A Perfect Core……..

By Margot Saher, Dave Roberts and Rich Chiverrell (Photography by Alex Ingle)

Darkness. A great mass of ice overhead. The eerie rumbling of a large, uncompromising mass, slowly but steadily on the move. Below a thick layer of stiff red sediment, ground off the red bedrock, crushed and churned into a lumpy, sticky blanket of glacial till.

Dark coasts

What would later be called Cape Wrath was only miles to the south, but there was no cape yet. Just the grinding of slow and unforgiving ice moving north into the North Atlantic. But the times were changing. The sun gained in strength, atmosphere and ocean started to warm and the gigantic ice mass, later to be known as the British-Irish Ice Sheet, was in decline. As its surface melted, more water reached its bed, and it began to slide helplessly over its own sediments. Slowly it thinned, and retreated in the direction of the Scottish mountains with the ocean lapping relentlessly at its edges.

There seemed to be no hope, but the ice sheet made one last bold dash towards the edge of the continental shelf before it faltered. The recently deglaciated seabed and freshly deposited grey ocean sediments were bulldozed and overrun again by ice on the move, and buried once more in a blanket of red till. Linear ridges (moraines) marked the limit of this temporary re-advance. But it was only a death throw; the re-advance didn’t get far. The ice sheet’s days were numbered. The advance stopped, and turned into irreversible retreat.

A geophysical search for the perfect core…….

Against a backdrop of rumbling, calving icebergs, station JC123-048VC slowly became ice free, as the snout of the ice sheet moved back over the site. A cold, shallow sea took its place; first, still close to the snout of the ice sheet, where streams of meltwater rushing into the waiting sea water lay down a blanket of coarse sand. As the ice retreated further, taking the meltwater streams with it, the sea fell silent. Only fine sediments spat out into suspension by the dying ice sheet made it to our site, slowly covering it in a thick, grey blanket.

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The ice sheet sent a final message as the ice margins retreated south towards the land; a message from an iceberg. As it passed, melting, overhead of station JC123-048VC, pebbles slipped from its icy grip. They plummeted into the depths, impacting into the soft fine clay sea bed. As soon as this excitement started it was over, and the pebbles were slowly covered by more of the same grey clay.

With the great weight of the ice gone, the Earth’s crust rose like an ancient giant from its slumbers, pushing the Scottish continental shelf closer to the sea surface. Over time, the waters shallowed, and the seabed currents became stronger. The last vestiges of the glacial seafloor were scoured by contour currents, which deposited the spoils of an energetic coast on the eroded sediment below. Millennia later coarse sand and shell debris formed a layer of several inches thick. And then on Sunday the 12th July 2015 all changed.

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There was an unfamiliar thud, and then the uncanny sensation of a vibrating tube burrowing into the sediment from above. It cut through the sand in a jiffy, passed the pebbles, and into the soft clays. The tube slid through it like a hot knife through butter. No struggle with the coarse sands lain down by meltwater streams either, only slowing on reaching the stiff, red till. It battled its way into it for a meter and a half. Then the friction became too much. The vibrocorer stopped, and then the whole tube, now full of sediment, was pulled back up to the sea surface, and hoisted back up onto the deck of the RRS James Cook, the ship it had come from. Peace returned once again on to the sea floor, at core site VC123-048VC, a few miles north of Cape Wrath, on the northwestern edge of Scotland; a land mass now devoid of ice sheets and glaciers.

The core came on board and was cut into sections, labelled, scanned, and split. Finally, we, the scientists who had planned the project, planned the cruise, sailed all the way from Southampton to Cape Wrath, and waited for the British Geological Survey (BGS) to deliver the core, first laid eyes on the sediment. The story was there: a stiff basal till deposited beneath the ice sheet; fines marking the first incursion of the sea; further glacial till documenting the ice re-advance, meltwater stream sediments deposited in front of the retreating ice margin; the fine clays deposited when the ice began to recede southwards containing drop-stones from the icebergs, and the marine sand of the modern seafloor. That was what we had come for. And this was the 48th core; none of the previous 47 had told the story of the vanishing British ice quite this clearly.

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Hopefully we’ll be getting more cores like this in the coming three weeks of the cruise. We need this story told in every sector of the British-Irish continental shelf. Only then will we have what we set out for: the complete saga of the Last British-Irish Ice Sheet.

A room without a view……

By Elke Hanenkamp (MSCL Operator)

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).

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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

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

By James Scourse

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.

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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!

