This stirred a memory and prompted a search:-
A basin of deposits of Oligocene age,about 10x4 sq.miles occurs in the Bovey
Tracey-Kingsteignton district.These deposits,over 650ft. thick contain
valuable
beds of pipeclay,possibly derived from the erosion of china clay off nearby
Dartmoor.
These beds were worked extensively by shaft and adit,up to recent times I
believe.
Associated with these clays are beds of lignite(brown coal),the most
important
seam being the 'Big Coal',up to ten feet thick.The seams are believed to be
rafts
of tree debris swept into the lake from which the Bovey Basin was formed.
The commonest species is Sequoia, the Redwood pine.Conjures up quite a
picture,Dartmoor as Giant Redwood forest.
These coals were mined by shaft and adit and used as fuel in the Bovey
potteries.
A similar basin,about 0.75x 4.5sq.miles in area occurs at Petrockstow in
North Devon with thin beds of lignite which were probably worked in
association
with the clays,this time by levels driven from inclined shafts.
A reference is 'The Lignites and Clays of Bovey Tracey' by W. Pengelly
in Phil. Trans. volclii
I don't know the last date of coal mining but does anyone know of a book
on this and/or the clay mines of this district(do they still work?)
Andrew Santer
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