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
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 downstream from the bridge.ย
๐จIf the river is running high, or in spate DO NOT ATTEMPT THE EARTHCACHE.๐จ
๐จ The limestone can be slippy when wet.ย ๐จ
๐จYou may get wet feet๐จ
ย
THE TERRAIN RATING REFLECTS THAT YOU MAY GET WET FEET, AND ALSO THE INCLINED NATUREย OF THAT LOCATION.ย
๐คThe geology of the location.ย
The River Lune runs under the bridge, with its origins high in the Howgills. It drains aย vast area, with a lot of geology, and in places that geology can be seen in clear view. This is one of those locations.ย 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 Asbianย Substage. This geological period was part of the Visean Stsge of the Carboniferous Period.ย It is between 337 and 330.9 million years old.ย
๐คย What is limestone?
Limestone is a sedimentary rock, thus means its origins were sediment deposited in layers. The sediment was lime mud , and the shells of ancient sea creatures.ย Over time these layers were compacted, and rock was formed which is limestone.ย In the case of Urswick Formation Limestone, the sediment was deposited in a shallow marine environment.ย Limestone is formed of calcium carbonate.ย ย
๐คย So, what are we here to look at?
The two photographs show where to look. We are here to look at a type of fossil, namely a Rugosa coral fossil.ย ย
๐คย What is a fossil?
It is the preserved trace of an animal, plant or evidence of activity which is now part of the rock.ย Fossils can help us understand the environmental conditions at the time the sediment forming the rock was deposited, and give us a windiw into our geological past. They can be formed in various ways.
๐คย How are fossils formed?
โฌ Replacement and permineralisation.
When an organism dies, and it is buried by sediment, which then compacts over time into rock, a process called replacement and perimineralisation can occur. Basically during the process of compaction of sediment, there can be immense pressures at force, this along seepage of water through the rock, can transform any remains into the rock, so the fossil actually becomes part of the rock, such as calcium carbonate with limestone.ย
โฌ Burial.
A dead animal, piece of wood or plant can become quickly covered in sediment, over time this sediment increases, fills the void left by the decomposing organism, compaction occurs and basically a trace remains which becomes part of the surrounding rock. At times the void left by the decomposed animal can be filled by Calcite. Also, a fossil can form if an organism is very quickly covered by sediment, which then causes it to die, but it is preserved as a fossil.
๐คย What are Rugosa coral fossils?
Coral was, and still is a marine animal, living in a tropical sea. There are different types of fossil coral, colonial and solitary. Colonial means lots of corals lived clustered together, whilst solitary means by themselves.ย We are here to look at an example of solitary coral. This type of coral was known as a Rugosa coral, which is now extinct. Now Rugosa, is the name for the type of coral, and there are many types. This is a horn coral.ย
๐คย Horn corals.
These were solitary corals, a coral is basically an animal that lives with a structure formed of calciteย The animal was known as a polyp, snd it lived within a calyx. They were carnivorous, and had tentacles to capture their prey. The tentacles are not preserved, but it is possible at times to see structures in the fossil.ย ย
๐ This being an EarthCache, in order to log it, I ask that you complete the aboveย tasks. Please send the answersย 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. This is a simple EarthCache.ย
1. Please look at the fossils indicated in both locations.ย Please describe their shape, and any specific structures you notice.ย
2. What process of fossilization has occured here?
3. What type of rock is it, and how was it formed?
4. Why will you find this type of fossil in this type of rock?
ย