Devil's Bridge is a place of much lore and history. The bridge crosses the River Lune, it's 3 arches harking back to Medieval times. The Devil has rumoured to have had dealings here, with the fabled story of the Old woman and her dealings with the Devil.ย ย
It is a busy place, though the bulk of folk stay up by the bridge. This EarthCache takes us to the limestone rocks which are upstream from the bridge.ย
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๐จIf the river is running high, or in spate DO NOT ATTEMPT THE EARTHCACHE.๐จ
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๐จ The limestone can be slippy when wet. ๐จ
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๐จYou may get wet feet๐จ
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๐คย The geology of the location.ย
The River Lune runs under the bridge, with its origins high in the Howgills. It drains a vast area, with a lot of geology, and in places that geology can be seen in clear view. This is one of those locations. You cannot help but notice the mass of tilted rocks which lie under and around the area of the bridge. This is limestone, part of the Urswick Formation Limestone, which was deposited during the Asbian Substage. This geological period was part of the Visean Stsge of the Carboniferous Period. It is between 337 and 330.9 million years old.
๐คย What is limestone?
Limestone is a sedimentary rock, this means its origins were sediment deposited in layers. The sediment was lime mud , and the shells of ancient sea creatures. Over time these layers were compacted, and rock was formed which is limestone. In the case of Urswick Formation Limestone, the sediment was deposited in a shallow marine environment. Limestone is formed of calcium carbonate.ย ย
๐คย What are we here to look at?
We are here to look for fossils, though these are rather small, indeed you will probably first look at the rock, and think what is Hillgorilla on about.ย
To get the best out of this EarthCache:
๐ฃ You will get wet feet.
๐ชจ Go to the end of the rock.
๐ฆ Wet the end of the rock.
๐ Then look.ย
๐ท Taking a few photographs will help, as you can then zoom in on what you can see.ย
๐ชAlternatively, sit on the rock, though leave the end unobstructed.ย ย
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The view from near the EarthCache location.ย
The rock that you need to look at.
๐คย What are fossils?
Well these are the preserved remains of plants, animals or traces of activity, that have been preserved in the stone. With limestone being formed from marine sediment, there are often fossils to be seen.ย ย
๐คย What are we here to look at?
We are here to look at Foraminifera fossils. Everyone talks about limestone being formed from the accumulation of the shells of ancient sea creatures, but these are rarely discussed, especially in the world of EarthCaches.ย Foraminifera, are a group of single celled organisms, known as protists, that had a shell. The shells were made of calcite, and this is what is preserved. They either lived in the sea, floating about, or lived on the sea floor. Though, they generally lived inย marine and brackish environments, so shallow marine conditions.ย The majority of Foraminifera were benthic, meaning they lived in amongst the bottom of the sea, near the sea bed.ย
They are important, as they formed a crucial part of the food chain in the marine environment. They are alike to modern day plankton. There are different types of Foraminifera, and this EarthCache just gives an insight into them. They are small, very small ๐ค๐ค๐ค๐ค.Though being small is important, they are one of the building blocks of limestone, as if you look closely you can often see Foraminifera in many limestones.ย ย
๐คย Types of Foraminifera.
SET A.
SET B.
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SET C.
SET D.
(Plates from ATHERSUCH & STRANK, 1989).
๐ This being an EarthCache, in order to log it, I ask that you answer some questions. Please send them to me, and do not include them in your log. You can send them to me by using the message facility or email, both of which can be found by looking at my profile.
1. Please describe the distribution of the Foraminifera fossils across the end of this rock.
2. Please describe the shapes.
3. Referring to the above plates, what types do you think you can see?ย
4. What part of the marine environment would you say this bit of limestone is from? What is your rationale for this answer?
References.
Athersuch, J. and Strank, A.R.E.(1989).Foraminifera and Ostracods from the Dinantian Woodbine Shale and Urswick Limestone.ย ย J. micropalaeontol., 8( 1) : 9-21, June 1989