Deepwater Channels, Slumps and Submarine Sand Volcanoes
North of the Shannon Estuary the Upper Ross Formation outcrops in cliffs of Namurian sediments along Atlantic shore at Fisherman's Point. At this locality deepwater fan lobes are channeled into one another and overlie the slumped horizons. The sheets of sand forming the fan lobes are characterized by incised stacked channels. The sandstone fill of the channels sometimes extends beyond the channels as wings (Elliot, 2000).
Locally sand volcanoes occur on bedding planes and were formed by sands transported upward from within slides by water released when the slide was compacted beneath its own weight. Flank slopes of the sand volcanoes reach 15° (Gill & Kuenen, 1958) with slightly concave outer slopes exhibiting flow runnels and ridges down the flanks with a central sand filled crater (Strachen, 2002). On other bedding planes ripples generated by currents in the deeperwater setting are common in the sandy sediments.
Photos by Christopher Kendall, Peter Haughton and David Pyles.
Elliott, T., 2000, Depositional architecture of a sand-rich, channelized turbidite system: the Upper Carboniferous Ross Sandstone Formation, Western Ireland. in P. Weimer, R. M. Slatt, A. H. Bouma, and D. T. Lawrence, eds., Deep-water reservoirs of the world: Gulf Coast Section SEPM Foundation, Twentieth Annual Research Conference, p. 342–373.
Gill, W. D., and Kuenen, P. H. 1958, Syndepositional sliding and slumping in the West Clare Namurian Basin, Ireland. Geol. Surv. Irel., Spec. Pub. 4, 1-121.
Strachan, L. J., 2002, Slump-initiated and controlled syndepositional sandstone remobilization: an example from the Namurian of County Clare, Ireland: Sedimentology, v. 49, p. 25-41.
Friday, December 13, 2013