BGS/SAMS shallow sampling programme in the Summer Isles region, NW Scotland : cruise report

This report presents a summary of the joint BGS/SAMS ten-day shallow sampling cruise to the Summer Isles region of NW Scotland, during August 2006. The focus of the cruise was to test the nature of the late to post-glacial fill of this fjordic landsystem, with a view to establishing (downstream) a chronology of deglaciation and landscape evolution in the last 15,000 years or so. The report begins with an introduction to the study area, which has an intricate coastal geography resulting from its position as the drainage outlet for a number of major valley systems. The glacial influence is everywhere manifest in the present-day shape and topography of the subaerial landscape; a landscape that is even more accentuated in the marine realm. This is followed by a summary of the background to the project. The underlying scientific rationale to this cruise is to unravel the history of deglaciation that is preserved in the sediment fill of the fjord basins, and its impact on the environment. There are three main reasons why the Summer Isles region was targeted for this work: 1) a 1:50,000 scale onshore–offshore map of the glacial geology and geomorphology is currently under development by the BGS; 2) the data will contribute to the SAMS core programme Oceans 2025; and, 3) it provides a unique opportunity for BGS and SAMS to collaborate in the general area of fjord research. Section 3 outlines the methodology employed in the survey. Gravity coring formed the bulk of the sampling programme, with most sites sampled using a 3 m-barrel length; a 1.5 m-barrel was utilised is areas of harder ground or coarse-grained lithologies. The megacorer recovered multiple core samples up to 0.5 m length, was utilised at selected sites in order to capture the sediment-water interface. The megacorer provides a record of the most recent depositional activity, to the present-day. A narrative of the operation forms section 4, and outlines some of the technical issues that were faced as the cruise developed, as well as the measures employed to solve any problems that arose. Section 5 presents a few conclusions. A summary of the sample sites and a preliminary description of the gravity cores is presented in appendices 1 and 3, respectively. A more detailed record of the daily log is presented in appendix 2. Post-cruise analysis of these data continues forward from this point in time, with a detailed programme of stratigraphic, sedimentologic and geochemical analysis scheduled to be undertaken.