U/Th dating at Oxford University
Hey everyone, this is Jade.
Oxford is beautiful in autumn, which is why it was the perfect time to spend in Oxford university’s laboratories to collect 238U /230Th dates for speleothem samples! We had a collection of 4 stalagmites from our usual Botovskaya cave and one from an all-new cave – Argarakan. These samples needed to be dated to improve age models we already have, but also to date completely new samples. Overall, there were 10 238U /230Th dates taken, of which 9 were successful.
Hi, we’re ISOPERM, an international team of scientists looking at permafrost. We’ll keep this page updated when we’re out in the field,
238U /230Th dating is a method that geochemists use to identify how old samples are, up to a limit of around 500,000 years. This relies on the relationship of radioactive nuclides U and Th. In our speleothems, soluble 238U is trapped in the speleothem matrix with every growth layer. After approximately 275,000 years this decays to 230 Th. Therefore, knowing the ratio of 238U /230Th helps us to identify how old a sample is!
It is a long journey from producing powdered samples of speleothems to producing an age, which meant a lot of time working on the chemistry in the clean labs. After this, we moved downstairs to run the samples through an inductively coupled plasma mass spectrometer, which I thought was very cool because the plasma source was argon, which made a funky green glow!
The handful of dates we received spanned from the Holocene all the way to late MIS 13, which is over 550,000 years ago!
Our results opened many new avenues for us, and we will likely be back in Oxford to do more U/Th dating soon.
Yukon, Canada, June 2022
Hello, ISOPERM’s permafrost expert Thomas here. I’ve spent the last month out in Canada on fieldwork with Trevor Porter and his PhD student Mickey Chen from the University of Toronto Mississauga (UTM). I’ve been collecting permafrost samples that we’ll use to reconstruct palaeo-seasonality and study its impact on permafrost stability.
I arrived in Whitehorse on May 25 via Frankfurt and Vancouver and spent the first two days preparing. After two years in storage, enforced by the pandemic-related fieldwork break, equipment needed testing and inventorying before we got underway. Cargo was packed and last-minute shopping was done. There was even time for a visit to the Yukon Beringia Interpretive Centre for some background research… as well as to combat jet lag.
We left early on May 28 by plane for Inuvik, with short stops in Dawson City and Old Crow. After checking in at the Aurora Research Institute, we purchased our food supplies and began planning to set out the next day. Our priority was to sample Holocene (last 11,000 years) ice wedges in the foothills of the Richardson Mountains. Ice wedges form from winter snow meltwater, entering frost cracks and refreezing in the ground. This allows reconstruction of past winter climates using stable water isotope analysis. Weather permitting (and often low cloud cover did not permit) we flew in each day by helicopter (A-Star) over the Mackenzie Delta to our study sites situated in the steep walls of permafrost thaw slumps.
Warming in recent years has led to a high number of thaw slumps in this region as underground ice becomes unstable. In the Richardson Mountains, this is mostly buried ice from the last ice age. During our flights we saw several dozen thaw slumps in various sizes and stages of activity. Although we didn’t spot anything as large as the Batagay Megaslump in Siberia, some of the steep walls were simply too high to reach the ice wedges, or to work safely.
Nevertheless, we were able to sample a total of 6 ice wedges using a battery-powered chainsaw and collect sediment and organic samples. We hope this dataset will provide a new regional winter climate reconstruction that will contribute to a better understanding of seasonal climate dynamics in the Arctic during the Holocene. We also scouted a lake near Inuvik from which a core will be taken next year for Mickey’s PhD work on reconstructing paleofires using various molecules produced by forest fires and deposited in lake sediments.
On June 6, we went by plane back to Whitehorse, where the frozen samples were stored and we prepared for the next part of the expedition. The next morning, we loaded the rental car, replenished our food supplies, and headed out on the Klondike Highway to Dawson City where we set up our headquarters for the next week. Dawson City is known as the center of the Klondike gold rush at the end of the 19th century. Traces of gold mining (especially the later industrial gold mining using dredges) are still clearly visible today around Dawson and the Klondike area. Even today, gold is still being mined.
The Klondike is located in the zone of discontinuous permafrost and is characterized by a very continental climate. The oldest directly dated permafrost in the Northern Hemisphere has been found in the southern Klondike, with an age of more than 740,000 years. Younger permafrost deposits from the last glacial cycle are also known, with fossil mammal bones and ice wedges widely distributed, making it a perfect fit for our ISOPERM Project.
Because gold mining in the Klondike is not stationary, outcrop locations and conditions change from year to year. Therefore, especially after the pandemic, it was important to get an up-to-date overview and learn about next year’s gold mining plans. The prospectors have always been receptive to our concerns and have kindly given us unrestricted access to outcrops. This was seen recently with the recovery of an almost completely preserved baby mammoth.
