Thursday, July 23, 2009

Oncolite Rudstone from the "Mumienbank"

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I am not getting ahead fast with my diploma mapping report and it keeps being a pain in the...well, you can imagine - a lot of headache. So there isn't much around that I have time or nervs to make some serious posting about. For your entertainment I decided to share another polished slab I made that will be part of my report. It is a piece of the "Mumienbank" - an oncolitic Rudstone from the Jurassic limestones that I am working on. You can observe some lovely oncolites, nucleus and laminae intact, bored and re-filled, some deformation on the grain contacts that are partially filled with some iron minerals (the black stuff) - guess haematite or stuff. Didn't yet have time to look at it with a binocular or microscope but the black stuff is actually quite shiny in the sun.


Oncolite Rudstone of the "Mumienbank"

Friday, July 10, 2009

Flowstone, cut and polished

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Another of the samples I cut and polished: This flowstone originates from an exposed karst cavity. The sample is taken from the floor of the former cave that is now infilled with flowstone and other sediments. These deposits form where water flows over rock walls or floors. Looks pretty cool, no?


Flowstone deposit. Upside is down.

Thursday, July 9, 2009

Two polished carbonate slabs

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There is no time to write great posts these days because of my continued work on my diploma mapping report. Though I can share some stuff. Today I cut and polished a number of samples to enhance the illustration of my report. I didn't manage to polish them all but a few samples are done and I want to share two of the more spectacular ones.

First, I cut and polished a sample I already discussed here. Back then I thought it to be a carbonate tempestive with an erosive base. Right now I am not that sure. Either way the cement is entirely sparitic from the shells upward. Below one can also find micritic and sparitic cement. Very few ooids are cut and truncated by shells. So maybe it is still a storm layer or a very proximal debris flow of carbonate sand. You can find a wild mixture of grains from shells, snails, foraminifera even, ooids, coated grains, aggregate grains, etc.


Event layer? The upside is up in the image.

Second is a cut sample of an oncoid bed that I also discussed earlier. These wonderful and easy to recognise oncoids show a great, irregular laminae, one as a gastropod as a nucleus and two of them are obviously bored with internal boring sediment. I am not so sure how to interpret the contacts between the oncoids. First I thought them to be slightly deformed by each other. Meaning they would have been still soft enough for that to happen. Some partial laminae seem to have broken off. But then some contacts look a little like pressure solution seams and the laminae are abrubtly truncated. The matrix is a carbonate mud with shells, snails and other stuff that I didn't bother to check out, yet.

(My excuses, I accidentally messed-up the scale. The scale in the oncoid image is suppossed to be 4 cm not 6 cm.)


Bored oncoids with snail nucleus

Monday, July 6, 2009

Finally some pages...

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I don't quite know what changed but today I finally managed to overcome my week-long writing blockade and succeeded in writing 3 and a half pages of outcrop descriptions. That's six outcrops described in detail - without images and rose diagramms, yet. Cross your fingers for me that I manage to keep up this daily routine and perhaps even increase it a little. Once I caught-up on my writing some good ideas to blog about will most likely return, too.

Thursday, July 2, 2009

Why it is so quiet here...

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Studying at an under-funded university that abandoned their department of economic geology just when I got here is highly unsatisfactory. Sadly changing places again is out of the option - I do not want to lose another semester or two or three. I don't even want to think of the financial problems that would come with that.

The recent lack of posting is somehow related to that. I am fighting with my motivation to get the diploma mapping report done. Gladly I do not have problems with the material itself but working without having any goal to work for is a fairly demotivating task. Unfortunately the only professor interested in and willing to help me with a thesis in economic geology (something with ore!) has no funds to work with. Remember we don't have a department anymore, thus no funds, no research, etc. I applied in the industry but only got two offers that are even worth considering as a thesis. None of them will bring me any closer to what I really want. Actually they'll be leading me right in the other direction. Limestones are nice and it's a resource but, well, where is my ore?

Please excuse the current lack of posting. It might continue for a while until I find something worthwhile to do.