Tag Archives: T3

No rest for the wicked: T3 marine sector rumbles into life…..

By Richard Chiverrell

Sites and surveys for transect 3

Sites and surveys for transect 3

Leaving the Celtic Sea and the delights of the Celtic Deep, noon on Sunday 27th July, the Royal Research Ship (RRS) James Cook homed in on Britice-Chrono Transect 3 and the delights of the Irish Sea. For me work levels already high increased, with Transect leader duties to fulfil, and the challenges of finding till – glacimarine mud contacts throughout the sector, and do not forget the shells/fossils for the critical dating targets. That said without Katrien’s (van Landeghem) constant input and support it would have been ridiculous, the work in advance of the cruise identifying targets and new locations drew on considerable effort and collaboration focused on this marine sector of T3 over the past 2-3 years. The success of the efforts for T3 obviously relied on the excellent work effort, diligence and company of the cruise team, science crew, BGS and NOC Piston coring teams and the RRS James Cook captain and crew, all whom did everything they could to help us. Not singling people out, but I thank Katrien for constant input, advice and support as co-leader on this transect and Colm as Science Lead on JC106 cruise.

In the Celtic Sea, the ship was home to the friendly academic interplay between James and Daniel, the Irish Sea also offered up a number of longer standing and perhaps more vociferous historical debates! Understanding and interpretation of the nature and extent of glacimarine conditions in the Irish Sea basin has ebbed and flowed for 4-5 decades, with some proponents holding for a full glacimarine ice margin, others subaqueous margins with more restricted access to the ocean and the other end member glacilacustrine basins separated from the sea. For all these views a comprehensive borehole and geophysical survey targeting environments across the sea floor had the potential to advance understanding, but for Britice-Chrono we clearly needed glacimarine conditions and sediments to provide the marine shells and microorganisms that we can radiocarbon date to gain a chronology for retreat of ice from the basin. Marine fossils have been recovered from coastal glacigenic sediment sequences surrounding the Irish Sea for centuries, but debate continues over whether they are in situ or derived, eroded from the sea floor, during ice advance and then redeposited in glacial sediment. If in situ they offer the potential to constrain retreat of ice margins and the development of glacimarine conditions, if derived they cannot really advance our dating control. Some challenging fieldwork and some painstaking analysis of the fossils and microfossils lies ahead.

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Our journey from the Celtic Deep ~ 51°25’N to our first survey and core sites west of Anglesey around 53°15’N took just over 12 hours at a steady ~10 knots. Our first sites, a bit of a late addition and product of general brain-storming, were ~ 13-14 miles west of Holyhead and targeted the deep waters of northern extensions of St Georges Channel. The location kind of bridges T4 and T3, and we wanted some indication of deglaciation of the deep waters between Holyhead and Dublin. On reflection I was not sure what to expect here, but we had planned a sub-bottom profiler SBP and multibeam survey line as an initial exploration, but circumstances and our temperamental SBP conspired against us. The multibeam data on the other hand were excellent, it was a decent trough 2 miles wide 30-40m deep and we used the multibeam to avoid surface sand waves. Our aims were to avoid surface sand and access the underlying laminated glacimarine units, 2.5 hours and two vibrocores later, some success >3m of mud ending in reddish (an Irish Sea glacial signature!) stiff muds. These laminated or bedded sediments hopefully were lain down under marine conditions fronting the ice sheet as the ice margin retreated to higher ground east and north between Anglesey and the Isle of Man.

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From noon 28th July we moved east and north between the Isle of Man and North Wales, and into a region a large part for me where my interest in this research started, working for and collaborating with Geoff Thomas on sections and sediment all around the Irish Sea. In the deeper waters between the Isle of Man and North Wales, our multibeam data gave us a view onto a very well preserved glacial landscape of drumlins and flutes, moulded elongate low hills shaped by the passage of ice. Uncovered as ice melted and then preserved beneath water probably ever since, their summits are grooved with markings probably formed by ice-bergs calving from and then grounding on the landform surface fronting this glacier. Guided by the multibeam sea floor topography and our shallow geophysical data we targeted hollows in the landscape with shallow fills of sediment overlying the glacial surface. Our vibrocorer can penetrate to ~5-6m depending on the sediments, absence of large cobbles or bedrock, heavy seas and luck. Fingers were regularly crossed and the only wooden items in the all metal BGS vibrocorer cabin are now getting quite worn by us touching them for luck and the right sediments. Broadly we divided the Irish Sea basin into four sub areas, 1. South of a line between the Isle of Man and Barrow-in-Furness completed by 21.30 on 30th July, the deeper waters between the Isle of Man and western Cumbria by 18.30 on 31st July, the Solway Firth (between the Isle of Man and Scotland) by 5am 1st August and finally the deep waters west of the Isle of Man by 11.30am 1st August. >500km of survey line, 34 cores in total, almost all of them reaching the reddish glacimarine muds often laminated some with dropstones and in many cores stiff diamicts with clasts typical in character of Irish Sea glacial tills seen in coastal cliff sections around the basin. We had the sediment contexts we desired, the subglacial to ‘glacimarine’ transition and water-lain ice marginal muds from settings across the transect. The nature of this water-body and answers to the Britice-Chrono geochronological questions must wait on many months of laboratory analysis, but I left the Irish Sea northwards for the Malin Sea and T7, satisfied and with the feeling that the sediments and geophysics alone will fill in a significant and long standing gap in our understanding of the last glaciation of the Irish Sea.

