Nutrient Level Change Based on Calcareous Nannofossil Assemblages During Late Miocene in Banyumas Subbasin

DOI:10.17014/ijog.3.3.183-194Hydrographic situation on surface waters is more challenging to be understood, related to global and regional climate change in tropical regions. In addition, records from these tropical areas are limited compared to other areas of subtropical and polar regions. The aim of this study is to reconstruct Cenozoic paleoceanography, in particular nutrient level, using outcrop samples from Kali Pasir, Banyumas, Indonesia. This study is focused on the relationships of the relative abundance of Discoaster, coccolith size of Reticulofenestra, and lithofacies characteristics. Nutrient level is reconstructed using quantitative analysis of calcareous nannofossil by counting calcareous nannofossils on 400 fields of View (FOV) for each sample. The abundance of Discoaster and the large Reticulofenestra represent a deep thermocline and nutricline, which is a typical of oligotrophic condition. This condition also associated with the muddy facies in the early stages of Late Miocene (NN8-NN10a). Conversely, decreasing Discoaster abundance and the abundance of small Reticulofenestra indicate a shallow thermocline and nutricline, resulting strong eutrophication of surface waters in the later stage of Late Miocene (NN10b-NN11). A high nutrient content in this stage is related to classical turbidite deposits. A change in a sea surface resulted in strong eutrophication, which is in this section similar to the eastern Indian Ocean micropaleontology records during the Late Miocene (NN10). This finding shows that strong eutrophication in Kali Pasir section is probably driven by nutrient-rich terrestrial material related to the onset of Indian monsoon during the Late Miocene

Calcareous Nannoplankton (Marine Algae) Analysis in Subsurface Sediments of Andaman Sea

Andaman Sea in the Indo-Pacific Warm Pool (IPWP) is influenced by Indo-Australia monsoon winds. Marine sediment cores in this area, BS36 (06°55\u2750.8”N; 96°07\u2728.51”E; ; Water depth 1147.1 meters) were acquired by Geomarin III research vessel andanalysed its morphology for nannoplankton occurences. Results from qualitative identification on marine sediment core in Andaman Sea obtained 11 genus of nannoplankton marine algae in this area. Dominated genus discovered in this site is Gephyrocapsa, Emiliania, and Helicosphaera. Although this research is qualitative and preliminary study phase; however, this reference of modern nannoplankton taxonomy and features using Scanning Electron Microscope (SEM) would enhance marine algae biodiversity along Andaman Sea of Indonesian water

FASIES DAN LINGKUNGAN PENGENDAPAN BATUAN KARBONAT FORMASI PARIGI DI DAERAH PALIMANAN, CIREBON

ABSTRAK Batuan karbonat Formasi Parigi tersingkap baik di Komplek Kromong daerah Palimanan, Cirebon dimana studi fasies karbonat ini dilakukan.  Berdasarkan karakter fisik dan biota yang dikandungnya, batuan karbonat Komplek Kromong dapat dikelompokkan menjadi  7 fasies, yakni : (1) fasies boundstone, (2) fasies rudstone, (3) fasies cross bedded grainstone, (4) fasies foraminiferal packstone, (5) fasies algal-foram packstone,  (6) fasies floatstone, dan (7) fasies thin bedded wackestone-packstone. Fasies boundstone dapat dibagi menjadi 2 subfasies yaitu subfasies bafflestone dan subfasies framestone. Lingkungan pengendapan Formasi Parigi diperkirakan  diendapkan pada lingkungan reef front, reef crest, back reef, lagoon-surge chanel dan tidal flat-tidal chanel. Hasil analisis  fosil foraminifera besar menunjukkan  umur Formasi Parigi adalah Miosen Awal. Berdasarkan pada  pola lingkungan pengendapan Formasi Parigi diinterpretasikan terumbu bagian depan berada di sebelah timur laut, sedangkan terumbu bagian belakang di bagian baratdaya