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A stratigraphic investigation of the Celtic Sea megaridges based on seismic and core data from the Irish-UK sectors.

Lockhart, Edward A. and Scourse, James D. and Praeg, Daniel and Van Landeghem, Katrien J.J. and Mellett, Claire and Saher, Margot and Callard, Louise and Chiverrell, Richard C. and Benetti, Sara and Ó Cofaigh, Colm and Clark, Chris D. (2018) 'A stratigraphic investigation of the Celtic Sea megaridges based on seismic and core data from the Irish-UK sectors.', Quaternary science reviews., 198 . pp. 156-170.

Abstract

The Celtic Sea contains the world's largest continental shelf sediment ridges. These megaridges were initially interpreted as tidal features formed during post-glacial marine transgression, but glacigenic sediments have been recovered from their flanks. We examine the stratigraphy of the megaridges using new decimetric-resolution geophysical data correlated to sediment cores to test hypothetical tidal vs glacial modes of formation. The megaridges comprise three main units, 1) a superficial fining-upward drape that extends across the shelf above an unconformity. Underlying this drape is 2), the Melville Formation (MFm) which comprises the upper bulk of the megaridges, sometimes displaying dipping internal acoustic reflections and consisting of medium to coarse sand and shell fragments; characteristics consistent with either a tidal or glacifluvial origin. The MFm unconformably overlies 3), the Upper Little Sole Formation (ULSFm), previously interpreted to be of late Pliocene to early Pleistocene age, but here shown to correlate to Late Pleistocene glacigenic sediments forming a precursor topography. The superficial drape is interpreted as a product of prolonged wave energy as tidal currents diminished during the final stages of post-glacial marine transgression. We argue that the stratigraphy constrains the age of the MFm to between 24.3 and 14 ka BP, based on published dates, coeval with deglaciation and a modelled period of megatidal conditions during post-glacial marine transgression. Stratigraphically and sedimentologically, the megaridges could represent preserved glacifluvial features, but we suggest that they comprise post-glacial tidal deposits (MFm) mantling a partially-eroded glacial topography (ULSFm). The observed stratigraphy suggests that ice extended to the continental shelf-edge.

Item Type:Article
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1016/j.quascirev.2018.08.029
Publisher statement:© 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
Date accepted:30 August 2018
Date deposited:19 September 2018
Date of first online publication:10 September 2018
Date first made open access:19 September 2018

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