From Earth Science On-Site
Apes Tor, Staffordshire
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The geological and geomorphological story of the Apes Tor, Ecton Hill area is based on the interpretation of evidence from the rocks and from the landscape, some of which may not be visible in this area. Here is the story and the evidence for it.
The rocks of Ecton Hill are shales and muddy limestones containing a few fossil brachiopods and crinoid fragments from the Carboniferous period (beginning 354 million years ago). These indicate deposition in a warm marine environment.
These layers of limestone, originally horizontal, are now folded into anticlines and synclines, which trend (run) in a north-south direction. The rocks were broken by a series of faults running in two major directons: NE to SW, and NNW to SSE. These folds and faults suggest compressive forces from a roughly east-west direction, during later Carboniferous times (295 million years ago), since younger rocks are not affected.
These limestones were buried during the Permian and Triassic periods (between 290 and 205 million years ago), and during this time it is probable that circulating ground waters, with metals in solution, deposited minerals in spaces and fractures in the limestone of Ecton Hill.
Unusually for mineralisation in the Derbyshire / Staffordshire area, these deposits contained copper deposited as chalcopyrite (CuFeS2, which is 34.5% copper). Other minerals deposited include sphalerite (ZnS); calcite (CaCO3 ; and barite (BaSO4).
The two major ore bodies at Ecton (The Deep Ecton Pipe and Clayton Pipe) are vertical (See Figure 1) and may be associated with the near vertical fractures caused by the meeting of the two fault directions in the rocks.
The rocks, which once buried the area, have now been eroded away. Although there is no direct evidence of glacial erosion, the area would have been covered during the Ice Age.
At the end of the last Ice Age (10 000 years ago) frost shattering produced large amounts of angular scree material at the foot of slopes. Surface water carrying dissolved calcium carbonate has cemented these angular fragments together in many places forming a breccia. Meltwater rivers swept through the valleys of the area. Subsequent weathering and erosion of the limestones formed the present day thin covering of soil over the hillsides.
Chemical weathering also attacked the original minerals in the ore bodies, dissolving and re-depositing the original copper sulphide minerals as hydrated copper carbonates (malachite, green, and azurite, blue) making the ore body richer, lower down.
There is evidence of copper mining in the Bronze Age. Documented mining of the copper deposits began in 1760, peaking at over 4000 tons per annum in 1785, and declined steadily through the 19th Century until about 1888. Remnants of mine buildings, and the “soughs” which carried vast amounts of water pumped from the deep mines, 400 metres below the valley floor, can still be seen. (See Figure 1).
Earth Science Principles
In this area it is possible to demonstrate the following Earth Science principles:
National Curriculum Links
In this area it is possible to:
A four minute animation with narration - A short history of Apes Tor quarries - is available: media:APESTOR04.exe (5.6 MB)
Please note: this animation is an .exe file, and although this file is safe to download, some computer systems may prevent you from doing so. It is also very large (5.6MB) - please consider whether you want to download a file of this size.