A revision of the biostratigraphy and strontium isotope dating of Oligocene-Miocene outcrops in East Java, Indonesia

The biostratigraphic ranges of identified larger benthic and planktonic foraminifera from Tertiary exposures in East Java Basin have been tied to the ages constrained from the Strontium isotope dating of some of the most abundant large benthic foraminifera. Foraminiferal assemblages and Strontium data have provided precise age ranges of the different stratigraphic units. The age of the exposed Lower Kujung Formation (late Early Oligocene, Rupelian P20 to Late Oligocene, Te1-4, equivalent to 28.78 - 28.27 Ma). The age of the exposed Upper Kujung Formation is Late Oligocene, Chattian, P22, Te1-4 to Early Miocene, Aquitanian, -N5a, -Te5, equivalent to 24.31- 23.44 Ma. The age of the exposed Tuban Formation is late Early Miocene, Burdigalian to Middle Miocene, Langhian, N5b to N9, Te5-Tf1, equivalent to 20.80 – 15.25 Ma. The age of the exposed Ngrayong Formation is late Middle Miocene, Serravallian, N12 to N13, Tf2, equivalent to ~15.00 to ~13.00 Ma. The age boundaries between the lithostratigraphic units have also been obtained such as Upper Kujung - Tuban (22 Ma), Tuban-Ngrayong (15.25 Ma) Formations and Ngrayong Formation-Bulu Member of Wonocolo Formation (12.98 Ma)