Day 4…Microscope Eyes

November 12, 2009

Today was much like the past few days. My approach to learning Soil Micromorphology has been working so I stuck with it. I did make one minor modification though. Rather than pair slides with their relevant publication and go over the identified characteristics, I pulled out one of the best guides to Archaeological Soil Micromorphology, Soil and Micromorphology in Archaeology by Courty et al. 1989, and went through the major concepts while trying to locate evidence for each one in a number of slides. It was a bit frustrating but overall it went well. Not really the best approach unless you have slides that have already been analyzed and are supposed to have these features but it worked for me today and I recommend it.

The best part of this course is the enormous reference collection of thin sections that is at our disposal. After each topic is introduced, remember the two lectures a day program followed by hours of examining slides, we are introduced to another set of thin sections relevant to the topic. That means every half of day the slides we can look at grows and grows. Now that I am feeling a bit more confident in my approach to soil micromorphology I have realized just how valuable this experience truly is. The only unfortunate part is I wish I had more time to look through all of these things and really thoroughly study each topic in detail. A week doesn’t really lend itself to that however.

Today we were introduced to two more topics. We shifted into more rural habitation and looked at occupation surfaces, such things as constructed living floors like plaster, mortar, daub. This was the morning. In the afternoon we were treated to a lecture on the vague term Dark Earth. This type of sediment dates to the post-Roman period and is related to urban deposits that have been the medium in which soil has formed. As per the name it is very dark and visually diagnostic, often producing an extremely homogenized deposit. I won’t go into to too much detail but take a look at Dr Richard Macphail’s work if you’re interested in learning more. It is an extremely ubiquitous sediment type in London in particular and is an amazing example of how soil micromorphology can be applied to archaeological questions.

In addition to all this my eyes have begun to revolt to excessive use of a microscope. It may have something to do with a lack of sleep but I don’t have that luxury for another day so I am going to pretend it doesn’t exist.

Back tomorrow with Day 5 update, the final day of the training week.

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Day 3…Over the hump day

November 11, 2009

Today was another whirlwind adventure in Archaeological Soil Micromorphology. The morning was spent listening to a lecture on the evidence for non-intensive cultivation and the afternoon built on this with a discussion of the evidence for slightly more intensive agricultural practices, particularly heavy manuring, burning, and ploughing. The topics are fascinating but the microscopic evidence in thin sections is extremely complex.

In attempt to ease the complexity added by time and post-depositional forces we discussed numerous experimental examples first, specifically the Butser farm site and the Umeå site (see Goldberg and Macphail 2006). The Butser farm experiment is a reconstruction of an Iron Age village that was thoroughly tested for many things before, during, and after occupation. The researchers also burned some of the dwellings and studied the resultant impacts on the subsurface. The Umeå site is similar but specifically tested the impact of slash and burn agriculture and ploughing (plus some other things). These examples are invaluable. The reason being that all the evidence for human modification to the landscape during occupation is masked by everything that has happened since abandonment; the pesky post-depositional process like pedogenesis, bioturbation, erosion, re-occupation, etc, etc. Therefore, these experimental projects were the first step, allowing us to understand the immediate impacts before moving into numerous examples of manured, burned, ploughed, and trampled soils and sediments that have been buried for a couple thousand years. It all makes sense when you think about it but the tough part is recreating the history of a sediment or soil after I identify numerous features in the thin sections.

Yes, that’s right, the features I can now identify. By no means am I an expert or even an intermediate. I am still 100% a beginner, well maybe 99%. Nevertheless, I feel as though this Wednesday was the day when I overcame some imaginary hurdle (perhaps a hump) toward proficiency in soil micromorphology. I am able to compartmentalize the sample into the coarse and fine fraction, identify the primary mineral components like quartz, glauconite, feldspar, mica, etc., say something about the structure (the porosity, the sorting, the shape, and abundance, etc.). I learned how to identified shell, egg shell, bone, phytoliths, calcium oxalate spherulites, phosphate enriched soils, charcoal, and organic matter. I also saw a fungal spore but didn’t locate it myself, although I feel I could now.

