The co-ords should bring you to some steps outside the Square Chapel, they are sandstone step, which are edged with granite, but we are not here to talk about types of rocks (plenty of EarthCaches about to describe that 
), we are here to look at the sandstone in close detail in association with Lithostratigraphy.
So what is Lithostratigraphy? Well it is the science of the study of rock layers or strata.The sandstone which makes up the steps was laid down as a sedimentary rock in layers (strata). Now sandstone, composes of sand grains, quartz and feldspar, but lets look a bit deeper. If you look closely at some of the steps, you will see that the grains are not all uniform (i.e the same), there are areas where there are bigger grains and then smaller grains. This is known as graduated bedding.
So what has caused it?
Well basically the speeed of deposition. What does that mean, I hear you ask. Well, the sediment which makes up the sandstone, was originally carried in streams and rivers. When there is a slow water speed, such as in a lagoon, then smaller grains can then sink to the bottom and build up laters, whilst with faster water speed, the smaller grains are carried along by the current, and only the larger grains can then sink to the bottom. In a fast flowing river in spate for example, it can be the case that only the large boulders / stones get to settle due to their size.
So which step are we to look at?
First go to to the top of the steps, there is a metal handrail. From this metal handrail go west one step - you are at the right spot, when the step is alligned with the nobbly paving slab. Now, take a seat and look down. You may find that wetting the step helps to bring out the definition.
Look closely at this step, you can see some bands of different sized grains.
1. How many distinct bands can you see?
2. How wide is the largest band - does this have large or small grains?
3. Please tell me the size of the largest grains in MM.
4. At what angle do the bands lie - are they straight or at an angle?
This being an EarthCache, in order to log it, I ask that you answer the above tasks. 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.