RAMDHANI, Ardo (2018) Mikrofosil Berbasis Silika Sebagai Bukti Rekonstruksi Perubahan Paleoekologi Kala Pleistosen Lapisan Diatomit di Formasi Pucangan, Sangiran. Skripsi thesis, Universitas Jenderal Soedirman.

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Abstract

Diatom, radiolaria, and silicoflagellate are siliceous microfossils that able to be preserved in sediment layer after their lifespan is over. This study was conducted to determine the profile of siliceous microfossils community in diatomite layer of Pucangan Formation, Sangiran. Microfossils profile analysis obtained the environmental reconstruction of the Pleistocene epoch in this area. The association between environmental variable measured and microfossil community change among samples illustrated the regional environmental change. This study has diatom assemblage as the primary response variable, and the secondary response variable was the radiolaria and silicoflagellate assemblages. The direct measurement obtained total Organic Carbon (TOC) and Biogenic Silica (BSi), the salinity and pH were obtained by transfer function calibration of modern diatom database in European Diatom Database (EDDI), both were the exploratory variables in this study. Identification revealed the species diversity of diatomite layer composed of 33 diatom, 4 radiolaria, and 9 silicoflagellates. The abundance of each species changed dynamically across the depth of diatomite layer. Visual interpretation by CCA ordination showed that BSi and TOC were the most associated environmental factors with microfossil assemblages. The diatom diversity was found vary from 18 to 26 species in each sample dominated by Cyclotella meneghiniana, Fragilaria fasciculata and Coscinodiscus kutzingii. This study interpreted the environmental change during Pleistocene epoch was caused by glaciation cycle and geomagnetic reversal. The salinity and TOC were tending to significantly increase followed by BSi decline and marine diatom domination which indicated a marine transgression event has occurred. The global sea level rise has induced a marine transgression event causing a more humid atmosphere and a colder climate. The domination of freshwater diatom and the high value of TOC which was not linear with the diatom diversity and abundance has indicated that the terrigenous matters discharge to the estuarine occurred. The CCA ordination showed that Coscinodiscus kutzingii and Coscinodiscus normanii had a definite positive association with salinity and a clear positive association with TOC for Aulacoseira distans and Fragilaria fasciculata.

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