Rose, Graham; (1995) Late Triassic and Early Jurassic radiolarians from Timor, eastern Indonesia. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Rich fossil assemblages are used in a biostratigraphic and taxonomic study of the radiolarians occurring in the Aitutu and Wai Luli Formations of West Timor, Indonesia. The emphasis of this study is upon the abundant and diverse Late Triassic age radiolarians recovered from the River Meto sections of central West Timor and their comparison with other taxa found in Tethyan areas. The lower Mesozoic sediments of Timor form part of a displaced Gondwanan terrane and the Upper Triassic (Carnian, Norian and Rhaetian) taxa which are present in the Aitutu Formation compare closely with radiolarians reported from North America, Europe, Japan, China and the Philippines. Early Jurassic (Sinemurian, Pliensbachian and Toarcian) assemblages were also encountered, recorded and compared to those found in other regions. Sequences of co-occurringmicrofossils (including conodonts, foraminifera, ostracods and calcareous nannofossils) offer a control in confirming the age of the radiolarian assemblages encountered during this study. One new genus (Pseudolivarella) and fifteen new Upper Triassic species (Capnuchosphaera kapanesis, C. metoensis, C. timorensis, Deflandrecyrtium rhaetica, D. kozuri, Kahlerosphaera petalouda, Orbiculiforma kyklica, Palaeosaturnalis ovalis, Paronaella leebyi, Pentactinocarpus longispinosis, Pseudoheliodiscus carteri, Stauracanthocircus tozeri, Squinabolella. maxima, Pseudolivarella barkhami) are described and their biostratigraphic significance discussed. Informally, three assemblages and two subassemblages are recognised in the radiolarian faunas from Timor and these are as follows: 1) Capnodoce-Capnuchosphaera Assemblage (upper Carnian to lower Norian). 2) Palaeosaturnalis Assemblage (middle Norian). 3) Kozurastrum-Citraduma Assemblage (upper Norian-Rhaetian) with two subassemblages. 3a) Deflandrecyrtium-Livarella Subassemblage (upper Norian) = Betraccium deweveri Zone 3b) Parahsuum sp. A-Pseudolivarella n. gen. Subassemblage ( upper Norian- Rhaetian). The associations of taxa are defined using the abundant and highly diverse radiolarians from samples provided by Dr. S. T. Barkham. These were then tested on the less abundant and diverse assemblages collected by the author and proved to be of use for age correlation. Assemblages from Indonesia were found to have more species also occurring in European Tethys, North America and the Philippines than elsewhere. This may be the result of patchy sampling/preservation in some regions or genuine palaeobiogeographical differences in faunal assemblages. The other studies which contain highly diverse and abundant assemblages have more species which also occur in Timor than reported assemblages containing low abundances and diversities of radiolarians. The Lower Jurassic (Wai Luli Formation) contains less well-preserved radiolarians of Sinemurian-Toarcian age faunas and is briefly examined. These assemblages contain examples of the genus Parahsuum Yao, 1982 which occur frequently in the Lower Jurassic of Japan and are thus compared to taxa found in that region.

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