Paleogeomorphology of Kulon Progo during the oligocene-early miocene

Exploration of natural resources in the Kulon Progo dome often faces obstacles. This is because the paleogeomorphological and stratigraphic dynamics of the region are not yet understood, including stratigraphic relationships at the same time but having different stratigraphic contact forms, as happened in the Oligocene - Early Miocene. At that time, two different stratigraphic contacts were formed, first the unconformity contact between the OAF and the Jonggrangan Formation above it, and the conformity contact between the OAF and the Sentolo Formation. Stratigraphic contact between the Jonggrangan Formation and the Sentolo Formation itself cannot be found. This study aims to provide an overview of what actually happened in the Late Oligocene to Early Miocene, including the paleogeomorphology of the basin and its stratigraphic succession. The research was conducted using a field investigation method on the stratigraphic contacts of OAF-Jonggrangan Formation, and OAF-Sentolo Formation, field data were then analyzed in the laboratory including rock age and depositional environment. The results show that the Jonggrangan Formation is formed in a basin that is not integrated with the Sentolo Formation. Both are limited by a height in the form of an active volcano until the Early Miocene.