Quaternary – Recent Reef Facies Model in Seribu Islands – Jakarta Bay, DKI Jakarta

The research area is located on the Seribu Island in North Jakarta, DKI Jakarta Province, Indonesia. The Seribu Islands are a unique area of carbonate system that makes the presence of small islands which separate from one another in the research area. The necessary to study the history of formation and the processes that occurred thus we could understand the geometry of the reef system in the Seribu Islands. The purpose of the research is that the authors aim to know the changes in the development of the QuaternaryRecent reef model as a facies model or comparison for older reefs or ancient reefs and identify tectonic processes that affect carbonate rocks which grow in the Seribu Islands. The research methodology was by conducting field observations through underwater observation by photos of reef biodiversity and soft sediment sample on four islands including Harapan Island, Tidung Island, Pramuka Island, and Putri Island. From the observations under seawater, the biota on the four islands consists of branching coral, globular coral, massive coral, platy coral, and encrusting coral. Based on the presence of the coral biota and supported by lands at imagery on Harapan Island, Tidung Island, and Pramuka Island, the facies are coralgal sand, lagoon, reef flat, reef crest dan front reef. Meanwhile, Putri Island does not have a lagoon facies. The soft sediment sample shows that there are foraminifera organisms that support the facies interpretation in the study area. The tectonic factor of the structure that highly affects the height of the Seribu Island is the existence of a Seribu Island fault so that carbonate rocks can grow. Therefore, the Seribu Islands could be categorize as isolated reefs due to the reef that grows with a patch reef geometry on the Seribu platform