JNCC Report No. 430 Understanding the marine environment – seabed habitat investigations of submarine structures in the mid Irish Sea and Solan Bank Area of Search (AoS) Paul Whomersley, Christian Wilson, Annika Clements, Craig Brown, David Long, Alick Leslie and David Limpenny March 2010 © JNCC, Peterborough 2010 ISSN 0963-8091 For further information please contact: Joint Nature Conservation Committee Monkstone House City Road Peterborough Cambridgeshire PE1 1JY Email: [email protected] Tel: +44 (0)1733 866840 Fax: +44 (0)1733 555948 Website: www.jncc.gov.uk This report should be cited as: Whomersley, P., Wilson, C., Clements, A., Brown, C., Long, D., Leslie, A. & Limpenny. D. 2010. Understanding the marine environment – seabed habitat investigations of submarine structures in the mid Irish Sea and Solan Bank Area of Search (AoS). JNCC Report No. 430. Understanding the marine environment – seabed habitat investigations of submarine structures in the mid Irish Sea and Solan Bank Area of Search (AoS)` Contents 1 Summary ........................................................................................................................................ 1 1.1 Submarine structures in the mid-Irish Sea ............................................................................. 1 1.2 Solan Bank ............................................................................................................................. 2 2 Introduction .................................................................................................................................... 3 2.1 Location of Areas of Search .................................................................................................. 3 2.1.1 Submarine structures in the mid-Irish Sea ........................................................................ 3 2.1.2 Solan Bank ........................................................................................................................ 4 2.2 Main Aims of Project ............................................................................................................ 4 2.3 Submarine structures in the mid-Irish Sea AoS ..................................................................... 6 2.4 Regional geology of the Submarine structures in the mid-Irish Sea AoS ............................. 7 2.4.1 Bedrock Geology .............................................................................................................. 8 2.4.2 Quaternary Geology ........................................................................................................ 10 2.4.3 Seabed sediments and morphology ................................................................................. 12 2.4.4 Shallow gas ..................................................................................................................... 13 2.5 Biological context ................................................................................................................ 15 2.6 Solan Bank AoS .................................................................................................................. 17 2.6.1 Regional geology of the Solan Bank AoS ....................................................................... 18 2.6.2 Major structural features ................................................................................................. 21 2.6.3 Post-Jurassic history ........................................................................................................ 23 2.7 Biological context ................................................................................................................ 23 3 Survey design and methods .......................................................................................................... 25 3.1 Equipment used ................................................................................................................... 25 3.1.1 Hull mounted multibeam echo-sounder system .............................................................. 25 3.1.2 Towed sidescan sonar ..................................................................................................... 25 3.1.3 Camera sledge, camera and video equipment ................................................................. 25 3.1.4 Benthic ground-truthing equipment (Hamon grab and Rock dredge) ............................. 26 3.2 Submarine structures in the mid-Irish Sea AoS ................................................................... 26 3.2.1 Acoustic survey design and methodology ....................................................................... 26 3.2.2 QTC Multiview and CLAMS processing of mid-Irish Sea EM3000D data ................... 29 3.2.3 Video footage and still image acquisition ....................................................................... 31 3.2.4 Video footage and still image processing ....................................................................... 31 3.2.5 Biotope Analysis ............................................................................................................. 32 3.2.6 Stills Analysis .................................................................................................................. 33 3.2.7 Benthic grab sampling ..................................................................................................... 33 3.2.8 Particle size analysis ....................................................................................................... 34 3.3 Solan Bank AoS .................................................................................................................. 34 3.3.1 Acoustic survey design and methodology ....................................................................... 34 3.3.2 QTC Multiview and CLAMS processing of Solan Bank EM3000D data ...................... 34 Understanding the marine environment – seabed habitat investigations of submarine structures in the mid Irish Sea and Solan Bank Area of Search (AoS)` 3.3.3 Video footage and still image acquisition ....................................................................... 36 3.3.4 Biotope Analysis ............................................................................................................. 36 3.3.5 Stills Analysis .................................................................................................................. 36 3.3.6 Benthic grab sampling ..................................................................................................... 38 3.3.7 Particle size analysis ....................................................................................................... 38 3.4 Quality Assurance (QA) procedures .................................................................................... 38 3.4.1 Acoustic data collection and processing ......................................................................... 38 3.4.2 Video and stills analysis .................................................................................................. 38 3.4.3 Infauna sample identification .......................................................................................... 39 3.4.4 Epi-faunal sample identification ..................................................................................... 39 3.4.5 Particle size analysis ....................................................................................................... 39 4 Results .......................................................................................................................................... 40 4.1 Submarine structures in the mid-Irish Sea AoS ................................................................... 40 4.1.1 Geology ........................................................................................................................... 40 4.1.2 Background seabed topography ...................................................................................... 40 4.1.3 MDAC ............................................................................................................................. 41 4.1.4 Formation of the MDAC ................................................................................................. 45 4.1.5 Distribution of MDAC .................................................................................................... 46 4.1.6 Weathering of the MDAC ............................................................................................... 46 4.1.7 MBES and SS (Bathymetry and Backscatter) ................................................................. 48 4.1.8 Surface sediments (From PSA, MBES backscatter/sidescan data) ................................. 54 4.1.9 Epi-fauna (Video, stills and rock dredge samples) .......................................................... 55 4.1.10 Infauna (Hamon grab samples) ................................................................................... 62 4.2 Solan Bank AoS .................................................................................................................. 63 4.2.1 Geology ........................................................................................................................... 63 4.2.2 Seabed morphology ......................................................................................................... 64 4.2.3 MBES and SS (Bathymetry and Backscatter) ................................................................. 66 4.2.4 Surface sediments (From PSA,