Minching about on a sunny Isle of Lewis

By Rich Chiverrell

Port Skigersta delta

One of the smaller ice-masses draining the former British-Irish Ice Sheet, the Minch palaeo ice stream drained much of the NW sector of the British–Irish ice sheet (∼15,000 km2) feeding sediments to the large Sula Sgeir fan fronting the continental shelf. But if this is small, standing on the east coast of Lewis (Outer Hebrides) looking across the sunlit, blue seas and skies east to the feeder fjords and mountains of the Summer Isles and Wester Ross helps one visualise how large this former ice sheet really was. Our aim for this ongoing Briticechrono Transect 8 fieldwork was to secure a series of targets for Optically Stimulated Luminescence (OSL) dating from outwash sands from Lewis, one of the outermost land-masses on the western flank of the Minch Ice Stream. This work will support previous sampling efforts targeting boulders on the Scottish Mainland and the Hebrides for cosmogenic nuclide dating. Previous OSL sampling had targeted the inner sector of the Minch on Skye and north of Ullapool. The team (Rich Chiverrell, Matt Burke, OSL Postdocs Rachel Smedley and Alicia Medialdea) set off first thing on Tuesday morning to join Transect Leader (Tom Bradwell) on Lewis. Departing a cloudy Manchester via Glasgow Airport we landed before lunchtime to blue skies, sunshine and searing temperatures at Stornoway Airport.

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Inspired by our surroundings, the weather and the prospect of excellent sediments the four newcomers sped off to meet up with advance team Tom Bradwell, Adrian Hall and Maarten Krabbendam (from the Netherlands) at Port Skigersta in the far north of Lewis. The site an embayment on the western flank of the Minch Ice Stream gave stunning views across the water back to the ice source areas in western Scotland and beautiful turquoise seas. The sediments were very impressive with the sequence a stacked delta sequence with steeply dipping fore-set sands capped by top-set horizontally stratified gravel. Intriguingly the basal delta is buried by laminated bottom-set muds, in turn buried by a second delta fore-set and top-set couplet. The repeating delta suggests changes in water level probably lake level, dammed between the ice stream and bedrock rise into Lewis. We sampled both deltas close to the fore-set – top-set contact. And then for some geological tourism, the raised beach at Galsom guided by Adrian Hall, stunning and confusing sediments, all contributing to produce a plethora of hypotheses. Difficult to address under the banner of Briticechrono, the beach deposits (guess the isotope stage) appear altered by over-ride by ice, locally there is a surface diamicton and the beach pea/rounded gravels are probably thrust or stacked. We have targeted an outwash (ish!) deposit above a glacial diamicton, fingers-crossed for contributing to the debate. Excellent food followed at the Cabarfeidh Hotel our home for the next few days (well some of us!).

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Day 2, still warm, still still (no winds) and the sunshine popped in later! After an epic breakfast (Lewis did us proud) back to the north and just south of the Butt of Lewis the west coast Swainbost Sands offered much promise. The sections were epic more glaciotectonics, tills, shells than you can shake a stick at, and the beach!!!! One of the best beaches I have seen in the British – Irish Isles…. Selecting targets was challenging, much of the outwash deposit was rich with shells, thrust, tectonised and not where it was deposited! How? Well by marginal movements and override by ice and at a substantial scale. Three sample locations were found and in the back, along with crucial in gamma detector comparisons, duplication with different detectors at some of the samples. The sampling completed our targets after ~36 hours on the islands, and so we racked our brains for other targets. After a quick visit ~5/6km south down the west coast of Lewis where we encountered convincing striae in steeply foliated Lewisian gneiss, where the glacial lineation trends cross obliquely the metamorphic structure heading northwest. We also prospected for sites further up-ice around Stornoway; another fine meal at the hotel and some gin-assisted colour-by-numbers approaches to former ice geometry and let’s see what tomorrow brings for our last 3-4 hours on this eye-opening island (hopefully a final sample)….

Many a mickle makes a Muckle (Roe)….

Contributed by Tom Bradwell (1.75m tall) and Rich Chiverrell

Dawn broke at 0430 (we understand but not by experience) with clear skies and wide views across the hills around Lerwick. The team assembled slightly later than this, well 4 hours later actually – at around 0830 – after a good night’s sleep following our 2-day extravaganza on Unst. The prospect of great weather called for a slight change of plan and we decided to split into 3 teams for the day: Derek, David & Tom headed west in the Hilux to hopefully find some nice big rocks on Muckle Roe; Rich and Matt went south in the Vito MPV in search of glacial sands; and Chris, Saskia and Vince went to gather more footage of the Project Leader in his well worn and very practical Drizabone field gear.

The island of Muckle Roe lies in St Magnus Bay but is only 25 m from the Shetland mainland at its closest point and is conveniently joined by a sturdy bridge spanning Roe Sound. Taking advantage of this team Hilux drove to the end of the public road at Muckle Ayre, parked and set off on foot into a chill NW wind towards the furthest tip of the island. Muckle Roe is composed almost entirely of Silurian/Devonian granite and is quite rightly a national scenic area. The landscape is quite different to that across much of Mainland Shetland, with distinctive red granite crags, precipitous cliffs, and an abundance of glacially transported boulders – so many boulders in fact that it soon became apparent that the cosmogenic sampling team were in for a good day! After a couple of kilometres walk they found the first signs that glaciers had once crossed the island from east to west, with a number of rounded ultramafic and meta-sandstone boulders scattered across glacially polished and broken bedrock surfaces. These boulders could only have come from the Shetland mainland and their presence was a clear indicator that a large ice mass covered the whole island group probably with a 30-km wide ice lobe flowing into St Magnus Bay. Unfortunately, these boulders in particular could not be sampled as they don’t contain quartz: the mineral needed for the cosmogenic nuclide analyses. Instead the team took quartz-rich granite samples from a glacially deposited boulder, a smaller cobble and some ice-worn bedrock. If only all sample sites were this good!

