Tag Archives: transect 4

1 o’clock, 2 o’clock, 3 o’clock rock (well…compressed mud), you can rock around the clock….

By Margot Saher and Lou Callard

Take some of the ‘finest’ brains in the country. Put them on a state-of-the-art research vessel which is filled to the brim with geophysical equipment, and has its own core scanning lab. Imagine what one could do with that! And what do we do with it? What is the scientific treasure we hunt? Mud. Six weeks at sea for mud (occasionally sand…)? We’ll be scrutinising it for years to come! Without mud the whole endeavour would be a failure; the mud must be treasured, cared for. It is the sedimentary archive that could answer the question of when and how the British-Irish Ice Sheet vanished. It is the wet lab coring teams that handle, care for and love the mud. There are two shifts: the Night-watch from midnight to noon, and the Day-team from noon to midnight. Whilst in the lab and, more importantly, out on deck, these have to wear armour: PPE (Personnel Protective Equipment) – a hard hat, hobnailed boots and some rather unflattering (generally oversized) overalls. The overalls are optional, but a sensible option at that; the job is a messy one, so unless you have an endless supply of clothes…. As the British Geological Survey (BGS) core team recover the mud to deck we have to wait – impatiently. How much have we recovered, and is it the right stuff? Even before the barrel is laid down we swarm expectantly around its end to get the first glimpse (and touch) of the treasure. The strength of the mud gives us so much information; we prod it, taste it…. Does it feel like silt, sand, clay; is it stiffened, reflecting the weight of former ice sheet bearing down on it? We recover everything from the core shoe, the core catcher; whatever sticks or falls out of the liner gets bagged, labelled, photographed and stored cool. But what is inside the liner is what we really want, it contains the story of the ice coming and going from the waters around these islands.

The liners are not easily released from the barrel; muscles are needed to get it out, and a tug-of-war ensues of scientists, BGS engineers, crew, random passers-by, anyone versus the barrel. But once the liner is out, it’s ours. The muds we desire are only useful if we know exactly where they are from, so labelling is everything. Every single core section has its own unique label, which will end up on its liner, caps, wrapping material, and the box it’s stored in. There are yellow caps for the tops and black for the base of each segment; which way is up matters! And that is only the beginning; there is no such thing as over-labelling, and that holds for cores sections, record sheets, scanned records, spreadsheets, photographs……

Lou: “The day shift consists of Steve, Zoe, Catriona, Kevin and me. Whilst Colm and Katrien spend the day planning where we will core next, we collect and process the cores. Generally our day starts at 11:20 with breakfast, which also happens to be lunch for the other crew members. Breakfast can be anything from a curry to fish and chips. Today’s option was Thai fish cakes, with noodles and sweet chilli sauce. Although having such a large meal first thing was rather odd to begin with, six weeks in it seems quite normal and a bowl of cereal would now disappoint. Shift begins with the midday handover meeting and our goodnights to the night team.

This slideshow requires JavaScript.

Then work begins! We spend most of our shift either out on deck collecting and cutting the cores, or in the wet lab splitting, logging and packing the cores away with a constant dual stream of material either from the deep or from the MSCL cave. Frequently we split over 20 sections during our shift, and often it’s more than 25. Each section is 1 m long with each 1 m weighing between 10-12 kg, so after 12 hours of carrying, splitting, logging and packing it is a good workout. So the coring job may seem rather unglamorous and exceptionally mucky, and involves hard manual labour; it is also an exciting and rewarding part of the cruise. The sub-bottom profiles and bathymetry data provides a tantalising look at what might lie beneath, but it is only when the core is taken and the material viewed that you know whether or not we have captured the right material needed for the project, and whether there is something we can use for dating. Sometimes we are disappointed normally if we fail to guess correctly in the ‘guess-the-core-length’ sweepstake (Steve is slightly in the lead at the moment), but when a good core is opened, it changes the mood of everyone involved.

