Late Cretaceous - Early Palaeogene sandy-to-gravelly debris flows and their sediments in the Silesian Basin of the Alpine Tethys (Western Outer Carpathians, Istebna Formation)

Abstract

The study fo cuses on Up per Cre ta ceous-Paleocene de pos its from the Beskid Śląski moun tain range in south ern Po land con sti tut ing the Istebna Beds. The Istebna Beds, also re ferred to as the Istebna For ma tion, are part of the Silesian tec tonic unit, which forms the Outer Carpathian fold-and-thrust belt (part of the Al pine-Carpathian sys tem). The re sults of qual i ta tive and quan ti ta tive lithological-sedimentological stud ies were the ba sis for the in ter pre ta tion of lithofacies types, sed i men tary pro cesses and palaeoenvironment as well as for the re con struc tion of the ar chi tec ture of the depositional sys tem. The anal ysis con ducted on the ba sis of field de scrip tion of the de pos its shows the prev a lence (nearly 70%) of siliciclastic strata rep resent ing a sand stone-con glom er ate as so ci a tion (S-C), which is the main sub ject of this work. The S-C lithofacies: sand stones, grav elly sand stones, sandy con glom er ates and con glom er ates con sti tute the de pos its formed mostly by mass grav ity-flows such as sandy-to-grav elly de bris flows. The dis tri bu tion of the coarse-clastic ma te rial in di cates a sed i ment supply from south erly di rec tions and im plies the pres ence of an ac tive source area in the rear part of the Silesian Ba sin. A succes sion of the sand stone-to-con glom er ate de pos its with the sec ond ary par tic i pa tion of other lithofacies, with a thick ness of ap prox i mately two thou sand metres, in di cates tem po rary in creased di a strophic ac tiv ity in the Silesian Ridge (source area) and the in tense de nu da tion of this area. The up lift of the alimentation area and its de struc tion co in cid ing with en forced rel ative re gres sion and the un cov er ing of the prox i mal depositional zone of the ba sin led to resedimentation of the older intrabasinal ma te rial and re peated mass de po si tion to gether with de liv ery of extraclasts of pre-ex ist ing rocks and min er als. The lithofacies de vel op ment of the sand stone-to-con glom er ate debrites and the re lated sed i men tary palaeotransport di rections sug gest an ac cu mu la tion do main in the form of a lin ear apron depositional sys tem de vel oped in a deep-wa ter set ting. Ex per i men tal mod el ling of sub aque ous sandy flows has con trib uted to a better un der stand ing of the com plex gen e sis of deep-wa ter sed i ment grav ity flows de vel op ing in depositional sys tems rich in sand ma te rial.

Sedimentary processes and architecture of Upper Cretaceous deep-sea channel deposits: a case from the Skole Nappe, Polish Outer Carpathians

“…Fillings of the mega-flutes record a variety of depositional conditions which are expressed by lateral changes in the texture and primary structure of sediments (e.g., Leszczyński 1989 and references therein). Coarse-grained flute filling and coarse-grained amalgamation zones are basal lag deposits, which represent the thickest material carried by traction near the bottom (e.g., Dżułyński & Sanders 1962;Lowe 1982;Postma et al 1988;Sohn 1997;Strzeboński 2015). Vertical multiple grain-size coarsening surfaces within some megaflutes indicate deposition from an unsteady fluctuating flow or multiple filling of the flute by different events.…”

“…Most of the elongated mudstone clasts suggest transportation on top of the highly concentrated bottom part of the high-density turbidity current, which prevented their further erosion and allowed them to keep their longitudinal shape. However, some authors suggest that preservation of mudstone clasts and their planar concentration to the top of bed is rather typical of sandy debrites (e.g., Shanmugam 2006;Strzeboński 2015). The well-rounded marlstone clasts imply relatively long traction transportation.…”

“…Numerous, chaotically oriented huge clasts could be transported only by matrix supported debris flows (e.g., Shanmugam 2006;Strzeboński 2015). Moreover, patchy and nest distribution of coarse-grains imply poor conditions for grain segregation, which is the feature typical of laminar flow.…”

Facies heterogeneity of a deep-sea depositional lobe complex: case study from the Słonne section of Skole Nappe, Polish Outer Carpathians

“…Interpretation: The deposits of facies F5 are interpreted as debrites emplaced by the en masse freezing of non-turbulent dense flow (cf. Breien et al, 2010;Strzeboński, 2015). From the bed characteristics, it is unclear as to whether the debris flow was a parental mass movement, diluted at the top (turbidite cap T CDE ), or whether it was spawned by a large turbidity current excessively charged with mud and plant detritus (with the T CDE cap as low-density flow relic).…”

Environmental stress in the northern Tethys during the Paleogene: a review of foraminiferal and geochemical records from the Polish Outer Carpathians

“…Hemipelagic de po si tion which pre vailed in the Subsilesian Zone and in part of the Magura and Skole zones was fre quently in ter rupted by the abrupt sup ply of coarse-grained terrigenous ma te rial in the Silesian and Dukla zones (Leoeniak et al, 2001;Strzeboñski, 2015; Fig. 3).…”