We were very happy with our explorations. We identified and described ice-rich permafrost from Marine Isotope Stage 3 (around 50,000 years ago) and ice-poor permafrost from MIS 2 (around 23,000 years ago), as well as Holocene permafrost at several sites. We took diverse samples (ice wedges and pore ice for initial climate reconstruction, organics and volcanic ash layers for stratigraphic and chronological classification) at several study sites which we will use to prepare for next year’s fieldwork.
On June 14, we drove back to Whitehorse and spent the last few days with our colleague Igor Lehnherr from UTM collecting surface sediment cores from Spindly Pine Lake in preparation for a larger lake coring operation next year.
On June 18, I began the long journey back to Berlin where I arrived with only with a small temperature shock. It’s been great working with an international team and we’ve collected some exceptional samples to work on back in the lab. I’m excited for some additional exploration in the coming years to address many of the exciting and relevant issues in the Yukon region.
Siberia, February 2022
3 March 2022
Home sweet home! We’re back in Newcastle after a slightly frantic journey home from Siberia, hampered by the terrible events underway in Ukraine. Thanks to all those that have been messaging the team with concerns about our welfare. We’re safe and sound and, aside from a slight detour via Cairo, have been unaffected. Everyday life in Russia continues as normal. Our thoughts go out to all those impacted by events in Ukraine.
We spent our final days in Irkutsk enjoying some downtime, cataloguing our samples, and forging links with academic institutions. We took a day off to visit Lake Baikal – a stunningly beautiful lake with some equally impressive statistics to match. Baikal is the deepest lake on Earth, the largest freshwater lake by volume – containing ~20% of the Earth’s liquid freshwater, and is home to its own species of (incredibly cute) seal, the nerpa. At this time of year Baikal freezes over almost entirely so that cars and hovercraft can be seen criss-crossing in the distance. The ice becomes a playground with ice sculptures, mazes, and skating rinks sitting atop a vast white plain stretching as far as the eye can see. Where the snow clears, you can look down through the perfectly clear ice into the abyss below… a very disconcerting feeling indeed.
After a few hours on the ice, we headed to the Taltsy Museum, a charming collection of traditional Siberian buildings showcasing the different cultures and architectural styles of the region. Many of the buildings are originals saved from abandonment and transported to the museum for preservation. We were treated to 17th century Kazakh style fortresses, traditional craft workshops and of course, the obligatory jail cells. A great day out if you’re ever in the region.
It wasn’t all fun; the following day was spent at the Institute of the Earth’s Crust and the Technical University of Irkutsk where our brilliant colleague Alexander Kononov had arranged for PI Seb to give two talks (in Russian) on our work. I couldn’t understand a word of it (Russian lessons are being booked as we speak), but an engaged audience of enthusiastic young students kept Seb on his toes with plenty of follow up questions.
We then made our way to the Institute of the Earth’s Crust workshops where we spent a few hours cataloguing our new collection of samples and cutting them ready for transportation. Cutting the samples in half not only reduces weight so we can take them home on the plane, it allows us to leave half of each sample behind in Russia. Should our bags get lost in transit, or should we encounter a problem at customs, we then have a backup half preserved with our Russian colleagues so that all is not lost. But you’ll be pleased to know that we all made it home with our samples fully intact.
After prepping our samples, we were treated to a tour of the Institute’s geological museum and impressive array of analytical facilities before being granted an audience with the directors of each institution to discuss future academic links. We were delighted to sign a formal agreement of cooperation between the Technical University and Northumbria and spent much time with both organisations discussing future expeditions and scientific collaborations. It’s been a great trip, and we can’t wait to come back and explore some of these collaborations over the coming years.
24 February 2022
We’ve spent the day visiting a school in the beautiful Siberian village of Kuret, where our PI Seb gave a presentation on our work in the area. The whole school packed into a small classroom to find out why four scientists had come all the way from Europe to study their local permafrost deposits (If you’re still wondering why, visit our scientific objectives page). We brought along several speleothem samples to show annual banding and the different forms a speleothem can take.
We were delighted to have the mayor greet us and sat down with him to discuss future caving expeditions in the region. We enjoyed some lunch with the teachers (Siberian school dinners were certainly an improvement on what I used to eat in suburban north London) and discussed ways we might get the children involved in our work, potentially taking temperature readings, or even cave samples which we could use in our research. It was a great day, and we hope it’s the start of an ongoing collaboration. No doubt we’ll be seeing them online over the next few months, and hopefully, in person for our next visit.
21 February 2022
We’re back! We split up into two teams for the last few days to make the most of our limited time in Russia. Jade and Seb travelled to Argarakan Cave, around ten hours northeast of Irkutsk, whilst Julia and I (Stuart) drew the short straw – we had the very difficult task of travelling to the spa town of Arshan.