Our work still isn’t quite complete, cleaning and maintaining the lab ready for the night team, labelling, cropping and archiving all photographs, and Zoe dutifully scans all of the deck sheets. At midnight the night team relieves us and then we head either straight to bed or take a detour past the kitchen to get a post shift snack. A day shift favourite is Nutella (somewhere in the multi-verse other nutty spreads might exist) on toast. It is hungry work, coring!”

Margot: “the Nightwatch consists of Kasper, Riccardo, Jenny, myself and occasionally Richard (if he can drag himself away from the Geophysics, picking core sites and mostly chatting on deck). As we start our shift, we tend to find ourselves in the middle of a coring transect that has been planned before, so we of the night often start our shift on station, vibrocoring. We’ve discovered that Riccardo has a special talent for working hard but still staying clean, while Richard has the useful talent for removing almost any sediment from an unwilling core catcher. Kasper’s Danish (or Viking) muscles come in handy for removing the liner from the barrel, and Jenny has useful BGS contacts (which saves us, for instance, from running out of sample bags). I myself have developed the modest knack of writing upside down, for liner labelling purposes.

This slideshow requires JavaScript.

Splitting and description has to wait until we receive cores from Elke and the core scanner cave, and she works 6AM to 6PM. The early part of the shift can be quite calm, if the core stations we have picked are far apart. Quite often nature festoons such a quiet early part of the shift with an amazing sunrise. The pace picks up dramatically as the cores start to emerge from the MSCL cave. It can get a bit hectic if we’re busily splitting and describing, interrupted by receiving new cores from the seabed. Core sections everywhere! But the splitting is exciting, as we get to see the whole sedimentary sequence for the first time. Do we have the ideal core, which consists of a subglacial till at the bottom, conformably overlain by marine sediments deposited after the ice retreated? Are there perhaps some nice shells in it for radiocarbon dating? When we see something we could use for 14C dating, we take it out. As we are coring, we have a competition running: guess the core length. It is very tight at the moment; Riccardo is in the lead, closely followed by Jenny, and Richard is trailing miles behind, but it all can still change, even with only two days to go. Eventually noon arrives, when we hand over to the day team, and then plonk down tiredly for lunch, which, for us, is more like late supper. After lunch and a cup of tea it’s bedtime! And then at around 11PM (ish) we get up again, and the sequence repeats.”

Treasure.....

Treasure…..

As we both write this, the 212th core has been recovered from the large moraine in outer Galway Bay. There is some 6 tonnes of mostly mud in our refrigerated container, and we have picked more than 100 shells for dating. But we know exactly where every kilo came from, what it looks like, and which ones we want to target for further research. When we get back on land, we can hit the ground running…..

Photography mostly by Alex Ingle, except where it isn’t….

A room without a view……

By Elke Hanenkamp (MSCL Operator)

Enter my lair

Enter my lair

Six o’clock in the morning on board the RRS James Cook somewhere on the edge of Malin Sea in 1500m of water, and my shift as the MSCL operator starts right now. The dayshift (midday to midnight) is still fast asleep and the nightshift (midnight to midday) scientists are eagerly (or maybe more fatalistically) awaiting my arrival. The beginning of my shift marks the start for them that cores can finally be split and described soon (meaning more work for them), therefore I have been jokingly nicknamed “the harbinger of cores”.

My role during this expedition is to collect physical properties data (density, porosity etc) from the vibro and piston cores before they are split on board. I am operating a Geotek Multi-Sensor Core Logger (MSCL) in a containerised lab (also known as “the container cave”, I am in there all the time holed up with the cores). So the obvious question is – what is happening behind the closed door of the container? After the cores come aboard, they are cut into sections and labelled, and then stored for at least 6 hours inside the container to equilibrate to ambient temperature. Only after this period, the cores will be measured on the MSCL, because some of the sensors are temperature sensitive. It is not possible to prop the door open during the measurements, fluctuations in temperature would influence the data. That’s why I am holed up in the container most of the time, every so often delivering already measured cores to the scientists for splitting or taking newly labelled cores into the container.

