Detailed palynological analysis of 230 core and sidewall core samples from the uppermost Plover, Elang, and lower Frigate formations, Bayu-Undan Field, Timor Sea, reveals the presence of diverse and moderately well preserved palynomorph assemblages (predominantly dinoflagellate cysts, together with acritarchs, spores, and pollen grains) that facilitate biostratigraphic, sequence stratigraphic, and palaeoenvironmental interpretations. The palynomorph assemblages, detailed systematically herein, comprise 96 spore and pollen species, 84 dinoflagellate species, and 15 acritarch species. Of these, the following 14 dinoflagellate cyst species are newly instituted: Ampulladinium aiax, Batiacasphaera macbethiae, Broomea fusticulum, Cauca bayuiana, Egmontodinium elongatum, Ellipsoidictyum fenestellum, Evansia? lacryma, Leberidocysta? strigosus, Leptodinium? ancoralium, Meiourogonyaulax baculata, Nannoceratopsis reticulata, Paragonyaulacysta? feneseptata, P. helbyi, and Yalkalpodinium playfordii. A further five species are not formally named due to a lack of adequately preserved specimens. One genus, Broomea COOKSON&EISENACK, is formally emended. The palynostratigraphic sequence has previously been assessed as latest Bathonian to early Oxfordian in age, based mainly on correlations with European dinoflagellate assemblages dated by ammonite faunas. Ten subzones (TB1-5 and VT1-5) are informally erected, collectively encompassing the Ternia balmei and Voodooia tabulata dinoflagellate cyst Interval Zones. The subzones are defined variously on first and last appearance datums, first and last common occurrences, and species acmes. The acme events are coincident with marine flooding surfaces and enable precise correlation across the Bayu-Undan Field. The Elang Formation the prime focus of this study is divided into three third order sequences, each comprising a lowstand, transgressive, and highstand systems tract. These tracts and their delimiting stratal horizons or flooding surfaces possess distinctive palynological or palynodebris assemblages. Qualitative and quantitative variations of these assemblages correlate very closely with gamma-ray log profiles and can be consistently placed within a sequence stratigraphic framework across the Bayu- Undan Field. Palynofacies analyses provide additional means to distinguish among the systems tracts; viz., microphytoplankton diversity increases through transgressive systems tracts to a peak diversity at the maximum flooding surface; atypically brown wood frequencies may also peak at maximum flooding surfaces; and black debris frequencies increase higher in the highstand systems tracts. Palaeoenvironmental interpretations based primarily on palynological assemblages (especially microphytoplankton groupings and palynodebris distribution) provide a means to identify depositional settings in non-cored intervals. For instance, the occurrences of Ternia balmei, the Meiourogonyaulax group, the Ctenidodinium group, and the Rigaudella group represent an approximate gradient from very nearshore to offshore environments or possibly an increase in salinities from euryhaline to stenohaline conditions.
| Identifer | oai:union.ndltd.org:ADTP/253123 |
| Creators | Mantle, Daniel |
| Source Sets | Australiasian Digital Theses Program |
| Detected Language | English |
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