Die Ober-Jura bis Unter-Kreide Entwicklung der nördlichen Trattberg-Schwelle im Bereich der östlichen Unkener Mulde (Nördliche Kalkalpen, Österreich)

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Abstract

The complex sedimentary succession of the so far only generally investigated eastern margin of the Unkener syncline adjacent to the Saalach unit is newliy studied. Main focus of this study was set on the basin evolution, biostratigraphic dating and microfacies analysis of the sedimentary successions and the geodynamic processes in Late Jurassic to Early Cretaceous times. The preliminary assumption that the Tauglboden Mélange adjoins the Saalach unit to the east can not be confirmed. According to geological mapping, radiolarian dating and microfacies analysis following results can be drawn: The oldest sedimentary rocks of the studied area north of the Unkenbach is the Rhaetian lagoonal Dachsteinkalk overlain by red condensed limestones of the Adnet Group, i.e. the Hierlatz Limestone and the Lienbach Member. The sequence continues with the thin bedded reddish Rupolding Radiolarite, which occurs as a weathered horizon. The Oberalm Formation with its intercalated Barmstein Limestones overlies the radiolarites. To the south of the river Unkenbach the basis is represented by the uppermost part of the Oberalm Formation dated with Calpionellids. The sequence is followed by the concordant overlaying marly Schrambach Formation, which represents the final stage of the fining-upward trend. The top of the succession in the south is the Roßfeld Formation, which is characterized by a high input of siliciclastic and ophiolitic material and showing a coarsening-upward trend. Based on this results, the studied area is interpreted as the northern part of the Trattberg Rise, which separates the Upper and Lower Tirolic nappe. The missing Tauglboden Formation doesn’t favour a position in the central or proximal part of the Tauglboden Basin. It is assumed that the sedimentary succession was originally deposited in an area of the Oxfordian Trattberg Rise which collapsed in the Late Tithonian. By this collapse steep and tilted escarpment were formed. Along the river Unkenbach one of these normal faults is preserved, reactivated at a later stage. A second fault system in the studied area is represented by the sinistral strike-slip fault system of the "Saalach-Westbruch". Based on these results a potential Hydrocarbon system is hypothesized. Early Jurassic organic-rich basin sediments (e.g. Sachrang Member) represent source rocks, the sandy Roßfeld-Formation conventional reservoir rocks. Radiolarites can be unconventional source and reservoir rocks.

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Translated title of the contributionThe Late Jurassic to Early Cretaceous sedimentary evolution of the northern Trattberg Rise in the eastern Unken syncline (Northern Calcareous Alps, Austria)
Original languageGerman
QualificationDipl.-Ing.
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Award date23 Mar 2018
Publication statusPublished - 2018