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The team enjoyed a brief lunch stop of cornish pasty, squashed sandwiches, dried mango and caramel logs sat on glacially polished granite slabs overlooking the western cliffs with fine views to Foula and Eshaness. Derek even found the time and signal strength to send a couple of tweets. More sampling followed in the afternoon including a very prominent granite erratic nicknamed simply “big white” taking the final tally to 9 for the day. As the sun beat down, and temperatures soared into the low teens the weary 3 made their way back to the Hilux via the coastal path taking in some of Shetland’s (if not some of the UK’s) best cliff scenery. Vertiginous granite cliffs at Picts Ness and the Hole of Hellier were carefully navigated around before the samples were safely deposited in the truck.

Team ‘Elusive Quaternary Sediment’ following up some precise instructions from T1 Leader of go to behind ‘a well-known supermarket chain store’ there will be something there, and failing that drive around and find some stuff…… Pausing for some quick digital recognisance, emergency lunch supplies and then the section- bedrock and 1-1.5m diamict, job well done part one at least. The driving around aimlessly took much much longer! The coastal sections on the journey down to Hoswick proved equivalently disappointing, though interesting if you like windblown sand and peats inter-bedded of Holocene age overlying a thin glacial diamict. Matt and I then headed for Burn of Mail, and an eventual rendezvous with ‘the making of….’ documentary team. A cracking valley and showing the first set of convincing retreat moraines with ice flow down the valley eastwards from the mainland of Shetland. No sections but cracking geomorphology and a good boulder spread with the potential to record passage of the ice margin on land from the east. There was the tremendous opportunity to watch a future movie star in the making, as our film and outreach crew (Vince and Saskia) collected some of the final footage on Shetland for the U-rated comedy prequel to ‘Silence of the Lambs’. We then headed west to check out the southern flanks of Papa Sound, a stretch of marine waters extending from our destination on Wednesday ‘Papa Stour’ to the hinterland of ice on Shetland around Voe. Our brief ‘brief’ was to find boulder and if possible OSL datable materials, lo and behold we did, much of the lower terrain between Voe and Aith was ornamented with moraine ridges and glacial sediment documenting in this case the retreat of ice margins from the west onto Shetland. 15 m off the road inland of Gon Firth a 5m thick borrow-pit section through a moraine shows a sequence of a coarse grained boulder (>1 m) diamict overlain by a finer grained (>0.3m) poorly stratified till, but separated by 0.5m of stratified outwash sands probably lain down as wash down the front of the moraine. OSL samples were recovered and have the potential to add to the age control in this sector of the former ice sheet, particularly with paired cosmogenic ages if possible.

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C3W team Vince and Saskia departed for home this afternoon, overloaded we know with excellent footage documenting the work of Britice-Chrono and the T1 team on Shetland, we thank them for their company, hard work and efforts, and wish them a speedy journey home…. A fine evening meal (cooked by chef Fabel) of Jalfrezi chicken with rice, poppadoms and indian snack selection was enhanced further with David’s home-made onion pickle accompaniment (recipe available on request). With ready made plans for tomorrow and Papa Stour hopefully on Wednesday, Transect 1 (onshore) feels like it is rounding the bend onto the home straight…..

Unst and back again…….

A hobbit’s tale by Tom Bradwell’s ghost writer……

Concerning Unst, it is a delightful island in the northeast of Shetland, and the peace and quiet was interrupted the last two days by a team of geoscientists hunting for treasure. In this case treasure would be boulders or sediments that would allow the dating of ice margin retreat across northeast Shetland. We set off from Lerwick around 8 am armed with tools of the trade; rock saw, hammers, ground penetrating radar (GPR), percussion corer, RTK dGPS and a film crew. Getting to Unst required driving to a short 30 mins ferry crossing from Toft on mainland to Ulsta on the island Yell. Our time on Yell was brief with views of the rugged peat covered island on the journey from Ulsta to the next ferry terminal at Gutcher (north Yell) suggesting little prospect of glacially transported boulders. Hopefully Unst would deliver the goods! Following the Yell to Unst crossing, also brief (20 mins), we were ready to explore.

The journey to Yell….

