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Mt. Medvednica, which has been for a long time treated as a part of the Northwestern Dinarides, is included in the Croatian part of the Mid-Transdanubian zone and positioned along the ZZL. However, Mt. Medvednica differs from the Dinarides with its mixed Alpine and Dinaridic lithologies which can be separated in 5 groups. 1) Paleozoic-Triassic metamorphic complex composed of mainly black metasediments, interlayered with orthogreenschists derived from tholeitic basalts. Its older part is Silurian to Permian and the younger part is spanned between Scythian and Carnian. The magmatic sedimentary complex was affected by very low- and low-grade synkinematic metamorphism which took place during the early Cretaceous (122-110). Based on this early Alpine metamorphism, this unit bears elements of the Eastern Alps. 2) Dinaridic ophiolite mélange is overthrust by the Paleozoic-Triassic metamorphic unit. This is Jurassic/Early Cretaceous olistostrome mélange, subsequently strongly tectonized, includes fragments of predominant native graywacke with basalt, diabase, gabbro, peridotite, shale, chert and exotic, stratigraphicaly and environmentally varied limestones, which are embedded in a pervasively sheared shaly-silty matrix. This complex has a typical Dinaric affinity. 3) Campanian-Maastrichtian-Paleocene flysch sediments are represented by conglomerate, sandstone, shale, calcite shale and limestone. They unconformably overlie Paleozoic-Triassic metamorphic complex and Dinaridic ophiolites. 4) Triassic platform limestone and dolomite, in some places underlain by Scythian sediments, represents the easternmost extension of the Sava nappe and displays Southern Alps affinity. Final emplacement of Mt. Medvednica along the ZZL took place during Pliocene Quaternary times. These youngest tectonic movements strongly obliterated mutual primary relations between the main lithologies originated in different parts of the Tethys. The Dinaridic ophiolites were probably displaced along the ZZL in Miocene time from the Dinaridic Ophiolite Zone. The Triassic carbonate platform fragments of the Southern Alps affinity, originally included in the Sava nappe, were probably transported in its position by escape tectonics. The most enigmatic is the origin of Paleozoic-Triassic metamorphic complex of the Eastern Alps affinity. Our data suggest that the ZZL could be treated as the northwestern boundary of the Dinarides. |
