You are required to visit the location and examine the rockface. Please feel free to take photos and include them in your log. Do not post your answers in your log, but email them to the cache owner. Anyone who does not send answers within a reasonable time, will have their log deleted.
Sedimentary rocks are formed by the breakdown of older rocks into smaller grains to form sediment through surface processes. Over time these are deposited, mainly with the use of water and build up in layers to form sedimentary rocks. In time these are buried to form sedimentary rock through the process of lithification. This process involves the sediment becoming cemented and then compacted to form the sedimentary rock. Common sedimentary rocks include Sandstone, Limestone and Mudstone. The rock that the road cuts through is visible at this point. It is a Keuper sandstone, which is softer than the nearby Delamere Sandstone. It has been quarried extensively in Runcorn, Frodsham and Helsby. It has been used for building walls in Preston on the Hill and nearby Preston Brook. Here the sandstone is multi coloured and is an estuarial deposit. It is possible to see ripple marks, worm casts, sun cracks, foot marks and tracks of creatures that walked on the sandy shore before it hardened into rock. As the sediments were being laid down, there were huge pressures put upon the layers which caused them to distort and change shape. At this point it is possible to see the layers of different coloured deposits.
There are 3 tasks to complete
1. Locate the dark band of rock running through the Sandstone at the GZ. Measure/ estimate it's thickness.
2. Look carefully at the exposed surface of the dark band, what feature can be seen?
3. Explain why this dark band is so prominent.