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…..

Luminescence dating sampling at Cherry Orchard Farm, near Delamere

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By Richard Chiverrell

Another day and another quarry, but this time the BriticeChrono Terrestrial team Rich Chiverrell and Matt Burke met up with some friends, with luminescence dating team Geoff Duller and Holly Wynne from Aberystwyth and stratigraphic geru Geoff Thomas to tackle the delights of rural Cheshire, Transect 3. Breaking all the rules for BriticeChrono quarry investigations the sun was out and not a snowflake in sight or site for that matter. Cherry Orchard Farm is one of a series of sand and gravel quarries to the east of the mid-Cheshire Sandstone Ridge, recently sampled for cosmogenic nuclide (CN) dating.

The site (location 17 on the map) makes an intriging pair with cosmogenic nuclide location ‘Urchin’s Kitchen’ (location 16), a deeply incised bedrock channel eroded subglacially. We hope to compare the performance of luminescence and CN dating techniques with pairings like this. The setting contains numerous the active and former sand and gravel extraction sites around Delamere Forest, and is located on an extensive (8x5km) gently undulating triangular terrace or bench raised >10m above the floodplains of the Weaver Basin. The terrace is fed by channels flowing from the Sandstone Ridge and presumably a former ice margin on the southern edge of zone 5 (see the map).

Quarry operator (Richard Wilding) was fanastically co-operative and allowed us full access to the sections which reveal shallow water sandur and fine-grained glaciolacustrine sands. The sands were a dream to sample, well sorted, stratified, the right grain size for luminescence dating and with excellent exposure throughout the section. Four samples were taken arrayed vertically through the sequence, though probably almost identical in age given the depositional environment, we sampled different lithofacies or depositional environments. The lengthly process was completed in 5 hours, it takes 60 minutes to record the gamma dosimetry (with a field gamma spectrometer) for each sample, which gave plenty of time for discussion, strategy and logging. Then for some differing journeys home, it can’t take that long to drive to Aberystwyth can it?! Can’t wait for the dates and the next phase of sampling on transect 3…..

Young London artist inspired by an Irish erratic

Peter Glasgow just spent a few hours at my home talking about erratics. He came across one in Ireland and has been inspired to do a piece for an exhibition in London this June. He needs to work out its source and then get artful. I gave him some clues to help. Here at BRITICE-CHRONO we will provide supporting information for him, and hey it might be of interest for us to visit and date. I am hoping it has a Scottish lithology. He might post a picture for us when he next visits.

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

Rapid retreat of the Irish Sea Ice Stream – just out in the Journal of Quaternary Science

Irish Sea Ice Stream

A new paper has just been published by Richard Chiverrell and a hefty team of Britice-Chrono co-workers (James Scourse, Katrien van Landeghem, Chris Clark, Colm O Cofaigh, Dave Evans, Danny Mccarroll, Colin Ballantyne) presenting the first Bayesian integration and modelling of all the dating control for the marine sectors of the largest ice stream that the last British-Irish Ice Sheet ~ 24,000 years ago. The modelling shows very rapid retreat for this marine-terminating ice stream over greater distances (650 km) and timescales (8000 years) than is available from short term (decadal) observations of present day ice stream margins. The modelling shows this retreat 24,000 years ago was rapid and linked with climatic warming, sea-level rise, mega-tidal amplitudes and reactivation of meridional circulation in the North Atlantic. But, significantly the pattern of retreat appears uneven with a pulsed pattern of retreat attributed to the passage of the ice stream between normal (sloping away from the ice margin) and adverse (sloping towards) ice bed gradients and changes in the geometry or marginal constriction of the ice stream. To read more click here.

The methodology and application kind of formed an important test case for Britice-Chrono as we attempt to constrain rates of and controls on marine ice stream retreat over millennial timescales for eight ice stream radiating out from the last British-Irish Ice Sheet. The methodology outlined in the paper will underpin and be used as a guide for our data collection for the wider British-Irish Ice Sheet. It would be quite good fun to play around with some of the available chronology for other ice streams…..

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