Facies Anatomy of a Sand‐Rich Channelized Turbiditic System: The Eocene Kusuri Formation in the Sinop Basin, North‐Central Turkey

Abstract

This study focuses on a basin-floor turbiditic system in an Eocene foredeep basin, using facies analysis supplemented with micropalaeontological and ichnological data. Sediment dispersal processes are interpreted from sedimentary facies, and the morphogenesis, spatial relationships and stratigraphic distribution of facies associations are used to reconstruct the behaviour and morphodynamic evolution of the turbiditic system. The case study sheds more light on the development of submarine channels and related patterns of overbank sedimentation in narrow foreland basins, and contributes to a better understanding of the geological history of the Central Pontides.The lower to middle Eocene Kusuri Formation in the Sinop Basin, north-central Anatolia, is a succession of siliciclastic turbidites ~1200 m thick, well-exposed on the Turkish Black Sea coast. The deposition occurred in a west-trending foredeep trough of the Central Pontides, ~30 km wide and > 150 km long, and involved a deep-water axial dispersal system supplied with coarse sediment by a fluvio-deltaic feeder draining the emerged adjacent foreland of the Eastern Pontides. Sedimentary facies include hemipelagic 'background' mudstones, thin muddy turbidites and 'classic' Bouma-type turbidites, a wide range of non-classic turbidites attributed to low-and high-density sustained currents, and gravelly debrisflow deposits. These facies form four major associations:1 mudstones interspersed with thin turbidite sheets; 2 broad depositional lobes with thickening-upward bedding trends; 3 poorly defined wide palaeochannels, solitary sinuous palaeochannels and multistorey palaeochannel complexes; 4 packages of thin overbank turbidites with tabular, wedge-shaped or sigmoidal bedding.The first assemblage forms the lowermost and uppermost part of the Kusuri Formation, whereas the others occur in its middle main part. The poorly defined palaeochannels are 20-25 m thick, typically overlie the depositional lobes and are themselves overlain by the sinuous palaeochannels, 20-30 m thick and ≤ 400-500 m wide, which suggests that the former channels tended to evolve into the latter. The sinuous channels show lateral accretion (point bars) indicating meander-bend expansion combined with a marked downstream translation, and their depth/width aspect ratios are much lower than those of many modern submarine channels. The multistorey complexes of sinuous palaeochannels are 100-160 m thick and estimated to be ≤ 3-5 km wide. The vertical stacking of multistorey channels is attributed to the growth of syndepositional blind-thrust anticlines on the basin floor. The overbank facies assemblages indicate basin-wide flows (tabular bed packages),

Response of unconfined turbidity current to deep‐water fold and thrust belt topography: Orthogonal incidence on solitary and segmented folds

“…Marini et al, 2016). Examples include: the Ordovician Cloridorme Formation of Quebec, Canada (Pickering & Hiscott, 1985); the Permian Laingsburg Formation of Karoo Basin, South Africa (Grecula et al, 2003); the Late Cretaceous Vallcarga Formation of south-central Pyrenees, Spain (Van Hoorn, 1970); the Eocene Hecho Group of south-central Pyrenees, Spain (Mutti & Johns, 1978;Shanmugam & Moiola, 1988;Remacha et al, 2005); the Eocene Kusuri Formation in Sinop Basin, north-central Turkey (Janbu et al, 2007); the Eocene-Oligocene Gr es d'Annot Formation of the Alpine foreland, south-eastern France (Kneller & McCaffrey, 1999;McCaffrey & Kneller, 2001;Salles et al, 2014;Tinterri et al, 2016); the Miocene turbidites of the Tabernas-Sorbas Basin, south-eastern Spain (Haughton, 1994(Haughton, , 2000Hodgson & Haughton, 2004); and several turbidite units of the Central and Northern Apennines, among which include the Miocene Marnoso-Arenacea (Tinterri et al, 2016), Laga and Castagnola (Milli et al, 2013;Marini et al, 2016) formations. The controversial issues include interpretation of turbidite sedimentation over the sea-floor palaeotopography of slump folds in mass-transport complexes (Pickering & Corregidor, 2005;Moscardelli & Wood, 2008;Kneller et al, 2016).…”

3D numerical modelling of turbidity currents

“…The anatomy of deposits originating from turbidity currents can be studied on a large scale, in order to identify the various depositional elements such as lobes, levees and submarine channels [2]. Furthermore, considerable research on the morphology of turbiditic systems and general deep-marine depositions is being increasingly done with the use of 3D seismic sections [3,4].…”

Numerical investigation of continuous, high density turbidity currents response, in the variation of fundamental flow controlling parameters

“…This is due to their rare and unexpected occurrence nature, as they are usually formed during floods. Therefore, field investigations are usually limited to the study of the deposits originating from such currents [3]. However, the last decades, considerable research on the morphology of turbiditic systems and general deep-marine depositions is being increasingly done with the use of 3D seismic sections [4].…”