Canyon Heads and Channel Architecture of the Gollum Channel, Porcupine Seabight

Pleistocene glacial history of the NW European continental margin

“…The seaward extent of the ridges, along 200 km of the shelf, implies that the last glaciation reached the shelf edge of both the northern Porcupine Seabight and eastern Rockall Trough and extended least part way across the saddle leading to the Porcupine Bank. This distribution supports suggestions that the canyons dissecting the eastern slopes of the Porcupine Seabight and the Rockall Trough, which extend upslope to breach the shelf edge, may have received coarse-gained sediment supplied by glacial meltwater (Tudhope and Scoffin, 1995;Unnithan et al, 2001;Weaver et al, 2000;Wheeler et al, 2003). The significance of glacial meltwater on the Irish margin is attested by the abundance of glacifluvial drainage features (eskers) of the last glaciation in Ireland (Warren and Ashley, 1994), as well as by the presence of buried drainage features (tunnel-valleys) in the Irish Sea (Eyles and McCabe, 1989) and at multiple stratigraphic levels in the NE Celtic Sea (Wingfield, 1990;Wingfield and Tappin, 1991).…”

“…The lack of sorted sediments is consistent with a more limited role of subglacial meltwater at high latitudes on tidewater ice sheet margins, where ablation may have taken place entirely through iceberg calving (Arnold and Sharp, 1992). In the south, the same subglacial drainage networks that left eskers and tunnel-valleys across Ireland and in the Irish-Celtic Sea (Wingfield, 1990;Warren and Ashley, 1994) may have supplied sorted sediment directly to the shelf edge south of the Donegal Fan, to be received by slope canyons, which have been inactive since the end of the last glaciation (Tudhope and Scoffin, 1995;Unnithan et al, 2001;Weaver et al, 2000;Wheeler et al, 2003).…”

“…2a). The age of formation of the canyons is unknown, but they do not appear to have been active during the present interglacial, based on observations in the Gollum Channel where less than 0.1 m of post-glacial sediments have accumulated (Tudhope and Scoffin, 1995;Wheeler et al, 2003). There are no canyons north of about 55830'N, where the NE Rockall margin protrudes westward towards the Hebrides Terrace Seamount as the Barra/Donegal Fan, the only glacial fed fan on the Irish margin (Fig.…”

The Enya mounds: a lost mound-drift competition

“…In contrast to the slopes of the Celtic and Armorican margins, which are located east of the Porcupine Seabight, only one major sediment-supplying channel system is present on the southern margin of the Seabight Kenyon et al 1978;Wheeler et al 2003). This east-west oriented Gollum Channel System is thought to be the downstream component of a large fluvial system, which extended from the southern Irish Mainland Shelf during glacial periods.…”

“…This east-west oriented Gollum Channel System is thought to be the downstream component of a large fluvial system, which extended from the southern Irish Mainland Shelf during glacial periods. Rice et al (1991) and Wheeler et al (2003) suggest that the present-day channels are inactive.…”