TY - THES

T1 - Microfacies, biostratigraphy and sequence stratigraphy of the Upper Triassic Dachstein fore-reef facies in the East Bosnian-Durmitor megaunit (northern Montenegro)

AU - Zöhrer, Oliver

N1 - no embargo

PY - 2024

Y1 - 2024

N2 - In this work the microfacies development, biostratigraphy, and sequence stratigraphy of four different successions of Upper Triassic Dachstein fore-reef limestones in Poros and Pra¿ica in northern Montenegro have been investigated, so far unknown in the Dinarides. The successions have a biostratigraphic age from the Tuvalian 3 to the Alaunian 3-?Sevatian (Upper Carnian to Upper Norian) dated by conodont assemblages. Generally five microfacies types could be distuinguished, ranging from an open-marine filament rich packstone deposited in a distal reef position, oligomictic microbreccias with different (fore-)reefal carbonate clasts, shallow-water influenced turbiditic grainstones, and rudstones as well as blocks of framestones with preserved in-situ reef building organisms in the blocks. The general sedimentation pattern shows a cyclic deposition of shallow-water influenced grainstones, rudstones and framestones in an open-marine lower slope environment. The shallow-water fauna consists of A) foraminifera: Agathammina austroalpina (Kristan-Tollmann & Tollmann), Alpinophragmium perforatum (Flügel), Decapoalina schaeferae (Zaninetti, Altiner, Dager & Ducret), Paraophtalmidium carpathicum (Samuel & Borza), Kaeveria fluegeli (Zaninetti, Altiner, Dager & Ducret), Endoteba sp, Duotaxis sp., Ophtalmidium sp., Duostomina sp., Trochamina sp., Reophax sp., Ammobaculites sp., B) microproblematica: Baccanella floriformis (Panti¿), Microtubus communis (Flügel), Tubiphytes obscurus (Maslov), Radiomura cautica (Senowbari-Daryan & Schäfer), Actinotubella gusici (Senowbari-Daryan), Muranella sphaerica (Borza), ?Porforitubus buseri (Senowbari-Daryan) and C) calcified sponges: Cryptocoelia sp., Uvanella sp., Celyphia sp., beside D) various not determinable corals of the Upper Triassic Dachstein reef habitat. For the biostratigraphic age dating following conodonts are determined: M. communisti (Hayashi), M. praecommunisti (Mazza, Rigo and Nicora), Q. tuvalica (Mazza & Rigo), E. primitia (Mosher), E. quadrata (Orchard), E. rigoi (Kozur), E. triangularis (Budurov), E. spatulata (Hayashi), E. cf. multitendata A sensu Krystyn , E. multitendata (Mosher), E. postera (Kozur &Mostler), N. navicula (Huckriede), N. hallstattensis (Mosher), and N. steinbergensis (Mosher). The combined sequence stratigraphic analyses of all investigated successions show the onset of the Dachstein Carbonate Platform in the Tuvalian 3 and aggradation in the lower Lacian 1 subsequently followed by progradation of the platform in the middle Lacian 1 to highest Lacian 2. Again, after a sea-level drop aggradation in the Lacian 3 is followed by progradation in the Alaunian and ?Sevatian, with a short interruption at the Alaunian 2/3 boundary. A comparison with the short-term sea-level curve of Haq et al. (2018) shows a generally good correlation with only minor offsets between the different system tracts. However, major discrepancies exist when they are compared with other time equivalent sequence stratigraphic developments located in the Northern Calcareous Alps and Southern Alps.

AB - In this work the microfacies development, biostratigraphy, and sequence stratigraphy of four different successions of Upper Triassic Dachstein fore-reef limestones in Poros and Pra¿ica in northern Montenegro have been investigated, so far unknown in the Dinarides. The successions have a biostratigraphic age from the Tuvalian 3 to the Alaunian 3-?Sevatian (Upper Carnian to Upper Norian) dated by conodont assemblages. Generally five microfacies types could be distuinguished, ranging from an open-marine filament rich packstone deposited in a distal reef position, oligomictic microbreccias with different (fore-)reefal carbonate clasts, shallow-water influenced turbiditic grainstones, and rudstones as well as blocks of framestones with preserved in-situ reef building organisms in the blocks. The general sedimentation pattern shows a cyclic deposition of shallow-water influenced grainstones, rudstones and framestones in an open-marine lower slope environment. The shallow-water fauna consists of A) foraminifera: Agathammina austroalpina (Kristan-Tollmann & Tollmann), Alpinophragmium perforatum (Flügel), Decapoalina schaeferae (Zaninetti, Altiner, Dager & Ducret), Paraophtalmidium carpathicum (Samuel & Borza), Kaeveria fluegeli (Zaninetti, Altiner, Dager & Ducret), Endoteba sp, Duotaxis sp., Ophtalmidium sp., Duostomina sp., Trochamina sp., Reophax sp., Ammobaculites sp., B) microproblematica: Baccanella floriformis (Panti¿), Microtubus communis (Flügel), Tubiphytes obscurus (Maslov), Radiomura cautica (Senowbari-Daryan & Schäfer), Actinotubella gusici (Senowbari-Daryan), Muranella sphaerica (Borza), ?Porforitubus buseri (Senowbari-Daryan) and C) calcified sponges: Cryptocoelia sp., Uvanella sp., Celyphia sp., beside D) various not determinable corals of the Upper Triassic Dachstein reef habitat. For the biostratigraphic age dating following conodonts are determined: M. communisti (Hayashi), M. praecommunisti (Mazza, Rigo and Nicora), Q. tuvalica (Mazza & Rigo), E. primitia (Mosher), E. quadrata (Orchard), E. rigoi (Kozur), E. triangularis (Budurov), E. spatulata (Hayashi), E. cf. multitendata A sensu Krystyn , E. multitendata (Mosher), E. postera (Kozur &Mostler), N. navicula (Huckriede), N. hallstattensis (Mosher), and N. steinbergensis (Mosher). The combined sequence stratigraphic analyses of all investigated successions show the onset of the Dachstein Carbonate Platform in the Tuvalian 3 and aggradation in the lower Lacian 1 subsequently followed by progradation of the platform in the middle Lacian 1 to highest Lacian 2. Again, after a sea-level drop aggradation in the Lacian 3 is followed by progradation in the Alaunian and ?Sevatian, with a short interruption at the Alaunian 2/3 boundary. A comparison with the short-term sea-level curve of Haq et al. (2018) shows a generally good correlation with only minor offsets between the different system tracts. However, major discrepancies exist when they are compared with other time equivalent sequence stratigraphic developments located in the Northern Calcareous Alps and Southern Alps.

KW - Montenegro

KW - Dinarides

KW - Microfacies

KW - Biostratigraphy

KW - Upper Triassic

KW - Norian

KW - Dachstein

KW - Reef limestone

KW - Fore-reef limestone

KW - Montenegro

KW - Dinariden

KW - Mikrofazies

KW - Biostratigraphie

KW - Obertrias

KW - Nor

KW - Dachstein

KW - Riffkalk

KW - Vorriffkalk

M3 - Master's Thesis

ER -