Architecture of coarse-grained gravity flow deposits in a structurally confined submarine canyon (late Eocene Tokaren Conglomerate, Slovakia)

Abstract

This study documents the coarse-grained fill of an upper slope, late Eocene Tokaren Canyon in the Carpathian Mountains, whose planform geometry and internal architecture were driven by normal faulting of an underlying carbonate platform. Facies analysis hints at a narrow shelf and a direct link to rivers draining a rapidly-uplifting hinterland. The axial part of the canyon consists of several meters thick, amalgamated conglomerate intervals deposited by debris flows and, to a lesser extent, by debris falls, slides and high-density turbidity currents. The sediments form sheets consisting of several tens to several hundreds of meters wide lobes occasionally entrenched by small erosional chutes. The deposits on the higher, fault-bounded blocks closer to the channel margins, include well-developed conglomerate–sandstone packages. They show a sheet-like geometry scattered with small channels. The textural immaturity of the sediment, grain-size caliber, the sediment thickness variation in the canyon, the sedimentary facies and their spatial distribution imply a dominant role of tectonics and sediment supply in the evolution of the canyon.Despite numerous studies of canyons in tectonically active settings, there are surprisingly limited studies on the depositional fill architectures of such canyons based on outcrop analogs. The detailed study of the Tokaren Canyon architecture brings a valuable insight into processes and distribution of proximal canyon fill facies controlled by syn-depositional faulting. It describes the architecture of such coarse-grained depositional system fed directly by rivers and governed by tectonics and supplements the knowledge from such systems obtained by different methodologies.