Depositional model of Volcaniclastic-Carbonate Facies of Sentolo Formation at Miocene

Intercalation between carbonate and volcaniclastic rock are abundance in Java Island especially at southern part. Although this intercalation has long been recognized, very few studies into the depositional models of the intercalation have been undertaken. An ideal site for such a study of an ancient example is Sentolo Formation of Kulonprogo area in south central Java. The aim of this research is to understand the depositional models of Sentolo Formation. This research based of petrography, and stratigraphic analyze from many stratigraphic section of Sentolo Formation outcrop. The stratigraphic section have represented of distribution at northern, middle, eastern, and southern part of Sentolo Formation in Yogyakarta area. Result of this study is three possibility facies models of Sentolo Formation paleoenvironment. The models have distributed at northern, middle-western, and southeastern part. High volcanic activity have founded at northern part, even in middle to the western part are fine fraction of volcanic rocks, while no volcanic rocks at southeastern part. Result of this research is also possibility a reef system at Sentolo Formation separated with Jonggrangan Formation. The old concept said that origin of Sentolo Formation was connected with Jonggrangan Formation it must be review again, it caused no stratigraphic contact between Jonggrangan Formation and Sentolo Formation