Middle Jurassic matrix radiolarians from the Meliata ophiolite melange at the type Meliatic sites Meliata and Jaklovce (Western Carpathians): palaeogeographic evidence

The Meliata Unit is crucial for understanding the West Carpathian geology. Its remnants mark an important suture zone which remained after the Meliata part of Neotethys Ocean which was open in the Middle Triassic and partly closed in Late Jurassic time. The key areas, in which occurrences of this unit are concentrated, are near Meliata village and in the wider surrounds of Margecany and Jaklovce villages. The first site lies southwest of the Gemeric Superunit, whereas the second occurs at its NE margin. Position of the Meliata Unit on the both sides of this crustal block (comparable with Greywacke Zone of the Eastern Alps) led some authors to oppinions about two branches of the Meliata Ocean surrounding the Gemeric Superunit, whereas others inferred that the northern occurrences do not represent a true suture but they were transported to its recent position tectonically by thrusting (obduction). If the first oppinion was true there would be some time difference between the closures of the two branches. Therefore, the two principal sites, Meliata and Margecany were revisited and new micropaleontological data were obtained, the first report of which is given herein.
   Margecany (the type outcrops of radiolarite-basalt succesion along the railway at the local cement factory were sampled)
   In a red cherty limestone intercalated in the basalts, Triassic radiolarians (together with some poorly preserved conodonts (similar conodont fauna was previously found here by Kozur & Mock) with a mixture of some Jurassic ones, were extracted by dissolution. Microfacies of most of the reddish cherty limestone to radiolarites, is evidently Triassic. From a reddisch cherty limestone to radiolarite overlying the basalts, following radiolarian fauna was extracted: Actinomma cf. siciliensis, Crucella squama, Crucella spp., Hagiastrum sp., Paronaella pygmaea, Praeconocaryomma spp., Spongotripus sp., Elodium cameroni and Hsuum parasolense. The assemblage indicates Middle Jurassic age (Aalenian to Bajocian with two species; Callovian to Oxfordian indicated by one species). Estimation of the exact stratigraphic position is problematic due to the actual knowlegde of the age range of the species.
   Meliata (the type locality of the meliata Unit)
   Late Middle Jurassic matrix between the olistostromes and slide blocks of the upper part of the succession has already been investigated. The Lower part of the section was interpreted as a continous Anisian to Carnian sequence. A sample from the basal part of the section below the Ladinian cherty limestones and radiolarites and above the Anisian limestones yielded Higumastra winteri, Dictyomitrella cf. kamoensis, Stichocapsa cicciona, and Zhamoidellum cf. ovum. The assemblage indicates the Callovian to Early Oxfordian age. A sample taken higher, but still in the basal part contained Sethocapsa cf. kodrai indicating late Middle Jurassic. Microfacies of the samples represent radiolarian bearing filament limestone (resembling silicified Bositra limestone with radiolarians). In the upper part of the Meliata type section occur several grey limestones and dolomites in a late Middle Jurassic mélange. Besides Carnian limestones also Norian grey limestones occur representing typical components which were derived from the grey Hallstatt facies (Pötschen sequence in the Eastern Alps).
   The studied samples all contain Jurassic or mixed Triassic-Jurassic fauna which is in accordance to the mélange character of the Meliata Unit with Triassic/Jurassic blocks and Middle to early Late Jurassic matrix. However, no new constraints concerning the time difference between the southern and northern occurrences of the Meliata Unit are possible.