang terdiri atas fasies runtunan breksi dan konglomerat di bagian bawah, diikuti oleh fasies batupasir kuarsa dengan sisipan batulempung, dan menerus ke atas menjadi suatu fasies perselingan batuan klastika halus berupa serpih, batulempung, dan batulumpur. Formasi batuan ini tersingkap baik di bagian barat dan utara Pulau Taliabu, Kepulauan Sanana-Sula. Formasi ini berumur Jura dan diendapkan di lingkungan fluviatil, peralihan, sampai laut dangkal. Lapisan batubara terdapat pada fasies batupasir kuarsa, serpih, dan batulempung-batulumpur yang merupakan bagian atas runtunan Formasi Bobong. Batubara di Pulau Taliabu ada dua lapisan dengan ketebalan 30-40 cm dan 100-120 cm. Analisis geokimia batubara menghasilkan nilai kalori yang berkisar dari 6.715 sampai 7.350 kal/g, kandungan belerang dari 3% sampai 4,65%, karbon padat berkisar dari 45,69-53,96%, dan kadar abu dari 7,86-16,37%. Berdasarkan parameter tersebut di atas, batubara Formasi Bobong memiliki peringkat subbituminous sampai high volatile bituminous.
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