The tephras Britta finds are all beyond the range of radiocarbon dating (up to ~60,000 years ago), and too young for the next isotopic dating range. That's why there's so much work to be done in this time period - different methods of dating have to be found. A popular one is fission-track dating, but for most volcanic ash this old the individual shards are too degraded for it to work too well. So Britta's been trying out something different - paleomagnestism. Many materials, on being laid down or cooled in the case of volcanic rocks, retain a memory of the direction of North. North is not a constant, the poles wander, sometimes all the way to the tropics, and sometimes they switch altogether. Humans have never lived through a switch, and we don't really know what happens to the inhabitants of planet Earth, but so far there's no evidence of mass extinctions associated with them.
Anyway, some materials fare better with fission-track dating than do volcanic ash shards, like lava. Lava can be dated well, and preserves paleomagnetism, so that the wanderings of the poles can be tracked over time when lava is out-poured continuously (e.g. as on Hawaii). If we can match those precise wanderings in our loess bluffs, we can date every tephra within them, simple!
Except of course it's not that simple. Loess is a tricky substance, meaning that in order to pick up these polar movements we have to take a sample every 5 cm. A sample that has to be the right way up. A sample that has to have it's declination from North recorded. A sample that is essentially compacted dust, and where all the particles have to stay in the same relative position until analysed back in the lab. So over the next week we took over 15 metres of these samples, until Britta got tendinitis from hammering and I couldn't distinguish between counting in 5 cm intervals and simple numbering of samples.
And that's not even the worst of it. That 15 m, with some overlaps, totalled over 400 samples. The machine in our university processes 8 samples a day. Per day! At that rate, those samples will never get processed (unless of course Britta really does intend on working on this for the rest of her life).
What's the solution? Well, did you know that as a scientist you have to be a charmer? A manipulator? Whether it's writing a grant proposal or requesting information from a surly scientist, you have to know how to get want you want. Britta is an excellent mentor when learning this fine art; charismatic and skilled in seeking out the right people to provide her with what she needs. For this particular problem, Britta has already scoped out two potential victims whose better-prepared labs she can commandeer to analyse these samples in a fraction of the time. I sure hope one of them works out, or else all those hours are wasted!
After one long day we stopped off, dusty and dirty, in a local pub that wouldn't mind the state of us; Skinny Dicks. Exactly as rude as it sounds, Skinny Dicks was a fun pub, and after the landlady had showed us a few of her more special treasures (including a couple of walking sticks you wouldn't want to lean on) she asked us what we do. Britta confidently said 'I'm a geologist'. I never really considered myself to be a geologist, but I suppose I am. In fact, I started my undergrad degree in geology, then changed to 'environmental geoscience', and had a year abroad in which I studied 'Earth science', and finally here I am in Alberta doing a Masters in 'Earth and atmospheric science'. And whenever anyone asks me, I somehow always feel the need to explain all that, when really, what they would understand the most is 'geologist'. And hey, I study volcanic ash, and what's more geological than volcanoes?
Later that evening, I got chatting to a couple of women in the laundry room at the campsite. They asked me if we were holidaying there. 'No,' I said self-assuredly, 'we're geologists, doing some research up here.'
Sure, I may be changing discipline, but I may as well enjoy it while I can!
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