engleski

Stratigraphy of Middle and Upper Triassic Deposits From Zumberak Mt. (W Croatia)

On the area of SE Žumberak Mt. we performed the detailed bio-, palino- and lithostratigraphic investigations of Triassic deposits. These deposits are represented mainly by early diagenetic dolomite, occasionally recrystallised into "sugar dolomite" along tectonic lines. Middle Triassic Ruškovlje formation consists of an alternation of dolopelmicrite, fenestral dolopelmicrite and agglutinated stromatolite, sedimented in platform peritidal environment. Within the Anisian dolomite we separated thin Berdiki member with reddish sandy marl, which presents an episode of clastic input onto platform. Ladinian Kolići member consists of marl, pyroclastic, siltit, chert, resedimented Anisian dolomite and, in upper part, limestone. This member, reflecting regional Ladinian events, presents the development of a small interplatform basin, which, after being filled, passed again into the peritidal environment. Carnian Slapnica formation consists of more or less regular alternation of dolomicrite, fenestral dolomicrite and agglutinated stromatolite, sedimented in the platform peritidal environment. At the base of this formation we separated the Vranjak member with thin layers of yellowish clay inside the dolomite, probably of pyroclastic origin. At the top of the formation Drenovac member is characterised by black dolomicrite layers, very rich in organic matter, deposited in anoxic lagoons. Very thick Norian and Rhaetian Main Dolomite formation consist of irregular alternation of dolomicrite, fenestral dolomicrite and skeletal stromatolite, sedimented in environment of tidal flats on wide and stabile carbonate platform. In the upper part we separated intraformational dolomite breccia as Gmajna member. We determined the geological age of these formations by comparative investigations of algae, foraminifers, palynomorphs and ammonites.

stratigraphy; Triassic; Žumberak; Croatia

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