Die Platznahme der Alpinen Haselgebirge Mélange: Die geodynamische Entwicklung der zentralen Nördlichen Kalkalpen im höchsten Ober-Jura und in der Unter-Kreide

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Abstract

New results from investigations of Upper Jurassic to Lower Cretaceous sedimentary rocks in sedimentary contact with Alpine Haselgebirge Mélange are presented. They entail a modified interpretation concerning the emplacement of the evaporitic series within the geodynamic evolution of the central Northern Calcareous Alps. At the Gutratsberg open pit mine the Alpine Haselgebirge Mélange occurs as submarine slide block within the Upper Tithonian Oberalm Formation. The Weitenau has to be subdivided into two blocks of different palaeogeographic origin. The successions of the eastern and central Weitenau unit were deposited in the proximal Trattberg-Rise domain. In contrast, the western unit (Mount Hochreith), including the gypsum and anhydrite deposit of Grubach-Moosegg, was originally situated in the distal Trattberg-Rise area. This Alpine Haselgebirge Mélange occurrence lies within the Upper Tithonian Oberalm Formation. In the Bad Ischl area three units of different palaeogeographic origin were juxtaposed. The Reiterndorf-Hubkogel unit is made up of a distal Tauglboden Basin sequence whilst the Gschwandtalm-Perneck unit is constituted by a proximal Tauglboden Basin succession. In contrast, the sedimentary columns of the Reinfalzalm-Mitterberg unit and around Kalkgrube can be correlated with those of the distal Trattberg-Rise. Mount Hoher Rosenkogel forms the primary substratum of this unit. The evaporite deposit of Bad Ischl, situated between Mount Hoher Rosenkogel and the Reinfalzalm-Mitterberg unit, is an inclusive part of the Upper Tithonian Oberalm Formation. The sedimentation ended at all investigated localities in the late Early Cretaceous (Barremian/Early Aptian). For the area of investigation, Early Cretaceous thrusting and nappe movements can be excluded on the basis of microfacies component analyses of the Rossfeld Formation and Grabenwald Subformation. Prägosauic fault systems disintegrated the former facies belts and juxtaposed units of different palaeogeographic facies zones. From that time on, the sedimentary successions show a common evolution. They were affected by the same tectonic-geodynamic processes during the Late Cretaceous to Neogene creation of the Eastern Alpine mountain chain. Late Eocene to Middle Miocene northwest-southeast to north-south directed compressional tectonic forces were subsequently most important for the final geometries of the salt and gypsum deposits. For the current and future exploration on salt, gypsum and anhydrite in the central Northern Calcareous Alps, not only the general occurrence of the Oberalm Formation is of basic importance. Moreover it is the succession´s Late Tithonian palaeogeographic position the knowledge of which will be the key for the identification of prospective evaporite deposits in the central Northern Calcareous Alps.

Details

Translated title of the contributionThe emplacement of the Alpine Haselgebirge Mélange: The geodynamic evolution of the central Northern Calcareous Alps in the uppermost Late Jurassic and in the Early Cretaceous
Original languageGerman
QualificationDr.mont.
Supervisors/Advisors
Publication statusPublished - 2012