A Recce in Nottingham - Geology 2

 

Rock House Cave in Castle Rock

Leaving the Park Tunnel by the central staircase, during the first part of a recce in Nottingham for the next Sheffield U3A Geology Group field trip, we stopped very briefly to look at the Bulwell stone walling on Upper College Street, which is nodular and has many vugh like cavities. 

 

Bulwell stone walling

Entering the gated Park Estate at Park Terrace, we continued down Newcastle Drive, which has for much of its a length a high, buttressed brick retaining wall on its northern side; however, there are further exposures of the pebbly sandstones of the Chester Formation, into which garages for the houses opposite have been excavated.

 

a Google Map view of Newcastle Drive

The rock exposures in the Park Tunnel exhibit a wide range of lithologies and sedimentary structures, which would be more than enough to keep the group occupied for a while, but at one of the exposures on Newcastle Drive there are numerous hollows that I think are sand martin nests. 

 

Sand martin nests on Newcastle Drive

 

Continuing our recce along Park Terrace, where a few ornamental caves have been cut into the cliff below, we carried on to the Park Steps and took a short diversion up Lenton Road where, over a distance of approximately 100 m, the Bulwell stone boundary wall on its south side is built on further exposures of the Chester Formation. 

 

The Chester Formation on Lenton Road

 

Retracing our steps along Lenton Road and continuing to Ogle Drive and Peveril Drive, we arrived at Rock Cottage and got our first view of the cliffs at Castle Rock, which are largely the product of the erosion of the Chester Formation by the River Trent and its precursors. 

 

Rock Cottage and Castle Rock

 

We noted that the outcrop of sandstone is extremely massive, with no obvious sign of the usual pattern of regularly spaced beds and joints typically seen in a sedimentary rock – both sandstones and limestones – and this scarcity of these provides the rock with its mass strength. 

 

Rock House Cave

 

Major bedding planes are widely spaced, and joints are mainly restricted to a single system aligned roughly NNW-SSE, and dipping steeply to the west; these have a mean spacing of about 15 m along the Lenton Road section. Joints in the same system are spaced more closely within a belt immediately west of the castle, creating the unstable rock slabs in this part of Castle Rock. 

 

Closely spaced joints in Castle Rock

Just beyond Rock House Cave, we stopped to have a quick look at this system of narrowly spaced joints, where there was a substantial rock fall in 1969. Large joint bound slabs fell from the cliffs on the south-western side of Castle Rock and concrete buttresses and steel straps from subsequent engineering work, which includes concealed rock anchors, can be seen. 

 

Castle Rock at Brewhouse Yard

Continuing along Peveril Drive, although a set of railings prevented us getting close up to the sandstone, I had expected to be able to get near to the cliffs by Brewhouse Yard, which adjoins the exit to Mortimer’s Hole and the Museum of Nottinghamshire Life, but the gate was locked. 

 

A blocked entrance to the air raid shelter caves

 

Continuing down to Castle Boulevard, we headed up Castle Gate past Ye Olde Trip to Jerusalem public house, without being tempted to pop in for a quick half pint, until we reached several blocked entrances to caves that were excavated for air raid shelters in WWII. 

 

An information panel at Castle Rock

 

Stopping briefly at the information panel, which provides a brief introduction to the extensive network of man made caves that underly Nottingham and were put to a wide variety of uses, we finished by having a quick look at the building stones – quarried from the Tarporley Siltstone Formation in the Mercia Mudstone Group.

 

A detail of the curtain wall at Nottingham Castle