

Lower Greensand 23 



Bourn, is never seen at the surface until one gets to 'near 

 the Cambridge-Huntingdon road between Dry Drayton and 

 Lolworth. There a strip of sandy land occurs and is con- 

 tinued by Oakington and Cottenham to the Fens. A similar 

 strip rests upon Kiuieridge Clay north of the Ouse and runs by 

 Haddenham and Wilburton to Stretham, where it was once 

 worked for the phosphates which occur scattered through its 

 mass. Ely, too, is built on an outlier of Greensand which, 

 though much drift covered, is exposed at the north corner of 

 the Roswell pit. 



Around the Upware ' island ' a thin representative of the 

 Lower Greensand occurs. Its greatest thickness is not much 

 more than ten feet, but the locality was unsurpassed for 

 fossils and phosphates. The Greensand of Upware rests 

 upon Coral Rag, Coralline Oolite, and Kimeridge Clay. Its 

 lowest layers consist of angular lumps of the limestones set in 

 a clayey matrix. A pebbly sand with abundant phosphate 

 nodules follows, and in places has a calcareous cement, and 

 the various indigenous brachiopods swarm in it. Above this 

 comes a layer of yellow sand and then another phosphate bed, 

 not so rich in fossils but still containing numerous lamelli- 

 branchs, gasteropods, and sponges. Another foot or two of 

 sand completes the series, which is topped by a layer of clay 

 and another nodule bed containing Gault fossils. 



Unfortunately phosphate working at Upware and-Wicken 

 has come to an end, and the only available exposure of 

 these interesting beds is that furnished by a shallow ditch 

 on the east side of the green road which runs from the South 

 to the North pit at Upware. The best exposure is about 

 300 yards north of the South pit. There the rock may be 

 examined and occasional oysters, Terebratulidae and Rhyncho- 

 nellidae can be collected. 



The section at the river entrance to the main South pit 

 when dry shows the- relations of the beds rather well. 



The study of the indigenous faunas found at these various 

 localities led Mr Teall in 1875 to refer the Lower Greensand 



