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Middle Triassic syntectonic sedimentation and volcanic influence in the central part of the External Dinarides, Croatia (Velebit Mts.)

Smirčić Duje, Aljinović Dunja, Barudžija Uroš, Kolar-Jurkovšek Tea

Geological Quarterly

2020

Vol. 64, No. 1

220--239

Middle Triassic deposits in the Velebit Mts. of the External Dinarides in Croatia show strong differentiation of sedimentary environments and facies. In the area of Donje Pazarište, a 90 metre thick section includes six different facies, each with its specific genetic characteristics (Flysch-like Facies; Carbonate Shale Facies; Pyroclastic Density Current Facies; Platy Limestone with Pyroclastics Facies; Limestone Breccia Facies and Slumped Limestones with Pyroclastics and Chert Facies). In the same area, in the nearby Top of Donje Pazarište section, a Pyroclastic Flow Facies was defined, and this was also recognized ~15 km to south-east, in the area of Brušane Village, in the foothills of Vinac. Throughout the area and section investigated, the effects of intense tectonic and volcanic activity can be traced. The pronounced differences in the facies determined facies are interpreted as consequences of syntectonic and volcanically influenced sedimentation in a graben/half-graben depositional system.

Lower Jurassic carbonate platform-to-basin transition at Mt. Rumija (Montenegro)

Crne A., Gorican S., Cadjenovic D.

Volumina Jurassica

2006

Vol. 4, no. 1

82-83

Mount Rumija, Montenegro represents one of the best-preserved Lower Jurassic platform-to-basin transitions in the Dinarides. Mt. Rumija is located in the High Karst Zone, overthrust on the Budva Zone. In the Mesozoic the High Karst Zone was a part of the Adriatic-Dinaric Carbonate Platform (ADCP), whereas the Budva Zone was a deeper basin. We describe two complete Lower Jurassic sections (Tejani and Livari) and a complementary Pliensbachian-Toarcian section (Seoce). The successions exhibit great facies differences across short distances and provide important new data for the reconstruction of the Lower Jurassic platform-to-basin system. At Tejani and Livari, the Upper Triassic Dachstein Limestone is overlain by micritic limestone, which begins with a few beds of fine- to medium-grained calcarenites. At Tejani, 100 m of thick-bedded coarse-grained oolitic limestone follow, at places displaying cross-stratification. Laterally, at Livari, the correlative succession is 180 m thick and consists of three calcareous turbididite packages. The first and the third package are lithologically identical: fine- to medium-grained calcarenites, which contain 50% replacement chert layers and nodules; the calcarenites contain pellets, echinoderm fragments, foraminifers, ooids and sponge spicules. The second package is an oolitic limestone that lacks chert. The overlying lithostratigraphic unit is common to both sections and aids in correlation. It consists of a 30 m thick succession of marly limestone and marl overlain by 30 m of medium-bedded bioclastic limestone. The marly limestone contains foraminifers, ostracodes, sponge spicules and rare radiolarians, while the bioclastic limestone contains abundant brachiopod shells, echinoderm fragments and several Fe-Mn crusts. The bioclastic limestone is overlain by oolitic limestone. The base of the Seoce section starts with a thick-bedded Lithiotis limestone. A nodular micritic limestone follows, containing mostly pellets and rare bioclasts - fragments of echinoderms, ostracodes and brachiopods. The succession ends with oolitic limestone. In the Budva Basin, the Upper Triassic Halobia limestone (pelagic lime mudstone with replacement chert) is overlain by Passée Jaspeuse (bedded calcareous chert). The overlying Bar Limestone (calcareous turbidites) was deposited beginning in the Late Sinemurian - Early(?) Pliensbachian. It is composed of Lower and Upper Member, divided by a marly horizon, probably Toarcian in age. The lateral transition from the lagoonal environment (Seoce) to the platform edge (Tejani) and deeper water environment (Livari) can be observed at Mt. Rumija. Vertically, two abrupt facies changes occur. The first one is the beginning of the micritic limestone sedimentation above the Dachstein limestone. The second change is observed both in the shallow-water environment (nodular limestone overlying Lithiotis limestone) and on the platform-to-basin transition (sedimentation of marly limestone with open-marine biota). Two abrupt facies changes on the carbonate platform are correlated to facies changes in the Budva Basin (Halobia limestone - Passee Jaspeuse, Lower Bar Limestone Member - marl, respectively). The facies changes correspond to two drowning events: at T/J boundary and at Late Pliensbachian - Upper Toarcian.