Indonesian Journal on Geoscience

7

Authors: M.K. Adisaputra and D. Kusnida

The sample studied was derived from the base of core MD 982156, one of the boreholes obtained during the IMAGES Expedition. The expedition was carried out as a research cooperation between Indonesia and French Governments using Marion Dufresne Research Vessel, belonging to IFRTP (French Institute for Polar Research). Within this sample, the phillipsite minerals were firstly found by the first author. Using SEM (Scanning Electron Microscope) at the magnification of x1,000 for group and up to x20,000 for individual photos, the nannoplanktons were shown to accumulate on the phillipsite minerals as a binding matrix. Different directions and velocity of the bottom current when the phillipsite minerals were originated, might have contributed in binding of the various mineral shapes. The calcareous nannoplankton in the studied area is preserved within the sediments between 3880 m to 3914 m depths below sea level (bsl). This interval possibly located between Lysocline and Carbonate Compensation Depth (CCD), is indicated by the presence of well preserved calcite minerals and calcareous nannoplankton within sediments. Discoaster multiradiatus, the dominant fossil within the sediments in the studied area, is Paleocene in age. Therefore, the binding of nannoplakton accumulation as a matrix of the phillipsite minerals occurred as a postgenetic deposition. Keywords: Paleocene, postgenetic, nannoplankton, phillipsite, Roo Rise, Indian Ocean

16

Authors: F. Hasibuan

The interregional and global correlation of the Triassic biota of Indonesia was based on the review of previous workers and the author himself. Scythian Epoch (Early Triassic) in Timor is subdivided into Early Scythian with Ophiceras demisso, Meekoceras sp., Pseudomonotis subaurita, Gervillia subpannonica, and Myophoria sp., whilst Late Scythian is indicated by the presence of Owenites egrediens and Sibirites sp. The presence of Anisian Stage (Middle Triassic) in Misool is indicated by ammonite Beyrichites and bivalve Daonella lilintana. In Timor, this stage is pointed out by the presence of Joannites cymbiformis, Monophyllites wengensis, Protrachyceras archaelus, Daonella indica, Tracyceras cf. aon, Brochidium timorense, and Lima subpunctatoides. Terebellina mackayi found above Beyrichites-bearing bed in Misool has an age range from Anisian to Ladinian. It is concluded that the boundary between Anisian and Ladinian lies between beds with Beyrichites and Terebellina mackayi. Early Carnian Stage (Late Triassic) in Timor is indicated by the presence of Joanites cymbiformis, Waldhausenites sp., Miltites sp., and Halogyra cipitiensis; whereas Late Carnian is indicated by the presence of Cladicites crassestriatus and Tropites subbulatus. The presence of Halobia verbeeki, Pinacoceras parma, Neobetites sp., Parabetites sp., Malayites sp., Amarassites sp., and Halorites sp., indicates the Early Norian Stage, whilst the presence of Cladiscites tornatus, Cyrtopleurits malayicus, and Trachypleuraspidites sp. implies the Late Norian. The Rhaetian Stage in Timor contains Choristoceras indoaustralicum, whereas in Misool it contains Choristoceras sp. and Cochloceras sp. Keywords: Triassic, biota, macrofossil, Scythyan, Anisian, Carnian, Norian, Rhaetian

17

Authors: D. Setiady

Based on the depth contour, the sea bottom morphology in southern part of the researched area is very steep, while in the northern area it is sloped slightly. It shows that sedimentation process is from south to the north and continues to the west. It is supported by the current process in studied area. Rock slope stability of hilly morphology in the Cimandiri River area is related to weathering, erosion, and transportation process in coastal and nearshore areas. The presence of mineral in the studied area caused by those processes, was accumulated in the mouth of Cimandiri River, coastal, and nearshore areas. Those minerals were deposited in Cibelendung to Karangbeureum nearshore area by the longshore current. Magnetite and pyroxene minerals are dominant along the coastal and offshore areas of Pelabuhan Ratu Bay. The presence of augite and diopside shows that the source rock is basic igneous rocks (basalt), while the presence of hornblende and biotite minerals tend to indicate that the source rock is intermediate igneous rocks (andesite). Kata kunci: augite, diopside, basalt, hornblende, biotite, Pelabuhan Ratu