Evidence for Jurassic subduction from the Northern Calcareous Alps (Berchtesgaden; Austroalpine, Germany)

Abstract

The closure of the western part of the Neotethys Ocean started in late Early Jurassic. The Middle to early Late Jurassic contraction is documented in the Berchtesgaden Alps by the migration of trench-like basins formed in front of a propagating thrust belt. Due to ophiolite obduction these basins propagated from the outer shelf area (=Hallstatt realm) to the interior continent (=Hauptdolomit/Dachstein platform realm). The basins were separated by nappe fronts forming structural highs. This scenario mirrors syn-orogenic erosion and deposition in an evolving thrust belt. Active basin formation and nappe thrusting ended around the Oxfordian/Kimmeridgian boundary, followed by the onset of carbonate platforms on structural highs. Starved basins remained between the platforms. Rapid deepening around the Early/Late Tithonian boundary was induced by extension due to mountain uplift and resulted in the reconfiguration of the platforms and basins. Erosion of the uplifted nappe stack including obducted ophiolites resulted in increased sediment supply into the basins and final drowning and demise of the platforms in the Berriasian. The remaining Early Cretaceous foreland basins were filled up by sediments including siliciclastics. The described Jurassic to Early Cretaceous history of the Northern Calcareous Alps accords with the history of the Western Carpathians, the Dinarides, and the Albanides, where (1) age dating of the metamorphic soles prove late Early to Middle Jurassic inneroceanic thrusting followed by late Middle to early Late Jurassic ophiolite obduction, (2) Kimmeridgian to Tithonian shallow-water platforms formed on top of the obducted ophiolites, and (3) latest Jurassic to Early Cretaceous sediments show postorogenic character.

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

“…Reconstruction of the Triassic shelf configuration after Gawlick et al (1999). Reconstruction of the Jurassic evolution after Gawlick et al (1999), Missoni & Gawlick (2011a for the Northern Calcareous Alps and Gawlick et al (2008Gawlick et al ( , 2014 for the Dinarides/Albanides on the basis of Kober (1914) concerning the genesis and emplacement of the Mirdita ophiolites and related radiolaritic-ophiolitic trench fills (see also Bortolotti et al 2005;Schmid et al 2008;Kilias et al 2010). Ages after Gradstein et al (2004).…”

“…Moreover, deposition of the Rossfeld Formation stopped contemporaneously with the onset of the late Early Cretaceous to early Late Cretaceous tectonic event, showing clearly that the Jurassic orogeny and the late Early Cretaceous to early Late Cretaceous orogeny must be clearly separated. Missoni & Gawlick (2011a) pointed out the existence of detrital chrome spinel grains in the Late Kimmeridgian but without geochemical analyses. The reason for the still missing detailed analysis was the lack of their occurrence in investigateable quantities.…”

Age and microfacies of oceanic Upper Triassic radiolarite components from the Middle Jurassic ophiolitic mélange in the Zlatibor Mountains (Inner Dinarides, Serbia) and their provenance

“…Although there are contrasting models about the palaeogeography in Triassic-Jurassic times in the western Tethyan realm (e.g., Stampfli & Kozur 2006;Schmid et al 2008;Missoni & Gawlick 2011b;Robertson 2012;Gawlick et al 2016 a, b), there is progress in the reconstruction of the age of lost oceanic domains and in the understanding of geodynamic processes in the Tethyan realm. Many new biostratigraphic data on Triassic and Jurassic radiolarites in mélange areas have recently been obtained in the Dinarides, Albanides and Hellenides (e.g., Gawlick et al 2008Gawlick et al , 2016Vishnevskaya et al 2009;Djerić et al 2010Djerić et al , 2012Chiari et al 2011Chiari et al , 2013Ozsvárt et al 2012;Bragin et al 2014;Ferrière et al 2015Ferrière et al , 2016Gawlick & Missoni 2015), but still a lot of questions remain open.…”

Age and significance of Lower Cretaceous mass flows: Ischl Breccia revisited (Rossfeld Formation, Northern Calcareous Alps, Austria)

“…A very high percentage of radiolarite pebbles in the basal mass flows of the Rossfeld Formation is only typical for the Gartenau section (Krische, 2012;Krische et al, 2014) and, to a less extent, also for the type locality Rossfeld (Missoni and Gawlick, 2011a).…”

“…A different tectonic model was introduced into the discussion by Gawlick et al (2008) who interpreted the Rossfeld Formation as deposits of the molasse stage within an underfilled foreland basin (Tauglboden/Oberalm Basin) in front of the Neotethyan Belt (Missoni and Gawlick, 2011a). In this alterna-_____________________ tive scenario, the process of nappe-emplacement started already in the Middle Jurassic and continued at least until the early Late Jurassic.…”