This study was conducted to investigate the profile of microfossils community in diatomite layer of Pucangan Formation, Sangiran. The environmental reconstruction on Pleistocene epoch in this area was obtained by microfossils profile analysis. Identification revealed 33 diatom species, four radiolaria species, and nine silicoflagellates. CCA ordination showed that BSi and TOC were the environmental factors that most associated with these microfossils assemblages. Diatom diversity was found vary from 18 to 26 species each sample, which dominated by Cyclotella meneghiniana, Fragilaria fasciculata and Coscinodiscus kutzingii. Environmental changes on Pleistocene epoch were caused by glaciation cycle and geomagnetic reversal at that time. Salinity and TOC were tended to increase significantly then followed by BSi decline and marine diatom domination which indicated of marine transgression event. Marine transgression was induced by a global sea level rise which made the atmosphere more humid and caused cooler climate. High TOC which was not linear with diatom diversity and abundance, also freshwater diatom domination indicated of terrigenous matters input to an estuarine water body. CCA ordination showed that Coscinodiscus kutzingii and Coscinodiscus normanii had a strong association with salinity, and strong association with TOC for Aulacoseira distans and Fragilaria fasciculata.

Ardo Ramdhani

Romanus Edy Prabowo

Rachmad Setijadi