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

Abstract

Deep-sea channels are one of the architectonic elements, forming the main conduits for sand and gravel material in the turbidite depositional systems. Deep-sea channel facies are mostly represented by stacking of thickbedded massive sandstones with abundant coarse-grained material, ripped-up clasts, amalgamation and large scale erosional structures. The Manasterz Quarry of the Ropianka Formation (Upper Cretaceous, Skole Nappe, Carpathians) contains a succession of at least 31 m of thick-bedded high-density turbidites alternated with clast-rich sandy debrites, which are interpreted as axial deposits of a deep-sea channel. The section studied includes 5 or 6 storeys with debrite basal lag deposits covered by amalgamated turbidite fills. The thickness of particular storeys varies from 2.5 to 13 m. Vertical stacking of similar facies through the whole thickness of the section suggest a hierarchically higher channel-fill or a channel complex set, with an aggradation rate higher than its lateral migration. Such channel axis facies cannot aggrade without simultaneous aggradation of levee confinement, which was distinguished in an associated section located to the NW from the Manasterz Quarry. Lateral offset of channel axis facies into channel margin or channel levee facies is estimated at less than 800 m. The Manasterz Quarry section represents mostly the filling and amalgamation stage of channel formation. The described channel architectural elements of the Ropianka Formation are located within the so-called Łańcut Channel Zone, which was previously thought to be Oligocene but may have been present already in the Late Cretaceous.

Evolution of a turbidite system in a narrow basin setting: the Ropianka Fm (Campanian–Paleocene) in the Skole Nappe of the Polish Carpathians

“…Only in the log of Basowy 1 borehole, the occurrence of marlstone with slump features was reported at a depth of ~1180 m, indicating a slope inclination large enough for at least rare mass-transport events, but overall, turbidity currents predominated. Similar deposits are widely described along the entire northern edge of the Skole Basin, representing the most proximal zone, exposed in the Skole Nappe (e.g., Bromowicz, 1974;Kotlarczyk, 1978Kotlarczyk, , 1988aŁapcik et al, 2016;Kowalczewska and Gasiński, 2018;Łapcik, 2018, 2019.…”

“…The bulk progradation of the depositional system is widely recorded in the Ropianka Fm of the entire Polish segment of the Skole Basin, as an abundant occurrence of mass-movement deposits (cf. Burzewski, 1966;Kotlarczyk, 1978Kotlarczyk, , 1988aŁapcik et al, 2016;Łapcik, 2018, 2019. However, in the eastern part of the basin, they mostly were derived from the northern margin of the basin.…”

Maastrichtian climate changes – the calcareous nannofossil record from flysch deposits of the Outer Carpathians

“…The deposits of the Ropianka Formation accumulated in the deep-sea part of the Skole Basin, i.e. the northern part of the Tethyan Ocean, bordering the East European Platform (e.g., Bromowicz, 1986;Łapcik et al, 2016;Łapcik, 2018).…”