Manchester Building Stones
The North West Geologist
|A Building Stones Guide to Central Manchester|
Third Edition (2014)
Four self-guided walks through the city centre
Now available to purchase
Newsletter - September 2016
The full, illustrated newsletter is available as a pdf for download.
Text extracts are given below.
The Upper Goyt and Shining Tor Trip Report
On a pleasant morning, but with rain forecast, I joined other members of the MGA for the field trip led by Paul Aplin to look at the geology of the Goyt Valley and Shining Tor area. We were also to investigate the dominance of the Goyt syncline in controlling the scenery and to see evidence of former coal mining at Goyt's Moss.
Paul introduced our route for the day, on this south west margin of the Dark Peak, which lies between the Red Rock Fault (running north/south near Macclesfield) and the Carboniferous Limestones around Buxton. He explained that the area is comprised of a dissected plateau (which became more obvious later in the day) with the highest point being Shining Tor. The rocks within this late-Namurian/early- Westphalian area are successions of weak shales and resistant sandstones. These were greatly affected by faults, anticlines and synclines that were generally aligned north/south. Within them are sub-parallel folds and faults; some of which we were to observe later.
Paul explained that, generally, anticlines formed valleys because the rocks under stress from folding tended to be weaker and 'crack' more easily thus enabling erosion. However, the Goyt Syncline was the exception: a syncline forming a valley - unlike the valley containing Todbrook Reservoir which followed the Todbrook Anticline. The Upper Goyt Valley is 14km long on an axis from Derbyshire Bridge to New Mills.
We set off to the first locality 'pursued' by many cyclists who were taking part in a 100 mile cycle round Derbyshire: pre-1987 bikes (and bikers!). All very polite: both sides taking care not to get in each other's way on the narrow road! Paul explained, as we looked down at the stream, that we would be climbing up the rock sequence during the day. The ribs in the stream are the Woodhead Hill Rock, dipping at 10º East and representing the western limb of the Goyt Syncline. The core of the syncline is, apparently, in the car park! A little farther back towards the car park there is a very fragmented rock face with lots of very thin shaley beds; coal can be found at the base (river level). Paul explained that the Goyts Moss Coafield is an outlier sitting on the Woodhead Hill Rock. The coal is very poor quality, but used at Grinlow for fuelling the lime kilns from 1600s onwards.
We followed the road down the Goyt valley back towards the car park (again avoiding the cyclists!) until we arrived at a fault in the valley side. The rock was generally very dark, but there were patches of a reddish colour. This colouring is from siderite - an iron carbonate. Continuing down the road brought us to Derbyshire Bridge. We left the road to visit a cliff area where, at stream level, organic material can be seen. Slickensides were found on some loose pieces of rock but not in situ.Occasional fossil plant roots were also found.
We also visited a drainage sough - the drain of workings from the Yard Coal Seam. Apparently 568000 litres of water per day were draining into the Goyt! Paul explained that the local coal workings were widespread and that a couple of other soughs were built after the one we could see. Also visible (though not easily due to vegetation) was a spring line - where the Woodhead Hill Rock and the underlying shales meet. The Woodhead Hill Rock contains quartz and angular orthofeldspars. Holes can be seen where active weathering is taking place. We continued to walk down the succession before turning off to visit Goytsclough Quarry. Had we continued down the road, we would have reached the Rough Rock - the top of the Namurian. From our path to the Quarry we got a good view of the series of dip and scarp slopes that characterise the Goyt Syncline. Generally the Rough Rock forms the slopes - dipping either west oreast from the syncline axis.
Returning to the road we continued downhill until we entered the quarry. The stone was initially used locally for roads, but later expansion resulted in deliveries to London for building. It was originally owned by Pickfords (of later removals fame). The stone was loaded onto pack horses for transport; 50 horses in a train!
The quarry is in the Rough Rock which is 30m thick and composed of coarse arkose (mainly quartz with some feldspar) sandstone; it is laterally very extensive over the north of England. Its source was from the north and north east - Scandinavia. We saw cross bedding that formed in a braided river environment and some planar bedding. Sandbanks formed in the river - foresets are inclined down current and the beds are truncated by the one above. Some straight crested ripples were also seen. We could identify a line of concretions, nucleated round fossil plant material, held together by calcite and ferroan calcite. The source of the calcite was possibly the shells of non-marine bivalves.
Our journey now turned away from the River Goyt and uphill. After a brief stop on the edge of some woods, we walked up Stakeside (Rough Rock) where we could see how the dip slopes face each other across the syncline. Unfortunately visibility was rather hazy and I did not get a good photograph of the slopes heading off into the distance. What we could see was the plateau dissected by rivers, but with summits fairly level. The resistant sandstones form the summits and the valleys are eroded into the shales.
The summits we could see were: Cat and Fiddle Stakeside and Shining Tor they are formed of different sandstones: Woodhead Hill Rock, Rough Rock and Chatsworth Grit respectively. This is known as stepped topography.
After a short descent, we climbed up the Shining Tor, the highest point in Cheshire at 559m. Whilst the far distant view was again rather hazy, we could see the near distance clearly.
Paul explained that the west facing scarp of the Chatsworth Grit formed a ridge 5km long to Windgather Rocks. The Todbrook Valley follows along the crest of an anticline (the Todbrook Anticline). The core of the anticline has been eroded - possibly due to the stresses caused by the upward 'bend' of the anticline with the scarp facing east and the dip facing west. The Todbrook Valley may have been at least partially glaciated.
We could see the Cheshire Plain below and the Red Rock Fault in front of us. We see its manifestation as a fault line scar rather than a fault plane. Later movement had lifted the beds up. Shutlingsloe, which is capped by Chatsworth Grit, stood out clearly with its unusual topography. This is an example of an outlier that has suffered extensive erosion. Further away Sutton Common (with its mast) and Bosley Minn, both anticlines, formed unusually upstanding 'crags'. Their cores are formed of resistant protoquartzite.
Turning away from the view, we retraced our steps to the top of Stakeside and then headed for the road, passing the Cat & Fiddle (regrettably closed!), at which point it started to rain, before returning to the car park. Thanks were expressed to Paul by everyone on the trip. It had been fascinating - especially to learn about the coal mining that had taken place. The moors above Buxton and Macclesfield are not the place I would want to be a miner!!
Members may remember Eric Foster, a MGA member for many years, who sadly died in July aged 93. He was for many years the auditor of the MGA accounts. He was also a long-standing member and former President of the Lancashire and Cheshire Antiquarian Society.