The Multi Sensor Core Logger is a quite versatile core measurement system, equipped with four sensors – Gamma Density, P-Wave Velocity, Non-Contact Resistivity and Magnetic Susceptibility. While the core is pushed past the stationary sensors, it is scanned, and data from all four sensors is collected at once when the core pauses at a measurement point (in this case every 2 cm). Sequential core sections are loaded on to the logger, this way a complete core can be logged in a continuous process while the data is displayed graphically in real time on the computer. Typically, with measurements being done every 2 cm, a 1 m section can be logged within 15 min, but overall measurement time for one whole core depends on the amount and length of each individual section the core is cut into earlier. The shortest core section we had so far measured only 21 cm. The amount of cores sections measured each day highly varies, but a couple of days ago, 45 sections were measured on the MSCL within my 12 hour-shift, with a total length of a little bit over 41 m (a new record).

This slideshow requires JavaScript.

The MSCL gives us a non-destructive way of analysing cores before they are split and sampled. The measurements can help to characterise the physical nature of the individual cores, e.g. lithology, density, porosity, and will be used in combination with core descriptions and various geochronological data to better understand the timing of ice sheet recession. The high-resolution dataset from the MSCL should also allow us to make correlations between individual core sites in the Celtic, Irish and Malin Seas fringing the North Atlantic.

A view of the world

A view of the world

Sun setting on the Celtic Sea and B-C Transect 4

By James Scourse

A wonderful place.......

A wonderful place…….

The first of the BRITICE-CHRONO marine transects (transect 4, Celtic Sea) was completed late on Saturday evening. It has been hugely successful – the result of unbelievably excellent weather and sea state, detailed planning and effective delivery by a great team. This has been a controversial and enigmatic part of the British-Irish Ice Sheet for decades with generations of Quaternary geologists attempting to reconstruct glacial events from meagre and sporadic sequences. It was the focus of my PhD back in the early 80’s. A lot of this was spent onshore on the Scillies where the evidence suggested that the Late Devensian maximum advance straddled the northern islands – a conclusion that caused me not inconsiderable grief at the time because large and influential parts of the UK Quaternary community could not accept that the last ice sheet reached this far south. Subsequent work with colleagues using new techniques has supported this original interpretation. I also analysed a series of 12 or so BGS vibrocore samples recovered in the 70’s from the central and southwestern Celtic Sea containing “glacigenic” facies. A northern suite resembling the Scilly Till I interpreted as basal till facies, whereas a southern group – containing spectacular microfossil assemblages – appeared to be glacimarine. On the basis of this available evidence I suggested a mid-shelf grounding line and marine terminus to the Irish Sea Ice Stream. I was unable to explain the origin of some apparently “basal” type diamictons very close to the shelf break; they might possibly be iceberg turbates. More recently I suggested – with additional information from palaeotidal simulations – that the huge Celtic Sea linear ridge bedforms are tidal features reworking the sediments of the terminal ice stream and the Channel River.

Then, starting in the late 2000’s, I became aware that Daniel Praeg from Italy and Steve McCarron from Ireland had become interested in these ridges and were suggesting in conference presentations (e.g. INQUA 2011) that the ridges might actually be subglacial “ giant eskerine” bedforms which, if it were true, would mean that the ice sheet reached right to the shelf break. In Daniel’s model the shelf break diamictons are just that – evidence for shelf edge glaciation. One of the original BGS cores – site 44 – recovered till from the flank of a sand ridge which might suggest that the ridges at least partly pre-dated the glacial event; Daniel, following Pantin & Evans (1984) suggested that the ridges have a carapace of glacigenic sediment and were therefore overridden by ice. But, alternatively, do the glacigenic sediments dive through and under the ridges? A major unanswered question was/is the stratigraphic relationship of the glacigenic sediments to the ridges. There was something faintly ironic in all this: I’d had a lot of grief having argued for an advanced southerly position for the ice sheet, and now here was another team arguing for an even more spectacularly extended southerly limit.

