Toarcian radiolaria from Mt. Mangart (Slovenian-Italian border) and their paleoecological implications

Diverse and well-preserved Toarcian radiolarians have been recovered from a succession of organic-rich shale with intercalations of siliceous limestone. The succession is located at the Slovenian-Italian border in the Julian Alps and was deposited on a subsided block pertaining to the south Tethyan passive continental margin. Twenty spumellarian and 17 nassellarian genera were found in total. Thirty-six taxa were identified to species level and one new species, Bistarkum mangartense n. sp., is described. The assemblages show a high predominance of spumellarians over nassellarians. Spongy spumellarians, especially Orbiculiforma ?, are markedly abundant. Pantanelliidae are generally rare but reach a pronounced peak of 13% in one stratigraphic level. Among nassellarians, Parahsuum is the most abundant but members belonging to Syringocapsidae are scarce to absent. In addition to paleolatitude and water column depth, ecological conditions accompanying the early Toarcian global anoxic event may have to a considerable extent determined the specific taxonomic composition of these radiolarian faunas. (C) 2003 Elsevier B.V. All rights reserved

Pliensbachian, Early Jurassic radiolarians from Mount Rettenstein in the Northern Calcareous Alps, Austria

One of the best preserved Early Pliensbachian radiolarian assemblages from the Western Tethys is described from the grey marly limestone exposed at Mount Rettenstein in the Northern Calcareous Alps, south of the Dachstein Massif. Fourty-five genera and 71 species are documented and illustrated here. Four species are newly described: Tozerium filzmoosense Cifer sp. nov., Loupanus pliensbachicus Cifer sp. nov., Thurstonia? robusta Cifer sp. nov., and Ares rettensteinensis Cifer sp. nov. Radiolarian age is in accordance with ammonoid data from the overlying red marly limestone, which was assigned to the upper part of the Lower Pliensbachian. The best equivalent for the radiolarian-bearing lithology is the Dürrnberg Formation, characteristic of the open-marine Hallstatt facies zone. Previously published radiolarian data from the Dürrnberg Formation were re-evaluated and the originally proposed age assignments revised. At two localities, the published Hettangian–Sinemurian age was emended to the early Early Pliensbachian that is in accordance with the age of radiolarians from Mount Rettenstein. We compared the studied fauna from Mount Rettenstein also with two other rich radiolarian assemblages, one from another locality in the Dürrnberg Formation and one from the Gümüslü Allochthon in Turkey, which were assigned to the late Early Pliensbachian and are somewhat younger than the assemblages studied herein

Geodynamic evolution of the Tethyan paleomargin of Oman

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Geodynamic evolution of the Tethyan paleomargin of Iran. Compaison with the Oman

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Bathonian radiolarians from an ophiolitic melange of the Alpine Tethys (Gets Nappe, Swiss-French Alps)

The determination of radiolarite ages of supraophiolitic rocks date the expansion age of oceanic crust. Radiolarites from the Gets nappe, a decollement cover nappe, provide the means of dating selected localities of outcropping oceanic crust based on their radiolarian faunas. Some studied samples from the ophiolitic melange (Perri re series) have a very well preserved and highly diverse radiolarian fauna of biochronological significance. The age of the radiolarites is established by correlation with the biozonation of Baumgartner et al. (1995b), which indicates a Bathonian age for the oldest radiolarian assemblages. Accordingly, these radiolarites represent remains of the oldest sediments recorded after the opening of the Piemont-Ligurian Ocean. This age is in agreement with those recently established by isotopic methods (166 +/- 1 Ma U-Pb and 165.9 +/- 2.2 Ma Ar-40/Ar-39) in the associated gabbros from the ophiolitic melange. The isotopic age and paleontological results are important because they represent the oldest dating of the oceanic crust of the Piemont-Ligurian Ocean, proving a Late Bajocian-Early Bathonian age for the oceanization in the western Tethys. The systematic part presents a complete Bathonian radiolarian assemblage from two of the best preserved samples; the illustrated assemblage contains 180 species attributed to 66 genera (44 nassellarians, 22 spumellarians and 1 entactinarian). Twenty new species and three new genera (Helvetocapsa, Plicaforacapsa and Theocapsomella) are formally described

Sedimentology and sequence stratigraphy of the southern tethyan margin: comparison of the Iran and Oman parts

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