Evolusi perairan Teluk Jakarta berdasarkan sedimen dan foraminifera

Abstract

Jakarta Bay is located in Special Region of Jakarta Province where the downstream of 13 rivers cut through the whole area of Jakarta. Jakarta Bay is cover approximately 514 km2. Based on the foraminifera characteristic as potential indicator for understanding both the recent and the ancient water environment. The aim of this research is to study vertically and horizontally ecological change that have had occurred in Jakarta Bay. The sampling of sediment samples in Jakarta Bay had been carried out using the Geomarine I. There are 25 collected samples location. The collected samples had been done in 1994 and had been storage in the cold storage in Cirebon. The sediment and microorganism observation and study has been carried out at Paleontology Laboratorium, Geological Technological Faculty of Padjadjaran University. Analitical of submarine core sample were included the description of sediment and indentification of benthic foraminifera. Analitical of Lost On Ignition (LOI) is a method to count organic material content and carbonate content in the sediment sample. The absolute dating for Holocen is based on radioactive (210Pb method) for sediment dating. Factorial Correspondence Analysis is for sediment group analysis and benthic foraminifera by using XLSTAT 2012 software. The result of sediment grain measurement analysis shows that sediment of Jakarta bay is consist of clay fraction (<0.004 mm) and shale (0.063-0.004 mm) based on grain measurement scale of Wenworth (1922). The result of Lost On Ignition analysis shows that carbonate and organic material content in the sediment change from time to time. Carbonate content in the sample is the opposite result with its organic material content. The dating from the core TJ-11 in the sediment layer 20- 22 cm was more than 173 years. Core TJ-21 in the sediment layer 30-32 cm was more 115 years. Core TJ -89 sediment layer less than 30-32 cm, which was more than 136 years. The study on Recent Benthic Foraminifera from the Jakarta Bay consist 177 species included 84 genera. The grouping based on shell: -Subordo Rotaliina was found 87 species included its 52 genera. -Subordo Miliolina was found 65 species included its 17 genera. -Subordo Textulariina was 25 species included its 15 genera. The result on Factorial Correspondence Analysis that the genus of benthic foraminifera with layers of depth shows the distribution pattern which is different in each layer of sample depth. The change of composition foraminifera genus can be seen in each layers has different genus composition. From here, it can be noticed the environment evolution that has been characterised by Benthic Foraminifera.