This EarthCache is up on Smearsett Scar, one of the wonders of the Dales. It is a great viewpoint, though BE CAREFUL, THERE ARE CLIFFS very close by.
We are here to look at the rock that makes up the top of the Scar. It is limestone, which is a sedimenatry rock.
So what is limestone?
Limestone is a sedimentary rock. Sedimentary rocks are types of rock that are formed by the deposition and subsequent cementation of that material at the earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle in place. The particles that form a sedimentary rock by accumulating are called sediment. Before being deposited, the sediment was formed by weathering and erosion from the source area, and then transported to the place of deposition by water, wind, ice, mass movement or glaciers. Sedimentation may also occur as minerals precipitate from water solution or shells of aquatic creatures settle out of suspension.
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate. Most limestone is composed of skeletal fragments of marine organisms.
Layers of limestone at Kinsey Cave, Giggleswick.
Now the limestones in this part of the Dales, can be seperated into a classification. In this part of the Yorkshire Dales, the tops of the mountains such as Pen-y-Ghent and Ingleborough are capped with a type of rock called mill stone grit, under which is a repetitive sequence of limestone, shale and sandstones. This repetitive sequence is known as the Yoredale Series. Under the Yoredale series are a series of limestone, which is classified into the Great Scar Limestone. The Great Scar Limestone, tends to be fine grained, and bioclastic, which means it contains small fragments of once living organisms. This type of limestone can be found around Malham and the base of Ingleborough, and here.
The limestones in the area, can be further subdivided into :D1 age and D2 age limestones.
D1 age limestone is the upper layer of the Great Scar limestone, and this tends to be fine grained, creamy/ grey in colour. Now, this limestone tends to be formed from the deposition of lime mud. Any fragments of fossils tend to be small and fragmented.
A piece of D1 Limestone.
A piece of Bioclastic D1 Limestone.
D2 age limestone is the lower layer of the Yoredale series. This limestone tends to be the most fossilarious in the area. This was laid in a much more geologically active environment, with shallow tropical seas producing limestone, followed by deposition of sandstones and siltstones.
A peice of D2 limestone, you will notice the fossils, which are crinoids.
Here the Yoredale limestone has been eroded away by glacial action(though there is some further along towards Pot Scar), leaving the Great Scar Limestone.
This being an EarthCache, in order to log it, I ask that you complete the above tasks. Please send the answers 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 limestone here, in terms of height of outcrop, colour, and feel (the top and side).
2. Is there any evidence of it being bioclastic? If so please describe what you see in terms of shapes, and size (in metric measurements).
3. Is the limestone D1 or D2.
4. Please take your photograph or of your device at the nearby trig point.