International Geologiical Congress - Oslo 2008

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HPF-01 General contributions to paleontology and historical geology

 

First evidence of Tuvalian (upper Carnian) radiolarians from the Kopría Mélange in Rhodos (Greece)

 

Patrice Moix, UNIL-GSE-IGP (Switzerland)
Alexandre Hungerbühler, UNIL-GSE-IGP (Switzerland)
Jean Guex, UNIL-GSE-IGP (Switzerland)
Gérard M. Stampfli, UNIL-GSE-IGP (Switzerland)
 

 

For a long time, the idea of a Hellenides-Taurides continuum has been discussed. The most external parts of the Hellenides-Taurides system present striking similarities. In particular, the platform development of the Beydaglar para-autochthonous sequence in Turkey correlates well with the pre-Apulian units of the Paxos-Zanthe-Kastellórizo zone in Greece. The small islands of the Dodecanese in Greece form an important milestone between the Hellenic system to the west, and the Anatolian-Tauric one to the east. The study of ophiolites related to these units and their associated mélanges are most important for any correlations in that region. The ophiolitic relics found in Rhodos are non-metamorphic and typical of a supra-subduction zone setting. K-Ar dating of these ophiolites yielded an early Late Cretaceous age around 90 Ma. The age and the geochemical compositions show more similarities with the south Turkish ophiolites than with the Hellenic-Dinaric ones.
Rhodos is composed of several thrust sheets characterized by continental-margin to oceanic series. The Kopría Mélange is situated between the early Oligocene Katavia flysch and the Carnian to Cretaceous slope-to-basin series of the Profitis Ilias Group. Upper Oligocene conglomerates (molasse) seal this assemblage. Previous work has shown that the Kopría Mélange contains various exotic blocks and few intact sequences. These blocks and series yielded shallow water faunas (mainly Foraminifera) of Mississippian, Pennsylvanian and Early Permian age. A northern Paleotethyan margin affinity is deduced from these specific assemblages. Similar conclusions have been obtained from the Lycian Nappes in southwestern Turkey.
For the first time, we present a Tuvalian radiolarian assemblage from a pelagic limestone block embedded in the Kopría Mélange. One sample yielded well preserved radiolarians among which Hexaporobrachia riedeli KOZUR & MOSTLER; Triassocrucella baloghi KOZUR; Spongotortilispinus moixi KOZUR & MOSTLER; Zhamojdasphaera rigoi KOZUR, MOIX & MOSTLER; Weverella tetrabrachiata KOZUR & MOSTLER and Capnuchosphaera triassica DE WEVER have been identified. These taxa clearly indicate the lower Tuvalian Spongotortilispinus moixi Zone.

 

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