The Celtic Sea banks: an example of sand body analysis from very high-resolution seismic data

Very high-resolution seismic data from the Kaiser-I-Hind sand bank (souther n Celtic Sea) recently highlighted the internal structure of the enigmatic Celtic Banks, which are among the deepest and largest shelf sand ridges. Th e main body of the bank is made up of 4 seismic/depositional units which re flect a transgressive evolution. New data on the detailed architecture of t wo of these units allow discussion of bank growth in terms of either (1) a channel-levee system preserved both by lateral migration and aggradation of the channels, or (2) a package of large offshore tidal sediment bodies (ba r chains and/or giant dunes). Careful geometrical observations of seismic d iscontinuities make the second hypothesis more likely. The unit architectur e is analysed in terms of long- to short-term processes of build-up. Long-t erm processes are evinced by the landward stacking of erosive sub-units in response of the last post-glacial sea-level rise, whereas short-term proces ses control the seaward progradation of sand bodies and fills due to the eb b predominance of the Western Channel Approaches. (C) 1999 Elsevier Science B.V. All rights reserved.