• S. Bachri Pusat Survei Geologi



The study area has been subjected to intense fracturing or brittle deformation resulting in five main trends of lineaments and faults, i.e. (1) the Group A (the Perantanaan Fault Group) with a mean of direction N95°E/ N275°E, (2) the Group B (the Gorontalo Fault Group) with a mean of direction N125°E/ N305°E, (3) the Group C (the Paleleh Fault Group) with a mean of direction 165°E /N335°E, (4) the Group D (the Randangan Fault Group) with a mean of direction N25°E/ N205°E and (5) the Group E (the Kuandang Fault Group) having a mean of trend of N55°E/ N235°E. The complexity of structural pattern in the study area has been interpreted to be due to stress system evolution during Neogene - Pleistocene. The changing stress system orientation has reactivated the preexisting faults of the five groups with different sense of movements from the older deformation.
The nearly E-W trending lineaments of Group A or the Perantanaan Fault Group coincide with trend of the long axis of ridges and valleys or depression areas which are covered by volcanic rocks, lake deposits, and alluvium of Quaternary age. This group of structures was presumably developed as reverse or thrust faults during Late Neogene which later on to have beem reactivated as normal faults due to extensional tectonics of the North Sulawesi area during Plesitocene.
The Gorontalo Fault, as a part of the Group B (the Gorontalo Fault Group), generally has been interpreted as dextral wrench fault. The present structural analysis suggests that this major fault was formerly developed as a dextral fault during Neogene, and later during Pleistocene it was reactivated in the sense of sinistral fault due to the changing of the stress system.
The Neogene stress orientation is supposed to be related to the subduction of the North Sulawesi Sea to the south, which during Pleistocene weakened as the Sangihe Subduction in the Mollucas Sea to the east commenced resulting in the change of field stress orientation.

Key words: Structural pattern, stress system, Neogene - Pleistocene, north arm of Sulawesi


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Bachri, S., and Apandi, T., 1997. Geological Map of the Kotamobagu Sheet, Sulawesi, scale 1 : 250,000. Geological Research and Development Centre, Bandung.

Bachri, S. and Baharuddin, 2001. Geological Map of the Malunda-Majene Sheets, Sulawesi, scale 1:100,000. Geological Research and Development Centre, Bandung.

Bachri, S., Partoyo, E., Bawono, S.S., Sukarna, D, Surono and Supandjono, J.B., 1997. Geologi Daerah Gorontalo, Sulawesi Utara. Kumpulan Makalah Hasil Penelitian dan Pemetaan Pusat Penelitian dan Pengembangan Geologi 1996/1997, p.18-30.

Bachri, S., Ratman, N, and Sukido, 1994. Geological Map of the Tilamuta Sheet, sclae 1:250,000. Geological Research and Development Centre, Bandung

Bergman, S.C., Coffield, D.Q., Talbot, J.P. and Garrard, R.A.,1996. Tertiary tectonic and magmatic evolution of western Sulawesi and the Makassar Strait, Indonesia: evidence for a Miocene continent-continent collision. From Hall,

Coffield, D.Q., Bergman, S.C., Garrard, R.A., Guritno, N., Robinson, N.M. and Talbot, J.P. , 1993. Tectonic and stratigraphic evolution of the Kalosi PSC area, and associated development of a Tertiary petroleum system. Proceeding of 22nd Indonesian Petroleum Association Convention, p.679-706.

Harding, T.P., Wilcox, R.E., and Seely, D.R., 1973. Basic Wrench Tectonics. Bulletin of Association of American Petroleum Geologist, 57(1) : 74-96.

Katili, J.A., 1978. Past and present geotectonic position of Sulawesi, Indonesia. Tectonophysics, 45: 289-322.

Kavalieris, I., van Leeuwen, Th. M. and Wilson, M., 1992. Geological setting and styles of mineralisation, north arm of Sulawesi. Journal of Southeast Asian Earth Sciences 7, 2/3, p.113-129.

Parkinson, C.D., 1991. The petrology, structure and geologic history of metamorphic rocks of central Sulawesi. Unpublished. Ph.D Thesis, University of London.

Silver, E.A, McCaffrey, R. and Smith, R.B, 1983. Collision, Rotation and the initiation of subduction in the evolution of Sulawesi, Indonesia. Journal of Geophysical Research, 88 (B11) : 9407-9418

Smith, R.B. & Silver, E.A., 1991. Geology of a Miocene collision complex, Buton,eastern Indonesia. Geological Soiety of America Bulletin, 103 : 660-678.

Sukamto, R., 1975. The structure of Sulawesi in the light of plate tectonics. Proceedings of Regional Convention on the Geolology and Mineral Resources of South East Asia. Jakarta.

Trail, D.S., John, T.U., Bird, M.C., Obial, R.C., Pertzel, B.A., Abiog, D.B., Prawoto and Subagio, 1974. The general geological survey of Block II, Sulawesi Utara, Indonesia. Unpublished report, P.T. Tropic Endeavour Indonesia, 68 p.