Monday 14 February 2022

Carstone and Chalk

'Carstone I will mention in order to abuse it" 

(Jacquetta Hawkes ('A Land', 1951).


Why not? This orangey-coloured Norfolk sandstone does not look attractive on its own nor does it combine attractively with other materials. It presents a burning, gingery face to the world and does not weather gracefully. It outcrops between Hunstanton and the Nar valley, where several quarries - such as Snettisham and Middleton - specialise in producing blocks of 'big carr' for masonry or 'small carr' for hardcore or shillet walling.  


The Carstone is at its finest and boldest in the famous geological layer-cake of Hunstanton Cliffs. It underlies the Red Chalk and Grey Chalk and forms a sort of solid biscuit base for those more mellow, pastel layers. Its only fossils are worm burrow traces, and it is laced with liesegang rings: patterns of dark and light cementation brought about by migrating iron compounds. Here, it looks like a sort of industrial slag. 



The only way the Carstone can achieve aesthetic lift-off is probably as a crude pigment. It is so gritty that its iron oxide is a chore to extract for creating home-made paint, but its bold, uncompromising colouration lends itself to astonishing, disharmonious juxtapositions in the landscape. At outcrop it colours the soil a rusty brown and on Hunstanton beach it yields a brown, exotic-looking sand. Hawkes called its effects 'strident': sometimes stridency is needed to shock us out of our visual complacency. Consider this photograph taken in the Snettisham Carstone Quarry.   

Image courtesy Frimstone Ltd

Grey Chalk is as different from the Carstone as cheese. It is indeed it looks like a type of moon-cheese, with a glimmering and dulcet milkiness which is readily ground into lime and - in the right circumstances - can be cut into blocks of stone known as clunch. The Grey Chalk and overlying White (Upper) Chalk span over 40 million years of time. They were deposited on the seabed in a world which was much hotter than our own and had a much higher percentage of atmospheric carbon dioxide. Hawkes calls the Chalk the 'prime creation of later Cretaceous times'. Indeed, the carbon dioxide went into the skeletons of countless billions of planktonic marine organisms whose lime-rich remains rained down through the water and were laid down as calcium carbonate mud. The Chalk now forms ancient seabed deposits as far afield as Russia and Kansas as well as the White Cliffs of Dover. 

Hillington Chalk Pit.
Image courtesy West Norfolk Lime Ltd

Unlike the White Chalk, the Grey Chalk does not contain flints. Instead, it has a variety of body fossils such as echinoids and bivalves and is composed of various horizons of harder or softer texture. It has been extracted in a series of quarries along its outcrop, as at Gayton and Hillington. Where they intercept the groundwater, flash ponds may result on the quarry floor and surprise the eye with a tropical turquoise-blue. 

Hillington Chalk Pit.
Photo with acknowledgements to West Norfolk Lime Ltd
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Some thoughts towards 'EXTRACTION : ART ON THE EDGE OF THE ABYSS' at Groundwork Gallery, King's Lynn, 2021.