Abstrak
Micropaleontological clues, particularly calcareous nannofossils in Miocene marine sediment from East Java, Indonesia were studied. Detailed biostratigraphic frame work is provided by the occurrences of diverse and well-preserved nannofossil. The nannofossil events used to date the Miocene of 5.2 to 25.2 Ma duration are based on datum planes of the first and last occurrence of marker species (FO and LO). For the Miocene interval of East Java, a total of 15 marker species have been selected, among all: Sphenolithus ciperoensis, Cyclicargolithus abisectus, Discoaster druggi, Sphenolithus heteromorphus, S. belemnos, Calcidiscus macintyrei, Helicosphaera ampliaperta, Discoaster kugleri, D. hamatus, D. neohamatus, D. bellus, D. neorectus, D. quinqueramus, Amaurolithus primus, and D. berggrenii. On the basis of these datum planes, 18 interval zones were established. Those are, beginning with the oldest: Sphenolithus ciperoensis – Cyclicargolithus abisectus interval zone (NN1/Early Miocene or 25.2 my), Cyclicargolithus abisectus – Discoaster druggi interval zone (NN1/Early Miocene), Discoaster druggi – Sphenolithus heteromorphus interval zone (NN2-3/Early Miocene), Sphenolithus heteromorphus – Sphenolithus belemnos interval zone (NN3/Early Miocene), Sphenolithus belemnos – Calcidiscus macintyrei interval zone (NN4/Early Miocene), Calcidiscus macintyrei – Helicosphaera ampliaperta interval zone (NN4/Early Miocene), Helicosphaera ampliaperta – Sphenolithus heteromorphus interval zone (NN5/Early Miocene or 16.2 my), Sphenolithus heteromorphus – Discoaster kugleri interval zone (NN6/Middle Miocene), Discoaster kugleri range zone (NN7/Middle Miocene), Discoaster kugleri – Discoaster hamatus interval zone (NN8/Middle Miocene), Discoaster hamatus – Discoaster neohamatus interval zone (NN9/Middle Miocene or 10.2 my), Discoaster neohamatus – Discoaster bellus interval zone (NN9/Late Miocene), Discoaster bellus – Discoaster hamatus interval zone (NN9/Late Miocene), Discoaster hamatus – Discoaster neorectus interval zone (NN10/Late Miocene), Discoaster neorectus – Discoaster quinqueramus interval zone (NN10/Late Miocene), Discoaster quinqueramus – Amaurolithus primus interval zone (NN11/Late Miocene), Amaurolithus primus – Discoaster bergrrenii interval zone (NN11/Late Miocene), and Discoaster bergrrenii – Discoaster quinqueramus interval zone (NN11/Late Miocene or 5.2 my BP). Throughout Miocene interval, nannofossils provide a high accurate biostratigraphy and are the prime tool for correlation. Sea level fluctuation, transgression and wide Intra-Miocene orogenic regression is recorded particularly in marine clastic sediment and detrital limestone from asymmetric back arch basins – north East Java. These events can be reconstructed by nannofossil biostratigraphy analysis and it can be correlated to foraminifera analysis.
