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Darwin A Siregar
Pusat Survei Geologi
Chemistry Earth & Planetary Sciences Energy

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MINERALOGI MATRIKS BREKSI GUNUNG API PLISTOSEN AKHIR – KUARTER BERDASARKAN DATA XRD DI DAERAH LOMBOK TIMUR, NUSA TENGGARA BARAT Sigit Maryanto; R. Hasan; Darwin A Siregar
Jurnal Geologi dan Sumberdaya Mineral Vol. 19 No. 1 (2009): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33332/jgsm.geologi.v19i1.189

Abstract

Late Pleistocene to Quarternary volcanic rock units of the Kalipalung, Kalibabak, and Lekopiko Formations are well cropped out at East Lombok area, composed predominantly of volcanic breccias. The volcanic breccia of the Kalipalung Formation composed of andesite, porphyry andesite, basaltic andesite, basalt, and altered igneous rocks fragments. The frequence of the occurrence of the andesites and basalts is balanced. The volcanic breccia of the Kalibabak Formation composed predominantly of andesite, porphyry andesite, and rarely basaltic andesite and basalt rock fragments. The volcanic breccia of the Lekopiko Formation composed predominantly of pumice and less of andesite rock fragments, as well as sand and conglomeratic sands. XRD analysis of selected volcanic breccias matrix shows that the plagioclase change from labradorite and andesine on the Kalipalung and Kalibabak Formation to andesine, oligoclase and albite on the Lekopiko Formation. From the old to young formations, the orthopyroxene and clinopyroxene change to orthopyroxene, and finally these minerals was dissapeared. The clay minerals of montmorilonite commomly preserved on the old formation, it dissapeared and replaced by kaolinite in the young formation. Based on the difference test between two means it appears that the Kalipalung and Kalibabak Formations are similar on their mineralogical characters. On the other hand, the Kalipalung Formatian has a real difference on the mineralogical character with the Lekopiko Formation, as well as the Kalibabak Formation with the Lekopiko Formations. Keywords: Earth Lombok, breccias matrix, mineralogy
POLA DINAMIKA AIR TANAH DI DAERAH BEKASI BERDASARKAN ANALISI RADIOISOTOP 14C Darwin A Siregar; Satrio satrio
Jurnal Geologi dan Sumberdaya Mineral Vol. 19 No. 1 (2009): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33332/jgsm.geologi.v19i1.190

Abstract

A study of deep groundwater dynamic pattern on the basis of radioisotope 14C analysis has been carried out in the Bekasi  area. Some samples of deep groundwater were collected for14 C analysis. The results were plotted on the locality map concerned and a contour pattern was obtained. The pattern shows that the deep groundwater age of the area south of Bekasi is younger than those of the north and northwest area. This suggests that deep groundwater in the study area flows in the north and northwest directions. Meanwhile, Bekasi area is the recharge area.  Keywords: Bekasi dynamic pattern, deep groundwater, 14C analysis 
PENARIKHAN RADIOKARBON DALAM PENENTUAN AKTIVITAS TEKTONIK KUARTER DI SEPANJANG ALIRAN SUNGAI OPAK DAN PANTAI SAMAS, YOGYAKARTA Darwin A Siregar; Asdani Soehaimi
Jurnal Geologi dan Sumberdaya Mineral Vol. 19 No. 2 (2009): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33332/jgsm.geologi.v19i2.199

Abstract

The Samas beach ridges and river terraces of Opak, Progo, Oyo and Berbah in the research area were formed by the neotectonic activities since ± 7000 years ago until Recent. Materials for Radiocarbon dating consists of mollusc and organic clay found in the beach ridge and river terrace deposits. The oldest Samas beach sand is 1980 ± 120 years BP and Opak River terrace at Berbah is 6950 ± 300 years BP. Meanwhile, the Oyo River terrace at Siluk is 2640 ± 100 years BP and Opak River terrace at Karang is 1220 ± 120 years BP. The dynamic neotectonic activities of Samas beach are represented by the uplifting and shifting of the coast line, meanwhile at Berbah, Siluk and Karang are indicated by uplifting end shifting of the river base level. These dynamic activities were caused by the regional tectonic activity related to subduction in the south of Java island and the local tectonic activity along the Opak fault zone. Keywords : Dynamic of beach sand, river terrace, elevation and radio carbon dating
PENGARUH TEKTONIK PADA RUNTUNAN ENDAPAN ALUVIAL DEPRESI PADANGSIDEMPUAN, SUMATERA UTARA Ungkap M Lumbanbatu; C Basri; S. Hidayat; Darwin A Siregar
Jurnal Geologi dan Sumberdaya Mineral Vol. 19 No. 3 (2009): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33332/jgsm.geologi.v19i3.202

Abstract

The investigated area, that is so called Padangsidempuan depression has been filled up by unconsolidated fluvial sediments. The sediments can be distinguished into five different environments, these are flood basin deposit, flood plain deposit, palaeo channel deposit, swamp deposit and colluvium deposit. To understand the influence of tectonic activities on lithological succession of the studied area several profiles were made. It reveals, that lithological successions have been disturbed by tectonic activities such as subsidence and uplifted. Subsidence can be identified by alternating of swamp facies deposit within different stratigraphic position and superimposed of the Batang Toru river on the palaeo channel deposit three (Ch-3). Further more the effect of uplifting caused palaeo channel deposit shifting horizontally. The data show that the tectonic activities in the studied area are not so very intensive. Keywords: quarternary tectonics, palaeo channels, pull-apart basin, sedimentary sequences
Co-Authors Asdani Soehaimi C Basri R. Hasan S. Hidayat Satrio satrio Sigit Maryanto Ungkap M Lumbanbatu