We journeyed about as far north as you can drive on Unst to Herma Ness in the northeast, here hopefully our targets would provide the most northerly of our Shetland grid of sites. To cover the ground we divided into two teams: OSL and sediment group (Rich, Matt, Chris, Vince and Saskia) and Rock gatherers (Derek, David and Tom). For one of us (Rich), the plan for finding sediments involved following the footsteps of a predecessor at the University of Liverpool, geologist Derek Flinn who published extensively on the glaciation and glacial geology of Shetland in the 1970-90’s. An article on ‘The Milldale Glacial Lake, Herma Ness, Unst’ by Derek Flinn appeared in The Shetland Naturalist in 1992. Part of the mapping by Flinn identified an enigmatic outwash fan raised above (70-110m OD) the valley floor on the west flank of Burra Firth valley. The attraction for us lay in the potential for glaciolacustrine deposits to include sands for that elusive deglacial outwash material. Matt and Rich hiked up Milldale Burn and examined numerous exposures on the left bank that showed 3-4 m of sandy diamict, but no outwash. Meanwhile Chris explored the feeder outwash channels and confirmed an inflow feeding the deposit from the south. Our plans to run GPR survey were sabotaged by the Holocene, a very annoying 3 m of undulating and hagged peatland. All in all not a great success (except for some TLC for a new-born lamb by Chris), and then we abandoned the feature as, probably an outwash fan but composed of materials coarser and problematic for sampling. We then explored the other end of the Loch of Cliff and there are other bench like features also suggesting the presence of a former glacial lake but no sign of the sediments. Disheartened, we investigated other possible sections for glacigenic material in Norwick and Bray of Skaw, but the only prospect on the north margin of the sandy beach at Bray of Skaw we later revised interpretation of coarse cobble gravels to that of a storm beach buried by interbedded wind-blown sand and peat.

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For the team searching for rocks, the day was exhilarating and slightly frustrating, exploring the stunning landscape of Herma Ness walking from the car park at Cleva Ness to the tip of the headland north of Hermaness Hill, the far northeast of Unst and Shetland, overlooking the remote offshore rocks of Muckle Flugga. A great circular walk, but the entire area was covered with peat, and little sign of bedrock or boulders, notwithstanding the promising bedrock lithologys. Thus no evidence of glacial activity, in the form of sculpted bedrock, erratics, pseudoerratics or striations, was found. The team drew a blank in the northeast on the headlands of Skaw. Hill of Clibberswick though covered with bedrock exposures sadly there was no clear evidence of glaciation, no boulders and the bedrock was ultramafic metagabbro. Even though not promising a sample was taken for possible cosmogenic nuclide dating using the 36Cl isotope.

Tired, dazed and confused the two groups reconvened in the lounge bar of the Baltasound Hotel, having acquired our chalet style hotel rooms, for some much needed Shetland Ale or Guinness. Much debate followed, focussing on the apparent lack of glacigenic sediment and boulders, as well as the challenges of some very complicated bedrock, much of it not suitable for cosmogenic nuclide dating. Baltasound Hotel did us proud for dinner with an excellent array of foodstuffs: scallops, salmon, haddock, fish cakes and steaks. The Baltasound Pub (same place different room) did us prouder with beers, single malt and Eurovision! A lengthy evening ensued of spirited debate, and a tantalising fragment of local knowledge; “try the boulders south of the ‘Westing Road’ they look out of place……..”

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Day 2, after an excellent breakfast and a detour to debate the beach deposits at Bray of Skaw, we continued the search for boulders starting at Keen of Hamar walking through extensive exposure of Serpentinite and Britain’s largest chromite mine, at the coastal cliffs, we finally discovered that elusive evidence for glacial activity we had been searching for a glacial diamict that buried the Serpentinite showing glacially smoothed and scoured surfaces, these striations testifying to erosion by ice. Sadly the slopes littered with debris from the mining offered no prospects for cosmogenic nuclide dating.

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Finding bedrock: returning to the extensive north-south valley containing the Loch of Cliff, we explored the hills around Hargal Burn examining bedrock ridges and erratic boulders marked on the BGS geology sheets. Though not completely ideal, the rock team sampled the stoss and lee side of roche moutonnee form composed of psammite. We then followed up the wisdom received in the pub the night before on our journey back to the ferry in the south of Unst. Sure enough on the Westing Road, many boulders were visible, and a short journey west, 100 m distance from the Standing Stone south of the road we found a series of psammite boulders potentially moved by ice and containing good quartz veins. So after a shaky start we were ready to leave with 7/8 samples promising cosmogenic nuclides from the northernmost target of our sampling campaign.

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The return home went like clockwork, catching both of the return ferries promptly and all for excellent value, £54 for two cars and eight people return travel! We left Unst at 17:55 and made it to the excellent fish and chips shop/restaurant in Brae by 19:00, and what a feast awaited. The second best Fish and Chips in the United Kingdom, Frankies, battered scallops, pan fried scallops, mussels in blue cheese, ham and garlic, battered haddock, sea food tagliatelle and smoked haddock fish cakes, this place is off the scale, exceptional we cannot recommend it more highly. The team tired, satisfied, happy and ultimately successful returned to our digs near Lerwick for some much needed rest. Tomorrow waits with further sampling planned and our sampling grid beginning to fill…….

