Silesian Ridge in the light of petrological analyses and LA-ICP MS U-Pb analyses of the cohesive debrites from the Istebna Formation (Silesian Nappe, Outer Western Carpathians, Poland)

Abstract

Ex otic clasts pres ent in flysch de pos its of the West ern Outer Carpathians en able in ves ti ga tion and re con struc tion of the eroded crys tal line base ment of the Silesian Ridge. The flysch rocks of the Istebna For ma tion (Jasnowice Mem ber: Paleocene) in the Silesian Nappe con tain mag matic and meta mor phic clasts de rived from the Silesian Ridge base ment. The crys tal line rock frag ments ac quired from co he sive debrites were an a lyzed petro graphi cally and geochemically, and zir con and rutile crys tals were sub ject to LA-ICP-MS U-Pb dat ing. Granitoid clasts yielded Meso-Variscan U-Pb zir con ages (325.7 and 330.6 Ma), with older (Neoproterozoic to Paleoproterozoic) in her ited cores and eNd 330 = -12.0 (TDM age of 1.98 Ga). The orthogneiss clast yielded a protolith age of 1635 Ma and fin ger print of ther mal re work ing at ~288 Ma. Zir con crys tals from the de tri tal clasts yielded sim i lar U-Pb zir con ages to the granitoid clasts (311.5 to 391 and 331 Ma). The rutile crys tals from sand stone yielded con cordia age of 344.7 Ma. Zir con crys tals from paragneiss, in ter preted as a granitoid en ve lope, yielded 238 U/ 206 Pb ages be tween 557 and 686 Ma and in clude an in her ited core of age ~1207.4 ±33.8 Ma. Age data from ex otic clasts and the de tri tal zir con and rutile frac tion sug gest the core part of the Silesian Ridge was a Neoproterozoic to Mesoproterozoic en ve lope in truded by Meso-Variscan granitoid plutons.

Residual rocky forms in the landscape of the Outer Carpathians (Silesian Beskid Mts, Poland) - geotourist and sedimentological case study

“…Burtanówna et al, 1937). These so-called exotics occur in the Istebna Formation predominantly in the form of megascopically recognisable fragments of crystalline rocks (e.g., Unrug, 1963; see also Strzeboński, 2005Strzeboński, , 2015Starzec et al, 2017Starzec et al, , 2018Gawęda et al, 2019;Strzeboński, 2022;Szczuka et al, 2022). In the region studied, the exotic clasts are mainly metamorphic rocks (mostly gneisses, granulites), to a lesser extent igneous rocks (primarily granitoids), and relatively rarely sedimentary rocks (e.g., hornstones or exceptionally limestones).…”

“…for the Istebna Formation deposits in the Western Beskids) were mainly the basic source areas of the clastic material that was delivered to the Carpathian Basin (incl. the Silesian Sub-Basin) (Unrug, 1963(Unrug, , 1968Golonka et al, 2000Golonka et al, , 2008Strzeboński & Uchman, 2015;Gawęda et al, 2019;Szczuka et al, 2022). Some of the exotics present in the flysch formations may also have come from the reworking of older parental clastic series (e.g., exotic conglomerates) building up fragments of the source area (Strzeboński, 2022).…”

“…18, 1-2 (64-65) 2021 https://journals.agh.edu.pl/geotour Simplified and partly modified from: Burtan et al, 1956;Burtan, 1972;Żytko et al, 1989;Golonka et al, 2000;Lexa et al, 2000;Strzeboński, 2015 Sediments accumulated in the Carpathian Basin, including those within the Silesian Sub-Basin, were involved in the Neogene geotectonic reorganisation (orogenic processes) of the Alpine Tethys (cf. Golonka et al, 2000Golonka et al, , 2008Poprawa et al, 2002;Jankowski, 2015;Szczuka et al, 2022). Therefore, as a result of the Alpine orogeny, the flysch series underwent the following: folding, detaching from the parent basin substrate, overlapping in the form of regionally sized tectonic units (so-called nappes), and together were tectonically and gravitationally transported to the foreland, thus forming a continental accretionary prism of the Carpathian orogen.…”

Neoproterozoic ophiolite exotic blocks in the Outer Western Carpathians, southern Poland: a record of the fast ocean-floor cooling and alterations

“…The West ern Outer Carpathian bas ins formed dur ing the Me so zoic and Ce no zoic in the west ern part of the Tethys Ocean. Their depositional base ment was both the Protocarpathians, formed in the Neoproterozoic and ex pe rienced prob a ble Variscan re work ing (e.g., Poprawa et al, 2006;Budzyñ et al, 2011;Burda et al, 2019;Gawêda et al, 2019Gawêda et al, , 2021Szczuka et al, 2022) as well as the rem nants of Tethyan oce anic crust (Stampfli et al, 2002;Szopa et al, 2014). As the Outer Carpathian nappes are up rooted and de tached from the orig i nal place of for ma tion, the Protocarpathian base ment is pres ent as ex otic blocks, which are the pri mary source of in forma tion on the na ture and pre-Al pine his tory of the base ment.…”