It’s raining again. This is this morning’s rain radar image from raintoday.co.uk

The Great British Summer - www.raintoday.co.uk

The Great British Summer - www.raintoday.co.uk

You are not going to get the Great British public believing in global warming until we start getting those Mediterranean summers that we were promised.

This week I went into the field and got absolutely soaked, despite having some expensive waterproof clothing. Torrential rain plus high humidity and a strenuous terrain including a fast flowing stream combined rainwater, riverwater and sweat to make one sodden geologist.

This is typical British geological fieldwork. In areas of soft mudrocks there is very little rock exposure and what little there is tends to be in stream sections where the river maintains a fresh exposure. Fieldwork therefore involves struggling up and down valleys, crossing and recrossing rivers and usually getting wet from above, below and inside the waterproofs. The exposure, when one finds some is typically uninspiring black mudstone with the occasional sandstone.
Namurian mudstone

You can now see why we send our students overseas to map.

Having said all that, it was a grand day out. It made a great change from working in the office. I really enjoyed been outside again. There was some minor folding …

Folded Namurian

Folded Namurian


and the occasional fossil …
Dunbarella bivalve

Dunbarella bivalve


Note: I’m being deliberately vague about the location of this Staffordshire valley as it is in part of a nature reserve not open to the public. It was visited with the the reserve warden.

 

What do Warwick Castle, Liverpool Cathedral and the doorway to 10 Downing Street have in common?

They are all made of sandstone from Grinshill in Shropshire.

This summer I am having a break from compiling geotrails but have ended up working on building stones. How a geophysicsist ends up working on building stones is a long story but I’m having to take a crash course in the local natural building materials. The biggest problem that I have is that most of the local building stones are red sandstones, but from a whole variety of different stratigraphic layers.

To try to get a handle on the characteristcs of some building sandstones I visited Grinshill Quarry in Shropshire which has supplied a variety of buildings including those listed above. This Lower Triassic sandstone is formally known as the Helsby Sandstone Formation, but to stonemasons it is the Grinshill Sandstone. In fact the nomenclature is quite bewildering. Its lateral equivalents to the east are, in West Staffordshire, the Bromsgrove Sandstone Formation and in East Staffordshire, the Hollington Formation. Hollington Stone is quarried for building stone at Hollington, near Uttoxeter and is commonly used in Staffordshire. All of these formations used to be called the Lower Keuper Sandstone. You see the kind of problems I have to deal with.

In just the Grinshill Quarry there are three predominant colours, a red, a white and a pale yellow.

Grinshill Red
Grinshill Yellow and White

The quarrying operation is quite interesting. In order to split the rock into large blocks without damage from blasting, a series of holes are drilled in a line and then liquid expanding mortar is poured into the holes. The stress induced by the expanding mortar causes fractures to connect the holes with very little other damage to the rock.
Rock Splitting 1

Rock Splitting 2

The split blocks are then cut to the required shape on this rock saw.
Rock Saw 1

Rock Saw 2

So that is just one of the formations I have to work with. Now I just have to get my head round all the Carboniferous gritstones…

The Winking Man

 Staffordshire  Comments Off
Apr 132009
 

After being away in the field for the past week I’m just catching up on things (over a thousand blog posts in my google reader feed for starters). I went for a walk yesterday in the Staffordshire part of the Peak District. This is the “Winking Man” on Ramshaw Rocks near the Roaches. It is so called because as one passes along the A53 from Buxton to Leek the view of the sky though the ‘eye’ gets briefly obscured by the ridge giving the illusion of a wink. Geologically, it is a Marsdenian (Bashkirian, Carboniferous) gritstone.

The Winking Man

Also, here is a tree growing in a rock cleft on Hen Cloud.

Tree - rock

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