Modes of Emplacement of Prospective Hydrocarbon Reservoir Rocks of Outer Continental Marine Environments
Joseph R. Curray, 1977. "Modes of Emplacement of Prospective Hydrocarbon Reservoir Rocks of Outer Continental Marine Environments", Geology of Continental Margins, Joseph R. Curray, William R. Dickinson, Wallace G. Dow, Kenneth O. Emery, Donald R. Seely, Peter R. Vail, Hunter Yarborough
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Potential hydrocarbon reservoir rocks may be emplaced on or under the outer continental margin by several different processes or combinations of processes: I. Normal processes of distribution of sediments are reasonably well understood from studies of the modern oceans, but the lessons of these studies cannot be applied indiscriminately to interpretation of pre-Quaternary sediments and continental margins because of the profound effects of Quaternary sea level fluctuations. II. The products of these processes of deposition may be displaced relative to present sea level by several mechanisms. These displaced facies may constitute prospective reservoir rocks only if they could otherwise have been favorable before displacement and if their reservoir characteristics are not adversely affected during the displacement processes. IIA. Eustatic sea level changes of the past may have resulted in accumulation of shore zone sediments, for example, as much as a few hundred meters below the present shore zone. IIB. Crustal thinning and block faulting are common during early rifting stages of formation of what become intraplate continental margins, followed by subsidence of porous and permeable continental, shore zone, and shallow marine sediments to abyssal depths, where they may be covered by pelagic sediments and/or prograding wedges of normal continental margin facies. IIC. The process of subduction may be accompanied by transfer of sediments from the underthrusting plate to the leading edge of the overriding plate, followed by uplift in imbricate thrust sheets to the crest of a non-volcanic ridge or edge of a marginal plateau lying outboard of a volcanic arc or Andean Type continental margin. This phase of uplift may then be followed by subsidence under the forearc basin. IID. Sediment accumulations of outer shelf or slope environments may be displaced into deeper water base-of-slope environments by submarine sliding. Such slides or olistostromes may occur on either intraplate or plate edge margins. Slope instability may result from either depositional or tectonic over-steepening and may be triggered by either oceanographic or tectonic disturbance.