Sains Malaysiana 41(12)(2012): 1629–1634

 

Gravity Investigation of the Bukit Bunuh Impact Crater at Lenggong, Perak, Malaysia

(Kajian Graviti Kawah Impak Bukit Bunuh di Lenggong, Perak, Malaysia)

 

Abdul Rahim Samsudin*, Abdul Rahim Harun, Mohd Hariri Arifin & Umar Hamzah

Geology Program, School of Environment and Natural Resource Sciences

Faculty of Science & Technology, Universiti Kebangsaan Malaysia43600 Bangi, Selangor, Malaysia

 

Mokhtar Saidin & M Shyeh Sahibul Karamah

Geophysics Program, School of Physics, Universiti Sains Malaysia11800 USM, Penang,Malaysia

 

Diserahkan: 9 Mac 2012 /  Diterima: 6 Ogos 2012

 

ABSTRACT

An archeological study, conducted by the Archaeological Global Research Centre, Universiti Sains Malaysia shows the evidence of shock metamorphisms (suevite breccia) and crater morphology at Bukit Bunuh in Lenggong area of north Perak, Malaysia. A regional gravity survey focusing at Bukit Bunuh and its surrounding area was conducted to justify the occurrence and to determine the diameter and subsurface geological structure of the Bukit Bunuh impact crater. The gravity survey, using a Scintrex CG5 gravity meter, comprises 476 gravity stations with a 500 m spacing covering an area of approximately 160 km². The elevation of the gravity stations were obtained by using a pair of Wellace and Tiernan altimeters. The gravity data were corrected for drift, free air, bouguer, latitude and terrain in order to produce a corrected gravity data of the study area. The data were processed and analysed using Oasis Montaj (Geosoft software) to produce bouguer, residual, Total Horizontal Derivative (THD) residual, regional and Total Horizontal Derivative (THD) regional anomaly maps for qualitative and quantitative interpretations. The bouguer gravity map shows relatively low negative anomaly with nearly circular shaped contour around the Bukit Bunuh area. This anomaly was interpreted as the remnant of meteorite impact structure with rounded shaped crater in the study area. The bouguer anomaly map shows that the Bukit Bunuh impact crater has a diameter of approximately 2.5 km. The impact structure was successfully modeled as a complex impact crater with maximum depth of about 300 m. The bouguer anomaly map also showed the possible occurences of at least two more impact craters located in the northeast and southeast areas of the Bukit Bunuh crater and these structures need further investigation for confirmation.

 

Keywords: Archaeology; complex crater; gravity anomaly; meteorite impact structures

 

ABSTRAK

Kajian arkeologi yang telah dijalankan oleh Pusat Penyelidikan Arkeologi Global, Universiti Sains Malaysia menunjukkan bukti kewujudan metamorfisme kejutan (suevite breksia) dan morfologi kawah di Bukit Bunuh, Lenggong, Utara Perak, Malaysia. Kajian graviti rantau dengan penumpuan di Bukit Bunuh dan kawasan sekitarnya telah dilakukan untuk mengesahkan pembentukan dan menentukan diameter serta struktur geologi permukaan bawah kawasan hentaman di Bukit Bunuh. Tinjauan graviti menggunakan meter graviti Scintrex CG-5, mengandungi 476 stesen graviti dengan jarak antara stesen 500 m meliputi kawasan seluas 160 km². Ketinggian stesen graviti telah ditentukan menggunakan sepasang altimeter Wellace & Tiernan. Data graviti telah dilakukan pembetulan hanyutan, udara bebas, bougeur, latitude dan terain untuk menghasilkan data graviti yang sebenar bagi kawasan tersebut. Data kemudiannya diproses dan dianalisis menggunakan Oasis Montaj (Perisian Geosoft) untuk mendapatkan peta anomali bouguer, baki, rantau, terbitan mendatar jumlah (THD) baki dan terbitan mendatar jumlah (THD) rantau untuk pentafsiran kuantitatif dan kualitatif. Peta graviti bouguer menunjukkan anomali relatif yang rendah dan negatif dengan kontur membulat di sekitar Bukit Bunuh. Anomali ini ditafsirkan sebagai sisa struktur hentaman meteorit dengan diameter 2.5 km. Struktur hentaman telah berjaya dimodelkan sebagai kawah kompleks dengan kedalaman maksimum 300 m. Peta anomali bouguer juga menunjukkan kemungkinan pembentukan paling kurang dua atau lebih kawah hentaman di bahagian timur laut dan tenggara kawah Bukit Bunuh dan struktur ini memerlukan kajian lanjut untuk pengesahan.

 

Kata kunci: Anomali graviti; arkeologi; kawah kompleks; struktur hentaman meteorit

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*Pengarang untuk surat-menyurat; email: abrahim@ukm.my