17 January, 2008

Six thin sections, a day of work and a lot of patience...

That's what it took to make the fotos for my seminar paper I am working on and that's also what it took to make me wonder if I am halucinating or indeed seeing something that is not just plain dirt again and at the end, that's what it will take to perhaps prove something previously unknown - or perhaps it will all have been a lot of wasted time of driving, taking samples in the snow, cutting them, grinding them, glueing them and bothering half the faculty to please, please give me a decent microscope.

Today I was fortunate enough to have some time with the best microscope I could get my hands on including a digital camera firmly installed with it.


But what is this all about? Last year during my last field mapping in the Erzgebirge with my previous university we discovered some pieces of "black shales" or bituminous clay slate, highly deformed but undescribed, actually unknown to even the local geologist. They somehow got stuck in my mind and now there was the chance to take a closer look at them. I had some clues there might be acritarchs inside. Maybe from the Carboniferous, maybe from the Ordovician or Cambrian. There indeed are a lot of organic leftovers, however, it soon became clear actually finding something that still resembles what it used to would require a lot of patience.

I uploaded the two images that turned out best. I used a normal polarisation microscope from Leica. Images were taken at a magnification of 63x. As you may see the thin sections aren't the best but that is the best you get if you don't want to pay.

I encircled what remotely resembles an acritarch (or perhaps chitinozoa). Their size might fit. The flask-shaped sacs resemble my literature. Carboniferous would be a bit on the edge but possible and the age of the black shales is still undetermined. Here is another one.

Using a normal thin section and microscope for searching these kinds of microfossils isn't exactly standard procedure. However, if you have no funds and nothing better to do it does seem to work. That is if I am not halucinating and seeing shapes that don't exist. As you can imagine I will be digging the literature even more now to find sources about palaezoic acritarchs and chitinozoa.


GeologyJoe said...

I would check the slide with a hand lens to make sure they are not air bubbles or a hole in the thinned sample.

The Lost Geologist said...

I did. Those are definitly not bubbles or holes. I had a lot of bubbles in some thin sections and holes, too, they are seperable. I had some holes with only resin in it though. The resin is the same refraction index like quartz and I was pretty perplex why the quartz was full of scratches till I realised what it was. I am more worried of mistaking some oddly shaped pieces of organic goo or clay minerals for microfossils. Considering the significant deformation and metamorphism of these rocks they are extremely hard to distinguish.