Out Skerries, the eastern edge of Shetland.

A boiled egg and toast to start the day, excellent, the only downside was the time 5.30 am which hurt slightly! That said Day 4 on Shetland was pretty special. Our numbers had swelled to 8 with the arrival yesterday of BriticeChrono P-I Chris Clark and C3W Outreach Team Vince Jones and Saskia Pagella.  We set off for the ferry to Out Skerries at 6 am. The first of two ferries departed Laxo at 7.10am and sailed to Whalsay, where we caught a second ferry to the dock in Bruray on Out Skerries, the easternmost islands of Shetland around half nine. Slightly cloudy start, but that quickly changed to glorious sunshine and the views from this inhabited collection of rocks in the north North Sea were absolutely stunning.

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The BriticeChrono T1 Team are on Shetland to try and constrain the timing of retreat of ice from the last glacial maximum in this sector of the last British Irish Ice Sheet (BIIS). Running in parallel to this land-based research will be a marine cruise examining the landforms and sediments preserved on the sea floor around Shetland scheduled for July 2015. Our task for 12-13 days is to sample boulders and sediments that will allow us to work out the timing of ice retreat across Shetland. From the distribution of these ages we intend to work out the pattern and directions of ice retreat. So far (see our previous blogs) we have sampled the far south of mainland (day 1), Foula in the south west (day 2), the northwest tip of Mainland; North Maven (day 3) and, today it was the turn of the east and Out Skerries. We are building a grid like pattern of dating sites across the islands aiming to get as far North, South, West and East as we can.

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From the dock on Bruray we walked across the bridge to Housay (the western island) to the end of the road and then onwards to a boulder strewn low (~28m high) hill. Here the bedrock displays clear signs of subglacial streamlining, with striae (scratches made by glaciers) and block removal on roche moutonnee showing ice flow to the northeast. The team split up slightly with Vince and Saskia collecting footage of all the action and interviews with Chris (Project P-I) and Tom (Transect Leader). Derek, David and Matt kept their eyes on the ball, or round boulders to be specific.  Some nice round-ish and very tough granodiorite boulders needed action from the rock saw (once the batteries had been recovered)! The granodiorite boulders lie on schist bedrock (containing quartz veins also sampled for cosmogenic nuclide or surface exposure dating) and these were probably carried to the island from mainland by the ice. Glacial transport was confirmed by an interesting exposure of glacigenic sediments, which showed striated bedrock covered by ~2m of till also containing examples of the granodiorite boulders and a pronounced macrofabric.

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Delighted with our endeavours in the west we headed to the eastern end of the island for a lunch with a view and more boulder sampling, two pegmatite and one granodiorite. This left a very satisfied team to adjoin to the village shop once abandoned by academic moth (Bradwell) who continued his exploration of bright lights: boulders, tills and scenery providing informative updates by walkie-talkie. Both activities provided important sustenance and rest before the ferry back to mainland.

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Last but very definitely not least: T1 comes to the BriticeChrono party

and finally we begin….

Cast: Tom Bradwell, Derek Fabel, David Small, Matt Burke and Rich Chiverrell (the Advance party), with the imminent arrival of Consortium P-I Chris Clark (first foray into the field on the project so far) and film crew Vince Jones and Saskia Pagella due in Thursday….

Early Monday morning (and following the very excellent timing schedule of logistics guru Bradwell) the teams departed. Chiverrell (without side-kick) laden with Ground Penetrating Radar, RTK GPS, Gamma Spectrometer and Vibrocorer departed Liverpool (36 hours after returning from EGU2014) to collect Matt Burke from Glasgow and journeyed to the ferry terminal in Aberdeen. Meanwhile Cosmogenic Nuclide (CN) dating team (Derek and David) travelled ‘light’ with lump hammers, rock saws to Edinburgh, meeting Tom B with the BGS pickup truck loaded, somewhat unusually for a glacial geology trip with a ‘peat corer’ and a dedicated functioning Shetland glaciations GIS database and maps. Around 18.30, the MV Hjaltland Ferry departed the port of Aberdeen, and Briticechrono team reconvened to the bar for a further planning session. Replete with an excellent nosh, a calm crossing and monster breakfast on the boat in the Port of Lerwick, what passes for an early summer’s day on Shetland awaits: drizzle and a cloud base slightly above sea level……

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Further confirmation of the excellent Tom logistics waited at the accommodation, excellent choice Shetland Self-catering at the Decca located on the edge of Lerwick a building that was Shetland’s Radio Navigational Signal Station for 35 years until the early 1990’s. About lunchtime the rains ceased and the clouds fell even lower and we departed for the southernmost sites on mainland Shetland. We drew a blank at Fitful Head, where five blokes wandered somewhat systematically looking for boulders on grassy hillslopes with 20m visibility! Learning quickly we ran away and went to Dalsetter, visited the famous ‘Dalsetter’ Norwegian boulder by repute from the Olso region but in a dry stone wall and not a viable CN target. However success quickly followed with eight boulders (pseudo-erratics) in the immediate environs that are glacially sculpted and sat proud of ground level. The boulders were all coarse grained to conglomeratic mid Devonian sandstone and sampled in two nice clusters. Eight down on day one, many to follow…….

