GeologyRocksRock Presentation
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Not sure if you have
Thu, 11/15/2012 - 10:13Not sure if you have visited/ are visiting these sites, or if it is just a presentation. So you will need to make up your own mind on how valid my comments are. I've never done any geology around Stirling.
Taking them in order.
Picture 1 Not enough showing to confirm a U shaped valley. Any glacial striations? Any morraines? Terminal, medial, side? Unlikely chalk would have survived an ice sheet sliding over it. It would have been eroded by the water and plucked by the ice.
Picture 2 - could this be blue schiest? Really the photo isn't clear enough to tell, so 'blue' may be your interpretation, whereas it may just be weathering.
picture 3 - it could be a conglomerate, but it could be a terminal morraine - (poorly sorted, angular). In that case the matrix would be glacial till (rock flour), clay etc. Could it be a lahar? Again, that would be poorly sorted and angular.
I think you probably need to do a little more field work with these ideas and an open mind.
John
“Civilisation exists by geological consent, subject to change without notice.” - Will Durant
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Mon, 11/19/2012 - 09:29picture 3 - it could be a conglomerate, but it could be a terminal morraine - (poorly sorted, angular). In that case the matrix would be glacial till (rock flour), clay etc. Could it be a lahar? Again, that would be poorly sorted and angular.
Sorry for my bad english ...I'm french
hello, I don't think taht it could be a terminal moraine, clasts are too rounded and the rocks seems to be cimented and not so loose.
So we can distinguished some rounded clasts, some are not rounded, generally poorly sorted." . I think it is a conglomerate build by some fluvial and partly torrential debris flow, it could be a "fanglomerate facies"
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Thank you very much for your
Mon, 11/19/2012 - 09:47Thank you very much for your replies guys.
Ive actually broken down my presentation now and am focusing on the rock shown in picture three at the moment. Going back up to the site today to take another look.
Quaternary, I was leaning towards an alluvial deposition. I understand a fanglomerate is conglomerate rock that was created by an alluvial fan? Would that be accurate?
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Tue, 11/20/2012 - 06:56.
Quaternary, I was leaning towards an alluvial deposition. I understand a fanglomerate is conglomerate rock that was created by an alluvial fan? Would that be accurate?
Yes, it is. I don't think think that is is purely alluvial because some of the clasts seems to be angulous and taht it is poorely sorted, but don't forget that I am not in front ouf the outcrop. So it is up to you to evaluate the shape of the clasts. If 99% are rounded, it is a purely fluvial transport system. If some are angulous, it measns that there is some pebbles coming from "lateral" parts of the global system. It is hard for me to explain in enfglish sorry.
I wonder if the alluvial fan facies is not covering a more fluvial sequence (below the conglomerate) belonging tio the principal paleovalley of o braided river system.
Have a look there: http://www.usouthal.edu/geology/haywick/GY402/402-pp14.pdf
Last thing, alluvial fan can also be classify as a kind of fluvial sedimentological archive. So you are not wrong if you say that it is fluvial, you can just highlight that probably it was an alluvial fan.
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Rock Presentation
Submitted by Danielsan on Wed, 11/14/2012 - 19:34.Hi guys,
Hope im posting on the correct section, apologies if not. I have a six minutes presentation on a Devonian rock exposure located in Stirling, Scotland. Just started this class and struggling a bit so just hoping to ask some questions and any help would be greatly appreciated. Im going to post some pictures too, Ill try get the best quality ones up. I have more if that would help but dont want to post too many to start. Thanks for any help.
Rock exposure. Possibly created by glacier? Bottoms also a lot smoother and appears to have some chalky bedding planes. Any help on possible formation would be great.
Any idea as to what the blue tinge in this rock could possibly be? Tried researching this but found nothing.
Varied sizes of poorly sorted clasts. Thinking conglomerate so the matrix would be some sort of sandstone? Higher up there appeared to be some basalt rocks?