The oldest stage of the Outer Carpathian evolution in the light of Oxfordian\u2013Kimmeridgian exotic clast studies (southern Poland)

Abstract

In the Late Jurassic, the rifting process led to the disintegration of the southern margin of the North European Platform and to the opening of the Outer Carpathian flysch basin sedimentary system. The initial sediments accumulated in the northern part of the basin are related to both the destruction and resedimentation of older platform deposits. Since the sedimentary succession of this pre-flysch phase was consumed by the Miocene subduction, its only traces are represented, nowadays, by clasts preserved as exotics in the succeeding flysch deposits. Our analysis of foraminifers as well as calcareous and organic dinoflagellate cysts found in these exotics confirms the Oxfordian–early Kimmeridgian timing of the platform phase that preceded the opening of the flysch basin. The exotics are represented by three main facies types: sponge–microbial limestones, oncoid–intraclastic–Crescentiella limestones and fine-grained, biodetrital limestones with Saccocoma. These deposits are related to mid-ramp to outer-ramp settings. The land influence was rather weak, and these sedimentary settings were dominated by pelagic/hemipelagic accumulation. The studied facies are similar to facies types widely distributed over the northern shelf area of the Western Tethys (e.g., extra-Carpathian southern Poland, Carpathian Foredeep basement, southern Germany). In turn, coeval strata known from the part of the Magura Basin and of the Penninic–Pieninic Ocean, which were situated in more southern part of the Tethys, yielded different microfacies reflecting significant differences between the sedimentary settings of the study area and its southern extensions.