May 16, 2009

My Third Field Trip Part 3

In part 3, I finally show you something about an outcrop I really know about. It's located close to a small village called Neuerode north of Eschwege, Hesse. We spent one and a half days at this outcrop called "Grillhütte Neuerode". Grillhütte means barbecue cottage.

The outcrop is an old limestone quarry (like so many we saw at our field trip). Even though it was our choice to work at this one, we were a bit desperate at first glance because it looked just like a grey limestone wall. So we ( 'we' actually means our prof) decided to work with a bioturbation index. The dominant facies (80% of the outcrop) is an alternating sequence of grey, poorly up to moderately bioturbated, sometimes sinusoidally deformed marly mudstones and marlstones. Every now and then, there are thin tempestite layers - grey oo-grainstones with some bivalve fragments but of course without any bioturbation - which sometimes appear in association with hardgrounds at the basement. Moreover, we recorded one yellowish bio-floatstone band which possibly stands for another tempest event but a different source area .

This picture is a combination of four merged outcrop photos and my artwork skills. Sometimes, I'm too much into all this graphic stuff but I think that it actually looks pretty nice. The tempestites are shown as grey bands. All in all, we recorded nine of them.

Here you can see what those oo-grainstones of the tempestite layers look like. There even is a bivalve fragment right in the middle of the photo. But, to be honest, it's still a bit boring. The only interesting thing about this outcrop is to combine all the observations so that one gets a comprehensive idea of what the depositional system looked like. Actually, this should be the aim of most work on the stratigraphic record, shouldn't it?

The freestone of the tempestite layers was quarried at three levels. At the base of the second level we found the sedimentary structures shown in the photo. We identified them as Hummocky cross stratification. Together with many other observations, the Hummocky cross stratification helps to reason that the depositional system was a tempest-affected mid continental shelf.

3 comments:

Lost Geologist said...

What programm did you use to stich together the fotos of the outcrop? I remember you told me but I forgot.

Maple Leaf said...

I used GIMP 2.0. There might be better options but it actually was quite easy, just a bit scaling and rotating.

effjot said...

For more complicated stitching, you could use the free software Hugin (based on panotools). Works great with Linux (I didn't test Windows and Mac), and you can export the transformed images as separate layers to the Gimp, if you want.