unrestricted use, copyright acknowledgement
Geophysical Survey WESSEX4: (01/Jul/2003 to 28/Sep/2003)
Available under the Open Government Licence subject to the following acknowledgement accompanying the reproduced Wessex Archaeology materials "Contains Wessex Archaeology materials ©Wessex Archaeology [year]"
CP2 Regional Sea Boundaries: Eastern Channel, Offshore 1:250k: Wight, SeaVoX Sub-Ocean: ENGLISH CHANNEL
Seabed Prehistory: Gauging the effects of Marine Dredging. Palaeo-Arun. Wessex Archaeology (WA) was commissioned, in April 2003, by the Mineral Industry Research Organisation (MIRO) to undertake the research project 'Seabed Prehistory - gauging the effects of marine aggregate dredging' under the financial support of the Sustainable Land Won and Marine Dredged Aggregate Minerals Programme (SAMP). The Survey Area for this study was chosen as a result of prospecting within the Owers Bank area following consultation with representatives from the marine aggregate industry. It is in the palaeo-Arun area approximately 10km south of Littlehampton, off the coast of West Sussex in the English Channel. Survey work took place between 1st and 18th July 2003 and 27th and 28th September 2003 on the Emu Surveyor and included single-beam echosounder, sub-bottom profiler, multibeam and collection of vibrocores. The geology and geophysics component of the data are archived at British Geological Survey (BGS) MEDIN Data Archive Centre (DAC) for Geology and Geophysics. Data were also provided to other archive centres as appropriate.
Twenty vibrocores and 245km of seismic survey data were collected over a 3.5km by 1km area, but primarily in a central 1km² around a buried palaeo-channel feature. The geophysical dataset was acquired in three phases. Initially a series of prospection lines were acquired. The survey grid for the second phase had survey lines 3.5km long, orientated NE-SW, at a 50m line spacing. Cross lines were 1km long, orientated NW-SE and at a line spacing of 500m. The aim of this phase of the survey was to collect data in order to confirm the position and orientation of the palaeo-channel feature identified during the propection lines. Once this survey had been completed and the position of the palaeo-channel had been delineated the third phase of surveying was implemented. This involved surveying a 1km block that encompassed the palaeo-channel feature in this area. This 1km block had survey lines 1km long, orientated both NE-SW and NW-SE at a 10m line spacing in both directions. Based on the geophysics results a judgement-led sampling strategy was developed in order to investigate specific research questions. Locations were chosen through the initial interpretation of the sub-bottom profiling data in order to calibrate the geophysical data and confirm the presence of an infilled palaeochannel. On 27th and 28th September 2003, a 6m hydraulic vibrocorer was used to acquire the twenty vibrocores. This work was carried out by a sub-contractor to EMU Ltd. The geophysical survey was conducted aboard the Emu Surveyor between the 1-18 July 2003. The data acquisition was conducted by Emu Ltd under the supervision of WA staff. Single-beam echosounder and sub-bottom profiler data were acquired. Bathymetric data was recorded throughout all stages of the survey using a single beam echo sounder acquired using a Knudsen 320M dual-frequency echosounder. Sub-bottom profiler data were acquired using an Applied Acoustics AA200 surface-tow boomer system and the data were recorded on an Octopus 360 sub-bottom processor. The sub-bottom profiler were originally acquired in *.cod format and were then converted to .sgy format using Coda Utilities 2.6.0 software.