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| Titel |
Late Miocene fossils from shallow marine sediments in Brunei Darussalam: systematics, palaeoenvironment and ecology. |
| VerfasserIn |
Amajida Roslim, Antonino Briguglio, Laszlo Kocsis, Stjepan Ćorić, Hazirah Razak |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250121583
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| Publikation (Nr.) |
 EGU/EGU2016-362.pdf |
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| Schlagwörter |
Sediment, Flachwassersediment, Stratigraphie, Biostratigraphie, Fossilien, Systematische Paläontologie, Systematik, Paläoenvironment, Palökologie, Paläofauna, Meeresspiegelschwankung, Chemostratigraphie, Sedimentationsrate, Miozän, Neogen |
| Geograf. Schlagwort |
Brunei, Borneo |
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| Zusammenfassung |
| The geology of Brunei Darussalam is fascinating but difficult to approach: rainforests and
heavy precipitation tend to erode and smoothen the landscape limiting rocks exposure,
whereas abundant constructions sites and active quarries allow the creation of short time
available outcrop, which have to be immediately sampled.
The stratigraphy of Brunei Darussalam comprises mainly Neogene sediments deposited
in a wave to tide dominated shallow marine environment in a pure siliciclastic system. Thick
and heavily bioturbated sandstone layers alternate to claystone beds which occasionally yield
an extraordinary abundance and diversity of fossils. The sandstones, when not bioturbated,
are commonly characterized by a large variety of sedimentary structures (e.g., ripple marks,
planar laminations and cross beddings).
In this study, we investigate the sediments and the fossil assemblages to record
the palaeoenvironmental evolution of the shallow marine environment during the
late Miocene, in terms of sea level change, chemostratigraphy and sedimentation
rate.
The study area is one of the best in terms of accessibility, extension, abundance and
preservation of fossils; it is located in the region -’Bukit Ambug’ (Ambug Hill), Tutong
District. The fossils fauna collected encompasses mollusks, decapods, otoliths, shark and ray
teeth, amber, foraminifera and coccolithophorids.
In this investigation, sediment samples were taken along a section which measures 62.5
meters. A thick clay layer of 9 meters was sampled each 30 cm to investigate microfossils
occurrences. Each sample was treated in peroxide and then sieved trough 63 μm, 150μm,
250μm, 450μm, 600μm, 1mm and 2mm sieves.
Results point on the changes in biodiversity of foraminifera along the different horizons
collected reflecting sea level changes and sediment production. The most abundant taxa
identified are Pseoudorotalia schroeteriana, Ampistegina lessonii, Elphidium advenum,
Quinqueloculina sp., Bolivina sp., Globigerina sp.
Coccolithophorids assemblage recovered from one horizon dates the sediment to the
biozone NN11a due to the presence of Discoaster berggrenii and D. quinqueramus, which are
both also warm water indicators. The absence of Amaurolithus primus reduces the
stratigraphic range to the uppermost Tortonian only (∼7.5-8 Ma). |
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