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Tomorrow hopefully Tom, Derek and David fly to Foula (Scotland’s remotest inhabited island) if the clouds and fog abates, to collect cosmogenic nuclide dating samples of mainland Shetland erratic boulders transported by the last ice-sheet. Chiverrell and Burke will explore key sites on the mainland and assess possible OSL dating locations.

And there they rest……

From the Twelve Bens to Inis Meáin and then Inis Cathaigh : T5 Fieldwork – April 2013

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By Matthew Burke and Rich Chiverrell

A belated blog from the BRITICE-CHRONO terrestrial sampling programme in April 2013 when Rich Chiverrell and Matt Burke joined the Durham team – Colm Ó’Cofaigh, Dave Roberts and Dave Evans – for some Transect 5 sampling around Galway Bay. The team were greeted by glorious sunshine as they arrived in Dublin before hightailing it through the Irish Midlands to meet Colm at Clifden in Co. Galway. Surprisingly, for the west of Ireland, the great weather became a constant companion during sampling, for the first week at least, and made it a very pleasant fieldwork programme overall.

WEEK 1: Co. Galway & Co. Mayo: The first week was spent in and around Co. Galway and given there was a lot of ground to cover, we split into two teams during reconnaissance work: rock (Colm O’Cofaigh, Dave Roberts, Dave Evans) and sand (Rich Chiverrell, Matt Burke) hunters. It seems that there are lots of nice erratic boulders in Galway (if they aren’t too angular that is), but only limited sand and gravel. However, Rich and Matt managed to bag samples from Rich’s old stomping ground at Tullywee Quarry, Leenane Delta, Srahlea Quarry, Glennacally Bridge and an unexpected site at Glashmore stream. All in all, a successful start to the Transect 5 OSL programme. Unfortunately, these proved to be the only OSL sites in on the northern side of Galway Bay. Thus, attention was focussed on erratic boulders and bedrock suitable for cosmogenic nuclide (TCN) dating. Although finding the elusive well-rounded boulders could often be a challenge, it would become apparent during the second week, we were spoilt for choice in County Galway.

Following initial success with OSL sampling and having identified a number of targets for TCN sampling, the team set sail for an overnight trip to Inis Meáin (Arran Islands), and hopefully, to collect some well positioned samples. After a smooth and entertaining crossing we were greeted by the team from Inis Meáin Restaurant and Suites who, after conversations over coffee and cake, not only told us where to find the best erratics, also drove us there so we could get a full afternoon of sampling. Word of our arrival soon spread across the small island along with a number of varied rumours as to our purpose. Perhaps the most colourful being that we were filming a horror movie – I suppose the rock saw likely fuelled that one, though the only victims were boulders on this occasion. Inis Meáin proved to boast a lot of very nice erratics and, with some spectacular scenery, was one of the highlights of the trip. Another successful day was followed by a very nice meal, courtesy of our very hospitable hosts at Inis Meáin Restaurant and Suites, and then a well-earned Guinness in the local where many of the islanders were queuing to find out our purpose and about BRITICE-CHRONO generally.

Upon returning to the mainland the following day we completed our final day as a full team with further sampling around the stunning Galway coastline: a further six samples from some roche moutonée and erratics at Rossaveel‐Oughterard.

WEEK 2: Co. Clare: As Rich and Dave Evans returned to the UK (in a noisy fashion due to Rich’s car exhaust falling off), the remaining team (Colm, Dave Roberts and Matt) bagged the final sample sites in Galway during what proved to be a very long and wet day. Almost on cue, after Dave Evans suggested we might be on for continued dry weather during the second week, the heavens opened at the second sample site of the day. Although some good TCN samples were collected at Kilkieran‐Maam Cross a very tired and wet team headed south to County Clare. Despite the long day we still managed to find a spare moment (once we had dried off) for a quick Guinness in the excellent O’Loclain’s Irish Whiskey House.

