207 



NOTES ON THE UPPER CHALK OF LINCOLNSHIRE. 



ARTHUR BURNET. 



Leeds. 



The following description of the Upper Chalk of Lincolnshire is 

 based upon field work done by myself in 1902 and 1903,* and 

 may be considered supplementar}' to that of Mr. William Hill, 

 who had visited Lincolnshire a few years previously, and had 

 discovered the existence of Upper Chalk in that county. 



There is now no doubt whatever that the zone of Holaster 

 planus can be traced continuously from a point just north of 

 Louth right up to the Humber, but we have as yet no positive 

 information as to the western boundary of this zone. The 

 general direction of the dip of the beds is north-easterly, but it 

 is very slight, and there are few faults or flexures of any 

 magnitude. 



In its lithological aspect, the chalk of the Holaster planus 

 zone of Lincolnshire presents a marked contrast to that of the 

 zone below, for, in addition to the scattered nodular flints which 

 characterise the Terebralulina zone, there is in the higher zone 

 a large number of immense bands of continuous tabular flint. 

 The chalk is hard, and fossils are usually rare, and difficult to 

 extract in good condition. Seams of grey or yellow marl, about 

 two or three inches in thickness, are not uncommon. In the 

 upper part of the zone the chalk becomes a little softer and 

 rather flaggy in places. Above this there are some bands of 

 continuous tabular flints intermingled with chalk. These bands 

 are probably the base of the Micraster cortestudinarium zone. 

 There are no beds having the lithological peculiarities of the 

 'Chalk Rock' of the southern counties. The following account 

 of the sequence of the beds near North Ormsby is taken from 

 the Geological Survey Memoir on 'Cretaceous Rocks,' vol III, 

 p. 273, and may be regarded as fairly typical of the exposures 

 in other parts of the Upper Chalk area in North Lincolnshire. 



ft. in. 

 Thill-bedded white chalk witii flint nodules ... 6 o 



Course of grey flint interlaminated with chalk .. 6 



Firm creamy white chalk ... ... ... ... 30 



Seam of dark grey shaly marl ... ... ... 3 



Hard dull white chalk with flat lenticular flints ... 60 

 Continuous floor of flint ... ... ... ... 6 



Hard white chalk in thick beds without flints ... 76 

 Hard dull white chalk with small lenticles of flint 10 o 

 Hard white chalk in more massive beds ... .. 60 



* See also Geol. Mag., 1904, pp. 172-176. 

 1906 July 1. 