Arshan is in the Buryatia region of Russia, deep in southern Siberia where the Mongolian influence permeates. Our friend Slava, an independent filmmaker who’s worked with us on previous expeditions, and his daughter Inna escorted us around, stopping of at several Buddhist temples for us to admire. The forested hills soon opened up to an incredible rift system with the highway running through flat plains with picturesque mountains and extinct volcanoes far off in the distance.
It wasn’t all sightseeing and spa treatments; our task was to make use of Arshan’s hot spring around which a booming tourist industry has developed offering hot water treatments. We were looking for calcium carbonate precipitated underwater, at constant temperatures. If we know the temperature at which the carbonate forms, we can use it as a laboratory standard – a ‘known’ temperature point against which we can compare our unknown measurements. In a spa, what scientists call carbonate precipitate, you might call limescale – it’s the chalky stuff that builds up every day on your taps. But because we know the temperature of the thermal spring is constant, this particular limescale makes a particularly good standard.
Our spa gave us just ten minutes to soak ourselves in the ‘healing’ spring water. Instead, we shut the door and got to work chipping off carbonate from the pipework with a knife. The spa attendant looked a little confused to find us dry and her baths a little cleaner after our session. But no further questions were asked… I guess nobody wants to antagonise the strange Europeans that bring their knives and sampling bags to the spa. We collected two further samples from a spa outlet (pictured below) and public fountain, each of which had different, but constant temperatures.
Jade and Seb had a much harder job. They were picked up by our colleagues at Speleoclub Arabika in the frankly awesome truck you can see in the photos below. Whilst it looks cool, I’m assured it wasn’t all fun. Seb and Jade endured several break downs, including a frozen diesel tank, which had to be thawed with a fire underneath. Coming from a country that grinds to a halt after a few inches of snow, I’m in awe of the Siberian ability not to let any amount of cold faze them. The truck eventually made it to Argarakan and served as home for two nights with everyone bunking together in the back.
It’s important for us to sample as many caves in the region as possible as this allows us to build up a picture of spatial variations in palaeo-permafrost extent and sample different time periods that might not have been available at a single cave. Argarakan is a very different beast to Botovskaya. Entering the cave requires a ten metre abseil into the abyss below, where it opens to several chambers on different levels, transcending up to 90 metres in depth.
The hunt was on for more carbonate samples and opportunities to set up monitoring equipment to measure temperature and environmental conditions. Such monitoring will help us interpret our palaeoclimatic measurements back in the lab. Jade and Seb bagged lots of cryocarbonate samples – calcium carbonate that rapidly precipitates out of water when it freezes or melts. If we can date these samples, we will know the exact timing of the onset/end of sub-zero conditions in the region. We also obtained several flowstones, and a stalagmite which we can use to infer palaeo-environmental conditions. But we were careful not to take too much – it’s important to ensure that the material contains enough Uranium to obtain reliable formation dates – and we won’t know this until we can get it back to the lab. If it proves fruitful, we know there’s plenty of great material still to collect at Argarakan.
15 February 2022
We’re back from the field after an incredible ten days of science and adventure. We left Irkutsk early on 5th February and travelled in convoy along the dark Siberian highways. The impact of thawing permafrost could already be felt as road subsidence gave us a bumpy ride most of the way. We scraped the frost off the inside of the windows with our credit cards to catch fleeting glimpses of the vast Siberian plains, covered in undisturbed white snow and taiga forest.
By the evening we’d reached Konozhanova (pop. 11) and were enthusiastically welcomed into the homes of our hosts for the night, Lyosha, Sveta and Katya. Life in this part of the world was different to anything we’ve experienced before. No running water or wifi. Yet the traditional wooden Siberian homes were cosy enough and we were treated to an immense spread of local delicacies, each one derived from home grown, or hunted food.
The following day we made our way to Botovskaya, a 10 km drive atop the frozen Lena River before unloading our equipment and beginning the 5 km trek through deep snow to the Botovskaya base camp. It’s exhausting work and this author quickly realised he should have spent a bit more time in the gym instead of putting on some extra ‘insulating’ body mass in the final weeks before he left Newcastle.
The camp consists of two sleeping huts with fireplaces and dining tables, as well as a traditional Russian Banya, or sauna, in which we can wash and relax. The huts were originally built by Siberian berry foragers who would use them as a base to explore the nearby taiga forest. They were abandoned some time in the 1990s and adopted some 20 years ago by our colleagues at Speleoclub Arabika who have worked tirelessly to turn them into warm, comfortable accommodation that would be our home for the next eight days.