Most of this learning is thanks to my great classmates. There are about 12 of us (give or take a couple) and today everyone opened up a bit, the atmosphere was a little more collegiate and it made a huge difference. Maybe it was the group outing to the pub yesterday….either way, everyone had something to offer, except for me now that i think about…let’s say I added the enthusiasm. We even had a short presentation on phytolith morphology. I now know what a banana phytolith looks like and know way more about the domestication of bananas than I ever imagined I would. Sorry, that isn’t true. I’ve never even thought of banana domestication until today. It has a very interesting and complex history goes back to Papua New Guinea about 6000 years ago. I don’t have a reference but this seems to line up generally with what was said today if you want some more general information.

Personally, I stuck to my same strategy as yesterday: pairing slides with their publications and reviewing basic identification concepts and locating the appropriate feature or component in a number of slides. I am almost finished with the major concepts so tomorrow afternoon I move onto systematic thin section description from start to finish. By tomorrow night I will know whether I did actually make it over the hump or am still teetering somewhere near the top…let’s just hope I fall forward if it’s the latter.

I ended the day with a tall dark Guinness and walked home with a some fish and chips wrapped in newsprint. Mmmm!

Back tomorrow with another update.

References:

Goldberg, P. and R. Macphail, 2006   Practical and Theoretical Geoarchaeology. Blackwell Publishing, Oxford.


And it Begins….Ever so Slowly

November 9, 2009

Hello to everyone from sunny old England. I arrived in London this past Saturday, the overnight flight from Ottawa of course, only to be treated to a quirky British tradition surrounding Guy Fawkes day. In a small, yet enormous by London’s standards, back yard I spent the evening watching people set off fireworks and stare into a bonfire in honour of the parliament not being blown up back in the day. There’s a lot of information out there on this so I won’t dwell on it.

Sunday might as well not have existed thanks to jet lag but I did catch up on sleep. This was a good thing because today was the first day of my Archaeological Soil Micromorphology course at the Institute of Archaeology at UCL. The course is focused on a technique that involves collecting intact sediment samples, embedding them in resin, slicing and dicing, sticking them to a glass slide, and finally grinding them down to 0.03mm thick before sticking them under a microscope for description and interpretation (includes both geological and archaeological sediments). I have been looking forward to this course for months, reading as much as I could and looking at as many images of thin sections as possible. I thought I was somewhat prepared…boy was I way off.

The course started with an introductory seminar, followed by 3 hours looking at reference thin sections under the microscope. Lunch break was great! I found a nice sandwich and bag of crisps (aka chips) for 3 pounds. Then the afternoon was a lecture on buried soils and the numerous taphonomic factors that act upon them. This included marine water fluctuations and the resulting cycle of pyrite formation and oxidation, as well as other things like the velocity of deposition in flash floods and the sorting patterns produced. This lecture was again followed by a few hours of browsing reference samples under the microscope.

Today’s class was not overly uplifting. The lectures were great, the concepts all make sense and the interpretation that follow are somewhat satisfying. Even the basic principles of deposition, soil formation, and post-depositional alterations all fit nicely into my head. My biggest stepping stone is understanding the identification process. How do I know which minerals are quartz, pyrite, tourmaline, muscovite, etc. from clay, shell, bone, flint, and ash fragments.  Coming from a purely archaeology side of things (specifically North American archaeology rooted in an Anthropology department) my optical mineralogy, and mineral crystallography are a little weak…if not non-existent. So, some pretty major hurdles and there was quite a bit of frustration today but at least I know what I need to learn. To me, that’s a pretty good first day. I already know what I need to get out of this 2-week course.

So after 6 hours with the microscope today and a couple more reading, the screen is starting to go a bit blurry. It’s time for me to stop and do some more reading on birefringence. I’ll be back tomorrow night with some updates on the course and my progress.

 

 


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