We expected some difficulty finding granite erratics in the Burren where they are primarily sourced from limestone. However, we started the sampling in Clare with three reasonably well rounded granite boulders after only a little bit of hunting. The success of the first day gave the team some optimism for sampling here. Unfortunately, this was short lived as we found over the coming days that the granite boulders in the Burren seemed to be the only ones along the entire Clare coastline! We spent the next day driving zigzagging along what seemed to be every road in the area, none of which led to any samplable bedrock or sediment. After another long day we eventually found a Bed & Breakfast in Kilrush, where we landed on our feet once again; the owner knew a man with a boat who could to take us to Scattery Island, where we were hopeful to find some samplable outwash sands for OSL. As we were led to believe the weather would be too bad to travel to Scattery Island we began the next day with reconnaissance of a moraine and meltwater channel belt between Kilrush and Kilkee. However, following a last minute phone call to say the boat could make it to Scattery Island and a mad dash back to Kilrush, the team set sail. On the island were greeted by a very nice coastal section that, although containing only limited sand, yielded two OSL samples, as well as a monolith (for radiocarbon dating) from a kettle hole infill.

Although our expectations for finding material for sampling had been somewhat lowered, the final two days of fieldwork proved to provide arguably the best OSL samples from the county. During reconnaissance of the moraine and meltwater channel belt between Kilrush and Kilkee we unexpectedly came across a suite of landforms that appeared to be ice contact subaqueous fans/deltas. Thankfully, being the only source of sand in the area, they had also been quarried, allowing us to finish the fieldwork on a high. Although the last sample of the trip was “less than ideal” from an OSL point of view, a meltwater channel infill identified during earlier reconnaissance work was sampled before a very tired team started the drive to Dublin and found a very comfortable hotel on route for the final night.

Although finding datable materials proved challenging, the weather was good (for the most part), the scenery beautiful, and ultimately a good distribution of samples was collected around Galway Bay. Colm, Dave Roberts and Colin Ballantyne followed up the April fieldwork later in the summer with an equally successful sampling programme from the Connemara coast into Killary Harbour. And Transect 4 fieldwork during March 2014, which allowed a further Hobbitesque ‘there and back again’ visit to the Burren coastline for deltaic sediments at Doolin….. Finally  finally  completing the T5 fieldwork, or has it……..

BRITICECHRONO Fieldwork on the Isle of Man ~ November 2013

The leaving of Heysham is nothing like the leaving of Liverpool

By Richard Chiverrell

For Transect 3 of BRITICECHRONO, THE Irish Sea East, north from the terrestrial component in Shropshire-Lancashire, much of the remainder will be be dealt with during the marine cruises. The Isle of Man is the clear exception with excellent terrestrial exposure of the Quaternary geology; it is an excellent candidate region for dating the decline of the ISIS. The Isle of Man occupies a position astride successive ice advances through the Irish Sea Basin and records evidence of fluctuations of ice in the Irish Sea basin. The glacial geology of the Isle of Man is extremely well known, and this knowledge forms the basis for recent BRITICECHRONO fieldwork on the Isle of Man.

Geomorphology of the Isle of Man (Thomas et al., 2006)

Team Isle of Man consisted of Richard Chiverrell, Matt Burke, Daniel Schillereff (all Liverpool University), and David Roberts (Durham University), with meticulous planning (and no hastily rearranged flights) the intrepid team took off for autumnal bedock, erratics, sands, Manx queenies, cliff sections, gravels, sands, buried soils (?), kettlehole basins and ground penetrating radar on 4^th to 9^th November 2013….. We divided the Island five sectors documenting the northwards retreat, a) the Plains of Malew and adjacent hills (the South); b) the Peel embayment (the Central Valley) and on the northern plain c) outwash deposits of the Shellag Formation (the initial retreat); d) ice marginal sandar deposits associated with the Orrisdale Formation ice marginal oscillations (previously dated by Ian Thrasher) and e) outwash deposits of the Jurby Formations lain down during a more substantial 2-3km readvance. Together geochronology from these sectors would document the phased retreat across the Isle of Man and secure the timing of two well defined readvance episodes (Orrisdale and Jurby events).

Day 1 Monday – Travel and reccie day for some: Roberts, Dave, was first to arrive, apparently having set off before dawn, from whence he set gainfully on reacquainting himself with some former haunts, having spent a happy 12 months on the Island as a post doc in the mid- to late 1990’s. A very good day followed, bedrock sites on the southern flanks of Man, and a search for the famous Foxdale erratic train….. Meanwhile following a 9am lecture to the second years on European peat climate records, Chiverrell (Rich) tried to find his unusually elusive postdoc, Burke (Matt) who had been set the not insignificant challenge of cramming too much equipment into a car that had now seen better days. But second success of the day followed, 2x GPR antennae, 1x RTK Trimble GPS, tripods and staffs, monolith tins, 3x gamma detectors, the Roberts Rocksaw and cosmo kit, luminescence tubes and gearing, plus two scientists, can fit….  Third success, catching the boat from Heysham to Douglas, only 60 mins early for check in this time….. By 10.30 we had all collected in Andreas in the far north of the Islands, via in Dave’s case some old haunts in Douglas and a fine meal in the Sulby Glen Hotel for Matt and Rich.