Daniel, with great persistence and motivation, has organised a series of geophysical and coring campaigns with Italian, Irish and BGS colleagues – the last in February-March this year – to attempt to resolve the two models. Spectacularly their last cruise recovered overconsolidated diamicton and normally consolidated glacimarine sediments close to the shelf edge at the southern end of Cockburn Bank (for further details). I won’t steal their thunder because their work is being prepared for publication, but it is fascinating and has injected energy into our researches in this area. Daniel and Steve and colleagues Dayton Dove and my former research student Gill Scott, are now working alongside BRITICE-CHRONO colleagues to help address these questions. Having Daniel as a participant on this James Cook cruise has been a delight and the two hypotheses have been constructively batted to and fro, day and night, with lots of jocular repartee on the nature of things emerging on the sub-bottom profiler; “that’s clearly a buried drumlin”, “no, it’s a proto tidal sand ridge” etc etc.! Were that all scientific controversies were discussed in such a friendly, stimulating and constructive way.

This slideshow requires JavaScript.

So, what have we found? Searching for glacigenic sediments in this area is like looking for a needle in a haystick, so aggressive was the subsequent transgressive episode. Much of the sedimentary evidence has simply been eroded (incorporated into sand ridges??!) or buried. The BGS only found glacigenic sediments in 12 cores of the hundreds that were taken. Well, about a third of all our coring deployments recovered glacial or glacimarine sediments, from sites extending from the shelf edge to the Celtic Deep, a total of 14 vibrocores and 5 piston cores. This success is a testament to painstaking preparation – including a reconnaissance geophysical cruise – led by Katrien Van Landeghem, Sara Benetti, Lou Callard and colleagues – so that our targets were well defined. Excellent onboard sub-bottom data has also been crucial, pored over night and day by Daniel, Katrien, Colm, Richard and myself, and the expertise of the BGS and NOC coring teams. There is no doubt that these samples and their contextual geophysical data will transform our understanding of the LGM in the Celtic Sea, a topic that continues to fascinate, bemuse and, occasionally, infuriate. One of our key targets, site 44, stubbornly refused to yield anything but sand – dubbed the “sands of woe” by Lou Callard – that left Daniel, head in hands, muttering “Oh bloody, bloody, hell”!

What about the two hypotheses…well, I already have some modified interpretations emerging – new working hypotheses if you like – but I’m not going to be pushed on these until we have the data analysed from the cores. Having said that, I think Daniel might be partly right and partly wrong, and that I, too, might have been partly right and partly wrong. Such is science!

Cruise 1: a perspective from the stern…..

By Jenny Gales and other more reluctant bloggers….

The corer has landed

The corer has landed


The BGS team (Davie, Keith, Mike, Alan, Joe and Jenny) have been busy collecting sediment cores using the BGS remotely operated vibrocorer, with 39 successful cores recovered so far, 14 of which were in the last 24 hours.

The BGS vibrocorer weighs in at 5000kg, in the super-heavyweight class, and can be deployed to a water depth of 2000m. The system consists of a 6 m hollow tube of steel, called a barrel, which is driven into the seafloor by a 1 tonne vibrating pot at the top of the barrel. The whole thing is held in a vertical upright position by a three legged metal frame that keeps it from tipping over on the seabed we hope… Our team, all six of us operate a round-the-clock 24 hour operation, in two shifts of three people, (day-watch Davie, Keith and Alan) and (night-watch Mike, Jenny and Joe) given we occasionally need sleep and time off to read and drink tea.

This slideshow requires JavaScript.

