SUBSURFACE GEOLOGICAL IMAGING OF ATAMBUA, WEST TIMOR BASED ON THE INTEGRATION OF MAGNETOTELLURIC (MT), GRAVITY, AND MAGNETIC METHODS
Timor Island located in the eastern Indonesian archipelago has a complex geological structure related to its tectonic history. The tectonic history is recorded in the outcrops that show various types of deformation. Various tectonic models are proposed mainly based on regional geological and geop...
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Format: | Dissertations |
Language: | Indonesia |
Online Access: | https://digilib.itb.ac.id/gdl/view/71170 |
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Institution: | Institut Teknologi Bandung |
Language: | Indonesia |
Summary: | Timor Island located in the eastern Indonesian archipelago has a complex
geological structure related to its tectonic history. The tectonic history is recorded
in the outcrops that show various types of deformation. Various tectonic models are
proposed mainly based on regional geological and geophysical data. However, the
available geophysical data to support geological studies on a more detailed scale
are still very limited. Therefore, this study aims to map sub-basins and sub-regional
sub-surface geological structures in Atambua, West Timor, and its surroundings
using magnetotelluric (MT), gravity, and magnetic methods. The estimation of the
geoelectrical strike direction from the phase tensor analysis and the lineament
analysis on the gravity anomaly confirm that the regional structure orientation is
Southwest - Northeast. The MT dimensionality analysis shows the validity for the
2-D approach in that direction. Based on the interpretation of the low gravity
anomalies, two main basins that extend following the Southwest - Northeast trend
have been identified, namely the Soe Basin and the Atambua Basin. Meanwhile,
qualitative interpretation of magnetic anomaly shows the distribution of crystalline
rocks which are not demagnetized are generally located in the southwest compared
to crystalline rocks that are strongly demagnetized in the northwest, among
sedimentary rocks that are evenly distributed in the study area.
The modelling of 2-D MT as well as 2½-D and 3-D gravity from the selected
profiles perpendicular to the direction of the regional structure depicts the main
sequence and its boundaries, based on its resistivity and density, respectively. The
integration of this model with magnetic anomaly and geological data produces a
thick-skinned geological model which shows the rock sequence from the youngest
(near the surface) to the oldest (deep) are: the Viqueque Sequence and Bobonaro
Formation (orogeny), the Kolbano Sequence (post-rift), the Kekneno Sequence
(syn-rift), and the basement (pre-rift) dominated by rocks with Australian affinity.
The thickness and depth of the main rock sequences represent the regional basininfill sediments resulting from tectonic events on Timor Island. This study suggests
that the best sequence of petroleum systems in the study area is Mesozoic,
Paleozoic, and Cenozoic plays. |
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