Hasil Pencarian  ::  Simpan CSV :: Kembali

Abstrak :
Pantai Bagedur berada di Kabupaten Lebak, Banten memiliki karakteristik sedimen yang diduga terendapkannya endapan tsunami purba. Daerah penelitian termasuk ke dalam Endapan Aluvium (Qa) dan Endapan Undak Pantai (Qc) pada Peta Regional Lembar Cikarang (Sudana & Santoso, 1992). Sampel sedimen lepas bawah permukaan diambil menggunakan metode lubang bor tangan pada delapan stasisun penelitian dengan kedalaman yang bervariasi. Penelitian kali ini berfokus terhadap studi provenance dari endapan tsunami purba dan juga karakteristiknya berdasarkan geokimia. Metode analisis yang digunakan berupa analisis petrografi, X-Ray Diffraction (XRD), dan X-Ray Fluorescence (XRF). Hasil analisis petrografi menunjukkan bahwa tipe provenance utama dari daerah penelitian menurut diagram Q-F-L dan Qm-F-Lt (Dickinson & Suzcek, 1979) adalah recycled orogen. Kerangka tektonik yang mempengaruhi dari tipe provenance recyceled orogen merupakan zona subduksi dan diinterpretasikan ada kaitannya dengan subduksi di selatan Pulau Jawa. Berdasarkan analisis XRD dan XRF, didapatkan bahwa didominasi oleh senyawa SiO2, Al2O3, dan Fe2O3 dan pada stasiun BG 06 memiliki unsur yang dominanas berasal dari Laut. Endapan tsunami mengalami erosi dan pelapukan yang cukup tinggi. ...... Bagedur Coast in Lebak Districts, Banten has sediment characteristic that assumed as deposit of paleotsunami deposit. The Research area consisted of Alluvium Deposit (Qa) and Beach Terrace Deposit (Qc) from Geological Map of Cikarang (Sudana & Santoso, 1992). Loose Sediment sample have collected using Hand Auger drilling methods from eight observation stations with various depth. This research is focused in provenance study from paleotsunami deposit and geochemistry characteristics. The method that used is petrography analysis, X-Ray Diffraction (XRD), and X-Ray Fluorescence (XRF). The result of petrography analysis show the type of provenance from research area according to Q-F-L dan Qm-F-Lt diagram (Dickinson & Suzcek, 1979) is recycled orogen. Geological setting that control provenance type of recycled orogen is subduction tectonic regime and interpreted to be related with subduction in South of Java. Based on XRD and XRF analysis, SiO2, Al2O3, and Fe2O3 are the dominating compound and from BG 06 station can be concluded the dominant deposit is originate from marine environment. Paleotsunami deposit have been undergone extreme erosion and weathering.

Abstrak :
Daerah penelitian berada pada Formasi Klapanunggal, Kecamatan Klapanunggal, Kabupaten Bogor, Provinsi Jawa Barat. Formasi Klapanunggal berumur Miosen Tengah hingga Miosen Akhir yang merupakan bagian dari Cekungan Jawa Barat. Daerah penelitian memiliki jenis litologi berupa batugamping. Tujuan dari penelitian ini adalah untuk menganalisis dan melakukan rekonstruksi lingkungan purba daerah penelitian. Metode penelitian terdiri dari pengukuran penampang stratigrafi, analisis petrografi, dan analisis mikropaleontologi. Pada daerah penelitian, terdapat klasifikasi fasies yang terdiri dari fasies Coral Framestone, Skeletal Floatstone, Larger Foraminifera Floatstone, dan Skeletal Rudstone. Keempat fasies tersebut berasosiasi dengan Platform-margin Reef dengan lingkungan zona koral yang terdiri dari back reef, reef front, dan fore reef. Berdasarkan analisis yang dilakukan, daerah penelitian memiliki rentang umur dari N9 hingga N16 (Zonasi Blow) dan Tf 1 hingga Tf 3 (Letter Stage) berdasarkan biozona dari foraminifera Asterorotalia yabei. Hasil rekonstruksi daerah penelitian menunjukkan lingkungan purba dengan karakteristik energi tinggi, intensitas cahaya mesofotik hingga oligofotik, salinitas euhalin hingga sedikit mengarah ke hipersalin, temperatur 18°C hingga lebih dari 25°C yang mengindikasikan iklim subtropis hingga tropis, dan kedalaman laut sekitar 0 meter hingga 70 meter. ...... The research area is located in Klapanunggal Formation, Klapanunggal District, Bogor Regency, West Java Province. Klapanunggal Formation is formed in Middle Miocene to Late Miocene which is part of the West Java Basin. The research area has type of lithology in the form of limestone. The purpose of this study is to analyse and reconstruct the paleoenvironment of the research area. The research method consisted of measuring section, petrographic analysis, and micropaleontological analysis. In the study area, there are facies classification consisting of Coral Framestone, Skeletal Floatstone, Larger Foraminifera Floatstone, and Skeletal Rudstone facies. The four facies are associated with the Platform-margin Reef with a coral zone environment consisting of the back reef, reef front, and fore reef. Based on the analysis conducted, the research area has an age range from N9 to N16 (Blow Zone) and Tf 1 to Tf 3 (Letter Stage) based on the biozone of the foraminifera Asterorotalia yabei. The results of the reconstruction of the study area show a paleoenvironment with high energy characteristics, mesophotic to oligophotic light intensity, euhaline salinity to slightly hypersaline, temperatures from 18°C ​​to more than 25°C indicating a subtropical to tropical climate, and sea depths of 0 to 70 meters.

Abstrak :
Nenering Formation is essentially made up of semi-consolidated sediments, which are divided into basal conglomerate beds, conglomeratic sandstone, cross-bedded sandstone, and siltstone to muddy layers facies. It is overlie unconformable to the Berapit Formation, but conformable to the Kroh and Grik Formations. The stratigraphy of Nenering Formation is a fining upwards sequence where the thickness of conglomerate beds become thinner upwards and become thicker for conglomeratic sandstone. The thickness varies from 0.5 m to tenths of meters. The more sandy in the upper portion (cross-bedded sandstone) overlie with thin siltstone and mudstone facies. The clast and grain composition suggested that the material making up the sedimentary sequence were derived predominantly from the erosion of granitoid rocks and sedimentary and metamorphic rocks constitute a minor provenance. Imbrications and the trend sizes of clasts indicate that the palaeo-current flow toward northeast. Cross bedding that was found in conglomerate and sandstone indicates the main channel depositional environment. The sequence stratigraphy of this area match with the Saskatchewan fluvial braided channel model.