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The last 5.1 million years (Pliocene) of climate changes

Abstrak

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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By vijayaisnania – March 4, 2021

Pengaruh tingkat kecerahan dan turbiditas terhadap kelimpahan foraminifera bentik di Perairan Tambelan, Laut Natuna

Abstrak

Berbagai penelitian kelautan dan pengambilan sampel dilakukan di perbatasan Indonesia-Malaysia dengan menggunakan Kapal Riset Baruna Jaya VIII. Indonesia memiliki wilayah laut > 70%, namun masih dirasakan terbatasnya jumlah publikasi / informasi  mengenai foraminifera pada sedimen laut Kuarter. Pengamatan sedimen megaskopis maupun mikroskopis terutama dimaksudkan untuk mengetahui tektur dan komposisi sedimen serta kandungan mikroorganisma. Kajian ini bertujuan untuk mengetahui pengaruh tingkat kecerahan dan turbiditas terhadap kelimpahan dan diversitas foraminifera di muara hingga laut terbuka. Perairan Tambelan merupakan bagian dari wilayah Perairan Natuna, berbatasan dengan wilayah daratan Kepulauan Tambelan dan Pulau Kalimantan.

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By vijayaisnania – March 4, 2021

Sediments and Foraminifera Distribution in Response to Environmental Changes of Jakarta Bay in Last +- 150 years

Abstrak

The research covered a study about sediments and microorganism content in marine sediment to find out the environmental changes of Jakarta Bay. This shallow marine northern Jakarta is marked by shell fragment. Seventy-five samples from twenty cores of + 30 cm in length were taken from the depth of 2.1 – 30.1 m. The actual research was started by the collection of secondary data and samples. Laboratory analysis upon sediment samples were conducted to describe sediment texture megascopically and microscopically adopted some basic method to identify foraminifera. The 210Pb dating on samples were carried out to determine the age of sediments. The sandy silt, clayey silt, silty mud and silty clay deposited during + 150 years generally contain abundant benthic foraminifera besides ostracods and mollusk shell. The 78 benthic foraminifera species were identified in sediment samples. Asterorotalia trispinosa was the most commonly found species in marine samples we collected. It was found that the assemblages, abundance and diversity of benthic changes in accordance with fluvial and marine influence during deposition. Less abundance and diversity of foraminifera assemblages as well as typical of some opportunistic genera (Ammonia, Asterorotalia, Elphidium, Nonion and Quinqueloculina) indicated high fluvial influence from Citarum and Cisadane rivers. In open marine, the assemblages were composed over 90%% calcareous benthic forms. This favorable condition was recorded by both high abundance and diversity as well. During the deposition of this sediment sequence, the relative environment changes frequently occurred due to anthropogenic affinity.

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By vijayaisnania – March 4, 2021

Miocene calcareous nannofossil biostratigraphy of East Java, Indonesia

Abstrak

Micropaleontological clues, particularly calcareous nannofossils in Miocene marine sediment from East Java, Indonesia were studied. Detailed biostratigraphic frame work is provided by the occurrences of diverse and well-preserved nannofossil. The nannofossil events used to date the Miocene of 5.2 to 25.2 Ma duration are based on datum planes of the first and last occurrence of marker species (FO and LO). For the Miocene interval of East Java, a total of 15 marker species have been selected, among all: Sphenolithus ciperoensis, Cyclicargolithus abisectus, Discoaster druggi, Sphenolithus heteromorphus, S. belemnos, Calcidiscus macintyrei, Helicosphaera ampliaperta, Discoaster kugleri, D. hamatus, D. neohamatus, D. bellus, D. neorectus, D. quinqueramus, Amaurolithus primus, and D. berggrenii. On the basis of these datum planes, 18 interval zones were established. Those are, beginning with the oldest: Sphenolithus ciperoensis – Cyclicargolithus abisectus interval zone (NN1/Early Miocene or 25.2 my), Cyclicargolithus abisectus – Discoaster druggi interval zone (NN1/Early Miocene), Discoaster druggi –  Sphenolithus heteromorphus interval zone (NN2-3/Early Miocene), Sphenolithus heteromorphus – Sphenolithus belemnos interval zone (NN3/Early Miocene), Sphenolithus belemnos – Calcidiscus macintyrei interval zone (NN4/Early Miocene), Calcidiscus macintyrei – Helicosphaera ampliaperta interval zone (NN4/Early Miocene), Helicosphaera ampliaperta – Sphenolithus heteromorphus interval zone (NN5/Early Miocene or 16.2 my), Sphenolithus heteromorphus – Discoaster kugleri interval zone (NN6/Middle Miocene), Discoaster kugleri range zone (NN7/Middle Miocene), Discoaster kugleri – Discoaster hamatus interval zone (NN8/Middle Miocene), Discoaster hamatus – Discoaster neohamatus interval zone (NN9/Middle Miocene or 10.2 my), Discoaster neohamatus – Discoaster bellus  interval zone (NN9/Late Miocene), Discoaster bellus – Discoaster hamatus interval zone (NN9/Late Miocene), Discoaster hamatus – Discoaster neorectus interval zone (NN10/Late Miocene), Discoaster neorectus – Discoaster quinqueramus interval zone (NN10/Late Miocene), Discoaster quinqueramus –  Amaurolithus primus  interval zone (NN11/Late Miocene), Amaurolithus primus – Discoaster bergrrenii interval zone (NN11/Late Miocene), and Discoaster bergrrenii – Discoaster quinqueramus interval zone (NN11/Late Miocene or 5.2 my BP). Throughout Miocene interval, nannofossils provide a high accurate biostratigraphy and are the prime tool for correlation. Sea level fluctuation, transgression and wide Intra-Miocene orogenic regression is recorded particularly in marine clastic sediment and detrital limestone from asymmetric back arch basins – north East Java. These events can be reconstructed by nannofossil biostratigraphy analysis and it can be correlated to foraminifera analysis.

