Monday 20 October 2014

English churches - building stones


Drewsteignton village square, Devon. Looking east. Drewsteignton village is sited high on the northern edge of Dartmoor. Holy Trinity Church and Church House with its large chimney stack are both built of Dartmoor granite blocks. Drewsteignton village is typical of many on the the northern fringe of Dartmoor. The church tower is built of Dartmoor granite (imported to the district). The house to the right of the lych gate is built largely of rough hewn granite blocks. The wall to the left of the lych gate is built of blocks of impure limestone and hornfelsed mudstone from the local quarries (now disused). The granites of Devon and Cornwall and their associated intrusive and metamorphic rocks have commonly been worked in the past for building stone, both for local housing and for major building projects elswhere in the United Kingdom such as the many 19th century dock construction schemes in London.
BGS Image ID: P209976
Drewsteignton village square, Devon. Looking east. Drewsteignton village is sited high on the northern edge of Dartmoor. Holy Trinity Church and Church House with its large chimney stack are both built of Dartmoor granite blocks. Drewsteignton village is typical of many on the the northern fringe of Dartmoor. The church tower is built of Dartmoor granite (imported to the district). The house to the right of the lych gate is built largely of rough hewn granite blocks. The wall to the left of the lych gate is built of blocks of impure limestone and hornfelsed mudstone from the local quarries (now disused). The granites of Devon and Cornwall and their associated intrusive and metamorphic rocks have commonly been worked in the past for building stone, both for local housing and for major building projects elswhere in the United Kingdom such as the many 19th century dock construction schemes in London.

Snettisham Church, Norfolk. Looking east. This large, late medieval church at Snettisham is typical of many in this area where a mixture of local building stones are used for the main walling material, chalk, flints and ferruginous carstone, with better quality oolitic freestones of the Lincolnshire Limestone Formation imported for more ornate mouldings and carved stonework. Built in the 14th century decorated style, Snettisham Church has its nave and tower constructed of partially dressed blocks of chalk and flint. The spire, pinnacles, copings, buttresses and window tracery are made of oolitic limestone, one of the Middle Jurassic freestones. The wall in the foreground is made of dressed Carstone blocks which have suffered some frost damage. While this area of Norfolk produced a wide variety of local building materials, including sandstones, limestones and flints, none were good enough to qualify as freestones. Consequently from medieval times onwards the oolitic limestones of Lincolnshire were commonly imported for the stonework in all the more prestigious buildings.
BGS Image ID: P210728
Snettisham Church, Norfolk. Looking east. This large, late medieval church at Snettisham is typical of many in this area where a mixture of local building stones are used for the main walling material, chalk, flints and ferruginous carstone, with better quality oolitic freestones of the Lincolnshire Limestone Formation imported for more ornate mouldings and carved stonework. Built in the 14th century decorated style, Snettisham Church has its nave and tower constructed of partially dressed blocks of chalk and flint. The spire, pinnacles, copings, buttresses and window tracery are made of oolitic limestone, one of the Middle Jurassic freestones. The wall in the foreground is made of dressed Carstone blocks which have suffered some frost damage. While this area of Norfolk produced a wide variety of local building materials, including sandstones, limestones and flints, none were good enough to qualify as freestones. Consequently from medieval times onwards the oolitic limestones of Lincolnshire were commonly imported for the stonework in all the more prestigious buildings.


St Mary's Church, Purton, Wiltshire. Looking north-west. This Norman / Medieval church with its spire and crossing tower is constructed of Jurassic Coral Rag limestones. The term Rag refers to the coarse grained shelly (or ragged nature) of the limestone when fractured. The ragstone beds are generally very hard and durable stones but are consequently, therefore, very difficult to work, commonly they are used as undressed rubblestone blocks. This church at Purton is largely built of local 'Coral Rag' Limestone from the local Osmington Oolite Formation.The roof of the church is covered with stone slates which in this area are likely to be from the Forest Marble Formation, although some use of local Purbeck limestones is also known. The hard, pale grey, coarsely oolitic and shelly limestones of the Corallian Group were widely used in buildings along their outcrops in Dorset, Wiltshire and Oxfordshire.
BGS Image ID: P210855
St Mary's Church, Purton, Wiltshire. Looking north-west. This Norman / Medieval church with its spire and crossing tower is constructed of Jurassic Coral Rag limestones. The term Rag refers to the coarse grained shelly (or ragged nature) of the limestone when fractured. The ragstone beds are generally very hard and durable stones but are consequently, therefore, very difficult to work, commonly they are used as undressed rubblestone blocks. This church at Purton is largely built of local 'Coral Rag' Limestone from the local Osmington Oolite Formation.The roof of the church is covered with stone slates which in this area are likely to be from the Forest Marble Formation, although some use of local Purbeck limestones is also known. The hard, pale grey, coarsely oolitic and shelly limestones of the Corallian Group were widely used in buildings along their outcrops in Dorset, Wiltshire and Oxfordshire.

Posted by Bob McIntosh

Tuesday 7 October 2014

BGS maps portal — maps and sections 1832 to 2014

Sheet 10 [Isle of Wight, Lyrnington, part of Portsmouth Harbour.] Geological Survey of England and Wales Old Series. 1:63,360. 1856.
Sheet 10 [Isle of Wight, Lyrnington, part of Portsmouth Harbour.] Geological Survey of England and Wales Old Series. 1:63,360. 1856.
Two sheets separated by 157 years. Both available as high resolution scans on the new BGS Maps Portal  

Isle of Wight special sheet. Geological Survey of England and Wales 1:50,000 map. 2013
Isle of Wight special sheet. Geological Survey of England and Wales 1:50,000 map. 2013

The British Geological Survey (BGS) has  released high resolution scans of over 6000 geological maps which were previously published on paper. The “BGS Maps Portal” provides free to view small and medium scale maps produced by the BGS since geological mapping began in 1832. The Maps Portal includes the recent 1:50,000 mapping of England, Wales and Scotland, geochemical and geophysical maps and also the historical maps that were in the former BGS historical maps website. 

Posted by Bob McIntosh