Perturbatacrusta leini n. gen., n. sp. a new microencruster incertae sedis (? sponge) from Late Jurassic to earliest Cretaceous platform margin carbonates of the Northern Calcareous Alps of Austria

Facies ◽  
2010 ◽  
Vol 57 (1) ◽  
pp. 123-135 ◽  
Author(s):  
Felix Schlagintweit ◽  
Hans-Jürgen Gawlick
Keyword(s):  
Late Jurassic ◽  
Northern Calcareous Alps ◽  
Northern Calcareous ◽  
Incertae Sedis ◽  
Platform Margin

scholarly journals Ophiolite derived material as parent rocks for Late Jurassic bauxite: evidence for Tithonian unroofing in the Northern Calcareous Alps (Eastern Alps, Austria)

2021 ◽  
Author(s):  
Timotheus Martin Christoph Steiner ◽  
Hans-Jürgen Gawlick ◽  
Frank Melcher ◽  
Felix Schlagintweit
Keyword(s):  
Shallow Water ◽  
Late Jurassic ◽  
Xrd Analysis ◽  
Eastern Alps ◽  
Major And Trace Elements ◽  
Parent Material ◽  
Northern Calcareous Alps ◽  
Carbonate Platforms ◽  
Northern Calcareous ◽  
Platform Margin

AbstractIn shallow-water limestones of the Plassen Formation in the Tirolic nappe of the Northern Calcareous Alps, bauxite was formed on karstified and tilted platform margin grainstones to boundstones around the ?Kimmeridgian/Tithonian boundary, or in the Early Tithonian as proven by Protopeneroplis striata Weynschenk, Labyrinthina mirabilis Weynschenk, and Salpingoporella pygmaea Gümbel. The platform established on top of the obducted ophiolite nappe stack. The onset of unroofing at the Kimmeridgian/Tithonian boundary exposed ophiolites to weathering, forming laterites, and bauxites. The weathered ophiolitic material was shed on the tilted, emerged, and karstified platform, where the bauxite accumulated. Continued subsidence led to flooding, and a Tithonian transgressive carbonate sequence sealed the bauxites. XRD analysis of the bauxite yields a composition of mainly boehmite with hematite and some berthierine, kaolinite, and chromite. SEM analysis verified magnetite, hematite, rutile, chromite, zircon, ferropseudobrookite, ilmenite, monazite, xenotime, and garnet distributed in pisoids and within the matrix. The pisoids reach a millimeter in size and partly show cores of older, larger pisoids. The composition of the chromites indicates an ophiolitic origin. Geochemical examination using major- and trace elements points to a mafic andesitic to basaltic parent material contaminated with highly fractionated rocks from an island arc. Formation of Early Tithonian bauxites in shallow-water limestones confirms Middle to Early Late Jurassic ophiolite obduction. This was followed by uplift and unroofing of the orogen from the Kimmeridgian/Tithonian boundary onwards after a period of relative tectonic quiescence with an onset of carbonate platforms during the Kimmeridgian on top of the nappe stack and the obducted Neo-Tethys ophiolites.

scholarly journals Ophiolitic detritus in Kimmeridgian resedimented limestones and its provenance from an eroded obducted ophiolitic nappe stack south of the Northern Calcareous Alps (Austria)

2015 ◽  
Vol 66 (6) ◽  
pp. 473-487 ◽  
Author(s):  
Hans-Jürgen Gawlick ◽  
Roman Aubrecht ◽  
Felix Schlagintweit ◽  
Sigrid Missoni ◽  
Dušan Plašienka
Keyword(s):  
Late Jurassic ◽  
Carbonate Platform ◽  
Eastern Alps ◽  
Northern Calcareous Alps ◽  
Western Carpathians ◽  
Chrome Spinel ◽  
Geochemical Composition ◽  
Northern Calcareous ◽  
Tectonic Processes ◽  
Building Process

Abstract The causes for the Middle to Late Jurassic tectonic processes in the Northern Calcareous Alps are still controversially discussed. There are several contrasting models for these processes, formerly designated “Jurassic gravitational tectonics”. Whereas in the Dinarides or the Western Carpathians Jurassic ophiolite obduction and a Jurassic mountain building process with nappe thrusting is widely accepted, equivalent processes are still questioned for the Eastern Alps. For the Northern Calcareous Alps, an Early Cretaceous nappe thrusting process is widely favoured instead of a Jurassic one, obviously all other Jurassic features are nearly identical in the Northern Calcareous Alps, the Western Carpathians and the Dinarides. In contrast, the Jurassic basin evolutionary processes, as best documented in the Northern Calcareous Alps, were in recent times adopted to explain the Jurassic tectonic processes in the Carpathians and Dinarides. Whereas in the Western Carpathians Neotethys oceanic material is incorporated in the mélanges and in the Dinarides huge ophiolite nappes are preserved above the Jurassic basin fills and mélanges, Jurassic ophiolites or ophiolitic remains are not clearly documented in the Northern Calcareous Alps. Here we present chrome spinel analyses of ophiolitic detritic material from Kimmeridgian allodapic limestones in the central Northern Calcareous Alps. The Kimmeridgian age is proven by the occurrence of the benthic foraminifera Protopeneroplis striata and Labyrinthina mirabilis, the dasycladalean algae Salpingoporella pygmea, and the alga incertae sedis Pseudolithocodium carpathicum. From the geochemical composition the analysed spinels are pleonastes and show a dominance of Al-chromites (Fe3+–Cr3+–Al3+ diagram). In the Mg/(Mg+ Fe2+) vs. Cr/(Cr+ Al) diagram they can be classified as type II ophiolites and in the TiO2 vs. Al2O3 diagram they plot into the SSZ peridotite field. All together this points to a harzburgite provenance of the analysed spinels as known from the Jurassic suprasubduction ophiolites well preserved in the Dinarides/Albanides. These data clearly indicate Late Jurassic erosion of obducted ophiolites before their final sealing by the Late Jurassic–earliest Cretaceous carbonate platform pattern.

Sign in / Sign up

Export Citation Format

Share Document