Tuesday, 29 September 2015

Sandstone in Pontefract

Sandstone in Pontefract

In all of the places that I have visited in Yorkshire, where they are underlain by hard rock geology, the stone has been widely used for construction – from dry stone walls to intricately carved details; however, in Pontefract, even though both Carboniferous sandstone and Magnesian Limestone form the bedrock, I only saw a handful of stone buildings whilst walking around the old town centre.

The Market Hall

Nonetheless, the buildings that you can see provide a good opportunity to look at the very distinctive weathering characteristics of the best sandstones available at the various times when they were built – The Town Hall, the Market Hall, the Buttercross and St. Giles' church all provide very fine examples of stone built architecture...


Thursday, 17 September 2015

Pontefract Castle

Liquorice at Pontefract Castle

The 1940 edition of the British Geological Survey Memoir notes that the old mediaeval store houses of Pontefract Castle are hewn into Pontefract Rock, a massive - but loosely cemented - medium grained sandstone from the Pennine Upper Coal Measures Formation

Pontefract Rock
Pontefract Rock is generally buff/grey in colour, but it also contains partings of reddish-purple stained shale, from which the iron oxides have sometimes permeated into the body of the rock.

It is further recorded that much of the castle is built from this sandstone and that there are several old quarries on its north side so, having had a quick look at All Saints church, I set off up the hill to explore its rocky foundations. 

Having noted the principal physical characteristics of the sandstone that I had seen, I retraced my steps and walked up Castle Garth - where there is a mixture of stones - to see Pontefract Castle itself.

Building stones on the Garth

Completely destroyed at the end of the English Civil War, by the order of Oliver Cromwell himself, there isn’t much stonework to see apart from the remains of the keep; however, there is a good opportunity to study the characteristics of both the Pontefract Rock and the Magnesian Limestone, with the latter possessing a distinct yellow/orange colour here.

Carboniferous sandstone and Permian limestone at Pontefract Castle

With the first leg of my field trip now completed, I carried on up the hill to look at the various fine historic stone buildings that can be seen in the town centre.

Tuesday, 15 September 2015

All Saints Church - Pontefract

All Saints Church in Pontefract

The historic town of Pontefract occupies a fault bound outlier of Lower Magnesian Limestone that unconformably overlies a variety of Upper Carboniferous sandstone, which was once known as the Pontefract Rock but is now called the Newstead Rock by the British Geological Survey. At the north-eastern end of this prominent ridge, Pontefract Castle commands views over a low lying area, which comprises much softer, finer grained sediments upon which All Saints church is set.

The Geology of Pontefract

I first visited All Saint's church in 1999, to survey the stonework and help the archaeologist with the unravelling of its construction history - and to advise the architect on the most suitable stone to be used for an extensive programme of restoration to the tower. At this time, I noted a variety of sandstones and limestones that have been used in what I consider to be the most interesting church that I have ever visited.

Views of the tower at All Saints church

Laid to ruin during the exchange of cannon fire with the castle at the end of the English Civil War, and subsequently partially rebuilt, remodelled and restored, it provides an excellent opportunity to study the various building stones and their weathering characteristics - this very special place also records a pivotal point in England’s history.

All Saints church

Friday, 11 September 2015

West Yorkshire

The Pontefract Rock

It was a positive connection with Spain, earlier in the year, that really focussed my attention on Geotourism as a way to apply all of my professional skills, but I had already been exploring a few places in West Yorkshire during the previous few months – just for pleasure.

The Yellow Sands Formation

Looking at the geological map of the British Islands, which hangs on my office wall, much of the bedrock geology in West Yorkshire is essentially the same as found in South Yorkshire – Carboniferous sandstone, shale and coal, with Permian dolomitic limestone and Triassic sandstone overlying them – but I had never explored any of its natural rocky exposures.

The Oaks Rock

Using buses, trains and my own two feet, I have discovered a few places that I will certainly add to an itinerary of field trips; the geology, ancient monuments, architecture and art of West Yorkshire are all waiting to be seen and fully appreciated.

Kirkstall Abbey