GEOLOGY 



brackish water forms ; plant beds occur, from which it would appear that 

 a kind of equisetum covered a great many square miles of the swampy 

 ground ; and false-bedded and ripple-marked sandstones indicate shallow 

 water. It is probable that the river or rivers came from the north- 



west.' 



The Lincolnshire Oolite 



The latter part of the Inferior Oolitic period in this district was 

 characterized by a local depression over an area of some ninety square miles, 

 embracing chiefly north-east Northamptonshire and Lincolnshire. The 

 extreme westerly (Maidwell) and southerly (Wold) limits of the Lincoln- 

 shire limestone now to be seen are probably not far from the boundary of 

 the original depression in these directions. 



The main mass of the Lincolnshire Oolite consists of compact, 

 subcrystalline, oolitic, fossiliferous, and slightly argillaceous limestones ; 

 and of shelly ragstones (Barnack Rag, etc.), towards the formation of which 

 coral contributed much. The beds thicken in a north-easterly direction 

 to about 75 feet at Stamford, in which direction no doubt the deeper 

 water lay. Nearness to land and shallow water is indicated by wood, 

 plants, and rolled shells, indeed the limestone appears to have been in 

 places a dead-shell bank. The lower beds may be marly and soft, but a 

 good portion of the stone furnishes a cream-coloured freestone suitable for 

 ornamental work, as well as general building purposes. A hard shelly 

 variety takes a good polish, and is known as Weldon marble, Stamford 

 marble, etc., according to the place from which it comes. All forms 

 produce lime of good quality. 



Collyweston Slates. The lower beds of the Lincolnshire Oolite 

 formation in those parts that may be looked upon as the margin of the 

 depression in its earlier stages, are either sands or sandy limestones or 

 both. The arenaceous limestones have been largely worked at Dene, 

 and between Stamford and Collyweston and elsewhere, under the name 

 of Collyweston Slates. At Collyweston the workable bed varies from 6 

 inches to 3 feet in thickness, but more or less slaty beds occasionally 

 encroach on the main mass of limestone to the thickness of 18 feet. 

 Ripple marks, worm tracks, and plant remains in the slates, as also the 

 sands, indicate shallow water and nearness of land." 



' John W. Judd, ' The Geology of Rutland,' etc., Memoin of the Geological Survt\'t 



P- 129- 



^ For more detailed description of these and other beds of the Inferior Oolite consult 

 Sharp and Judd. John W. Judd, 'The Geology of Rutland,' etc., Mnnoirs of the Geological 

 Survey ; Samuel Sharp, ' The Oolites of Northamptonshire,' pt. i., Quart. Journ. Geol. Soc. 

 (Aug. 1870), p. 354 ; pt. 2, ihid. (1873), P- 225. 



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