Each deployment of the beast starts with the vibrocorer lying horizontal on the back deck of the ship. First, a hard plastic core liner is put into the barrel. Next, a metal core catcher is added to the end of the plastic liner, to stop sediment falling back out when the core is raised back onto the ship. Finally, a core cutter is attached to the end of the barrel, which cuts through the seafloor. The vibrocorer is then raised up into a vertical position by a BGS winch system and the ship’s A-frame. It’s then lowered over the back deck to the seafloor at about 30 meters per minute. When the vibrocorer lands on the seabed, the corer is started from a purpose built container on the back deck which is fitted with a control and acquisition system. The barrel is driven into the seafloor by the weight filled vibrating pot and collects a core of sediment as it goes down. This usually takes between 15 minutes to 1 hour depending on how hard the sediment is or how persistently nagging the science team are. The materials in the south Celtic Sea have been a little challenging, with coarse sands and other materials proving tough to penetrate. Also the much sought after glacial muds have been tricky to find! Once the coring is finished, the vibrocore is easily (for the most part) extracted from the sea bed and raised back onto the deck of the ship and the now sediment filled barrel is removed. The sediment-filled core liner is taken out of the barrel and is carefully labelled and cut into 1 m sections. The sediment core is now ready to pass on to an expectant science party craving muds……

This slideshow requires JavaScript.

Cruise 1: Our looking glass onto the sea-floor…..

Dr. Fabio Sacchetti from the Marine Institute (INFOMAR program) has joined the BRITICE-Chrono survey cruise as Irish Observer and multibeam/geophysical support. As Irish Observer Fabio is overlooking survey operation when in Irish water and makes sure that the survey does comply with Irish standard practices. From a scientific point of view, Fabio has spent the last 11 years mapping the seabed offshore Ireland and the last 4-5 years studying its glacial geomorphology. Back in Ireland Fabio works for the INFOMAR program as hydrographic team leader and onboard the RSS James Cook looks after the multibeam and geophysical data acquisition and processing during the night shift.

This slideshow requires JavaScript.

So far the collection of good quality multibeam data has been quite challenging for a number of reasons. The ship is equipped with 2 Kongsberg multibeam systems, the EM710 (for shallow to medium water) and the EM120 (for deep water). The data from both systems are routinely collected day and night and they need to be quickly cleaned and tidally corrected in order to be able to create useful bathymetric surfaces. These info are then used for many purposes including geomorphological interpretation, core site selection and ultimately to make sure that the sampling gear are not deployed over risky seabed. At the start of the survey both multibeam systems had to be calibrated in order to provide the best data quality. After few days and with the weather picking up a bit it was also obvious that the motions sensor (which is needed to precisely correct the swath data) wasn’t performing properly. Further modifications to the standard setup had to be done in order to remove motion artefact that were affecting the usability of the data.

3D image of a canyon head used to calibrate the multibeam systems.

3D image of a canyon head used to calibrate the multibeam systems.

Fabio says: so far this has been an exciting scientific cruise simply due to the sheer amount achieved by the scientists and crew aboard the RSS James Cook, especially in light of anticipated challenges posed by the type of glacial sediment required to be cored, which is proving to be incredibly hard to penetrate. Working with some of the best marine glaciologists in Europe is exciting and challenging at the same time. Data are not just collected but analysed and interpreted on the fly and this contributes to a more hectic, clever, and scientific hands on approach, which makes the all survey way more interesting. It is also a pleasure to see how much projects such as INFOMAR can support and help the scientific communities providing top quality multibeam and geophysical data free of charge, which has been fundamental during the planning of this ambitious research project. The RRS James Cook is an exceptionally good platform for survey and sampling operation with top class facilities and lab space. This is an incredible experience and allows me to learn how things are done onboard one of the best research ship in the world.

Fabio: more than just geophys, a dab hand at DIY.....

Fabio: more than just geophys, a dab hand at DIY…..