H. Moechtar, H.
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KONTROL SIRKULASI IKLIM DAN TEKTONIK TERHADAP ENDAPAN SEDIMEN SUNGAI PURBA BERUMUR PLISTOSEN DI DESA MULYASEJATI, KARAWANG DAN CILANGKAP, PURWAKARTA Moechtar, H.; Subiyanto, Subiyanto
Jurnal Geologi dan Sumberdaya Mineral Vol 21, No 2 (2011): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

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Abstract

A study on the conglomeratic sandstone and siltstone unit (Qoa) in the Mulyasejati Village (Kabupaten Karawang) and Conglomeratic and tuffaceous sandstone unit (Qav) of Pleistocene age in the Cilangkap Village (Kabupaten Purwakarta) has been carried out. The objectives of this paper are to reconstruct the mechanism of Depositional Period Intervals (DPI) of each lithologic unit. Sedimentological and stratigraphical analyses were carried out in the field based on seven vertical measured section of 1:50 scales. The thickness of the sections range from 1.20 to 7.70 m. Based on the correlation, both of lithostratigraphic units belong to into fluvial systems, and can be divided into four DPI (A to D). The sedimentary facies pattern of each DPI is controlled by the thrust structure, and are shown by stacking channels (FAS) 1 to 4. Whereas, the vertical composition of sediment is controlled by the fluctuation humidity related to climate change following Milankovitch cycles. Changes in the colour and composition of the sediments of the fluvial systems during the depositional processes of DPI A-D, can be interpereted as the result of climate changes. The climate circulations starting from nearly climatic optimum to climatic minimum or even dry.Keywords: facies, fluvial, climate, Interval of Deposition Periods
SEDIMENTOLOGI DAN STRATIGRAFI ENDAPAN SUNGAI CITARUM DI WILAYAH PERALIHAN MORFOLOGI PEGUNUNGAN DAN DATARAN TINGGI BANDUNG ANTARA DESA CIKAWAO DAN DESA NAGRAK (KEC. PACET) DAN DESA SUKAMAJU (KEC. MAJALAYA), KAB. BANDUNG Moechtar, H.
Jurnal Geologi dan Sumberdaya Mineral Vol 21, No 4 (2011): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

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Abstract

Citarum River deposits, which located at near Cikawao and Nagrag villages (Sub-district of Pacet) and Sukamaju village (Sub-district of Majalaya), Bandung District, consist of cobbles to boulders, sands to pebbles, sands, and clays. The research was carried by analysed sedimentology and stratigraphy of five vertical profiles with 1:20 scales, and the thickness of sediments vary from 1.6 to 4,0 m. Base on correlation, the sediment bodies can be devided into three Interval of Deposition Periods (IPP A to C), and ten of Sub-Interval of Deposition Periods (Sub-IPP A.1 to C.3).The lateral changes of sediments represented by each Sub-IPP, interpreted as result of internal processes such as morphology, energy, and flow. Vertically, changes of sediments that form nine steps of cobble to boulder resulted from the change of flow systems following climate change . It is understood that, the period of energy and flows correlate with climatic changes.Keywords: River channel, morphology, energy and flows, climate
PERKEMBANGAN LUAS LINGKUNGAN PENGENDAPAN SEDIMEN PLISTOSEN AKHIR HINGGA HOLOSEN DI DATARAN ALUVIAL RENGASDENGKLOK DAN SEKITARNYA, KAB. KARAWANG (JAWA BARAT) Moechtar, H.; Subiyanto, Subiyanto; Samodra, H.
Jurnal Geologi dan Sumberdaya Mineral Vol 21, No 3 (2011): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

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Abstract

Study of area development on depositional environments during the Late Pleistocene to Holocene in the alluvial plain of Rengasdengklok surroundings, Karawang Regency (West Java) based on sedimentology and stratigraphy aspects. The study was based on analyses of nine borehole informations obtained along the West to East with the thickness of sediments varied from 6.75 to 10.20 m.Study on Quaternary deposits from boreholes , revealed four depositional environments. These are swamp, floodbasin, floodplain, and river channel environments. Based on correlation of the lateral and vertical variation of the sediment bodies, three Interval of Deposition Periods were recognised. Each of the interval is characterized by increasingly and decreasingly of environments which was controlled by climatic changes and tectonic. The climatic changes were recorded as (1)minimum climate into climatic optimum under warming conditions during deposition of Interval of Deposition Period A into the middle of Interval of Deposition Period B, and (2)optimum climate into climatic minimum under cooling conditions during deposition the middle of Intreval of Deposition Period B into Interval of Deposition Period C. The tectonic activities which controlled the deposition processes were recorded as two stages. These were the change posisiton of river channel deposits 1 to river channel deposits 2 and shifting of river channel deposits 2 into Recent Citarum river (river channel deposits 3).Key words: Sediment, depositional environemnt, climate, tectonic, Rengasdengklok