5 research outputs found
New radiolarian biostratigraphic age constraints on Middle Triassic basalts and radiolarites from the Inner Hellenides (Northern Pindos and Othris Mountains, Northern Greece) and their implications for the geodynamic evolution of the early Mesozoic Neotethys
The Avdella Me´lange in the northern Pindos
Mountains and its equivalent formation, the Loggitsion Unit
in the Othris Mountains expose early Mesozoic (Mid-Late
Triassic) oceanic fragments beneath the Western Greek
Ophiolite Belt of the Inner Hellenides, Northern Greece. The
me´lange consists of locally interfingering blocks and slices
of ribbon radiolarite, radiolarian chert and pillow basalt and
is usually overthrust by Jurassic ophiolites. New Middle and
Upper Triassic radiolarian biostratigraphic data are presented
from radiolarites and basalt-radiolarite sequences
within me´lange blocks. Pillow basalts associated with the
radiolarites provide clues to the opening of the Neotethyan
ocean basin. The radiolarians indicate a Middle Triassic
age (latest Anisian, probably early Illyrian), which is
documented for the first time in the northern Pindos Mountains.
The new radiolarian biostratigraphic data suggest that
rift-type basalt volcanism already began in pre-Ladinian
time (late Scythian?—Anisian). These basalts were then
overlain by Upper Anisian to Carnian (?Norian) radiolarites
Lithofacies and age data of Jurassic foreslope and basin sediments of Rudabanya Hills (NE Hungary) and their tectonic interpretation
Jurassic sedimentary rocks of the Telekesvölgy Complex (Bódva Series), Telekesoldal Complex (Telekesoldal Nappe) and the Csipkés Hill olistostrome in Rudabánya Hills (NE Hungary) were sampled for microfacies studies and interpretation of the depositional environments. The Telekesvölgy Complex is made up of reddish to greenish marl, occasionally containing limestone olistoliths — gradually progresses from the Norian Hallstatt Limestone of the Bódva Series — then grey marl, which may correspond to the latest Triassic Zlambach Formation. This variegated marl progresses into grey marl and calcareous marl, containing crinoid fragments. It may be interpreted as a hemipelagic facies, relatively close to submarine highs. Bajocian to Lower Bathonian black shales, rich in radiolarians and sponge spicules representing typical deep pelagic facies, are also assigned to the Telekesvölgy Complex. The Telekesoldal Complex represents a mélange-like subduction-related complex that consists of black shales, sandstone turbidites and olistostrome beds, and deposited by gravity mass flows. A relatively deep marine basin in the proximity of a submarine slope is likely to be the depositional environment of this unit. The clasts of the olistostromes are predominantly Middle to Upper Triassic pelagic limestones, rhyolite and basalt. Subduction related nappe stacking of the ocean margin during the Middle to Late Jurassic may have created suitable conditions for this sedimentation pattern. Bajocian-Callovian age of the complex was proved by the revision of the radiolarian fauna and new palynological data, the first from the Jurassic of the Aggtelek-Rudabánya Hills. The Csipkés Hill olistostrome consists of carbonate turbidite beds containing Jurassic platform derived foraminiferal and olistostrome horizons with Middle-Upper Triassic limestone clasts of red Hallstatt facies