Pliocene to Pleistocene Stratigraphy of Rembang Zone, North East Java Basin, Indonesia

Abstract

We studied benthic faunas and planktonic foraminiferas in seven stratigraphic sections in Rembang Zone to understand the paleoecology of the area. Rembang Zone is an interesting object for further examination especially during Plio-Pleistocene. That time fragment holds a very important information of ecological changes in Java Island. We observed the following sections: upper-part of Ledok fm, calcareous shales/marls of Mundu fm, glouconitic Globigerinid sands of Selorejo fm, and blue-green shales of Tambakromo Member of Lidah fm. We identified N21 sequence in the Late Pliocene, with a sequence boundary (SB-21) which is superimposed with irregular contact between marl of Mundu fm and Globigerinid sands of Selorejo fm. This irregular contact is interpreted as the base of an incised valley, which was generated by a falling sea-level event in Late Pliocene. We spot changes in biostratigraphy, paleobathymetry, and paleoclimate. There are three Pliocene biostragraphies in this section: Globorotalia margaritae zone (N19); Globorotalia miocenica zone (N20 - N21) and Globorotalia tosaensis tosaensis zone (the top of N21). Using cluster analysis with Past computer software, we describe the correlation between variation of foraminifera and environmental change and the bathymetry zone. We find paleoclimate changes by the presence of sub-tropical transitional faunas (Globorotalia tosaensis tosaensis) and the increasing of tropical fauna (Globorotalia truncatulinoides) in Plio-Pleistocene sediments.