Late Triassic sedimentary evolution of Slovenian Basin (eastern Southern Alps): description and correlation of the Slatnik Formation

Abstract

Successions of the Slovenian Basin structurally belong to the easternmost Southern Alps. During the Late Triassic, they were part of the Adriatic continental margin. Norian-Rhaetian successions of the Slovenian Basin are characterized mainly by dolomite of the Baba Dolomite Formation. However, in the northern part of the basin, Late Triassic limestone is preserved above Baba Dolomite Formation and is formalized as the Slatnik Formation. It is composed of hemipelagic limestone alternating with resedimented limestones. The succession documents an upward progradation of the slope environment composed of three high-frequency cycles. Most prominent progradation is referred to the second, i.e., Early Rhaetian cycle. The Slatnik Formation ends with thin-bedded hemipelagic limestone that records the end-Triassic productivity crisis, or rapid sea-level fall. The overlying resedimented limestones of the Early Jurassic Krikov Formation, document the recovery of production and shedding from the adjacent carbonate platform.

Microfacies of Mesozoic Carbonate

“…Among fossils foraminifers Ophthalmidium leischneri and Involutina liassica, radiolarians and sponges occur. Along basin margins thicker packets of calcareous brec cias sedimented sliding down the shelf edge (roži~, 2006roži~ & PoPit, 2006;Buser & oGorelec, 2008). Between breccia fragments also ooides are found.…”

“…Med fosili sta prisotni foraminiferi Ophthalmidium leischneri in Involutina liassica ter radiolariji in spongije. Ob robovih bazena so se odlagali debelej{i paketi apnen~evih bre~, ki so splazele po pregibu z roba {elfa (roži~, 2006roži~ & PoPit, 2006;Buser & oGorelec, 2008). Med kosi bre~e so pome{ani tudi ooidi.…”

Extent of the Upper Norian – Rhaetian Slatnik Formation in the Tolmin Nappe, eastern Southern Alps

“…1c and 1d, c) Geological map of the Javor area with location of the studied section, d) Geological map of the Kobla area with location of the Povdnar section and previously studied Kobla and Slatnik sections Biostratigraphy The Slatnik Formation was extensively sampled for conodonts and their distribution is shown in detail in Figure 2. The Norian-Rhaetian boundary is set at the Lowest Occurrence of Misikella posthernsteini (Kozur & Mock) in the lowermost part of the formation, whereas the highest occurrence of conodonts represents a proxy of the Triassic-Jurassic boundary (see Roži~ et al, 2009;Gale et al, 2012). Conodont data are supported by determinations of foraminifera, found in a few packstone layers distributed throughout the formation (see Fig.…”

“…2). The first correlative marker is the Lowest Occurrence of M. posthernsteini, which is currently considered the best criterion for the Norian-Rhaetian boundary (krystyn et al, 2007a;McroBerts et al, 2008;Roži~ et al, 2009;GiorDano et al, 2010;lucas, 2010;Gale et al, 2012). The second marker event is the Triassic-Jurassic boundary, which, however, is set at the highest occurrence of conodonts (and also, in the case of Mt.…”

“…Kobla. (Roži~, 2008;Buser & oGorelec, 2008;Roži~ et al, 2009;kolar-JuRkov�ek, 2011;Gale et al, 2012). Such a facies association enabled an integration of conodont biostratigraphy with benthic foraminifera derived from the adjacent platform edge .…”