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By vijayaisnania – March 4, 2021

Relative sea level during Holocene responses to environmental changes of Malaka Strait

Abstrak

Microorganism analysis have been used to study environmental and sea level changes at Kepulauan Riau site, Malaka Strait. Four cores were taken for microorganism as foraminifera, nannoplankton and palynomoph analysis. Samples were taken about 5 cm interval from these cores. A cross section reconstructed based on the core description. The sediment from the core base are grey clay and greenish sand with mollusk, foraminifera and nannoplankton. The site was a shallow marine environment at Early Holocene (0.01 Ma). The middle part is marked by higher abundancy and diversity of marine species indicated deep marine environment. They suggest this sediment were deposited during the Holocene transgression, perhaps in response to sea level rise in mid-Holocene. The period following mid-Holocene, sea level stabilization is marked by coastline progradation. Marine species decrease in upper level suggesting seaward shifting of deposited environment due to relative sea level fall. Sea level fall and accretion of sediment might have altered the environment to shallower. This establishment then promoted further sedimentation at the site. During the deposition of upper part, minor relative sea-level rise and fall frequently occurred, altering depositional environment of the study slightly deeper and shallower. The Kepulauan Riau site was at or close to the low sea level due to increased fluvial activities.

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By vijayaisnania – March 4, 2021

Pliocene to Holocene nannoplankton climatostratigraphy (case study: Northern East Java Basin Indonesia)

Abstrak

Nannoplankton assemblages were studied in core samples from neritic sediments of Northern East Java Basin. Paleoclimate changes are reconstructed using of total individual and species abundance as well as ratio of temperature indicator taxa. Discoaster group, Coccolith group, Discoaster asymmetricus, D. pentaradiatus, D. quinqueramus and Gephyrocapsa oceanica were recorded as warm taxa; whereas Coccolithus pelagicus, Discoaster challengeri, Gephyrocapsa caribbeanica and Thoracosphaera saxea are known well adapted to cold zone. Calcidiscus leptoporus and Discoaster variabilis had a preference for temperate zone. Based on temperature diagnostic and other potentially correlate able events, from Late Pliocene to Holocene can be recognized three climatostratigraphic zone in the Madura Strait section, Northern East Java Basin (from bottom to top): (a) Zone I: warm, NN12 to NN14 (Lower Pliocene); (b) Zona II: temperate, NN15 to NN18 (Upper Pliocene); and (c) Zona II: warm, NN19 to NN21 (Lower Pleistocene to Holocene).

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By vijayaisnania – March 4, 2021

Nannoplankton and foraminifera assemblages and their relations to bathymetry in Madura Waters

Abstrak

Nannoplankton and foraminifera assemblages were studied in eight surface sediment samples from Madura Strait and 33 surface sediment samples from open marine water north of Madura. Twenty-two nannoplankton taxa, 37 benthonic foraminifera taxa, and 16 planktonic foraminifera taxa were identified. Nannoplankton assemblages are very rare in water depths of less than 20 meters in the Madura Strait, being about 1 percent of the total sediment. These nannoplankton assemblages are made up of a single species, Gephyrocapsa oceanica. Planktonic foraminifera do not occur in these relatively shallow depths. However, benthonic foraminifera assemblages occur and are dominated by Florilus angulatus. In the neritic zone, which is indicated by accumulation of very fine-grained, nannoplankton assemblages are dominated by Gephyrocapsa oceanica, though Emiliania huxleyi and Florisphaera sp. are common components in the assemblages. Benthonic and planktonic foraminifera assemblages are increasingly more abundant and have higher diversity indices in the neritic zone. In shallow neritic open marine water, which is indicated by silt, nannoplankton assemblages are also dominated by Gephyrocapsa oceanica. The abundance and diversity index of both nannoplankton and foraminifera assemblages increase with increasing water depth. In water depths greater than 70 meters, neritic open marine foraminifera species are common. The occurrence of nannoplankton and foraminifera assemblages in the study area is closely related to bathymetry.

