What is Sandstone ? The Geology Lesson.
Sandstone is sedimentary rock composed mainly of feldspar and quartz and varies in colour, through grey, yellow, red, and white. Sandstone often forms highly visible cliffs and other rock formations, certain colours of sandstone may be strongly identified with certain regions. For instance, much of the American West is well-known for its red sandstones.
Rock formations that are sandstone usually allow percolation of water, and are porous enough to store large quantities, making them valuable aquifers. Being fine grained they are more apt to filter out pollutants from the surface than other rocks with cracks and crevices such as limestone or other rocks fractured from seismic activity.
Origins of Sandstone
Sandstones are clastic in origin (as opposed to organic, like chalk or coal). They are formed from the cemented grains that may be fragments of a pre-existing rock. The cements binding these grains together are typically calcite, clays and silica. Grain sizes in sands are in the range of 0.1mm to 2mm.
The formation of sandstone involves two principal stages. First, layers of sand accumulate as the result of sedimentation, either from water (as in a stream, lake, or sea) or from air (as in a desert). Typically, sedimentation occurs by the sand settling out from suspension; i.e., ceasing to be rolled or bounced along the bottom of a body of water or ground surface (e.g., in a desert or erg). Finally, once it has accumulated, the sand becomes sandstone when it is compacted by pressure of overlying deposits and cemented by the precipitation of minerals within the pore spaces between sand grains.
Colours will usually be tan or yellow (from a blend of the clear quartz with the dark amber feldspar content of the sand). The addition of Iron Oxide in some sands, such as in the south-western United States gives a reddish tint to the sand, with additional manganese gives a purplish hue. Red sandstones are also seen in the Southwest and West of Britain, as well as central Europe and Mongolia.
A Geological Study has found the principle mechanism for the formation of sandstone is by the sedimentation of grains out of a fluid, such as a river, lake or sea. The environment of deposition is crucial in determining the characteristics of the resulting sandstone, which on a finer scale include its grain size, sorting, composition and on a larger scale include the rock geometry. Principal environments of deposition may be split between terrestrial and marine, as illustrated by the following broad groupings:-
Terrestrial environments
1. Rivers (levees, point bars, channel sands)
2. Lakes
3. Deserts (Sand Dunes)
Marine environments
1. Shoreface sands
2. Deltas
3. Turbidites (submarine channels)
Once the geological characteristics of a sandstone have been established, it can then be assigned to one of three broad groups
Arkosic sandstones, which have a high (>25%) feldspar content.
Quartzose sandstones which have a high (>90%) quartz content. Sometimes these sandstones are termed "orthoquartzites", e.g., the Tuscarora Quartzite of the Ridge-and-valley Appalachians.
Argillaceous sandstones, which have a significant clay or silt content.
Sandstones are often relatively soft and easy to work which therefore make them a common building and paving material.
The Chiding stone, itself is a “Tor” like structure, million’s of years old. When this area lay in a swamp-like Sussex basin, Fine grains of sand were laid down forming the sandstone structure that can be seen here today, the name given to the rock that has been formed here is called “Old Tunbridge Wells Sandstone”.
The Tunbridge Wells Sandstone Formation is a geological unit which forms part of the Wealden Group and the uppermost and youngest part of the unofficial Hastings Beds. These geological units make up the core of the geology of the Weald in the English counties of West Sussex, East Sussex and Kent.
Tunbridge Wells Sandstone is Lower Cretaceous in age. It was lain down in large braided river channels. Today it's outcrops form upland regions across the Weald of Kent. In the Tunbridge Wells area there are several locally famous sites. These are :-Mount Edgecumbe Rocks,Wellington Rocks, Toad Rock, Happy Valley Rocks, High Rocks, Eridge Rocks, Harrison Rocks. The rock makes for good rock climbing in the SE of England.
One of the local legends about the Stone is that nagging wives or wrong-doers were brought here to be told off or Chided by the assembled villagers. It is also believed to be an Old Saxon Boundary maker and a Druids Alter. There is no strong evidence to support or disprove any of these theories and, indeed, either all or none may be true at all.
The first reference to this ancient village of Chiddingstone was recorded in 814 when King Coenwolf of Mercia gave a stretch of land to the Archbishop of Canterbury. Pig farming prospered with the abundant supply of acorns from the Oak forests and by the time of the Doomsday Book, Chiddingstone had a Church and the beginnings of a street. The iron industry brought prosperity to the area and Chiddingstone grew. The National trust bought the entire village, including the pub, houses and Post Office in 1939, to ensure its preservation. The houses in the village are generally of the 16th and 17th Century. However, the building that is now the Post-Office is mentioned as far back as 1453 and many of the other buildings probably took materials from earlier settlements here. Although the village is owned by the National Trust and is open all year, the houses themselves are not open to view. Chiddingstone Castle is not owned by the National Trust but by the Denys Eyre Bower Trust and is open to the public to look around.
In order to complete this Earth Cache you will need to visit the Village of Chiddingstone and find the Chiding stone here, near the Church where there is also plenty of parking.
You will need to answer the following questions and email me through my profile. Please do not include answer to the questions in your Log, Thank you. Please feel free to log as found once you have the answers but any logs without an email to me with the required information will be deleted.
There is no need to climb on the Rocks to get any of the answers to the questions. Good luck and Enjoy.
Although it is not now an Earth Cache requirement, it would be great if you could take a photo of yourself, and / or your GPSr, standing at the Chiding stone and add the pictures to your logs for us all to enjoy!!
1. Look carefully at the Chiding Stone, especially look close up at the make up of the rock. What type of Sandstone is the Chiding stone made of (Arkosic, Quartzose or Argillaceous) ??? Please explain your reasons for this and what colouring is the Sandstone ???
2. How old is the rock of the Chiding stone believed to be when was the rock formation first created ???
3. Please Estimate the Distance around the base of the Chiding stone by pacing it out, staying on the grass. Answers in Metric or Imperial are both OK.
4. Just to the East of the Chiding stone is a smaller rock that you will have walked pass, estimate the height of this stone, please ???
5. From the information at the Chiding Stone, what percentage of the properties in the village are more than 200 years old ???
We hope you have enjoyed The Earth Cache and Look forward to reading your Logs.