Distinguishing between Deep-Water Sediment Facies: Turbidites, Contourites and Hemipelagites

Abstract

The distinction between turbidites, contourites and hemipelagites in modern and ancient deep-water systems has long been a matter of controversy. This is partly because the processes themselves show a degree of overlap as part of a continuum, so that the deposit characteristics also overlap. In addition, the three facies types commonly occur within interbedded sequences of continental margin deposits. The nature of these end-member processes and their physical parameters are becoming much better known and are summarised here briefly. Good progress has also been made over the past decade in recognising differences between end-member facies in terms of their sedimentary structures, facies sequences, ichnofacies, sediment textures, composition and microfabric. These characteristics are summarised here in terms of standard facies models and the variations from these models that are typically encountered in natural systems. Nevertheless, it must be acknowledged that clear distinction is not always possible on the basis of sedimentary characteristics alone, and that uncertainties should be highlighted in any interpretation. A three-scale approach to distinction for all deep-water facies types should be attempted wherever possible, including large-scale (oceanographic and tectonic setting), regional-scale (architecture and association) and small-scale (sediment facies) observations.

Upper Cretaceous bottom current deposits, north‐east Greenland

“…The sediment structures in fine‐grained laminated to flaser bedded siliciclastic sediments show similarities with published examples of fine‐grained turbidites (Stow & Smillie, 2020), potentially indicating a significant contribution from gravity flows in these deposits. The generally upward fining bed motif characteristic for surge‐type turbidites (cf.…”

“…6E). Such syn‐depositional burrowing from base to top is rare in turbidites (Stow & Smillie, 2020), which are normally characterized by post‐depositional and pre‐depositional trace fossil suites (Uchman & Wetzel, 2012). The biodeformational structures coupled with soft‐sediment deformation structures indicate low initial substrate consistency and local soup‐ground conditions (Fig.…”

“…8B) and in some cases are concentrated in the intervals where sandstone–claystone couplets are thinnest (potential neap tides). This is not trivial, since similar sandstone‐dominated heterolithic deposits such as mud‐draped ripples can be formed by decelerating, mud‐rich gravity‐flows (for example, base of the Stow sequence; Stow & Smillie, 2020). The flow process in such cases is characterized by modulated turbulence (cf.…”

Late Miocene contourite channel system reveals intermittent overflow behavior

“…Contourite features have been recognized in modern and ancient sedimentary records along continental margins and in deep-water settings. Despite growing scientific interest, these deepmarine systems remain relatively poorly understood (Rebesco et al, 2014;Stow and Smillie, 2020), since very few ancient contourite deposits have been identified in outcrops and cores (Hüneke and Stow, 2008;Mutti et al, 2014). Here, we describe an unprecedented archive for unravelling the initial stages of MOW and the controls on overflow behavior based on two ancient contourite channels in the former Rifian Corridor, Morocco.…”

X-ray fluorescence core scanning, magnetic signatures, and organic geochemistry analyses of Ryukyu Trench sediments: turbidites and hemipelagites

“…No foraminifera or fragments thereof were identified in either core. Based on deep-sea turbidite classification criteria (e.g., Shanmugam 2000;Patton et al 2015) and deep-water sediment facies (Stow and Shanmugam 1980;Stow and Smillie 2020), the silty sand beds are interpreted as turbidites and the mud layers as hemipelagites.…”