58 SPEETON CLAY. 



SPEETON CLAY. 



The Speeton Clay, of Yorksliire, is a dark blue or black 

 clay, generally laminated, and containing distinct layers of 

 large and small nodules of argillaceous ironstone; the 

 fissures of tlie larger nodiiles are more or less partially 

 filled with calcareous spar, selenite and iron pyrites, and 

 occasionally contain fragments of fossd shells, as A.mmo- 

 nites, Crioceras, &c. In the smaller nodules, remains of 

 Crustacea and other fossils are frequently enclosed. This 

 deposit has hitherto only been observed in Yorkshire, and 

 is well exposed for about a mile in the Speeton Cliffs 

 adjoining Filey Bay. At one part of the Cliff, the Clay 

 attains an elevation of about 300 feet, but decreases in 

 thickness towards the north, and becomes lost beneath the 

 level of the sea. Southwards of the spot where it is most 

 elevated, and dipping with the superincumbent beds in the 

 same du-ection, it may be traced immediately underlying 

 the Eed and White Chalk of the Speeton Cliffs. 



The real position of the Speeton Clay* has not yet, we 

 believe, been satisfactorily detennined, as some of the 

 fossils have a great analogy to those occm'ring in the 

 Gault of Kent and Sussex, whilst others bear a great 

 resemblance to some from the Kimmeridge Clay. 



Of the seventy-one species mentioned in the ' Geology 

 of Yorkshire,' p. 96, five appear to be found in the Kim- 



* The Lower Green Sand, Wealden Formation, and Portland Strata, are all wanting iu 

 this district. M. Roemer considers the Hilsthon of Germany as the equivalent of the 

 Speeton Clay. 



