72 A. E. Trueman — The Lias of South Lincolnshire. 



The zone is evidently that of Pentacrinus tiilercidatus, and the 

 horizon near that of the Plungar ironstone. The fauna resembles 

 that recorded bj' the Rev. J. E. Cross in the ironstones of the "sew^^- 

 costatus zone" {tulerculatus zone of Oppel) at Scunthorpe, in North 

 Lincolnshire.' It is interesting to notetlie absence at Sedgebrook of 

 all species of Cardinia, one of the commonest and most characteristic 

 fossils in the north of the county. Cardinia does occur, hovpever, 

 within a few miles of Sedgebrook, near Bottesford and Allington,^ 

 and this suggests that the horizon seen here is not precisely that of 

 the Scunthorpe ironstone. 



The strata between the two horizons just described were penetrated 

 in 1916 by an nnsuccessful boring for water, which was made at 

 Plungar, about a quarter of a mile south-west of the church. The 

 section was roughly as follows : — 



Feet. 

 Ironstone and clay with Gryj^hea, Lima, and Avicula about 4 

 Dark-grey marl ......... 30 



Dark shale with shelly bands ....... 40 



Light-blue shale ......... 10 



Several beds of fine blue limestone with C. Bucklandi . . 2 

 Blue shale .......... 6 



It is probable that with the exception of the uppermost few feet, 

 all the rocks passed through belong to the JBucklafidi zone, which 

 apparently has a thickness of more than a hundred feet. 



Higher beds were shown by another boring a few yards east of the 

 Stathern Station; it was made in 1916 by Messrs. Le Grand and 

 Sutcliffe, who gave permission to examine the core and supplied 

 some of the following particulars: — 



ft. in. 



Blue-grey clay ......... 69 



Shell beds and shales. Earthy limestone with Ostrea . 5 



Soft dark clay 27 



Light-grey clay with thin limestone . . . . . 10 



Light-blue, hard limestone ; Ostrea ..... 1 



Light-blue marl ......... 35 



Massive limestone . . . . . . ' . . 16 



Black pyritie marl . . , . . . . . 17 6 



Grey sandy marl with Lamellibranchs . . . . 2 



"'^Grey marl with bands of earthy limestone, with Ostrea, 



Pecten, Avicula incsquivalvis . . . . . 29 



Clay with bands of limestone . . . . . . 26 



(Boring abandoned ; no water reached.) 



The bed indicated * contains an association of fossils which 

 resemble those in the ironstone band at Plungar, and is probably its 

 equivalent. The outcrop of the ironstone can only be traced for 

 two and a half miles south-west of Plungar,^ and it appears to have 

 a similarly restricted extension towards the south-east, for no 

 indication of it is shown in the boring, the strata passed through 

 consisting almost entirely of clays and shales. 



^ J. E. Cross, " Geology of North-West Lincolnshire " : Q.J.G.S., vol. xsxi, 

 p. 123, 1875. 



^ Geology of South-West Lincolnshire (Mem. Geol. Surv.), 1885, p. 30. 



' W. Gibson, Geology of Melton Moiobray, etc. (Mem. Geol. Surv.), 1909, 

 p. 33. . 



