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. 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
๐จIf the river is running high, or in spate DO NOT ATTEMPT THE EARTHCACHE.๐จ
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ย ๐จ The limestone can be slippy when wet. ๐จ
๐จYou may get wet feet.๐จ
The below photographs show where you need to look.ย
๐ค The geology of the location.
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. The limestone was deposited in a shallow tropical sea, though with varying depths at times.ย It was also full of marine life, and whilst it was millions of years ago, it is still possible to see fossils which show what the lifeforms were like. Now, fossils are the preserved remains of plants and animals, but these tend just to show a structure such as a shell, bone or part of a tree.ย
Take a minute to look where you have stood, if it is in the sandy river sediment, you will be able to see your footprint.ย This is evidence of you being there, and also your locomotion.ย There is a type of fossil known an ichnofossil.ย ย
๐คย What is an Ichnofossil?
An ichnofossil is aย trace of a biological activity, preserved in the form of a geological record. They are also known as trace fossils, and thus show a trace of an impression made on the substrate, and can be root cavities, burrows,ย feeding marks, footprints, and remains of excretia, such as fossilized droppings.
๐คย Bioturbation.ย
Here there is evidence of bioturbation. We imagine that when sediment is deposited, it just forms layers, and eventually limestone is formed.ย Though a marine environment is not just the lifeforms in the water, there is also animals living on and in the sediment itself.ย These animals included shellfish, worms, crabs and prawns. In the process of moving about, and firming burrows, they bioturbated the sediment.ย Basically it was moved about by their actions. The ichnofossil here is evidence of bioturbation occuring. The specific ichnofossil type is a burrow, but what type of burrow?
๐คย Types of burrows.ย
โก๏ธ Domichnia burrows.
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โก๏ธ Thalassinoides burrows.
โก๏ธย Chondrites burrows.ย
๐This 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.
1. Please look at the specific rock. What type of ichnofossil burrows are there here?
2. Amongst the burrows is another fossil, it's bear the upper centre, please describe it.
3. This rock has evidence of bioturbation on it, but some other limestone rocks don't.ย Why do you think this is?