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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.; Scourse, James D.; Praeg, Daniel; Van Landeghem, Katrien J.J.; Mellett, Claire; Saher, Margot; Callard, Louise; Chiverrell, Richard C.; Benetti, Sara; Ó Cofaigh, Colm; Clark, Chris D.

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


Authors

Edward A. Lockhart

James D. Scourse

Daniel Praeg

Katrien J.J. Van Landeghem

Claire Mellett

Margot Saher

Louise Callard

Richard C. Chiverrell

Sara Benetti

Chris D. Clark



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.

Citation

Lockhart, E. A., Scourse, J. D., Praeg, D., Van Landeghem, K. J., Mellett, C., Saher, M., …Clark, C. 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, 156-170. https://doi.org/10.1016/j.quascirev.2018.08.029

Journal Article Type Article
Acceptance Date Aug 30, 2018
Online Publication Date Sep 10, 2018
Publication Date Sep 10, 2018
Deposit Date Sep 19, 2018
Publicly Available Date Mar 29, 2024
Journal Quaternary Science Reviews
Print ISSN 0277-3791
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 198
Pages 156-170
DOI https://doi.org/10.1016/j.quascirev.2018.08.029

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