An Earthcache is a virtual cache designed to draw attention to and explain an interesting or significant geological feature. More details can be found at www.earthcache.org
Some 333 - 318mya (during the Marsdenian sub-stage of the Namurian stage of the Carboniferous Period) sediment which would eventually form The Roaches, Hen Cloud and the Ramshaw Rocks was being deposited by large rivers flowing from the South-East (heading North West) into the sea which covered the area. The sea covered a sinking (then later rising) limestone floor known as the Pennine basin. The sediment originated from a landmass to the south known as the Wales-Brabant Massif which stretched across Wales and the Midlands during the Lower Carboniferous period.
The rivers were heavily laden with sediment such as sand, pebbles, mud and silt and as they entered the sea, they deposited the sediment in layers on top of the underlying limestone. Even though the limestone is older than the rocks which form this earthcache - a great deal of limestone is exposed at the surface in the surrounding area and is quarried locally. The so called White Peak (to the East and North) is predominantly made from this older lighter-coloured limestone rock.
A similar process of sediment deposition is happening today around the mouth of the river Nile; with sand and silt spreading out to form deltas and associated river channels.
Today, the areas covered by this steeply sloping, rough (coarse-grained) sandstone are called the Dark Peak and South West Peak; and this earthcache marks the western edge of the South West/Dark Peak forming a part of its dramatic rocky exposures.
Ramshaw Rocks are sandstone. The sand grains are coarse and angular and are mixed with small pebbles which have been rounded during their journey along the ancient riverbed.
Research has shown that the grainy sandstone (known also as Millstone grit) was deposited in layers which kept expanding the front of the delta in a pattern known as cross bedding.
It is likely the sandstone and pebbles which form this rock outcrop were deposited as "topset beds" in river channels at the top of the progressing delta front.
Over time - the wind and rain have eroded the sandstone creating patterns resembling faces. Perhaps the most famous face is the Winking man who can be seen from the top of the escarpment or by walking North along the escarpment and dropping down to the East of it to the coordinates N 53o 09.577 W001o 58.228.
As you walk along the ridge look out for the other "characters" in the rocks. And don't forget to look out for the "wink" as you drive away from the cache on the A53. As you drive past you will see him "wink" (Please don't look if you are driving!)
To claim this cache - please answer the following questions
1. At coordinates N53o 09.548 W 001o 58.293 - what is the elevation? (You can see the Winking man from here if you look over the escarpment edge)
2. Why do the rocks show clear banding at location N 53o 09.462 W 001o 58.352
3. Is the sandstone rock slippery under foot? Can you suggest an explanation?
4. What size (range) and colours are the pebbles which have eroded out of the gritstone? (The best place to find these pebbles is on the worn paths/track leading from the car park up to the top of the escarpment)
You must NOT include the answers to these questions in your log; please email the answers to me separately using the email details associated with my profile name. Logs without an accompanying email with the answers may be deleted.
***Congratulations to Gushoneybun on being the FTF.***
Can you discover any more "faces" in the rocks? If so - please attach a photograph to your log.
My sincere thanks to The Peak National Park Authority for permission to set-up this earthcache
Reference
Jones, C.M. & Chisholm, J.I. (1997) The Roaches and Ashover Grits: sequence stratigraphic interpretation of a `turbidite-fronted delta' system. GEOLOGICAL JOURNAL, VOL. 32, 45±68
