engleski

Middle Triassic of the Belski Dol quarry

The succession in Belski Dol quarry illustrates the evolution of a sedimentary environment from reef and platform margin, through platform slope to basin, and back to shallow platform. During the Anisian, carbonate platform sedimentation existed in the area. With the beginning of extensional tectonics in the younger Anisian, disintegration of the platform and opening of deeper basins began. Limestones with peculiar ‘ nest-like’ structures were formed on the platform margins, while in deeper areas pelecypod limestone was deposited. With increasing tectonic activity, margin disintegration also increased, followed by the formation of slope breccias, accompanied by the as yet poorly understood mechanism of dissolution of platform limestone clasts. In the older Ladinian volcanic activity increased, , and previously lithified breccia was resedimented into tuff material, while platform environments ceased to exist, as shown by the absence of shallow-water Ladinian fossils. Subsequently, younger Ladinian limestones, siltites and cherts were sedimented on the drowned parts of the platform(s). With the change of sedimentary conditions, probably in the oldest part of the younger Ladinian, turbidite sedimentation of fine-grained clastics with intercalations of pyroclastics occurred. With the significant relative sea-level fall at the end of Ladinian, carbonate platform facies prograded over basinal deposits and shallow-water carbonate sedimentaton was reestablished, continuing into the younger Triassic. In the limestones, limestone clasts and boulders from the lower part of the section, several taxa of dasycladalean algae have been found: Oligoporella pilosa PIA, Oligoporella cornuta (PIA), Oligoporella varicans (PIA), Physoporella pauciforata (GÜMBEL) PIA var. pauciforata, Physoporella pauciforata var. gemerica BYSTRICKÝ, Physoporella pauciforata var. sulcata BYSTRICKÝ, Teutloporella peniculiformis OTT, Macroporella alpina PIA, and Diplopora cf. proba PIA, together with the foraminifera Meandrospira dinarica KOCHANSKY-DEVIDÉ & PANTIĆ and Endotriadella wirzi (KOEHN-ZANINETTI). This fossil association indicates an Anisian age, more precisely a Pelsonian– early Illyrian age. The dasycladalean alga Scinderella scopuliformis GRGASOVIĆ & SOKAČ was described from this locality.

Triassic, Ivanščica, stratigraphy, sedimentology, fossil algae

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