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Oligocene Palynological Zonation Scheme From East Java Sea Lelono, Eko Budi; Morley, Robert J
Scientific Contributions Oil and Gas Vol 34, No 2 (2011)
Publisher : PPPTMGB "LEMIGAS"

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29017/SCOG.34.2.797

Abstract

Systematic biostratigraphic analyses have been undertaken on the Oligocene clastic and carbonate Kujung Formation from the East Java Sea, North of Madura. The succession has been examined mainly using cutting samples in two wells, using a combination of foraminiferal, nannofossil and palynological analyses at regular spacing. Nannofossil analysis indicates that the Late Oligocene to basal Early Miocene succession is more or less complete, with zones NP24, NP25 and NN1 are all being well developed. In addition, the Early Oligocene is indentified by larger foraminifera indicating the Tc/ Td Letter Stage. Because the traditional palynological zonation of Morley (1978) does not work well in this area, the succession has been divided into broad assemblage zones, which appear to be controlled mainly by climate. These zones are OL-1, OL-2, OL-3, OL-4 and OL-5. Zone OL-1 is based essentially on the absence of seasonal climate and riparian elements, whilst zone OL-2 is characterized by the regular occurrence of seasonal climate elements, especially of Malvacipollis diversus. Zone OL-3 is indicated by common to abundant Dacrydium and Casuarina pollen, with a strong acme of dinoflagellate cysts dominated by Operculodinium spp. and Spiniferites spp., whereas zone OL-4 is marked by abundant Dacrydium and regular Casuarina pollen, but low representation of riparian elements. Finally, the youngest zone is OL-5 which is characterized by reduced Dacrydium and Casuarina pollen, and increased riparian elements. The above palynological zonation suggests climate change, which closely parallels the climate succession from West Java Sea (but with changes less pronounced). Therefore, this study provides a well dated Oligocene palynological zonation which can be applied across Java.
Oligocene Climate Changes of Java Lelono, Eko Budi; Morley, Robert J
Scientific Contributions Oil and Gas Vol 34, No 3 (2011)
Publisher : PPPTMGB "LEMIGAS"

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29017/SCOG.34.3.803

Abstract

The study of palynology performed on the Oligocene marine sediment of the East Java Sea provides excellent recovery which allows the construction of palynological succession which applies regionally (Lelono et. al., 2011). In fact, this succession is characterized by assemblages that suggest climatic changes. These assemblages are divided into two major groups including mangrove and hinterland. The hinterland pollen group shows the most interesting succession, with elements on the one hand suggesting everwet climates (Dacrydium and Casuarina), and seasonal elements on the other (Gramineae, Schoutenia and Malvacipollis diversus). Mangrove pollen however suggests strong environmental control since mangrove pollen shows different abundance variations in the two wells. The age of the studied succession is independently defined using combined marine micro-fossils of foraminifer and nannoplankton which indicate Early to Late Oligocene. Although for most of the Oligocene in Southeast Asia, seasonal climate assemblages are the rule, this study interpretes the appearence of everwet climates. The Early Oligocene is characterized by common rain forest elements, suggesting an everwet rain forest climate at that time. The early part of the Late Oligocene, however, contains much reduced rain forest elements, and the presence of regular Gramineae pollen, suggesting a more seasonal climate, whereas for the latest Late Oligocene, rain forest (and peat swamp) elements return in abundance, suggesting a very wet rain forest climate. In fact, Java region experienced the wettest climate during Oligocene which probably reflected a wet climate fringe to the eastern margin of Sundaland prior to the collision of the Australian and Asian plates at the Oligo-Miocene boundary.