engleski

Tracing Late Cretaceous geodynamics in the Dinarides from mixed siliciclastic-carbonate detritus of synorogenic basins

The complex system encompassing the Dinarides, Pannonian Basin crystalline basement, and their adjoining areas, is a geologically intriguing area of Europe. In the Cretaceous period, significant evidence of large-scale geodynamic processes have been identified in the geological record within crystalline basement rocks, as well as in clastic synorogenic sediments, and even on the previously very stable Adriatic Carbonate Platform, and are the focus of an ongoing research project funded by the Croatian Science Foundation (IP-2014-09- 9541). The sediments of intermediately situated basins are being studied along an orogen perpendicular transect using biostratigraphy, petrography and heavy mineral analysis in order to constrain the timing and character of clastic influx generated from neighboring geodynamically active areas. Following Early to early Late Cretaceous orogenic events, many parts of the Internal Dinarides underwent transgression and widespread establishment of deep-water sedimentation. A period of quiescence marked by deposition of Campanian pelagic limestones was followed by a gradual, relatively rapid increase in siliciclastic influx which heralds the collision of Adria and Europe derived continental units following closure of an ocean remnant of the Neotethys (Ustaszewski et al., 2009). Preliminary assessment by planktonic foraminifera and nannoplankton suggests that this first impulse of renewed clastic input occurred still in the Campanian in NE parts of the basin system (Mt. Medvednica) and advanced towards the present day SW (Banovina and Cetingrad areas). The arenites contained in Campanian to Paleocene sediments that follow record multiple ‘crystalline’ and ‘carbonate’ sources. Sandstone composition indicates erosion of a largely metamorphic terrain typified by abundant mica, polycrystalline quartz and quartz-mica lithoclasts. Ophiolites also formed parts of the source area. Heavy mineral suits contain zircon, tourmaline, Cr- spinel, apatite, rutile and garnet. Meanwhile, calcarenites which are interbedded with sandstones lack any siliciclastic material and are composed entirely of bioclasts, which include lamellar-perforate larger benthic foraminifera (including orbitoidal foraminifera: Lepidorbitoidinae and Clypeorbinae), fragments of echinoderms (echinoids and crinoids), corallinaceans (mostly Subfamily Melobesioideae), and bryozoans (mostly fragments of erect rigid colonies). A similar association has been identified within the Adriatic-Dinaric Carbonate Platform (e.g. Brlek et al., 2013) and suggests re-deposition of carbonate material from a shelf break environment. Coarser grained carbonate breccias indicate erosion of older stratigrafic units of the platform as well. Sediment supply to the basin thus occurred from multiple source areas located on both sides of the basin system, the inner Adria-Europe active collision zone and the outer Adriatic Carbonate Platform whose margin was also starting to experience the effects of tectonic activity.

Cretaceous ; geodynamics ; Dinarides ; clastics

nije evidentirano