, Volume 100, Issue 7, pp 1605-1631
Date: 24 Jun 2010

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

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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.