17:15 〜 19:15
[MIS06-P05] Paleoecological Reconstruction of Jatiluhur, Indonesia, Through the Benthic Foraminifera
キーワード：Paleoecology, Foraminifera, Middle Miocene, Jatiluhur Formation
This study explores the paleoecological conditions of the Jatiluhur Formation in West Java, Indonesia, during the Middle Miocene (range from 14.4 – 11.3 Ma), a period influenced by global climate changes affecting sea levels. The Jatiluhur Formation is an intriguing research site due to its well-preserved foraminiferal assemblages, diverse sediment composition, and its location in a tectonically active region. Investigating this formation can provide valuable insights into paleoenvironmental conditions, particularly sea-level fluctuations, temperature shifts, and oxygenation levels during the Miocene.
The formation primarily consists of marl and quartz sandstone members, including dark gray marl, clay shale, and marl limestone. A geological cross-section reconstruction from 2019 provided a framework for analyzing eighteen sediment samples, revealing 70,300 individual benthic foraminifera, representing 185 species and 102 genera. This study employs a quantitative approach by analyzing the dominance of specific genera across different samples to infer environmental conditions. Nine genera were selected for further analysis: Anomalinoides, Bolivina, Elphidium, Textularia, Cyclammina, Heterolepa, Lagena, Lenticulina, and Uvigerina. The dominance of Bolivina suggesting adaptation to dysoxic, temperate, and normal salinity conditions. Other genera reflect localized environmental variations. The estimated seabed temperature was relatively cold (<10°C), with cyclical fluctuations between cold and cold-warm conditions. Salinity remained stable at normal marine levels (32–40‰), except for one sample indicating hyposaline conditions. Oxygen levels were persistently low (dysoxic, 0.1–0.3 mL/L), suggesting either deeper waters with limited oxygen exchange or high organic productivity leading to oxygen depletion. These findings align with global climatic events, including the Middle Miocene global cooling and the expansion of the East Antarctic Ice Sheet.
By integrating paleoecological data with a quantitative methodology, this research aims to refine interpretations of past environmental conditions in the Jatiluhur Formation. The findings contribute to a broader understanding of marine ecosystem responses to climate change, with potential applications for predicting future environmental shifts. Nevertheless, further research is needed to deepen the knowledge of paleoecology in the Jatiluhur Formation during the Middle Miocene.
The formation primarily consists of marl and quartz sandstone members, including dark gray marl, clay shale, and marl limestone. A geological cross-section reconstruction from 2019 provided a framework for analyzing eighteen sediment samples, revealing 70,300 individual benthic foraminifera, representing 185 species and 102 genera. This study employs a quantitative approach by analyzing the dominance of specific genera across different samples to infer environmental conditions. Nine genera were selected for further analysis: Anomalinoides, Bolivina, Elphidium, Textularia, Cyclammina, Heterolepa, Lagena, Lenticulina, and Uvigerina. The dominance of Bolivina suggesting adaptation to dysoxic, temperate, and normal salinity conditions. Other genera reflect localized environmental variations. The estimated seabed temperature was relatively cold (<10°C), with cyclical fluctuations between cold and cold-warm conditions. Salinity remained stable at normal marine levels (32–40‰), except for one sample indicating hyposaline conditions. Oxygen levels were persistently low (dysoxic, 0.1–0.3 mL/L), suggesting either deeper waters with limited oxygen exchange or high organic productivity leading to oxygen depletion. These findings align with global climatic events, including the Middle Miocene global cooling and the expansion of the East Antarctic Ice Sheet.
By integrating paleoecological data with a quantitative methodology, this research aims to refine interpretations of past environmental conditions in the Jatiluhur Formation. The findings contribute to a broader understanding of marine ecosystem responses to climate change, with potential applications for predicting future environmental shifts. Nevertheless, further research is needed to deepen the knowledge of paleoecology in the Jatiluhur Formation during the Middle Miocene.