Diskordanci Prehodnega območja med Zunanjimi in Notranjimi Dinaridi na južnih pobočjih Orlice : raziskovalna naloga

Kolman, Tija (author), Žvab Rožič, Petra (mentor)

Namen raziskovalne naloge je bil s podrobno sedimentološko analizo raziskanega zaporedja na južnih pobočjih Orlice prispevati k boljšemu razumevanju stratigrafskega in strukturnega razvoja območja jugovzhodne Slovenije. Posnetega je bilo 35 metrov detajlnega sedimentološkega profila vzdolž cestnega odseka na Vrhovnici. Profil je razdeljen v tri litostratigrafske enote, ki so med seboj ločene z dvema diskordancama. Ti nakazujeta na večfazno prekinitev sedimentacije na obravnavanem območju. Najstarejšo enoto na profilu predstavlja Glavni dolomit, ki ga opisujeta mikrofaciesa drobnozrnat dolomit in mikrokristalen dolomit z intenzivno piritizacijo. Definirata ga zrna drobnozrnatega, neplanarnega dolomita. Prvotna struktura kamnin je zaradi izrazite poznodiagenetske dolomitizacije povsem zabrisana. V vzorcih se pogosto pojavljajo nepravilna oksidacijska polja, ki nakazujejo ostanke bioturbacije, ter pojavljanje nepresevnih mineralov pirita. Nad Glavnim dolomitom je z diskordanco odloženo zaporedje Biancone apnenca, ki ga karakterizira mikrofacies delno dolomitiziran mudstone z minerali dolomita unimodalnih oblik, ki so razpršeni znotraj mikritne osnove. Prav tako je v teh zbruskih prepoznan proces piritizacije, ki je bolj zgoščena ob območjih bioturbacije. Drugi mikrofacies, ki se pojavlja je peloidni bioklastični packstone. Ta je laminiran, v njem pa prevladujejo radiolarji, spikule spongijev in peloidi. Zaporedje Biancone apnenca pod kotom odreže kotna diskordanca, nad katero leži Litotamnijski apnenec. Mikrofacielno je ta razdeljen v tri skupine; bioklastični rudstone s posameznimi velikimi klasti, intraklastični rudstone in bioklastični grainstone. Vsi trije tipi vsebujejo enako osnovno združbo fosilnih ostankov, le da se delež posameznih zrn po mikrofaciesih nekoliko spreminja, prav tako pa se spreminja tudi velikosti bioklastičnih zrn znotraj skupine. Mikrofaciesi Litotamnijskega apnenca tako odražajo dinamične hidrodinamske razmere neogenskega plitvovodnega okolja. Raziskovalna naloga potrjuje večfazne prekinitve sedimentacije, ki zaznamujejo prehod iz plitvovodnega v globjevodno okolje ter kasnejšo neogensko transgresijo in s tem dopolnjuje razumevanje tektonsko-sedimentacijskega razvoja ter regionalnih stratigrafskih vrzeli v Prehodnem območju med Zunanjimi in Notranjimi Dinaridi.

• Language: Slovenian
• Keywords: diskordanci, Glavni dolomit, Biancone apnenec, Litotamnijski apnenec, sedimentološka
• Work type: Final paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Place of publishing: Ljubljana
• Publisher: T. Kolman
• Year: 2026
• Number of pages: X, 44 str.
• PID: 20.500.12556/RUL-188833
• UDC: 55
• COBISS.SI-ID: 293671171
• Publication date in RUL: 29.09.2026

Secondary language

• Language: English
• Title: Discordants of the Transitional area between External and Internal Dinarides on the southern slopes of Orlica : research paper

Abstract

The aim of this research was to contribute to a better understanding of the stratigraphic and structural evolution of southeastern Slovenia through a detailed sedimentological analysis of the succession exposed on the southern slopes of Orlica. A 35-metre-thick detailed sedimentological profile was logged along a road section at Vrhovnica. The profile id divided into three lithostratigraphic units separated by two unconformities, indicating multi-phase sedimentation breaks in the study area. The oldest unit is the Main Dolomite, represented by fine-grained dolomite and microcrystalline dolomite microfacies with intense pyritisation, defined by fine-grained, non-planar dolomite crystals. Pervasive late-diagenetic dolomitisation has completely obliterated the original rock texture. Irregular oxidation zones indicating remnants of bioturbation, as well as opaque pyrite minerals, frequently occur in the samples. Overlying the Main Dolomite above an unconformity is the Biancone limestone succession, characterized by a partially dolomitised mudstone microfacies containing unimodal dolomite crystals dispersed within a micritic matrix. Pyritisation concentrated around bioturbated zones is also recognized in these thin sections. The second microfacies present is a laminated peloidal bioclastic packstone, dominated by radiolarians, sponge spicules, and peloids. The Biancone limestone sequence is truncated by an angular unconformity, overlain by the Lithothamnium limestone. Microfacies-wise, it is subdivided into three groups: bioclastic rudstone with individual large clasts, intraclastic rudstone, and bioclastic grainstone. All three groups share same core fossil assemblage, with slight variations in grain proportions and bioclast size across microfacies. The microfacies of the Lithothamnium limestone reflect the dynamic hydrodynamic conditions of a Neogene shallow-water environment. This study confirms multi-phase sedimentation breaks marking the transition from a shallow-water to a deep-water environment and a subsequent Neogene transgression, thereby enhancing the understanding of the tectono-sedimentary evolution and regional stratigraphic gaps in the Transitional Area between the External and Internal Dinarides.

• Keywords: unconformity, Main Dolomite, Biancone limestone, Lithothamnion limestones, sedimentological analysis, Orlica