This area overlooks Ribblehead viaduct, and towards Ingleborough. It is a wild area, rough underfoot, but demonstrates a good example of limestone bedding.
So, the grey rock you can see is known as limestone. It is formed of calcium carbonate, and was once something much different, and in a different environment. Imagine a tropical sea, and over time lime mud and the shells of dead sea creatures settles to the bottom of the sea. This is known as sediment, and over time it builds up thickness. Imagine the dust in your house, at first it is a very thin layer, but over time it gets thicker.
Now, as the sediment built up, it developed sedimentary layers. Over time, the sedimentary layers got compacted by overlying layers, and in doing this they lithified, and eventually limestone was formed.
Now, geology has certain words for certain features.
BEDS.
These are the different layers of sedimentary rock, in this case limestone.
BEDDING PLANES.
These are the horizontal definitions between different beds. They can represent a change in deposited sedimentary rocks or a pause or slowing down of sedimentation.
INTERBEDDING.
This is when one rock type intermingles with another.
INTERCALATION.
This occurs when a different rock type is invetween different rock types, which indicates a change in depositional environment.
When we talk about deposition, there is a question, actually how quickly did all this limestone get laid down? In the modern world, we can see buildings and structures erected quickly in terms of weeks and months, but geology takes a rather slower pace. First, the geological periods are millions of years ago, you are really in an very old and ancient place. Then there is the question about at what rate limestone, or rather the sediment was laid down.
First of all, it depends on the environment at the time. Areas which are near the coast, such as intertidal lagoons, and areas which have a shallower depth where there is more lifeforms, have been said to have a quicker rate of limestone deposition, compared with the deep ocean, where there is less sediment being laid down. There have been theories about at what rate limestone is deposited, with some saying a rate of 1 to 5mm per 1000 years, but more recently it is suggested that a rate of 1.9mm per 1000 years. Now, that does not seem a lot, but in order for the sediment to be compacted and lithified into rock takes time.
When we describe limestone, we tend to associate it with deposition of dead sea creatures, and thus fossils should be present we think. Though at times, it might just be accumulation of lime mud, or the immense pressures involved in the compaction and lithification of the sediment into limestone, can mean that some areas of limestone have few or no apparent fossils. The area of Malham Cove, and the limestone pavement there is a prime example, you will struggle to find a fossil there, but go north to Littondale or Upper Wharfedale, and there are oodles of them.
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. How many beds of limestone can you see here?
2. How thick is the bottom bed? Using the above information, please calculate how many of thousands of years it would have taken to form.
3. How is the top bed different from the others?
5. Looking at the beds, can you see any apparent fossils?
6. Please have your photograph taken, or that of your device pointing towards Penyghent.