Day 2 Tuesday – The Plain of Malew: The excellent recognisance by Dave helped us make short work of the very south of the Island. Bedrock samples a quartz arenite and quartz vein (sample 1 and 2) from Cregneash Peninsula overlooking the Calf of Man, where ice skirting the western flank of the Island has scoured and streamlined the topography and permission given by a very helpful landowner. The search for outwash sand and gravels for OSL proved slightly more taxing, with in the late afternoon a former bedrock quarry near Ronaldsway airport, Turkeyland Quarry, yielding a thin outwash deposit (sample 3) and a very enigmatic buried weathered soil, possible 14C target. And a fine dinner of Manx queenies and skate courtesy of chefs Matt and Dave. The final member, Schillereff (Dan), of the team flew in that evening to provide expertise on the kettlehole sediments, and revisit what might have been the locale for his undergraduate dissertation.

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Day 3 Wednesday – The Foxdale Granites and moving northwards:With permission from Manx National Heritage (Isle of Man Government) in order, the ‘holy grail’ site for BriticeChrono was very quickly lined up, the Foxdale granites. Ice flowing north to south penetrated through valleys from Glen Maye and Foxdale valley building to eventually bury and consume the Isle of Man. In Foxdale at the col at the head of the valley (~200m) a granitoid is exposed, and the erratic train holds a place of significance in the geological literature, including the attention of Charles Darwin (1842) as a classic example of transport of glacial boulders from low to higher ground including the summit of South Barrule. With the permission and assistance of Manx National Heritage several boulders were identified on the slopes of South Barrule near an Iron Age hillfort, 260-190m upslope and 1km distant from outcrop (samples 4 and 5). Foxdale granite is quite tough; boy did they take some chiselling. The four cosmogenic nuclide samples proposed for the Isle of Man form a coherent group in the south of the Island and a strong altitudinal gradient from 480m to 135m. There have been no previous attempts to obtain CN ages for the Isle of Man. Second success of the day, was Dan finding his kettlehole, perhaps not unexpected though given there are two on that stretch of coast with very similar stratigraphy. With the cosmogenic samples in the boot, Dave took his leave and departed for the UK.

Day 4 Thursday – the Central Valley, Kirk Michael and Orrisdale: With Dave gone, OSL sampling was very much to the fore. First up the Central Valley of the Isle of Man extending Peel in the west to Douglas in the east, where geomorphology shows moraine ridges arcing north and northeast indicating penetration of ice from the coast. The Ballaharra sand and gravel quarry shows a 12m sequence comprising basal 12-4m gently dipping fore-set planar sands and massive stratified gravels overlain by an upper (4-0m) top-set channel of horizontally stratified gravels with interbeds of planar and planar rippled sands. Western sectors of the current exposures are dominated by glacial diamicts and testify to an ice marginal setting. The sequence described is an ice proximal delta, with an ice contact slope immediately behind the worked exposures (samples 6 and 7). The late morning, saw a confrontation with high tides, the tides won. Slightly later, we began our run through the three retreat stage formations exposed on the Northern Plain of the Isle of Man. First Shellag Formation outwash at Kirk Michael (sample 8), with us filling the time taken to collect gamma dosimetry with sample the Kirk Michael (KM3/4) kettlehole deposits for our tephrachronologists to search for Icelandic volcanic ash layers. The KM3/4 kettlehole includes a basal cold stage lake muds that predate the lateglacial warming (sample 9). The Orrisdale Formation on the Island is quite well dated, with Ian Thrasher’s research, but we selected the northern most sandur trough in the sequence for further work (sample 10-11).

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Day 5 Friday – Jurby Readvance and the Dog Mills: The final day of OSL sampling, we tackled the Jurby Readvance, with two good lithofacies in off-lapping readvance over-ride sequence 3 (samples 12-13), just below a phenomenally well exposure kettlehole, including a prograding delta into the basin (one for the Quaternary community to revisit). The last sample of the day, on the east coast, the Dog Mills proglacial lagoonal sands (sample 14). Thus the sampling over 4-5 days spans the entire retreat sequence on the Isle of Man and two readvance episodes.

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Day 6 Saturday – Bride and seeing what you can do with GPR: With everything complete samples wise, the spare day was just that and with a 19.30 hours departure giving us some leisure time….. What do two Quaternary Geologists with a day spare? Well with 2x GPR antennae and a GPS set up, we assess the performance of GPR for Irish Sea glacigenic lithologies using the Bride Moraine, arguably one of the best if not the best exposure of glacitectonics on the NW European Archipelago. Do we need to know the internal structure of Bride?; well we could just go and look at the 60-80m high cliff sections or read a GSP Thomas paper for that. Again with helpful landowners guiding the way, we gained access to the cliff-tops above Bride, and surveyed 2.5km of the most undulating glacigenic terrain you could hope to meet. The very promising results in hand; we then also set sail for home…..