Provenance of Cretaceous synorogenic sediments from the NW Dinarides (Croatia)

Abstract

Scarce basin remnants of Cretaceous synorogenic sediments exposed in the Medvednica, Ivans ˇc ˇica, Z ˇumberak Mts. and Samobor Hills of northern Croatia record the early orogenic history of the NW Dinarides. The provenance of sandstones from five clastic formations (Os ˇtrc, Bistra, Kravljak, Vivodina and Glog) which cover a time span from Early to late Late Cretaceous was studied by combining petrography, whole-rock geochemistry, heavy mineral chemistry and detrital zircon fission track dating. These sediments record at least two major regional thermotectonic events which correlate well with those affecting both the Alps and the Tisza-Dacia unit to the north and east, and the central Dinaride region to the south. Short zircon fission track lag times in Barremian to Albian sediments indicate that continental fragments of the distal Adria plate margin underwent relatively fast, synsedimentary exhumation in the Early Cretaceous. Moreover, a clear dominance of Campanian zircon cooling ages (80-73 Ma) in Maastrichtian sandstones indicates detritus deriving from the erosion of newly and rapidly exhumed basement units which had undergone Late Cretaceous metamorphism in the Eastern Alps and/or the Tisza-Dacia region. Probably, the rapid Maastrichtian erosion generating metamorphic detritus occurred to a great extent on neighbouring Austroalpine basement units, and/or on the upper plate Tisza-Dacia unit during the subduction stage or the initial stages of the continent-continent collision with Adria. Development of the accretionary wedge probably resulted in a renewed availability of ophiolites for erosion within small and/or dynamically changing catchments, which can be deduced from the notable differences in reconstructed source lithologies for the coeval Glog and Vivodina formations. Combined evidence from sedimentary provenance indicators precludes the Dinaride (Adriatic) basement as a significant source for the Maastrichtian sediments.

The tectonic evolution of a critical segment of the Dinarides‐Alps connection: Kinematic and geochronological inferences from the Medvednica Mountains, NE Croatia

“…The Early Cretaceous ZFT cooling and provenance ages (126–127 Ma) obtained from outside the greenschist facies metamorphic core increased the precision of the time‐temperature curve in the same range detected by previous studies (Figure ). The short‐range sediment transport of Jurassic‐Earliest Cretaceous ophiolitic mélange detritus deposited in Upper Cretaceous sediments is in agreement with previous provenance studies [ Lužar‐Oberiter et al , ].…”

“…The metamorphosed Paleozoic‐Triassic sequence and the ophiolitic mélange are unconformably covered by Upper Cretaceous‐Paleocene sediments (Figure ). These show a gradual transgressive pattern from massive conglomerates and alluvial fan deposits at the base to sandstones and Scaglia Rossa hemipelagic carbonates higher up in the sequence [ Babić et al , ; Crnjaković , ; Lužar‐Oberiter et al , ]. These deposits are stratigraphically continuous with the uppermost Cretaceous turbidites (carbonatic and clastic) that are commonly observed elsewhere along the Sava suture zone [e.g., Ustaszewski et al , ].…”

“…A NE‐SW directed contraction is commonly observed in the Dinarides, but at later times, during the Late Cretaceous‐Eocene [e.g., Tari‐Kovačić and Mrinjek , ; Schmid et al , , and references therein]. In the upper tectonic unit, the deposition of Aptian‐Cenomanian shallow‐marine and near‐shore flexural basin sequence that unconformably overlays the Paleozoic‐Mesozoic and ophiolitic mélange units [ Lužar‐Oberiter et al , ] can be interpreted as synkinematic deposition to the late Early Cretaceous thrusting.…”

“…The geographical location of the AlCaDi system is shown in the inset figure. (b) Tectonostratigraphic map of the Medvednica Mountains and surrounding areas near the Alpine‐Dinaridic junction [simplified and modified from Haas et al , ; Lužar‐Oberiter et al , ; Matoš et al , ; Tomljenović and Csontos , , with the results of this study]. Location of figure is displayed in Figure a.…”

New data on the age of an Upper Cretaceous sediments in Brežđe (NW Serbia)

“…After the Late Jurassic obduction and subsequent erosion in the Dinaridic-Hellenic belt, Cretaceous synorogenic basins were formed and filled with clastic material composed of variable amounts of ophiolitic, terrigenous and carbonate detritus (LUŽAR-OBERITER et al, 2012). Therefore, the obducted ophiolitic sheets of the Dinarides are in many places unconformably overlain with Late Jurassic to Early Cretaceous shallow and/or deep marine sediments PAMIĆ & HRVATOVIĆ, 2000;SCHMID et al, 2008).…”