Deep-sea clastics: where are we and where are we going?

Abstract

Summary The transition from our belief in a deep calm ocean to a recognition that deep-sea clastics other than pelagic clays exist in the oceans, spanned nearly a century. In the last three decades enormous strides have been made in understanding these sediments and their deposition. There is a continuum of processes that transfer material from shallow to deep water and rework sediments within the deep sea. These include: (1) resedimentation processes, ranging from giant rockfalls and slumps to low-density turbidity currents; (2) normal bottom currents; and (3) pelagic settling through the water column. More than fifty distinct facies have been described from the deep sea and these can be interpreted in terms of depositional process via ten standard facies models for resedimented, normal bottom current and pelagic sediments. Environmental models can be constructed for: (1) normal, faulted, carbonate and ridge-flank slope-aprons; (2) radial, elongate and fan-delta submarine fans; and (3) under- and oversupplied basin-plains. These show the generalized horizontal and vertical distribution of facies and the chief morphological elements in each of the three major deep-sea settings. Sedimentary, tectonic and sea-level changes are the main groups of factors that control deep-sea sedimentation within these separate environments. Part of the interest in deep-sea clastics stems from their demonstrable economic importance for the generation and entrapment of hydrocarbons. Many areas of deep-sea sedimentology remain to be investigated and earlier models to be refined; these advances will depend significantly on improvements in our methodology.

Facies, Composition, and Texture of Mississippi Fan Sediments, Deep Sea Drilling Project Leg 96, Gulf of Mexico

“…We simply note here that, although clear trends of grain size and bed thickness are observed, vertical sequences are rather more variable than those classically related to fan deposits (Walker, 1978;Stow, 1985). In particular:…”

“…The structureless aspect of many of these thick sands and the possibility of coring disturbance makes conclusive interpretation difficult. The apparent graded top of the lone gravel unit from the channel thalweg Site 621 also suggests turbidity current transport, whereas the pebbly muds presumably were deposited from debris flows (Stow, 1985).…”

“…The thin-to very thick-bedded silts and sands commonly show evidence of deposition from high-concentration turbidity currents (Bouma, 1962;Stow, 1985). The thicker beds have perhaps been influenced by grain flow or fluidized flow in the final stages of deposition (Walker, 1978).…”

Palynologie et environnements des sédiments du Dévonien de Saïda (Algérie nord occidentale)

“…Ce faciès est qualifié dans la littérature de faciès B2 (MUTTI & RICCI LUCCHI, 1975) et décrit par WALKER (1978, MUTTI (1979) et MATTERN (2002. Les cycles strato-et granodécroissants permettent de reconnaître les dépôts de chenaux (MUTTI & RICCI LUCCHI, 1972WALKER, 1978 ;STOW, 1985 ;MUTTI & NOR-MARK, 1987NORMARK et al, 1993 ;GALLO-WAY, 1998 ;POSAMENTIER & KOLLA, 2003 ;MATTERN, 2005 ;MUTTI et al, 2009 ;ZHANG et al, 2015).…”

Stratigraphic framework of Cambrian and Ordovician rocks in the central Appalachian basin from Morrow County, Ohio, to Pendleton County, West Virginia

“…The dominant transport mechanisms active on the continental slope were first recognized by analogy with subaerial mass movement (Dott, 1963). The three dominant processes are slides, rockfalls, and sediment gravity flows (Middleton and Hampton, 1973;Carter, 1975;Lowe, 1979;Nardin and others, 1979;Cook and others, 1982;Middleton and Southard, 1984;Stow, 1985). Slides involve shear failure along a discrete plane and can be classified as either glides or slumps.…”