This EarthCache takes you to the centre of Settle, and a chance to look at some geology without having to head to the hills.
The below photograph shows the EarthCache location.
We are here to look at, and examine a stylolite.
🤔 What is a stylolite?
Well, basically it's a line in the limestone, but a line which can give a particular appearance. Stylolites start to form when there is high porosity and stress present. High porosity basically means that a lot of fluids can run through it. They then stop forming when there is low porosity and low stress. The literature also points towards clay particles as having an enhanced role in the pressure localisation and stylolites development.
🤔 Lets look at the stylolite much closer.
Stylolites can be filled with materials, and these materials can give an indication of when filling took place.
🔷️ Diagenesis.
This occurs when the rocks forms. In the case of this type of rock, it is limestone. Limestone is formed from the accumulation of lime mud and /or the accumulation of the shells of ancient sea creatures. Over millenia, the sediment is compacted and eventually stone forms. During the process of diagenesis, minerals precipitate out of water in the sediment, these then help to act as cement binding sediment together.
Stylolites can be filled with cementing material, such as calcite, and also insoluble materials such as clay can be left in stylolites as part of the diagenesis process. The calcite can appear blocky at times, with clay having now been transformed into rock can appear tan coloured.
🔷️ Hydrothermal fluids.
Stylolites can be said to be barriers to fluids moving through rocks, but they can also be conduits for fluids to move through, and they can also be opened by tectonic action. Due to tectonic forces, at times hot mineral saturated fluid can be forced or circulate through cracks, and weaknesses in rocks. They can also circulate through stylolites, and as a result once the fluid has cooled, crystals can form in the form of quartz and other minerals.
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. What type of stylolite can be found here?
2. What is it filled with? Please describe it.
3. Using the above information what process has occured for the stylolite to be filled?