Santi Dwi Pratiwi
Departemen Geologi Sains, Fakultas Teknik Geologi, Universitas Padjadjaran

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Journal : Bulletin of Scientific Contribution : Geology

Identifikasi Umur Batupasir Formasi Bentang di Pangandaran Berdasarkan Kumpulan Nannofosil Gampingan Santi Dwi Pratiwi; Vijaya Isnaniawardhani; Tokiyuki Sato
Bulletin of Scientific Contribution: GEOLOGY Vol 20, No 1 (2022): Bulletins of Scientific Contribution : Geology
Publisher : Fakultas Teknik Geologi Universitas Padjadjaran

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24198/bsc geology.v17i1.39353

Abstract

ABSTRAKSebanyak 15 sampel yang terdiri dari batupasir dengan semen karbonat dalam berbagai ukuran butir dari Formasi Bentang di daerah Babakan Kabupaten Pangandaran dianalisis pengamatan mikroskopis dan penentuan umur berdasarkan kumpulan nannofosil gampingan. Sisipan batulempung sesekali muncul di antara batupasir di bagian selatan lokasi pengambilan sampel. Kumpulan nannofosil gampingan umumnya banyak hingga sedikit dan preservation nannofosil terawetkan sedang - baik. Kerangka biostratigrafi terdiri dari 5 (lima) peristiwa Zonal berdasarkan kemunculan 21 spesies nannofosil gampingan. Lima spesies datum nannofosil yaitu terdiri dari kemunculan akhir Coccolithus miopelagicus (Zona 10.613 Ma atau NN8); kemunculan awal Discoaster hamatus (10,541 Ma) dan kemunculan akhir Discoaster hamatus (9.560 Ma) atau Zona NN9-NN10; kemunculan awal Discoaster berggrenii (NN11/NN10); dan interval atas Reticulofenestra kecil (7.167 Ma atau NN11 Zone). Lebih khusus lagi, interval umur pada Formasi Bentang daerah Pangandaran berkorelasi pada Miosen Akhir yaitu dari Zona NN8 hingga Zona NN11. Dominasi Reticulofenestra kecil di Zona NN11 menunjukkan korelasi positif dengan kelimpahan produktivitas coccolith di Formasi Bentang. Kata Kunci: Formasi Bentang, Nannofosil Gampingan, Miosen Akhir, Pangandaran ABSTRACTA total of 15 samples composed of sandstones with carbonate cement in various grain sizes from Bentang Formation in the Babakan area of Pangandaran regency were analyzed for microscopic observation and age determination based on the calcareous nannofossil assemblages. Claystone inserts occasionally appear between these sandstones in the southern part of the sampling location. The calcareous nannofossils assemblages are generally common to few  and preservation of sample is moderate to good. The biostratigraphic framework consist of 5 (five) Zonal events based on the occurrences of 21 species of calcareous nannofossil. Five nannofossil datum species are consist of  last occurrence of Coccolithus miopelagicus (10.613 Ma or NN8 Zone); first occurrence  Discoaster hamatus  (10.541 Ma) and last occurrence of Discoaster hamatus (9.560 Ma) or NN9-NN10 Zone; first occurrence of Discoaster berggrenii (NN11/NN10); and top of small Reticulofenestra interval (7.167 Ma or NN11 Zone). More specifically, an age interval at Bentang Formation of Pangandaran area was correlated for the Late Miocene from NN8 Zone to NN11 Zone. The dominance of small Reticulofenestra at NN11 Zone  shows a positive correlation with abundance of coccolith productivity in Bentang Formation.  Keywords : Bentang Formation, Calcareous Nannofosils, Late Miocene, Pangandaran
Identifikasi Umur Formasi Jampang Anggota Cikarang Berdasarkan Kumpulan Nannofosil Gampingan di Sungai Cikarang, Geopark Ciletuh Pelabuhanratu Santi Dwi Pratiwi; Shun Chiyonobu; Mega Fatimah Rosana
Bulletin of Scientific Contribution: GEOLOGY Vol 20, No 3 (2022): Bulletin of Scientific Contribution : GEOLOGY
Publisher : Fakultas Teknik Geologi Universitas Padjadjaran

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24198/bsc geology.v20i3.44145

Abstract

The Cikarang river, Ciletuh  Palabuhanratu Geopark is composed of sandstones and claystones in various grain sizes and thicknesses with carbonate claystone thicknesses varying from 10 to 20 cm, which is part of the Jampang Formation Cikarang Member. A total of 35 samples with 70 preparate slides of nannofossils from one station at Cikarang River  were prepared for microscopic observation and identification of nannofossil datum based on the nannofossil assemblages. The biostratigraphic framework consisting of 8 zonal and non-zonal events based on the occurrences of 40 species of calcareous nannofossil from 35 samples on the Jampang Formation Cikarang Member at Cikarang River. Biostratigraphic interval at Site Cikarang River was correlated for the NN1 (22.6 Ma) to NN 4 (17.973 Ma) in Early Miocene Zone. Eight nannofossil datum species covered the Early Miocene interval these are as follows: the first common occurrence of Sphenolithus heteromorphus (NN4); last common occurrence of Sphenolithus belemnos  (NN4/NN3); last occurrences of  Sphenolithus dissimilis (NN3); first occurrence of  Sphenolithus belemnos (NN3/NN2); first common occurrence Helicosphaera carteri (NN2); last common occurrence of Triquetrorhabdulus carinatus (NN2); the first occurrence of  Sphenolithus disbelemnos (NN2/NN1);  and the first occurrence of Sphenolithus dissimilis (NN1). The most unusual feature is the abundance of Sphenolithus, productivity of Discoaster is rare and Cyclicargolithus is a reticulofenestrid coccolith that dominates (more than 50% of the assemblage) from younger to oldest age boundary samples.