Morphology and development of the deeps and tunnel valleys

This publication has emanated from research supported in part by a research grant from Science Foundation Ireland (SFI) under Grant Number 13/RC/2092 and co-funded under the European Regional Development Fund and by PIPCO RSG and its member companies.

1 iCRAG - Irish Centre for Research in Applied Geosciences, Ireland; 2 University College Cork, School of Biologial, Earth and Environmental Sciences, Cork, Ireland; 3 University of Bremen, Faculty of Geosciences, Bremen, Germany;4 Maynooth University, Department of Geography, Maynooth, Ireland; 5 Gaelectric Developments, Dublin, Ireland* zsuzsanna.toth@icrag-centre.org

1,2*Zsuzsanna Tóth

1,2Andrew J. Wheeler

3Volkhard Spiess

Morphology and development of the deeps and tunnel valleys in the western Irish Sea

3Stefan Wenau 4Stephen G. McCarron 5Mark Coughlan

Whittington, R.J., 1977: A late-glacial pattern in the Kish Bank area and post-glacial sediments in the Central Irish Sea. In: Kidson, C., Toolet, M.J. (Eds.), The Quaternary History of the Irish Sea. Seel House, Liverpool, pp. 55–68.

The Pinger and bathymetry data were collected in the framework of the INFOMAR programme of the Geological Survey Ireland. We thank Aodhan Fitzgerald and Rosemarie Butler (Marine Institute) for their work in organizing the cruise CV17013 (twice!). We are grateful to the captain and the crew of R/V Celtic Voyager for their work, support, cooperation and patience during the surveys and sampling. We were using the VISTA Desktop Seismic Data Processing and the KINGDOM softwares for seismic data processing and interpretation. We are grateful to Schlumberger and IHS Markit for providing the academic licences for these software packages.

ACKNOWLEDGEMENTS

REFERENCES

SEISMOACOUSTIC DATA IN THE IRISH SEA

278800 298800 318800 338800

5849800

5869800

5889800

5909800

5929800

N

Dublin

Wicklow Head

278800 298800 318800 338800

5849800

5869800

5889800

5909800

5929800

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Bathymetry

Dublin

Wicklow Head

Seismic dataSparker data (2009, 2012)

Multichannel seismic data (2017, CV17013)

Sparker data (2017, CV17013)

EMODNet bathymetry

[TUNNEL VALLEY] SYSTEM?

Base of Unit III in Whittington (1977)

Codling Deep

Wicklow Trough

Lambay Deep

Deeps and valleys in the western Irish Sea such as the Lambay Deep, Codling Deep and Wicklow Trough, are believed to be part of a complex, linked valley system. During the last glaciation, the Irish Sea Basin was occupied by the Irish Sea Ice Stream that was fed by converging ice streams from British and Irish ice centres of the British-Irish Ice Sheet.

Interpretation of shallow seismic data by concluded that a till sheet blankets the pre-Pleistocene surface of the Irish Sea Basin and the valleys were cut into these subglacial sediments.The proposed formation of the channel system was (1) a sub-aerial fluviatile origin for the Codling Deep and Wicklow Trough during a period of low sea level based on morphology and minor tributaries from onshore rivers and (2) a subglacial stream erosion (tunnel valley) for the Lambay Deep. This late- to post-glacial, rectilinear drainage network is now partially infilled with Quaternary sediments and at present in parts it is undergoing active erosion.

The objective of our study is to reassess the morphology and formation theories of the deeps and valleys based on newly acquired seismo-acoustic data 40 years later and to define a Quaternary stratigraphic framework in the Irish sector of the Irish Sea. This poster displays the groundwork of our ongoing analysis.

Whittington (1977)

CV17013

Ÿ micro GI gun (central f=200 Hz)Ÿ Teledyne 96-channel streamer (220 m

max offset)Ÿ Sparker system (central f=600 kHz)

Seismic Survey

PRESENT MORPHOLOGY

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SouthRidge

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Codling Deep Wicklow Trough

INFOMARBathymetry

INFOMARBathymetry

deepest point: -134 m

deepest point: -119 m deepest point: -81 m

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Wicklow Trough

SEISMOSTRATIGRAPHY Whittington’s seismostratigraphyUnit I = Pre-PleistoceneUnit II = TillUnit III = Horizontally-bedded sedimentary depositsUnit IV = Sand banks, sand waves or recent muds and siltsLambay Deep

Lambay Deep

Lambay Deep

Lambay Deep

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[top of] Recent sediments

Shallow gas front

[top of] Sedimentary unit 2[top of] Sedimentary unit 1[top of] Till[top of] Bedrock

1st multiple of the seafloor

- Lambay Deep -

Codling Deep

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[top of] Recent sediments[top of] Sedimentary unit 2[top of] Sedimentary unit 1[top of] Till[top of] Bedrock

1st multiple of the seafloor

- Codling Deep,Wicklow Trough -

2nd multiple of the seafloor

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WicklowTrough

WicklowTrough