The results of marine geological and geophysical surveys using R/V Geomarin I in eastern Jawa Sea between Madura and Kalimantan in Masalembo Waters reveal the presence of several Quaternary seafloor sediment types e.g. Marine; Onland & coastal and Mixture between marine and terrigenous deposits. Two seismic sequences (A and B) are recognised to represent the Quaternary and Pra-Quater-nary layers and further classified in four seismic subsequences (Al, A2, B1 and B2). Core data in the sub-sequence Al perhaps to represent marsh or marine deposits and subseqence A2 more likely is the kaolinitic deposits. Thickness and geometry patterns of seismic subsequence Al and core data indicate two main sedimentation processes, first the onland & coastal deposits perhaps derived from northern direction (Kalimantan) and second the marine and shallow marine deposits may come from southern area (Madura & Java). In general the thickness of the Quaternary sediments is greater towards south and shallowing to the north. Two areas have sediment thickness greater than 100 m i.e., in the southeastern and south-western parts of the study area. The latter area indicates the presence of marsh deposits which contain many peat layers. The occurrence of the marsh deposits nonetheless proved that the Kalimantan and Jawa was connected during Holocene time with the Sunda River flowing in the middle of the area.
Authors : M. Situmorang, D. Ilahude, A. Faturachman, T. Kuntoro & D. Kusnida, D. Arifin