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By vijayaisnania – March 4, 2021

Foraminifera and nannoplankton assemblages and their relations to bathymetry in Madura Waters

Abstrak

Foraminifera and nannoplankton assemblages were studied in fifteen surface sediment samples from Madura Strait. Thirty-seven benthic and 16 plankton foraminifera taxa as well as 22 nannoplankton taxa were identified. Plankton foraminifera do not occur in water depths of less than 20 meters. However, benthic foraminifera assemblages occur and are dominated by Florilus angulatus. Nannoplakton assemblages are very rare, being about 1% of the total sediment in these relatively shallow depths. These nannoplankton assemblages are made up of single species, Gephyrocapsa oceanica. In the neritic zone, which is indicated by accumulation of very fine-grained sediment, plankton and benthic foraminifera assemblages are increasingly more abundant and have higher diversity. Nannoplankton assemblages are dominated by Gephyrocapsa oceanica, though Emiliania huxleyi and Florisphaera sp. are common components in the assemblages in the study area is closely related to bathymetry. The abundance and diversity index of assemblages increase with increasing water depth.

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By vijayaisnania – March 4, 2021

Penentuan Biodatum Foraminifera Planktonik dan Bentonik Formasi Batuasih

Abstrak

Penelitian ini dilakukan untuk mengetahui kandungan dan penyebaran fosil foraminifera planktonik dan bentonik pada Formasi Batuasih termasuk spesies petunjuk, serta menentukan biodatum berdasarkan pemunculan awal atau akhir spesies tersebut. Dari analisis laboratorium dapat diidentifikasi 27 spesies planktonik dan 15 spesies bentonik. Berdasarkan kandungan fosil dan ciri litologinya, dapat diketahui bahwa Formasi Batuasih diendapkan sejak Oligosen Akhir hingga Miosen Awal, dalam lingkungan transisi (bagian bawah) yang berkembang menjadi laut terbuka (atas). Berdasarkan enam spesies petunjuk foraminifera planktonik sebagai penciri datum, dapat ditentukan empat biodatum, berturut-turut dari tua ke muda adalah: Globorotalia opima Datum, Globigerinoides primordius Datum, Globigerinoides trilobus Datum dan Globorotalia peripheroronda Datum. Penyebaran dan kelimpahan foraminifera bentonik tidak menunjukkan suatu trend (kecenderungan) yang berarti untuk dapat menentukan biodatum.

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By vijayaisnania – March 4, 2021

KARAKTERISTIK PENURUNAN DASAR LAUT PERAIRAN TELUK JAKARTA

Abstrak

Penurunan permukaan tanah wilayah pesisir Teluk Jakarta diyakini sebagai dampak dari pembangungan. Dari tahun 1974 sampai dengan 2010 telah terjadi penurunan permukaan tanah di sejumlah daerah DKI Jakarta antara -0.25 m dan -4.1 m. Kawasan perairan Teluk Jakarta sebagian besar masih dalam kondisi alamiah, belum mengalami beban pengembangan yang dapat menimbulkan penurunan. Tujuan penelitian ini adalah untuk menghitung penurunan dasar laut Teluk Jakarta melalui pendekatan tektonik, lingkungan, dan kosolidasi sedimennya sebagai penyebab penuruan. Metode yang digunakan adalah pengembangan data sedimen inti bor dan rekaman sesimik pantul dangkal meliputi analisis besar butir, mikrofauna, pentarihan umur radiokarbon C14 dan analisis srtatigrafi seismik. Hasilnya penurunan lapisan sedimen perairan Teluk Jakarta telah terjadi sejak masa ribuan tahun yang lalu (Late Glacial Maximum, LGM). Penurunan tersebut terjadi akibat adanya gerakan vertikal lapisan sedimen (tektonik) dan konsolidasi sedimen. Penurunan lapisan sedimen di wilayah barat antara 0.1m dan 0.3m pertahun, dan 0.4m dan 0.5m pertahun di wilayah timur Teluk Jakarta. Kecepatan pengendapan sedimennya berkisar antara 0.57cm dan 1,84cm pertahun lebih kecil dari penurunan. Jika terjadi gangguan pada lapisan sedimen pasir maka penuruan dasar laut perairan barat Teluk Jakarta cenderung akan meningkat. Pengembangan perairan Teluk Jakarta untuk pembangunan infrastruktur sebaiknya mengikutsertakan data dan informasi geologi kelautan untuk memperkecil resiko dampak penurunan.

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By vijayaisnania – February 9, 2021