Normalization of the Gravity Anomaly Pattern of Africa reveals Deep Geology

Author(s):  
C.M. Doucouré ◽  
M.J. de Wit
2016 ◽  
Vol 12 (2) ◽  
pp. 65
Author(s):  
Saultan Panjaitan ◽  
Subagio Subagio

Anomali gayaberat di daerah penelitian merupakan anomali tertinggi di Indonesia, secara umum dikelompokkan ke dalam 2 (dua) satuan, yaitu: kelompok anomali gayaberat 160 mGal hingga 260 mGal membentuk pola rendahan/cekungan anomali, dan kelompok anomali gayaberat 260 mGal hingga 620 mGal membentuk pola tinggian anomali. Anomali sisa 0 mGal hingga 5 mGal membentuk tinggian anomali, diduga merupakan gambaran antiklin dengan diameter 10 – 15 kilometer. Perangkap struktur migas di daerah Minaluli, Madafuhi dan Lekosula Pulau Mangole berdekatan dengan lokasi rembesan migas, sehingga diusulkan untuk dilakukan pemboran eksplorasi. Sedangkan di Pulau Taliabu, Tolong, Pena, Samuya dan Teluk Jiko masih perlu dilakukan penambahan data. Batuan reservoir terdiri dari batupasir dan batugamping Formasi Tanamu berumur Kapur Akhir, menempati daerah beranomali sisa 0 mGal hingga 5 mGal, dengan rapat massa batuan sekitar 2.65 gr/cm³. Batuan induk adalah Formasi Buya umur Jura Tengah - Jura Akhir dari serpih hitam dengan rapat massa 2.71 gr/cm³, dan dapur migas terbentuk di sekitar daerah beranomali sisa -4 mGal hingga -28 mGal yang membentuk sub-cekungan di utara lepas pantai Pulau Mangole. Kata kunci: gayaberat, dapur minyak, cekungan, migas, serpih hitam, anomali sisa, rapat massa, antiklin, batuan induk. The gravity anomaly of research area is the highest anomaly in Indonesia, generally it can be grouped into 2 (two) units, that are 160 mGal up to 260 mGal anomaly groups formed low anomaly pattern, and 260 mGal up to 620 mGal anomaly groups formed high anomaly pattern. 0 mGal to 5 mGal residual anomaly formed high anomaly pattern, it is interpreted as anticline with diameter are 10-15 kilometers. The trap oil and gas structures of this area at Minaluli, Madafuhi, and Lekosula are near the location of oil and gas seepage, that is propose to explore and drill in that area. Whereas in Taliabu Island, Tolong, Pena, Samuya, and Jiko Gulf still need increasing datas. Reservoir rocks consist of sandstones and limestones of Tanamu Formations were Late Cretaceous age, that occupied the location of 0 mGal to 5 mGal residual anomaly with density 2.65 g/cm ³. Hostrock are Buya Formation are Middle Jurassic - Late Jurassic from black shales with density 2.71 g/cm³, and kitchen oil were formed in the area - 4 mGal to -28 mGal residual anomaly that formed low anomaly in the northern offshore of Mangole Island. Keyword: gravity, oil kitchen, basin, oil and gas, black shales, recidual anomaly, density, anticline, hostrocks.


2020 ◽  
Vol 20 (3) ◽  
pp. 80-84
Author(s):  
NOVIA PURNAMA SARI ◽  
TOMI AFRIZAL ◽  
FAISAL ABDULLAH ◽  
NAZLI ISMAIL

The gravity method was applied to the cultural heritage site of Cot Sidi Abdullah in Kuta Krueng Village, Samudera Pasai District, North Aceh Regency for mapping and reconstruction structure of the cultural heritage site and distribution of artifact objects buried in the subsurface. Data measurement was carried out in a grid with 2 meters spacing between the points to cover all area of the cultural heritage site. The model of gravity anomaly distribution from the vertical derivative results shows a square pattern of anomaly gravity surrounding the measurement areas. This anomaly pattern is thought as a response from the remaining walls of the site structure which are buried in the subsurface with anomalous values between 0.02 mGal/m - 0.08 mGal/m.  The estimation of the walls of the archaeological site from the anomalous response to this gravity value is proved by the excavation results in the southern part of the study area.  While the minimum value of the vertical derivative filter (-0.06 mGal/m to - 0.01 mGal/m) is the response from the area around the archaeological site.  The reconstruction results of the site based on the estimation of the walls with a length of ± 45 meters and a width of ± 40 meters.


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