Saturday, 5 September 2015

Sample, Log, Repeat: the quest for dating the retreat of the British Irish Ice Sheet

The BGS vibrocorer on the RRS James Cook
On 3 July 2015 EPC's Sally Morgan departed on a month-long research cruise (JC123) as part of the BRITICE-CHRONO project.

The JC123 cruise, led by Professor Colm O’Cofaigh of Durham University, is the second of 2 marine-based coring programmes that are central to the 5-year BRITICE-CHRONO NERC Consortium Grant which aims to collect and date material to constrain the timing and rates of change of the collapsing British-Irish Ice Sheet (BIIS).  This year’s project was staffed by scientists from a number of institutions across the UK, including the universities of Bangor, Durham, Leicester, Liverpool, Sheffield, Stirling, and Ulster, as well as the British Geological Survey.
Similar to the first BRITICE-CHRONO cruise (JC106) that took place in 2014, JC123 was on board the Royal Research Ship James Cook and set sail from Southampton. The cruise surveyed and sampled material along 3 main transects in The Minch, Shetland and the North Sea areas.  Coring targets in these transects were identified using the surveying data collected on board, notably multibeam echo sounder and sub-bottom profiler data.  Most of the cores were acquired utilising the British Geological Survey’s vibrocorer system (up to 6 m penetration), with a few cores sampled using the National Oceanographic Centre’s piston corer (up to 10 m penetration).  Over 170 individual cores were collected, totalling in excess of half a kilometre of core material. 
Once recovered to the ship, the cores were cut into metre-long sections and curated, after which they were measured on Leicester’s containerised Geotek multi-sensor core logger system, operated by Sally.  This system allows for the acquisition of the physical properties of the cores, including the bulk density, acoustic velocity, magnetic susceptibility and electrical resistivity.  Once the cores were measured they were returned to the core description team who split the cores in half lengthways, sampled and described the cores, and then packed them up ready for shipment to different institutions at the end of the cruise for further analyses (including C14-dating and optically stimulated luminescence dating) and archiving.  Used in combination with the descriptions and geochronological data derived from the cores, the physical properties data will be used to help better understand the timing of the BIIS recession at the end of the last glaciation.   
Work on these cores, the cores acquired during JC106, and material collected from the equivalent land-based studies, will continue through 2017, after which it is hoped that predictive ice sheet modelling will be significantly improved, with the BIIS forming an important benchmark.
Further information about the project is available via the BRITICE-CHRONO webpage and you can also follow the project’s progress on Twitter:  @BRITICECHRONO

Friday, 4 September 2015

Robots, rocks and research drilling

Seabed rock drills are a developing technology with the potential to offer a cost effective way of recovering geological materials from beneath the sea.  More conventional technologies drill and sample the sub-seafloor utilising drilling systems that are on board a ship or platform.  Seabed rock drills are robotic drilling systems that are deployed from a ship and lowered to the seafloor, attached to the ship by an umbilical which as well as providing a physical connection, also allows for the drill to be remotely-controlled and monitored by engineers on board. The latest version of the BGS rock drill is designed to drill and core up to 50 m below the seafloor and is set to be one of 2 such devices to be used on the International Ocean Discovery Program (IODP) Expedition to Atlantis Massif later in the year.  The second system to be utilised on this project is the MeBo80, a seabed rock drill developed by MARUM, University of Bremen, Germany.

On 17 August 2015 Sally Morgan, of the European Petrophysics Consortium (University of Leicester), joined the Northern Lighthouse Vessel Pharos with colleagues from the British Geological Survey (BGS) to test the latest iteration of their seabed rock drill, RD2. 

In addition to drilling and coring holes in the seabed, BGS have also purchased downhole logging probes to be deployed in the holes once drilling is completed.  These battery operated probes, will record in situ measurements of the physical properties of the formations that have been penetrated, as the drill string is retrieved to the rig.  Sally was invited by BGS to participate in the trials cruise in the Firth of Lorne as the downhole logging specialist.  She will be providing technical support and guidance on the logging tools and associated data during the trails and beyond.

The trials cruise on the Pharos is co-funded by the European Consortium for Ocean Research Drilling (ECORD), the BGS and industry partners.