Nannofossil Diversity and Climate Change of Rembang Zone, North East Java Basin

This study was conducted in the Blora Regency District. This study aims to comprehensively examine the diversity of nannofossil species and their significance to climate change from the Pliocene to the Pleistocene. The rock sample was taken by spot sampling and prepared using the smear slide method. The geology area is composed of lithology containing much carbonate from the Wonocolo, Ledok, Mundu, Selorejo, and Lidah formations. The results of nannofossil analysis showed that in the Jiken area, 17 genera and 54 species were identified, Sambong had eight genera and 41 species, and Kedewan had 19 genera and 51 species. The study area is (Late Miocene/Pliocene to Pleistocene). Age of Jiken is (CNM11-CNPL7) or (10.79Ma-1.71Ma); Sambong (CNM13-CNPL8) or (9.65Ma-1.93Ma) and Kedewan (CNM14-CNPL9 or 8.80M -1.14Ma). The Diversity Index (H') and Evenness/Homogeneity Index (E) for Jiken are H' (2.551) and E (0.422), Sambong area is H' (2.280) and E (0.377) and Kedewan (H'2.344 and E 0.388). The index ranges from H'(2.280-2.251), which means small to medium diversity and moderate community stability; for index E (0.377-0.42), the nannfossil population is small to medium. These results indicate that the dominance of species abundance and diversity increased during the Miocene-Pliocene and decreased during the Pleistocene. Climate change has had a significant impact on the life of nannofossils; it has been shown that during the Pliocene (warm period), the number of nannofossils showed high diversity and abundance, and during the Pleistocene (cold), it resulted in a decrease in diversity and abundance.