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

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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.
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