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
Sari
Percontoh batuan sedimen berasal dari bagian dasar sumur pemboran MD 982156 yang diambil dari salah satu sumur pemboran hasil ekspedisi kelautan IMAGES, suatu kerja sama penelitian antara Indonesia dan Pemerintah Perancis dengan menggunakan Kapal Riset Marion Dufresne milik institusi IFRTP (French Institute for Polar Research). Di dalam percontoh ini mineral phillipsit pertama kali ditemukan oleh penulis pertama. Dengan menggunakan SEM (Scanning Electron
Penelitian ini menggunakan tiga sampel sedimen bor inti dari di sekitar Pulau Siberut, Kepulauan Pagai Selatan dan Pulau Enggano, Perairan Bengkulu, pantai barat Sumatera. Sampel tersebut digunakan untuk mengetahui zonasi biostratigrafi berdasarkan foraminifera plankton. Sebanyak 23 subsampel sedimen diambil dari tiga bor inti dengan interval 1,5 m dan pada lapisan yang memperlihatkan perubahan jenis dan warna sedimen. Analisa foraminifera dilakukan secara kualitatif dan berdasarkan datum pemunculan awal spesies penunjuk untuk menentukan zonasi biostratigrafi. Hasil identifikasi diperoleh 46 spesies foraminifera plankton dalam jumlah sangat melimpah. Ditemukan Bolliella adamsi yang dikenal sebagai spesies penunjuk untuk batas antara kala Plistosen Akhir dan Holosen. Batas ini dijumpai pada kedalaman yang berbeda antara 700 – 950 cm bawah dasar laut (bdl). Berdasarkan penemuan spesies penunjuk tersebut akhirnya ada dua subzona foraminifera plankton, yakni subzona Globigerinella calida dan subzona Bolliella adamsi.Kata kunci: foraminifera plankton, spesies penunjuk, umur, subzona Globigerinella calida dan subzona Bolliella adamsi, pantai Barat Sumatera.This study used three core sediment samples from off Siberut, South Pagai and Enggano islands, Bengkulu waters, Westcoast of Sumatera. The samples were then used to determine biostratigraphic zonation based on planktonic foraminifera. A total of 23 subsample sediments from these three sites within 1.5 m intervals and at layers that showing colour and sediment type changes. Foraminiferal analysis has been carried out qualitatively and based on the initial appearance of the index species in order to determine biostratigraphic zonation. There are 46 identified species of planktonic foraminifera that were found very abundantly. It was also appeared Bolliella adamsi, as an index species for the boundary between Late Pleistocene and Holocene. This boundary was found at different depths between 700 and 950 cm below sea level. Based on the discovery of the index species, finally there are two subzonations of planktonic foraminifera; Globigerinella calida and Bolliella adamsi subzonations.Keywords: planktonic foraminifera, index species, age, Globigerinella calida and Bolliella adamsi subzonations, westcoast Sumatera
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