40 
MORTIMER : ORIGIN OF CHALK DALES. 
movements. Tlins we find the chalk beds contorted, squeezed, 
crumpled, shattered, fractured, and faulted in almost every direction, 
giving- clear indications of the effects of subterranean forces. We 
also seem to have evidence of considerable disturbances even during 
the formation of the chalk. In Silex Bay, near Flamborough, 
there are contortions in the strata, which though greatly masked by 
drift slipped from above, seem to be over-laid with nearly horizontal 
and almost undisturbed beds of chalk. Then again the black 
carbonaceous band 6 to 20 inches thick, observed about 50ft. from 
the base of the chalk near Londesborough at Drewton in pits on each 
side of the Wharram Station, and in the railway cutting on the west 
side of the line a little south of Hunmanby Station ; also discovered 
about 3ft. in thickness, in sinking a well at Fordham in 1857 ; and 
seen recently at the base of the cliff opposite Buckton Hall, a little 
north of Flamborough, is probably due to disturbances during the 
deposition of the chalk. At the latter place it is not thick, and there 
is a slight trace of unconformity, or false bedding in the adjoining 
beds ; a thin bed of broken and crushed chalk, somewhat brecciated, 
lies- immediately under the black band; and the two clearly divide, 
at this place, the grey chalk from the white chalk with flints. A 
somewhat similar bed of crushed chalk 4 to 6 in. in thickness, is 
observable in a pit, about | of a mile east of Market Weighton. 
These horizontal beds of crushed chalk, indicate local shearing of 
the beds, under great pressure; whilst there can be little doubt that 
the dark band is due to an abnornal deposition, after some violent 
disturbance of the sea; probably some subterranean movements 
caused the waves to break up and for a time hold in suspension, a 
large quantity of the adjoining and outcropping Lias, Kimmeridge, 
and Neocomian clays. On the subsidence of such a turbulent 
condition of the cretaceous waters, dark matter combined with 
calcareous and argillaceous particles, also held in suspension b}^ the 
troubled waters, would settle down into just such a band ; differing 
slightly in thickness and colour here and there as we now find it. 
In addition to the places previously named, Mr. C. Fox Strang- 
ways kindly informs me that this black clayey chalk was found in 
well-sections at Helperthorpe, Weaverthorpe, and Butterwick; 