The raging waters of the Irish Sea

The raging waters of the Irish Sea

Cruise 1: meet our Marine Mammal Observer

By Marian McGrath
dolph
Hello everyone! It’s been one week since we joined the RRS James Cook in Southampton, even though we didn’t actually leave the port till Friday the 18th due to technical problems with the vibro corer. My role on board is as the Marine Mammal Observer (MMO). The role of the MMO is to ensure the safety and protection of marine mammals from man-made noise pollution in the ocean. This can damage or kill cetaceans which have very sensitive hearing. The Marine Mammal Observer (MMO) is required by law to be aboard any vessel which is carrying out seismic surveys within Irish waters. On this vessel, Sub Bottom Profiler seismic equipment and Multibeam echosounder equipment are being used. In unprotected marine areas an MMO is required to carry out a 30 minute pre Multibeam echo sounder and Sub Bottom Profiler watch followed by a 20 minute watch during the soft start. Sound activity cannot commence until the MMO gives clearance after the 30 minute watch. If marine mammals are spotted within 500m range of the equipment during this watch then a further 30 minute watch is undertaken till marine mammals have left the mitigation zone. If no marine mammals were seen within this time then a soft start would commence. Once the ramp up procedure is started there is no need to stop the equipment during night time hours. The Multibeam and Pinger systems remain active during the survey unless we are on a coring station for longer than an hour in which case they are switched off. They are also turned off during the mid-cruise port call in Killybegs.

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Marine mammal observations are carried out from the bridge. This gives the best view point of both sides and in front of the vessel. The equipment is always started during daylight hours to allow for MMO watches to be carried out prior to soft starts. Observations are undertaken using a reticular binoculars, a range finder and also by the naked eye. Distance to marine mammals is determined using this reticular binoculars and height above sea level. To determine the range one of the divisions present in the binoculars is placed on the horizon. A formula is then used to determine the distance of the mammal from the ship. The formula is: Distance (m) = (height of eye above sea level (m) x 1000/ no. of mils down from horizon). Throughout the duration of the survey, watches are undertaken throughout the day and any sightings are logged in a computer supplied by The Irish Whale and Dolphin Group. This will feed into a database which is constantly updated regarding location and numbers of various species. Throughout the day recordings are taken of precipitation, sea state, visibility, ship speed, water depth, cloud cover, latitude and longitude, wind speed and direction. So far on this survey Common Dolphins have been seen near the shelf edge of the Celtic Sea. First 4 adult dolphins were seen on the 21st July and later the same day 11 adults and one calf were seen.

BRITICECHRONO Fieldwork on the Isle of Man ~ November 2013

The leaving of Heysham is nothing like the leaving of Liverpool

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)

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 4th to 9th 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…..

BRITICE-CHRONO: sampling bedrock in Cheshire/Shropshire for CN dating

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By Matthew Burke and Richard Chiverrell

Taking advantage of the improving weather and as the snows subside Rich Chiverrell and Matt Burke were joined by Derek Fabel and David Small (University of Glasgow) in getting the terrestrial sampling programme underway for BRITICE-CHRONO. The project a NERC-funded consortium that aims to constrain the rate of collapse of the last British-Irish Ice Sheet. The project will employ a number of dating techniques – Optically Stimulated Luminescence (OSL), Radiocarbon (14C), and Terrestrial Cosmogenic Nuclide (TCN) dating – in order to document the retreat of all major ice streams that drained the largely marine-based ice sheet. Terrestrial sampling along the Irish Sea East transect is now well underway after three days of intensive rock removal along the Mid-Cheshire Ridge for TCN dating. Although renowned for its flatness, the rolling farmland of Cheshire/Shropshire is broken by the enormous Mid-Cheshire ridge that reaches a whopping 227 m asl and is, conveniently, aligned roughly perpendicular to the retreating ice margin. As the ridge has been eroded by overriding ice and is cut by deeply incised meltwater channels it presents a great opportunity for us glacial geologists to do our thing: clamber around, stare at, chisel away at, and rest upon various rocks!

