January 2024 UPDATE - IMPORTANT PLEASE READ - Works are still ongoing at the new business park, the pile of earth is still there, but please answer as best as possible (most of the answers can be found on the notice board. If you are unable to see the answers then please just send a photo of you or your GPS beside the notice board in the interim until the pile of earth has been flattened.
The three main types of rock are igneous, sedimentary and metamorphic. The rocks visible in the quarry are pebbly sandstones of Triassic age, and are around 245 million years old. They are part of the Sherwood Sandstone Group. The sediment (the sand, mud and pebbles) that make up Sedimentary rocks come from other rocks that have been worn down by wind, rain and snow. When we find sedimentary rocks we can work out what the environment was like when those rocks were formed – old sand dunes and river channels are preserved in the rocks.
The Sherwood Sandstone is economically a very important rock unit. It forms a major source of water at outcrop (a rock formation that is visible on the surface) and at shallow depth in many areas it forms oil and gas reservoirs in the North Sea. It is worked for aggregates (a material or structure formed from a mass of fragments or particles loosely compacted together) and has been used as a building stone. There are many examples of the latter in the East Midlands, particularly in the Nottingham area (Nottingham Castle).
The Sherwood Sandstone Group, formerly known as the Bunter Sandstone, mainly comprises of sandstone and pebbly sandstone with lesser amounts of conglomerate (a composite rock made up of particles of varying size), and minor amounts of mudstone and siltstone. It was deposited between 230 and 260 million years ago in the late Permian and Triassic periods. The name is derived from Sherwood Forest in Nottinghamshire which is underlain by rocks of this age. The group consists of red, brown and grey sandstones, commonly pebbly at the bases of beds, interbedded with red and brown siltstones and mudstones.
At Acresford the sandstones were depositited by a fast flowing braided river that flowed northwards from northern France. Later in its life the river became slow and meandering, and all that is probably left of that river is Hooborough Brook which is between you and the rock outcrop. The climate in the Triassic period was very acrid and there were long, dry periods when no water was flowing. The sandstones and conglomerates deposited by this river are very widespread across England and indicate that the river has more than one course, flowing north eastwards through Leicestershire and Nottinghamshire, or northwards through Cheshire and into the Irish sea. Some well known localities where these sandstones and conglomerates can be seen include the cliffs at Budleigh Salterton in Devon, St. Bees in Cumbria, Cannock Chase in Staffordshire and Castle Rock in Nottingham. The pebbles visible in these rocks are mostly composed of quartzite.
The sand was deposited in a series of beds that show a number of different forms. Geologists use this information to help build up a picture of what kind of conditions the rocks were depositied in. Cross bedding is very common and is the result of dunes forming on the river bed. In geology, cross-bedding, also known as cross-stratification, is layering within a stratum and at an angle to the main bedding plane. The sedimentary structures which result are roughly horizontal units composed of inclined layers. These form in the same way as sand dunes in a desert or adjacent to beaches. The pebbles and large sand grains roll across the river beds and lighter sand grains are carried in suspension.
Questions to answer before logging a find :
Look at the rock face from the footpath (there is a step up behind the notice board or you may get a better view if you walk a little further along the footpath).
1) Please describe the layers of rock you can see
2) Please describe the colour variations of the rocks.
3) Using information from the notice board or in the description above, please describe whether the sandstone in this rock was formed when the river was fast flowing or slow and meandering
4) What kind of rock is Sandstone (use the three main rock types to decide)?
5) (Optional) Please send a photo of you or your GPS at the location in front of the nitice board.
Please submit your answers through the message centre