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The last 5.1 million years (Pliocene) of climate changes


Planktic marine microfossils and sedimentary analysis were performed on Latest Miocene (approximately 5.1 million years ago) to recent sections in North East Java Basin of Western Indonesia to determine paleoclimate changes. The composite stratigraphic section of 8050 feet length reveals that since the Pliocene (4.9 Ma) a bathyal to inner neritic (20 to 500 m sea level depth) depositional environment was being filled with the fine siliciclastic sediment in fluctuate of temperate to warm climate. In the lower part of section (7750-3450 feet interval), fine sediments with Globorotalia tumida, Sphaeroidinella dehiscens, Globigerinoides trilobus sacculiferus and Orbulina universa-planktic foraminifera fauna as well as Discoaster quinqueramus, D. asymmetricus, D. surculus, D.pentaradiatus, Gephyrocapsa omega and G.oceanica-planktic nannofossil marine flora remains indicated deposition in warm climate at Pliocene (1.8 to 0.07 Ma). Here, Globorotalia truncatulinoides-foraminifera, Discoaster variabilis and Calcidiscus leptoporus-nannofossils as taxa characteristic of slightly warm condition are locally abundant. In contrast, the middle part of section (3400 – 200 feet interval) deposited at Holocene (0.07 Ma to present) is dominated by marker species of temperate climate, notably Discoaster challengeri, Gephyrocapsa mediterranea, G. carribbeanica and Coccolithus pelagicus nannofossils. The relative abundance of warm marker species decreases as a consequence of temperature drop. This level is considerably correlate with global glaciation periods. Warm species are sometimes commonly found on strata which could be attributed to the slightly increased temperature. Highest in the section (150 to 0 m interval), warm marker taxa more abundant indicate the increase temperature condition.

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