Field Personnel: Derek Fabel (rock sculpting), David Small (rock sculpting & note taker), Matt Burke (dogsbody), Rich Chiverrell (Driver & lookout), Geoff Thomas (Local geological expert), Pat Alexander (Local gastronomic expert)

DAY 1: Northern sector

Whilst Rich was enthusing year 2 undergraduates about the joys of glacial geomorphology, Matt, David and Derek began the day by braving the wilds of the Wirral with a stroll around Thurstaston Common in order to take a look at the ‘controversial’ Thor’s rock: a site of much debate as to the origin of the numerous erosion marks that cover its surfaces. Some believe the marks record scalloping by glacial meltwater, a plausible argument given the rock sits within a meltwater channel, yet the obvious steps and chutes down its flanks are probably testament to the alternate hypothesis that these marks simply record 100+ years of children climbing over and sliding down the rock!

Meltwater or scallies: which was the greater erosive agent at Thor’s Rock?

Meltwater or scallies: which was the greater erosive agent at Thor’s Rock?

After careful consideration we decided to sit on the fence, concluding that many of the marks were originally scoured by meltwater, but have now been enhanced by the locals (us included) and so we decided to sample at a less controversial site: Thurstaston Hill. From here the team drove a couple of miles to Barnston Dale where we were joined by Rich, resisted the temptation of a 10 am pick-me-up at the Fox and Hounds, and hacked a piece of rock from the Barnston meltwater channel.Next stop Urchin’s  Kitchen at Primrose Hill Wood. Following what seems to be a tradition for this transect, Rich and  David did an excellent job of navigation (Rich: “we don’t need a map to navigate…”).

C3W film crew capturing Derek's activities

C3W film crew capturing Derek’s activities

Although  we did eventually arrive at the site, we seemed to take the scenic route as we zigzagged our way across the countryside, which was all part of the plan, of course. On site we met up with Saskia Pagella and Vince Jones from C3W who filmed the sampling procedure and interviewed Rich and Derek with the eerie backdrop of the Urchin’s Kitchen.

Unfortunately, although Derek gave us a great recital of a poem commemorating the discoverer of cosmic rays, it was not captured on film and it  was a one-off performance. Lesson learned; always have a video camera at the ready in case of any future Britice-Chrono poetry recitals….. After a rather late lunch at Delamere Forest, the team finished off northern sector sampling by bagging (literally) rock at Manley Knoll and Helsby Channel. All in all, a very successful day of sampling, but could we cope without Derek on day 2?

DAY 2: Central sector

Afraid to look down: David measures the shielding at Raw Head.

Afraid to look down: David measures the shielding at Raw Head.

As Derek whizzed off to Sheffield to give a talk, Rich, David and Matt were left to pick up the pieces and continue with another round of TCN sampling. This time the central part of the ridge was the target, where surprisingly little bedrock was exposed. However, after several hours of rock hunting, David stepped into Derek’s shoes admirably and showed his skills at Raw Head and Bickerton Hill. Raw Head proved particularly challenging (not including having to avoid the local fox hunt on route) given David and Matt had to clamber atop a block that had slumped from the main outcrop and was hanging precariously above the valley below. After a long and cold morning of walking the ridge, we were met for lunch by Geoff Thomas at the aptly-named pub “The Sandstone”. Along with a rather large lunch, Rich crumbled under the slightest of peer-pressure to enjoy a pint of “Scrum  Down” (BRITICE-CHRONO approved beer 1) with the rest of us.Luckily, after lunch the fully-awake and motivated team were able to expend their excess energy with a couple of steep hikes. The first proved fruitless as we discovered on arrival at the outcrop that it had been heavily quarried. Thankfully, the second hike to the head of the very deeply incised meltwater channel that is Peckforton Gap produced something we could sample. After another successful day, Matt was finally able to break the habit and navigate us home without any major detours.

Excellent lunch stop

Excellent lunch stop

DAY 3: Southern sector

Ahead only lowland Shropshire and the Severn basin

Ahead only lowland Shropshire and the Severn basin

Day 3 began with a long drive to the most southern extent of the ridge in Shropshire where the team were given unrestricted and free access to Hawkstone Park, despite it being closed to the public. After Geoff successfully found his way to the chute-like meltwater channels, the question was asked; have these actually been eroded by meltwater or were they excavated to produce nice walking routes for all those Victorian tourists? After careful consideration, we decided they were in fact meltwater channels, but unfortunately their steep walls and the resulting shielding meant TCN sampling was not possible. Instead, more precarious sites were chosen right at the top, and at the edge, of the escarpment. With bushes on one side and the prospect of quite drop a long fall on the other, Derek and David held their nerves to bag another two good samples. No fieldwork thus far appears complete without without a visit to the pub, the team stopped for another well-deserved lunch at “The Inn at Grinshill” where, alongside very nice fish and chips, a further sample was taken (“Six Nations” –BRITICE-CHRONO approved beer 2). After lunch the sun was shining and we were able to bag the final sample of the day (and the trip) from The Cliff at Corbett Wood. This proved to be a fitting conclusion to the trip: all TCN samples for the transect have now been collected, and the final site at the most southern tip of the ridge overlooked the outwash plains that will be now targeted for OSL dating over the coming weeks…

T3 sampling sites

T3 sampling sites