The Geology of Derbyshire and Nottinghamshire

Introduction

The Carboniferous period began around 360 million years ago, when present day Britain was located near the equator (Toghill 2011). The warmer climate which was experienced during this time led to the formation of distinct geological features in Derbyshire such as Calver Low and Mam Tor which are primarily made of limestone. This limestone was formed due to the warm, shallow, tropical seas of the time which caused a build up of sediment due to having an abundance of different life forms such as crinoids, as stated by the Canterbury Historical and Archaeological Society (2024). Around 120 million years after this, during the Permo-Triassic period, many sandstones such as examples found near Nottingham Castle were formed. This period of time also caused the geology of Radcliffe-on-Trent to be partially comprised of clay and gypsum. This gypsum was formed as highly saturated seas were evaporated leaving behind this mineral.

Methods

The first site that was visited was in Radcliffe-on-Trent where we examined the different rock types found alongside the banks of the River Trent. This was done by creating a stratigraphic log of an area just over two metres tall which had distinct layers of rock, using a compass clinometer to measure each individual layer and a particle size analysis chart, as well as our own observations, to categorise each layer from clay to gypsum. Later that day we visited the Tunnel Road sandstones located roughly North-West of Nottingham Castle and created a facies architecture diagram by drawing and labelling the main features of the geology such as faults, and estimating the height and therefore size of the layers by comparing to the height of a person stood at the bottom.

The second day we visited Calver Low, where the geology formed roughly 330 million years ago during the carboniferous period, leaving distinct layers of limestone. At this site we drew another facies diagram of an area with distinct with distinct differences in geology, whilst also using the compass clinometer to measure the angles of dip. We then also created another stratigraphic log, this time using the classification of carbonates to categorize each layer, as well as including specific fossils that were seen. In addition to this we visited Litton Mill Railway Cutting in order to identify different fossils and rock types that were found in this area. This was done by creating a facies diagram which shows a clear difference between the lighter limestone and darker basalt.

On the day after we visited Lathkill Dale which had a unique karst landscape unlike other areas we had been to previously, which then brought us to Ricklow Quarry. Here another facies diagram was drawn which showed a number of different features such as laminations and a cave which had formed. This was again done by using a person as an estimate for the height and the compass clinometer to measure the dip.

The final day focused solely on Mam Tor and the surrounding area, which had lots of evidence of how the landscape had changed over time, including hill slope failure and how a road had been built that is now out of use due to the ground underneath constantly changing. This was represented by doing a field sketch which included Mam Tor itself and the surrounding landscape, including the discontinued road. The height was estimated by using the map where we could work out what height we were above sea level and subtract this from the height given for the summit. Finally we created a stratigraphic log at the base of Mam Tor which primarily had distinct layers of limestone and shale.

Results

The geology along the banks of the River Trent primarily featured alternating bands of red rock and grey rock, which could be seen along the cliff face. These included layers ranging from clay to gypsum which altered in thickness as it went along. A portion of this can be shown in figure 1 seen below, which shows the thickness of each layer as well as what each layer was made of, which was done by estimating the size of their particles. The area near Nottingham Castle featured no clays or evaporites and was made up primarily of sandstone, which had been carved out during the nineteenth century. This meant that the layers of rock which had been built up over time could be more easily seen, see figure 2. This facies diagram shows many features including the large pebbles near the bottom and a huge fault running near enough down the middle.

Calver Low was located in an area with many examples of different facies, including a carbonate mud mound and storm facies for example, and was covered by a lot of vegetation. The geology can be seen in figure 3, which shows that the majority of this area was comprised of limestone as well as there being some examples of fossils such as brachiopods, which could be seen more clearly as we got closer. This can be seen more clearly in figure 4, which shows a stratigraphic log of an area towards the top right of figure 3. Figure 4 shows the alternating layers of stone and an estimate for the percentage grains found in each. This also shows examples of fossils such as the brachiopods that were abundant in the top layer and some crinoids found nearer the bottom.

Throughout Litton Mill Railway Cutting there were many fossils and rocks within the limestone which had been exposed in order to make way to the old railway which used to go through this area. At the location of the facies diagram seen in figure 5, there are distinct differences in the rock on the left hand side which is limestone, and the rock on the right which is basalt. This also shows the direction and severity of dip in different areas, in addition to other features such as pillow lavas found in the basalt.

The walk along Lathkill Dale featured a karst landscape made primarily of limestone, which also included a V-shaped valley with a curved cliff face, seen in figure 6 Here there was also evidence of some ancient coral reefs. Near this area was Ricklow Quarry, where there was many examples of limestone which had been discarded, creating a partially unnatural landscape. Near this area was where the facies diagram seen in figure 7 was done, which shows formations including a cave in the bottom right and examples of a chert and crystalline horizon. This rock was primarily made of carbonate mudstone so had little to no fossil content

The landscape near Mam Tor had many interesting features, including lighter grass found closer to the top of the hill, and the hummocky ground which was also prevalent, which can be seen in figure 8. This also shows the old Mam Tor road which had many faults and was very uneven. Closer to the bottom of Mam Tor itself was where figure 9 was drawn and shows the distinct layers of sandstone and shale which were found here.

Discussion

In the first location in Radcliffe-on-Trent, it was found that there were many examples of gypsum, which would be expected as during the Permo-Triassic period when these rocks were formed, Britain was located much closer to the equator than it is today and experienced hot, dry conditions (British Geological Survey 2020) which caused the evaporation of the highly saturated seas located hear at the time. This has left behind layers of grey rock which is synonymous with this region of Britain, mixed in with clay and sandstone which have also formed due to the past environment of this location.

