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 * [email protected] 1,2* Zsuzsanna Tóth 1,2 Andrew J. Wheeler 3 Volkhard Spiess Morphology and development of the deeps and tunnel valleys in the western Irish Sea 3 Stefan Wenau 4 Stephen G. McCarron 5 Mark 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. ACKNOWLE DGEMENTS 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 N Bathymetry Dublin Wicklow Head Seismic data Sparker 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 20 60 80 100 0 10000 20000 30000 Depth [m] Distance along profile [m] V V‘ B 40 120 Codling Deep South Ridge 50 20 30 40 0 2000 6000 Distance along profile [m] Depth [m] W W‘ C 4000 8000 Bray Bank 0.7° 1.4° 1.5° 0.7° 20 30 40 0 2000 6000 Distance along profile [m] Depth [m] X X‘ D 4000 South Ridge Wicklow Trough 1° 80 20 40 60 0 2000 Distance along profile [m] Depth [m] Y Y‘ E 1000 3000 70 50 30 Wicklow Trough 4.3° 2.7° 40 20 30 0 2000 Distance along profile [m] Depth [m] Z Z‘ F 4000 1000 3000 Wicklow Trough 4.4° 3° −6˚10' −6˚00' −5˚50' 52˚50' 53˚00' 53˚10' 0 10 km 0 30 60 120 m Water depth 90 V‘ V W W‘ X X‘ Y Y‘ Z Z‘ Frazer Bank Bray Bank Codling Bank Codling Deep South Ridge Wicklow Trough Arklow Bank India Bank A Dunes Wicklow Bray −6˚00' −5˚50' −5˚40' 53˚20' 53˚30' 0 10 km 53˚40' 0 30 60 120 m Water depth 90 V V‘ W X Y Z Z‘ Y‘ X‘ W‘ Dune fields Bedrock outcrops Bedrock outcrops Lambay Island A 60 80 100 120 0 10000 20000 30000 Depth [m] Distance along profile [m] V V‘ B 65 70 75 0 1000 2000 3000 Depth [m] Distance along profile [m] 4000 80 W W‘ 0.5° 0.4° C 120 60 80 100 0 1000 2000 3000 4000 Distance along profile [m] Depth [m] X X‘ 5.5° 8.4° 3.1° D 60 80 0 1000 2000 3000 4000 Distance along profile [m] 100 Depth [m] Y Y‘ 2.5° 1.6° E 75 60 65 70 0 1000 2000 3000 Distance along profile [m] Depth [m] Z Z‘ 1° 0.7° F Lambay Deep Codling Deep Wicklow Trough INFOMAR Bathymetry INFOMAR Bathymetry deepest point: -134 m deepest point: -119 m deepest point: -81 m 40 60 80 100 120 140 160 180 200 220 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 13000 14000 15000 16000 40 60 80 100 120 140 160 180 200 220 - CV17013 090417.222217-3 - 20 20 40 60 80 100 120 140 160 180 200 220 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 40 60 80 100 120 140 160 180 200 220 - CV17013 090417.171138-3 - 20 20 40 60 80 100 120 140 160 180 200 220 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 13000 14000 40 60 80 100 120 140 160 180 200 220 - CV17013 090417.150057-2 - 20 20 Wicklow Trough SEISMOSTRATIGRAPHY Whittington’s seismostratigraphy Unit I = Pre-Pleistocene Unit II = Till Unit III = Horizontally-bedded sedimentary deposits Unit IV = Sand banks, sand waves or recent muds and silts Lambay Deep Lambay Deep Lambay Deep Lambay Deep TWT (ms) Distance (m) TWT (ms) Distance (m) TWT (ms) Distance (m) Seismostratigraphic units [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 20 40 60 80 100 120 140 160 180 - GeoB17-079 - 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 20 40 60 80 100 120 140 160 180 20 40 60 80 100 120 140 160 180 200 - GeoB17-071 - 1000 2000 3000 4000 5000 6000 7000 20 40 60 80 100 120 140 160 180 200 20 40 60 80 100 120 140 160 180 200 220 - GeoB17-064 - 3000 4000 5000 6000 7000 20 40 60 80 100 120 140 160 180 200 220 TWT (ms) Distance (m) TWT (ms) Distance (m) TWT (ms) Distance (m) Seismostratigraphic units [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 Codling Deep Wicklow Trough Wicklow Trough