THE NEOCOMIAN CLAY AT KNAPTON. 



G. W. LAMPLUGH, F.G.S. 



We have practically no knowledge of the Lower Cretaceous beds 

 in Yorkshire except what may be gathered from that one magnificent 

 section of the Speeton Clififs. Inland, the ground at the foot of the 

 chalk escarpment where these beds should appear is covered deeply 

 with drift and alluvium, so that for over sixteen miles nothing 

 whatever of the 'solid' geology can be seen. At this distance from 

 the coast, however, the gradual rise of the base of the chalk brings 

 the underlying beds above the alluvial flat, so that, in the neighbour- 

 hood of the villages of Heslerton and Knapton, clay may be traced 

 obscurely outcropping from below the Red Chalk. 



Unfortunately, of this clay there has not been of late years a 

 single open section. Forty or fifty years ago several shallow jMts 

 were worked in it, some of which yielded fossils which are still 

 preserved. But these pits were already disused and obscure in 1869, 

 when Prof. J. W. Judd examined them, though some indications of 

 the character of the deposits still remained or could be gleaned from 

 the inhabitants of the neighbourhood ; and from data thus obtained 

 Prof. Judd partially described the pits.* 



The conclusion he arrived at was that these Knapton clays repre- 

 sented the lower part only of the Speeton series, from the ' Speetonensis- 

 beds ' downwards, and that the band of phosphaic nodules which 

 occurred in one of the pits was equivalent to the ' Coprolite-bed ' 

 found between the Neocomian and Jurassic clays at Speeton, 



The supposed absence of the upper beds of the Speeton series, and 

 the presence of the ' Coprolite-bed ' close under the base of the chalk, 

 led to the deduction that in this neighbourhood the chalk passed 

 unconformably across the lower members of the Neocomian clays, 

 and then off them altogether. This view was clearly illustrated by a 

 map, and by diagrammatic sections of the Wolds and Pickering Valley. 



The result of recent researches at Speeton, however, raised some 

 doubt in my mind as to the reality of the relationship thus set forth. 

 Fresh evidence was sought for in the field, but as there are no new 

 sections to replace those which have gone to decay, none was forth- 

 coming. The broad fact was palpable enough, that the Chalk 

 escarpment east and south of Malton rested upon the various 

 members of the Jurassic formation in turn ; but this in itself was no 

 proof that the unconformity affected the Neocomian beds also, for 

 these might just as reasonably be held to have disappeared through 

 an overlap of the chalk upon the old pre-cretaceous slope. And that 



* 'Additional Observations on the Neocomian Strata,' etc. (^uart. Journ. 

 Geol. Soc, vol. xxvi. p. 327. ^Naturalist, 



