Kimeridge Clay 19 



it becomes so bituminous as to be unfit for brick-making. 

 Thin bands of limestone are fairly common, but are incon- 

 stant. They often pass into lines of septarian nodules and are 

 generally unfossiliferous. 



The best exposure is that shown in the Roswell Pit, one 

 mile north-west of Ely, where all but the very lowest Ostrea 

 beds are at times exposed. Some seven feet below the ordinary 

 water-level of the Ouse is a thin band of fissile sandy shale 

 with crowds of Astarte supracorallina. Above that is about 

 ten feet of blue clay becoming sandy and papery towards the 

 top. A few calcareous nodules are met with about this horizon, 

 and just above them Aptychi of ammonites abound. Twelve 

 feet of variable grey sandy shales follow, and above them 

 darker shales crowded with Exogyra virgula. This horizon 

 is well marked by a band of large septaria, and above it come 

 seven feet of the very bituminous shales with Discina latissima. 

 These are the highest Jurassic beds known in the district, and 

 they are overlain by somewhat disturbed Lower Greensand. 

 Of other exposures those at Haddenham are interesting as 

 showing the lowest beds of the clay, which are ill exposed 

 at Ely. The pit to the west of the station shows the 

 basement phosphate bed, that south of the station shows 

 somewhat higher beds. Various exposures of the intermediate 

 layers also occur in three pits along the Ely-Littleport road 

 and in several brickyards at Littleport, but these add but 

 little to the knowledge obtained from the section at the 

 Roswell Pit. 



The Kimeridge Clay is generally quite rich in fossils. 

 Flattened ammonites and lamellibranchs are to be obtained 

 from nearly every layer, but solid ones are somewhat rare. 

 Few of the fossils are pyritized, but some are preserved as 

 phosphate nodules, and saurian bones in that condition are 

 not rare. The common ammonites are biplex, mutabilis, alter - 

 nans and calisto. 



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