TEGALREJO THRUST FAULT AS AN INDICATION OF COMPRESSIVE TECTONICS IN BATURAGUNG RANGE, BAYAT, CENTRAL JAVA

• Main Author: , Salahuddin Husein, Aswin Mustofa, Ignatius Sudarno and Budianto
• Format: Article NonPeerReviewed
• Published: [Yogyakarta] : Ikatan Ahli Geologi Indonesia 2008
• Online Access: https://repository.ugm.ac.id/95418/; http://repository.ugm.ac.id/digitasi/index.php?module=cari_hasil_full&idbuku=3236
• Institution: Universitas Gadjah Mada

<p>The Baturagung Range of the Southern Mountains of East Java is a southeasternward-dipping cuesta and composed of the 1600 m thick of volcaniclastic sediment of Kebobutak and Semilir formations. Its morphogenetics is still in open discussion. Some geologist had opinion that the range had been formed as block faulting due to extensional tectonics, whilst some argued that it was a remnant of eroded anticline flank. <br /> In the downstream of Tegalrejo River, on the break of slope of the Baturagung escarpment, a NE-SW trending thrust fault was recognized. It acted as a boundary of two groups of different dip angles of the Kebobutak Formation beds.<br /> To the north on the Bayat lowland, outcrop beds dip less than 200 , whilst to the south on the scarpment were more than 300 . Bedding planes were thus acting as the slip planes with some well-developed imbricated fault patterns. About 500 m to the south another thrust fault with a well-defined fault-propagation fold was also recognized.<br /> Those geomorphologic and geologic evidences indicate that the Tegalrejo thrust fault had an important role on the formation of the Baturagung Range and thus suggests that the range was formed under a compressive tectonic regime. It might imply that the Baturagung Range neither formed as block faulting nor normal folding but rather a fold-thrust belt system.</p>