Provenance of the Bosnian Flysch

Abstract

sandwiched between the Adriatic carbonate Platform and the Dinaride Ophiolite Zone, the bosnian Flysch forms a c. 3000 m thick, intensely folded stack of Upper Jurassic to cretaceous mixed carbonate and siliciclastic sediments in the Dinarides. New petrographic, heavy mineral, zircon U/Pb and fission-track data as well as biostratigraphic evidence allow us to reconstruct the palaeogeology of the source areas of the bosnian Flysch basin in late Mesozoic times. Middle Jurassic intraoceanic subduction of the Neotethys was shortly followed by exhumation of the overriding oceanic plate. trench sedimentation was controlled by a dual sediment supply from the sub-ophiolitic high-grade metamorphic soles and from the distal continental margin of the Adriatic plate. Following obduction onto Adria, from the Jurassic-cretaceous transition onwards a vast clastic wedge (Vranduk Formation) was developed in front of the leading edge, fed by continental basement units of Adria that experienced Early cretaceous synsedimentary cooling, by the overlying ophiolitic thrust sheets and by redeposited elements of coeval Urgonian facies reefs grown on the thrust wedge complex. Following mid-cretaceous deformation and thermal overprint of the Vranduk Formation, the depozone migrated further towards sW and received increasing amounts of redeposited carbonate detritus released from the Adriatic carbonate Platform margin (Ugar Formation). subordinate siliciclastic source components indicate changing source rocks on the upper plate, with ophiolites becoming subordinate. the zone of the continental basement previously affected by the Late Jurassic-Early cretaceous thermal imprint has been removed; instead, the basement mostly supplied detritus with a wide range of pre-Jurassic cooling ages. However, a c. 80 Ma, largely synsedimentary cooling event is also recorded by the Ugar Formation, that contrasts the predominantly Early cretaceous cooling of the Adriatic basement and suggests, at least locally, a fast exhumation.

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

“…14b). The same situation for the Early Cretaceous is known in the Pannonian realm (Császár 2002), the Dinarides (Dimitrijevic and Dimitrijevic 1987;Dimitrijevic 1997;Mikes et al 2008), and the Albanides (Bortolotti et al 1996).…”

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

“…Erosion of this platform started around the Jurassic/Cretaceous-boundary as is proven by the occurrence of Upper Jurassic shallow-water pebbles in the Lower Cretaceous Firza Flysch Schlagintweit et al 2008) in Albania, or the Lower Cretaceous Bosnian Flysch (Mikes et al 2008). Reworked pebbles from the different facies belts of this shallow-water platform (similar to the Kurbnesh carbonate platform - Schlagintweit et al 2008) were recently also described from the Berriasian-Valanginian of the Vardar zone by Kostaki et al (2013).…”

Deciphering the geodynamic evolution of the Dinaric orogen through the study of the ‘overstepping’ Cretaceous successions

“…The Late Jurassic/Early Cretaceous obduction event in the Dinaric-Hellenic orogen resulted in the lithospheric doming of the foreland continental crust with local emersion events in the Adriatic Carbonate Platform (AdCP; Vlahović et al 2005 and references therein). The crustal bulge was then followed by flexure in front of the obducting ophiolite load with the formation of a deep-sea foreland basin starting in latest Jurassic -Early Cretaceous times (Mikes et al 2008). In addition, specific sedimentary basins developed on top of the obducted ophiolites, and continental, littoral, shallow-water and deep-sea environments succeeded each other in the same area and sometimes in relatively rapid succession (Fazzuoli et al 2008;Lužar-Oberiter et al 2012).…”

“…The latter crops out along a NW-SEaligned thrust sheet known as the Pre-karst Unit (Schmid et al 2008 with references) that is lying below the East Bosnian-Durmitor Unit, which in turn is overlain by the Western Vardar ophiolites (Charvet, 1978). The Bosnian flysch consists of a lower lithostratigraphic unit, mostly reported as Tithonian to Valanginian (Blanchet, 1966(Blanchet, , 1968Charvet, 1967;Cadet, 1968;Rampnoux, 1969) and up to Aptian in age (Cadet & Sigal, 1969;Charvet, 1978;Mikes et al 2008), that is mainly composed of siliciclastic deposits (Vranduk Formation) followed upwards by lower Albian to Maastrichtian carbonate-dominated clastic deposits of the Ugar Formation (Mikes et al 2008 with references). According to Mikes et al (2008), the upper part of the Vranduk Fm is at least Aptian in age.…”