A Field Trip in Conisbrough - Part 5

 

Conisbrough Castle

In September 2020, six months after the start of the COVID-19 Pandemic and the subsequent lockdown, I spent an afternoon in Conisbrough to walk the route of a geology field trip that I had proposed for the Sheffield U3A Geology Group during the January indoor meeting. 

 

The route of the field trip

With the group not having yet had the time to prepare a full itinerary for 2022, following the resumption of its activities in July 2021 at Bretton Clough, this was ideal for our first field trip of the year; however, one concern that I had was that a couple of key sites along Constitution Hill that I had identified during the Doncaster Geodiversity Assessment had become quite overgrown and I could not find one of them but, on the suggestion of our group leader, Paul, we decided to do a bit of site clearance ourselves. 

 

Geological sites at Constitution Hill

A week after I had further explored the Rough Rock in Sheffield, we set off with another group member Dave on a reasonably fair February day and immediately discovered that one of the hidden rock outcrops, with fine examples of calcite mineralisation, was clearly visible now the bracken and other vegetation had died back. 

 

Constitution Hill

 

The most interesting rock exposure on the proposed walk that I had identified, however - an unusual outcrop of well cemented mid Pleistocene glaciofluvial gravel - was obscured by shrubs and well established saplings that had grown around it and on the sloping retaining wall below it. 

 

The overgrrown outcrop of glaciofluvial gravel

Although Doncaster MBC or the Sheffield Area Geology Trust should really have been doing this, and we had to jump through several bureaucratic hoops, which involved proof of public liability insurance by the Estates Department and approval by the Biodiversity Officer, we set about the clearance of the vegetation with the various garden tools that we had brought with us. 

 

Scrambling up the retaining wall to undertake clearance work

When first surveying this site in 1997 at the age of 37 and then 10 years later, I had no problems when scrambling up to this magnificent exposure but with me now 60, Dave a few years older and Paul in his 70’s, the ascent and descent proved quite demanding. 

 

The outcrop of glaciofluvial gravel

 

Once we had managed to undertake some essential cropping of the shrubs, which would make the outcrop visible to the group members who would be observing from the service road on the day, we checked the condition of a couple of other sites before returning to the car and driving to Conisbrough Castle.

 

A view of the partially cleared outcrop of glaciofluvial gravel

Having undertaken my previous investigations of Conisbrough and its castle and church on the X78 bus, I was unaware that the nearest car park to this English Heritage site no longer operated with cash and that payment had to be made by an online transaction. 

 

At Castle Hill car park

Briefly stopping at Conisbrough Castle, which I had designated as the meeting place, we then had a quick look at St. Peter’s church, which I had previously arranged to be opened for our field trip but was closed at the time. 

 

At St. Peter's church

Finding another place to park, we continued our walk along Denaby Crags on the south side of the River Don, until we reached North Cliff Quarry. I had been here a few times before, when undertaking surveys of the RIGS (Regionally Important Geological Sites) and when commissioned by XP School in Doncaster to lead field trips there. 

 

Conisbrough Viaduct

 

On my previous visits to North Cliff Quarry, I had approached it from North Cliff Road, Doncaster Road and Grasmere Road along various paths, and following the latter we encountered a great view of Conisbrough Viaduct, which is built with more than 12 million bricks. 

 

North Cliff Quarry

Arriving at the quarry edge, we consulted on the best way to descend down into the quarry, taking account of the age and mobility of the group and soon managed to get to the quarry floor, before negotiating our way across various overgrown waste rocks to look at the shelly and oolitic Cadeby Formation.

 

Massive shelly and oolitic beds in the Cadeby Formation

Having had a good look at the bryozoan reef, Paul then proceeded to show me a part of the quarry that I had not explored before, where it seems that there could be a fault that relates to the formation of the Don Monocline. 

 

Views of the possible line of a fault

Knowing the routes down to the River Don and Conisbrough railway station quite well, I didn’t think that it was necessary to carry on any further as part of our recce and we retraced our steps to the parking place that we had found earlier. 

 

An Ordnance Survey map of Conisbrough