TEKTONIK SESAR CIMANDIRI, PROVINSI JAWA BARAT
Abstrak
ABSTRACT
Cimandiri fault formed during stage II orogenesis is the oldest fault at the end of the middle Eocene. The Cimandiri fault is the active fault that developed a paleo high and uplifted the Ciletuh Formation within front arc basin. The stage III orogenesis at the Late Eocene indicated by regional compression in the Java that affected to reactivation fault. This fault known to be the same as the Baribis thrust fault. Finally, the compression tectonic decreased that it created the normal fault on Cimandiri thrust-fold. Therefore, we can define the Cimandiri fault into two regional fault patterns. The first pattern, the thrust fault that indicated by high bedding inclined. The second pattern, the next pattern is the normal fault that revealed by fault scarps inclination more than 50o or even vertical in some locations.
Keywords: Cimandiri fault, front arc basin, Ciletuh valley, Cimandiri Valley.
ABSTRACK
Sesar Cimandiri merupakan sesar tua yang terbentuk selama berlangsungnya orogenesa tahap II, yaitu pada waktu Akhir Eosen Tengah. Pada saat itu batuan sedimen Formasi Ciletuh berumur Eosen Tengah yang terbentuk di dalam Cekungan Depan Busur sudah terangkat ke permukaan. Sesar ini terus aktif hingga menyebabkan terbentuknya tinggian purba (paleo-hight) antara Lembah Ciletuh dan Lembah Cimandiri. Pada Akhir Tersier, tektonik kompresi kembali terjadi, menyebabkan untuk ketiga kalinya sesar Cimandiri teraktifkan kembali sebagai sesar naik. Peristiwa ini disimpulkan sebagai orogenesa ke III di Pulau Jawa. Salah satu struktur sesar regional yang terbentuk pada saat itu adalah Sesar Baribis. Setelah tektonik kompresi berkurang terjadi kesetimbangan menyebabkan terbentuknya sesar normal pada jalur lipatan anjakan Cimandiri. Oleh karena itu, Sesar Cimandiri terdiri atas dua sesar regional yang pertama sebagai sesar naik yang dicirikan oleh deformasi lipatan batuannya yang umumnya tegak, dan sebagai sesar normal yang dicirikan dengan terbentuknya gawir sesar dengan kemiringan di atas 50° bahkan di beberapa lokasi mendekati vertical.
Kata Kunci: Sesar Cimandiri, Cekungan Depan Busur, Lembah Ciletuh, Lembah Cimandiri.
Teks Lengkap:
PDFReferensi
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DOI: https://doi.org/10.24198/bsc.v15i3.15103
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