Turbidites and turbidity currents from Alpine ‘flysch’ to the exploration of continental margins

Abstract

The concept of turbidite has evolved so much since its original definition by Kuenen and Migliorini in 1950 -i.e. the deposit of turbidity currents exemplified by the sandy flysch successions of the Northern Apennines -that it is now used to define a variety of deposits, some of which have little in common with sandy flysch formations in terms of facies, geometry and geological significance. The extension of the concept to other geodynamic settings and deposits of nonsiliciclastic composition is considered only briefly in the concluding sections.With the diffusion of the concept of turbidity current, in the 1950s and early 1960s, an entirely new branch of sedimentology came into being, concerned with the inventory of sedimentary structures, palaeocurrent measurements and bedding patterns. The most representative expression of this branch came from the 'Dutch school' of Philip H. Kuenen and his students. Between the late 1960s and the mid-1970s, there was a new development: facies analysis, in terms of modern environments and depositional systems. This development led to the introduction and discussion of 'fan models' that became an increasingly thorny issue with the accumulation of data from modern deepmarine settings. In particular, most researchers emphasized the importance of channel and lobe elements and their mutual relationships in space and time. These models may differ in terms of specific features, e.g. canyon-fed versus delta-fed ramp settings and terminology, but the basic distinction between channels (sediment pathways), lobes and basin plains (sheet-like depositional features) was and still is widely retained -a model that simply refers to a system where a distributary channel passes downstream to a depositional zone, like in most fluvio-deltaic systems. Great caution should, however, be exercised when comparing modern and ancient fans -a problem discussed at length in the Committee on Submarine Fans I convened by A.H. Bouma and held in Pittsburgh in 1982. Different data sets and geological contexts, scaling problems and terminology still cast doubt over how meaningful such a comparison may be. Despite the many problems encountered, the elemental approach provides an easy, essentially descriptive tool to significantly compare recent with ancient, recent with recent, and ancient with ancient systems.Beginning in the 1970s, process-oriented facies analysis led to increasingly complex facies classification schemes, which showed substantial departures from the classic Bouma sequence and introduced many new concepts: proximal versus distal sedimentation, sediment bypass and flow efficiency, in addition to deflection, reflection and ponding of turbidity currents in confined basins. During the last two decades, there has been an increased interest in attempting to interpret the incredibly detailed submarine landscapes obtained through advances in marine geology, technology and Sedimentology

Turbidite and conglomerate successions in an Ordovician back-arc basin, Mid-Norwegian Caledonides: a result of long-term staging followed by catastrophic release of sediments

“…10). Although hummocky cross-bedding has traditionally been interpreted to result from storm wave action on the continental shelf, it has been found to originate from several different processes and can easily fit into a model involving high sedimentation rates and unidirectional flows (Southard et al, 1990;Mutti et al, 2007;Quin, 2011). The interpretation remains speculative, but the repeated pattern of graded, thin-bedded sandstones, hummocky cross-stratification and channellisation may represent an integral part of the turbidity system.…”

“…This will imply a stratigraphic base level different from mean sea level. Such a model will only be meaningful if there is a sustained flow from source to sink in the basin (Mutti et al, 2006;Mutti et al, 2009). …”

Distal turbidite fan/lobe succession of the Late Oligocene Zuberec Fm. – architecture and hierarchy (Central Western Carpathians, Orava–Podhale basin)

“…Riverine input of hyperconcentrated bedload during catastrophic floods that flow seaward due to inertia could generate voluminous flows (hyperpycnites) which deposited sandstone-siltstone beds [e.g. 67,[89][90][91] and could form hyperpycnal-fed turbidite lobe [e.g. 24].…”

Stratigraphic and tectonic control of deep-water scarp accumulation in Paleogene synorogenic basins: a case study of the Súľov Conglomerates (Middle Váh Valley, Western Carpathians)

“…1) is very complicated due to frontal thrust stacking of the Central Carpathian nappes and PKB Oravic units (Manín, Kostelec, Klape, Podháj, Podmanín units, etc. -Mello et al 2011), superposed by Late Cretaceous flysch units, Gosau-type sediments (Rašov facies), and Paleogene sediments of the Hričov-Žilina belt and Súľov-Domaniža Basin ("flysch" means a regional widely used term for turbiditic deep-sea fan sediments in the Northern Apennines, Alps and Carpathians -for historical review see Mutti et al 2009). …”