Transitional flow deposits on submarine lobe flank (Veřovice and Lhoty Fms, Albian – Cenomanian, Polish Outer Carpathians)

Abstract

The Zagórnik-Rzyki studied section includes the upper part of the Veřovice Fm and the lower part of the Lhoty Fm (Aptian–Albian), which are small fragments of the much thicker sedimentary succession of the Silesian Nappe (Polish Outer Carpathians). Logged section gives a good insight into the relatively proximal but muddy submarine fan environment with at least partially confined nature and widely distributed facies of heterolithic deposits and banded sandstone. Three distinguished facies associations represent a gradual lateral shift toward the depositional lobe flank in a relatively proximal setting, away from the main sediment distribution pathways. The studied heterolithic deposits show various internal sedimentary structures (muddy ripples, draped ripples, low-amplitude bed-waves, low-angle laminated bedforms, small lenticular bedforms and plane-parallel laminated mudstone) considered as a record of the dynamic of sedimentary processes on a submarine depositional lobe flank environment. Despite the predominance of finning upward grain size trends (wanning flow deposits), sedimentary structures in the heterolithic deposits may stack in a varied order, also forming coarsening upward trend (waxing flow deposits), bi-gradational trend (waxing to wanning flow deposits), and complex trends (deposits with multiple waxing to wanning flow pulses) indicating record of hyperpycnal flows. Lack of hybrid event beds despite the occurrence of transitional flow deposits is evidence that even in mud-dominated to mixed sand-mud submarine turbidite systems, the flow transformation from fully turbulent to cohesive laminar behaviour is incomplete in relatively proximal depositional environment. Instead, a variety of facies banded sandstone and heterolithic deposits may represent a significant fragment of the sedimentary record in the proximal depositional lobe flank setting.