Cooling Event in the Boundary of Middle/Late Eocene of Java

Eko Budi Lelono

R&D Center for Oil and Gas Technology "LEMIGAS", Indonesia

Abstract: The indication of Eocene climatic changes is defined based on the change of abundance and diversity of palynomorphs occurring in the Nanggulan Formation. This is possible because this formation has been found to yield the richest and most diverse palynomorph assemblages of Eocene age in Southeast Asia. Palynological evidence, from the distribution of index taxa and palynological events, indicates that the Nanggulan Formation was deposited during the Middle to Late Eocene as marked by the constant occurrence of Longapertites vaneendenbergi, Proxapertites operculatus, Proxapertites cursus and Cicatricosisporites eocenicus. The Middle Eocene age is characterised by high abundance and diversity of rain forest elements suggesting warm and wet climate which include Palmaepollenites kutchensis, Sapotaceoidaepollenites spp., Retitricolporites equatorialis, Campnosperma sp., Marginipollis concinus and Dicolpopollis malesianus. On the other hand, the Late Eocene age is marked by the appearance of the hinterland element Podocarpidites spp. and the disappearance of the main rain forest elements indicating cool and dry climate. In this case, cooling event is defined by the occurrence hinterland element of Podocarpidites spp. which can be used for recognising Middle/Late Eocene boundary.

Key words: cooling event, middle/late eocene boundary, palynomorphs