Interpretation of Paleo-Channel Based on Shallow Seismic Reflection Record in Banten Bay, Banten Province

Yogi Noviadi

Abstract


The objective of this study is to find out the pattern of paleo channel which was formed in Banten Bay and its surrounding.  The aims are to find out the paleo-channel pattern at study area. The study methods are including vessel positioning, and shallow seismic reflection work. Vessel positioning method is to locate the exact position of seismic work     when recording the data from single channel of shallow seismic reflection. Seismic line orientations are determined by regional geological setting of the area. Trend of seismic lines are dominantly north – south. In order to get the seismic data which could give geological setting configuration, seismic lines should be perpendicular to the strikes of the sediments.

Based on the calculation of velocity of seismic refraction in sea water 1,500 meters/second, while within sediment 1,600 meters/second, it could be concluded that the paleo chanels were more or less in 32 meters below sea floor depth.

This layer was the system that occur during the process of an interglacial on the Sunda Shelf when it was still a part of land that connects the Java, Sumatra and Kalimantan Islands. Paleo-channel deposits are characterized by subparalel - chaotic reflection character with a thickness between 5-35 meters.

Keywords: Paleo-channels, seismic records and Banten Bay

Maksud dari penelitian ini adalah untuk mengetahui pola sungai purba yang terdapat di Teluk Banten dan sekitarnya, yang tujuannya adalah untuk mengetahui pola penyebaran alur sungai purba di daerah penelitian. Metode penelitian terdiri dari penentuan posisi kapal dan penelitian  seismik pantul dangkal. Penentuan posisi kapal berguna untuk menemukan posisi yang tepat saat merekam data oleh perlatan seismik saluran tunggal dangkal. Lokasi lintasan seismik disesuaikan dengan kondisi geologi daerah penelitian. Arah lintasan seismik pada umumnya berarah utara – selatan. Untuk mendapatkan data seismik yang bisa memberikan konfigurasi kondisi geologi, lintasan seismik harus tegak lurus terhadap kedudukan lapisan batuan.

Berdasarkan cepat rambat gelombang seismik di air laut 1.500 meter/detik, dan sedimen 1.600 meter/ detik, dapat disimpulkan bahwa alur purba kurang lebih berada pada kedalaman  32 meter di bawah dasar laut.

Lapisan ini merupakan sistem pengendapan yang terjadi selama proses interglasial di Paparan Sunda yang pada saat itu masih  merupakan bagian dari daratan yang menghubungkan P. Jawa, Sumatera dan P. Kalimantan. Endapan alur purba  dicirikan dengan pola refleksi subparalel sampai tidak beraturan dengan ketebalan antara 5-35 meter.

Kata kunci: Alur purba, rekaman seismik dan teluk Banten

Keywords


Paleo-channels; seismic records;Banten Bay

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References


Anderson N and Akingbade A., 1995, Overview of the Shallow Seismic Reflection Technique Geophysical Atlas for Kansas: Kansas Geological Survey bulletin 237

Haeni, F.P., 1986, Use of continuous seismic reflection methods in a hydrologic study in Massachusetts, a case study, in National Water Well Association Conference on Surface and Borehole Geophysical Methods and Ground Water Instrumentation, Den-ver, Colorado, October 15- 17, 1986, Proceedings: Worthington, Ohio, National Water Well Association, p. 381-395.

Haeni, F.P., 1988, Evaluation of the continuous seismic refraction method for determining the thickness and lithology of stratified drift in the glaciated northeast, in A.D. Randall and A.I. Johnson,eds., Regional aquifer systems of the United States-The northeast glacial aquifers: American Water Resources Association onograph 11, p. 63-82.

Hadikusumo, S., Sarmili, L., Silitonga, F., Kurnio H., Hakim S., 1988. Laporan Penyelidikan Geologi dan Geofisika Kelautan Banten dan Sekitarnya, Pusat Penelitian dan Pengembangan Geologi Kelautan (Unpublished report)

Mitchum, R.M., Vail, P. R., Jr., and Sangree, J.B., 1977a, Seismic stratigraphy and global changes of sea level; Part 6, Seismic in-terpretation of seismic reflection patterns in depositional sequences, in Payton, C.E., ed., Seismic Stratigraphy—Applications to Hydrocarbon Exploration: American Association of Petroleum Geologists Memoir 26, p.117-133.

Mitchum, R.M., Vail, P.R., Jr., and Thompson, S., Ill, 1977b, Seis-mic stratigraphy and global changes of sea level; Part 2, The depositional sequence as a basic unit for stratigraphic analysis, in Payton, C.E., ed., Seismic Stratigraphy—Applications to Hydrocarbon Exploration: American Association of Petroleum Geologists Memoir 26, p. 53-62.

Ringis, J., 1986. Seismic Stratigraphy In Very High Resolution Shallow Marine Seismic Data. Proceedings of the Joint ASCOPE/CCOP Workshop I, 119 – 128

Susilawati, 2004. Seismik refraksi (dasar teori dan akuisisi data). Fakultas Matematika dan Ilmu Pengetahuan Alam, Jurusan Fisika, Universitas Sumatera Utara. Medan. 50 hlm.

WU Chen, 1991. Study of Paleochannels on The North China Plain [M]. Beijing: China Science and Technology Press, 172. (in Chinese)




DOI: http://dx.doi.org/10.32693/bomg.31.1.2016.344