After a day setting up camp, collecting firewood and water from the nearby Botovskaya river, the science began! The cave was still a 3 km hike from the base camp up a steep slope in dense snow – tiring work but worth the effort once we saw what awaited us! Botovskaya is a sprawling 70 km maze of tunnels, often only 40 – 50 cm tall so that you need to crawl through the thick mud that has settled in the base of the cave. Our Russian guides are the experts and safety is the priority at all times. These guys know the cave inside out and seem to move over boulders and through tunnels with unimaginable ease. I’m grateful for their patience waiting for five slow moving European scientists fumbling along behind!
We are targeting carbonate, water, and sediment samples. Carbonates, like stalagmites and stalactites, have long been used in palaeoclimate studies to infer records of historical environmental conditions. But our expedition is uniquely targeting subaqueous samples – geodes, cave pearls (carbonates grown in pool waters), and pool rims which are particularly well suited to deriving formation temperatures through a technique called clumped isotopes. We know these carbonates can only form when the permafrost above the cave thaws (since liquid water is required), and understanding the temperature at which this happens can help us better predict when permafrost may thaw in the future.
We also collect dripwater and pool water samples from which our carbonates precipitate. When we get these back to the lab, we can measure their isotopic composition, monitor how these change throughout the cave, and use it to help us interpret the isotopic signatures of our carbonates. Finally, we collect sediment samples from the floor of the cave. We will analyse these for organic signatures which might give clues as to the type of vegetation above the cave when the sediment was deposited, or the number of wildfires going back in time.
Jade, ISOPERM’s PhD student, got sent on a special mission to install an autosampler. This homemade piece of equipment collects water samples over a set timeframe so that we can monitor how the composition of cave dripwaters changes over time. This can help us interpret the isotopic records of our carbonate samples which form from the dripwaters. Our Speleoclub Arabika colleagues knew just the spot to install the autosampler – where drip rates were unusually high. Yet to get there, Jade had to spend two nights in the cave, sleeping in an underground camp. An amazing adventure considering Botovskaya was her first time inside a cave!
We now find ourselves back in Irkutsk, recouping after an exhausting ten days on the road. The next few days will be spent cataloguing our samples and making plans for our next excursion. We’ll keep you posted as things develop!
5 February 2022
An unexpected delay due to an unavailable vehicle gave us an extra day in Irkutsk and an opportunity for some last-minute preparations such as buying snow boots and prepping carbon dioxide loggers. We were also treated to a guided tour of Irkutsk University’s brilliant geological museum which had some stunning examples of local mineralogy. As you can see from the photos below, team member Jade was particularly enamoured with an enormous sample of… jade.
The evening was spent exploring Irkutsk – it’s a charming, prosperous, city. After some fun seeing ice sculptures (including an ice playground for kids!) we sampled the local cuisine. If you ever find yourself in Siberia, you must try buza – a meat filled dumpling, sort of like an extra filling dim sum.
Now it’s 6am and we’re about to set off for the village of Konozhanovo (pop 13) where we’ll stop for the night. Then it’s finally on to Botovskaya Cave for a week or two in a wooden hut and some fun sample collecting. We’ll update you again upon our return!
2 February 2022
We’ve made it to Siberia! We left Newcastle on February 1st and travelled for 17 hours, stopping at Amsterdam, where we picked up our colleague Julia Homann from the university of Mainz, then onto Moscow. Our PI Seb, always keen to promote our work, managed to brief the flight attendants on our project before we’d even taken off. In exchange for their newly acquired expertise in permafrost, they kindly gave us a send off with a few bottles of wine and snack – A great start!
A long layover in Moscow enjoying the world’s most expensive beer was followed by a five hour flight before finally arriving in Irkutsk in eastern Siberia. We received a warm welcome from Tobias Braun from the Potsdam Institute for Climate Impact Research, and our long-term Russian collaborators Sasha Osintsev and Sasha Kononov from Speleoclub Arabika.
We’ve spent our first day in Irkutsk recouping. For most of us it’s our first experience of life at -20 oC but aside from a few slips on the ice, we’re coping pretty well. Fun discoveries include crab flavoured Tuc biscuits and cechil – a smoky hard string cheese that’s divided opinion in our team. This author is a fan!
Our first stop is Botovskaya Cave, a sprawling system of subterranean corridors stretching over 70 km. We’re looking for calcium carbonate samples called speleothems that have formed over centuries, or millenia, and store a record of the environmental conditions under which they formed. In particular, we’re looking for slow forming, subaqueous samples such as geodes, pool rims, and cave peals that are particularly well suited for use in deducing palaeotemperatures using an analysis techniques called clumped isotopes. We’ll be setting up monitoring equipment that will give us ongoing temperature and carbon dioxide concentration measurements that we can use to interpret our speleothem measurements. Additional soil and dripwater samples will be collected to help interpret historical records of vegetation, wildfire, and hydrology. For an introduction to the science behind our trip, check out the scientific objectives page of the website.