Early Tertiary submarine fan deposits in the Porcupine Basin, offshore Ireland

Abstract

The Porcupine Basin, offshore western Ireland, contains up to 10 km of Mesozoic and Cenozoic sediments. Seismic sequence analysis of the Palaeocene-Eocene strata on the southwestern and southeastern margins of the basin reveals a mounded and draped geometry. Four seismic sequences are defined and are coeval with a series of deltaic deposits in the northern and central parts of the basin. In the southwestern area these are interpreted as stacked submarine fan deposits. In the southeastern area the lower two sequences are interpreted as shelf-slope deposits which are overlain by two submarine fan complexes. Funnelling of the sediment was controlled by erosive channelling through interfan topographic lows. The seismic response indicates that the fans are dominated by lower fan sheet sand deposits with minor amounts of upper fan channellized sandstones. They probably developed in response to an interplay of eustatic sea level changes, tectonic uplift on the basin margins, and thermal subsidence towards the basin centre.

Sequence stratigraphic analysis in deep-water, underfilled NW European passive margin basins

“…A number of progradational packages are observed, each separated by a continuous high-amplitude reflection consistent with an interpretation of a marine flooding surface. Similar correlateable seismic packages are identified in the coeval submarine fans sourced from the basin margins (Shannon, 1992). A conventional sequence stratigraphic interpretation suggests a pulsed lowstand to early transgressive wedge deposition in response to a relative sea-level fall.…”

“…A succession of sand-prone deltaics and coeval submarine fans in the Porcupine Basin are well documented and constrained by well and seismic data (Croker and Shannon, 1987;Moore and Shannon, 1992;Shannon, 1992). A number of progradational packages are observed, each separated by a continuous high-amplitude reflection consistent with an interpretation of a marine flooding surface.…”

“…Haughton et al, 2005;Stoker et al, 2001Stoker et al, , 2005c, (c) cessation of major shelfderived clastic input (e.g. Shannon, 1992;McDonnell and Shannon, 2001) and (d) onset of contourite sediment drifts within the deep-water basins, particularly to the south of the GSR (e.g. Stoker, 1997;Davies et al, 2001;McDonnell and Shannon, 2001).…”

A refreshing 3D view of an ancient sediment collapse and slope failure

“…Sediments were deposited in pre‐rift, syn‐rift (Jurassic) and post‐rift (Cretaceous to Tertiary) sequences, creating a total thickness of up to 10 km. Most of the Tertiary sediments consist of deep marine deposits, although in the Early Tertiary sequences, deltaic and fan deposits were recognized also (Shannon, 1992). From the Miocene onwards, sedimentation was dominated by drift deposition in which slumping occurred (Moore and Shannon, 1991).…”

Petroleum systems of the Atlantic margin of northwest Europe

“…Lower Cretaceous deltaic to deep-marine sandstones provide one post-rift play and Cretaceous strata have given oil flows in three wells (Moore & Shannon 1995). Paleocene to Eocene submarine fans can be interpreted on seismic lines (Shannon 1992) and represent a second largely untested play type with possible stratigraphic traps.…”