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Submarine Fan Stratigraphy: A Jekyll and Hyde Story


Elliott, Trevor E.1, Andrew J. Pulham2, Gillian M. Apps3 (1) Liverpool University, Liverpool, United Kingdom (2) Earth Science Associates, Boulder, CO (3) BHP Billiton Petroleum, Houston, TX


A hypothesis is presented that predicts that most delta-fed turbidite systems comprise distinctive stratigraphic signatures that record bimodal distributions of gravity flow events.

Evidence from outcrop investigations, modern and subsurface studies suggest that tur­bidite systems (submarine fans) are constructed by a combination of (1) numerous, rela­tively low volume and relatively low-density sediment gravity flows, and (2) rare, quasi-ran-dom, extremely high volume and relatively high density/concentrated sediment gravity flows punctuated by (3) periods of little or no sediment supply.

The large, rare events erode and sculpture the proximal and mid-parts of submarine fans and are responsible for the transfer of large volumes of coarse, reservoir quality grade sed­iments into most distal fan settings. Low volume events are the principal building blocks of sandy, proximal to mid-fan settings.

Key stratigraphic elements that define the fan architecture are regional by-pass surfaces that owe their origin to almost instantaneous re-setting of the fan surface palaeogeography. Recognition of regional by-pass surfaces results in descriptions of turbidite complexes as linked, often overlapping, but separate depositional systems that have their origins to con­trasting frequencies and volumes of gravity flows.