What the facies diagram taken on Tunnel Road shows is layers of light sandstone, again formed during the Permo-Triassic period, with examples of different features such as the large pebbles found near the bottom. These will have been transported here due to an event such as a flash flood which would have had enough force to move these rocks and put them where they are now, possibly also causing the sandstone to be less course. This agrees with the work of Strong (1993) which links sandstone becoming more porous with water flowing through during the Triassic, therefore weakening it. This may have also been the cause of the dune bedding seen in figure 2. The flash floods only reached a certain height meaning that the faults near the top will have formed due to aeolian processes eroding the sandstone over time.

Calver Low was one of the locations which featured a lagerstatten with many different fossils. These included examples of brachiopods which would have previously colonised the nearby carbonate mud mound (Gutteridge 1990) such as the gigantoproductus which were up to 16cm in size. As well as this there were also a few examples of crinoids, with one being 8cm in length and 16mm diameter. Calver Low also gave many different examples of facies such as the limestone flank facies which is a rock type that was formed during the Lower Carboniferous, as well as a storm facies which is evidence of a cyclone or hurricane which will have affected this area. There is also a clay wayboard, which according to Vincent (1995) will have been formed after the deposition of volcanic ash carried by the wind during this time period.

The limestone found in Litton Mill Railway Cutting had been cut through using dynamite to facilitate the railway tracks which were previously here. This left exposed the layering of limestone which had built up over time, starting around 330 million years ago. In addition to this was examples of basalt, which is evidence of extrusive volcanic rocks formed during the Lower Carboniferous (Thomas et al. 1991). The dip of this rock seen in figure 5 shows the angle at which this rock penetrated through the surface and meets with the limestone which formed also during this time period.

The area around Lathkill Dale and Ricklow Quarry was originally formed in the Lower Carboniferous period and featured a V-shaped valley seen in figure 6, which was eroded by the river which previously ran through this valley. The dendritic drainage network formed here due to the geology being mainly comprised of limestone layers, which have similar resistances to weathering, causing the tributaries to disperse in different directions similar to the branches of a tree. The facies diagram taken at Ricklow Quarry was mainly made up of carbonate mudstone, or as described by Adams (1980), a carbonate-mud build up. Due to this, unlike much of the surrounding area, there is little to no fossil content found in this specific location. Also featured were many examples of chert nodules and other features that formed due to deposition from silicon rich waters which had previously run through this rock.

The landscape around Mam Tor has been affected hugely by hill slope failure which occurred around 4000 years ago, now leaving hummocky ground which stands out clearly from the darker fields which are seen when looking further away from the base of Mam Tor. The stratigraphic log shown in figure 9 shows alternating bands of sandstone and shale found at the base of Mam Tor, with the trend being that each rock type tends to get finer as they go up the mountain, agreeing with the work of Allen (1960). This exposed rock from the upper carboniferous has been slowly eroded away over time, similarly to how the collapsed sediment underneath Mam Tor caused the road to begin to creep downslope, and is the reason why it is out of use today as it clearly looked unsafe to drive on.

Summary

In summary the Carboniferous and Permo-Triassic periods brought about, and have left distinct geological features in both Derbyshire and Nottinghamshire respectively. The main rock type formed during the Lower Carboniferous period was limestone, as was evident in Calver Low and Litton Mill Railway Cutting. These areas also had other formations such as a clay wayboard and storm facies which were both formed during hazardous conditions associated with the location of Britain during this geological time period. Also in the Carboniferous period was the formation of Mam Tor, in which the main rock types seen today are sandstone and shale, which both erode fairly easily. This was the cause of the formations seen around this area today such as the hummocky landscape which stands out from the rest of this area of Derbyshire. Finally the Permo-Triassic period formed many different geologies due to the environment Britain found itself in during this time. This includes the sandstones near Nottingham Castle which have been altered over time due to events like flash floods, creating features like the large pebbles that stand out in this area due to having a vastly different geology. As well as this, the warm environment allowed for the formation of gypsum, which is seldom seen in other areas which have similar climates to modern day Britain.

References

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Allen, J.R.L., 1960. The Mam Tor Sandstones: a 'turbidite' facies of the Namurian deltas of Derbyshire, England. Journal of Sedimentary Petrology, 30 (2), pp. 193-208.

British Geological Survey., 2020. Geological Timechart [online]. British Geological Survey: National Environment Research Council. Available at:  Geological timechart - British Geological Survey (bgs.ac.uk)  [Accessed 8 April 2024]

Canterbury Historical and Archaeological Society., 2024. Carboniferous Limestone [online]. Canterbury Historical and Archaeological Society:  Solidrock. Available at:  Carboniferous Limestone – Canterbury Historical and Archaeological Society (canterbury-archaeology.org.uk)  [Accessed 7 April 2024]

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Strong, G., 1993. Diagenesis of Triassic Sherwood Sandstone Group rocks, Preston, Lancashire, UK: a possible evaporitic cement precursor to secondary porosity?. Special Publications 73, pp.  279-289.

Toghill, P., 2011. Tropical Seas and Coal Swamps – The Carboniferous Period. The Geology of Britain An Introduction. Ramsbury: Crowood, 2013, pp. 272.

Vincent, P., 1995. Limestone Pavements in the British Isles: A Review. The Geographical journal, 161(3), pp. 265–274.