A HISTORY OF NORTHAMPTONSHIRE 



Any of the hard beds may yield water, but the only ones that can 

 be fairly well relied upon to do so, and that give permanent springs 

 within the district, are those marked thus *. 



The Junction bed. No. 7, is seldom to be seen ; the most interesting 

 exposure that has occurred was near to Welton Station.' Beds included 

 under 6 may be examined in the deep valleys around Catesby and 

 Hellidon ; beds 3 to 5 near to Staverton and Byfield, etc. 



The Marlstone rock-bed, No. i, may be found over much of the 

 area shown as Middle Lias on the map ; it is by far the most important 

 bed, having been worked for ironstone in the south-western parts of the 

 county, near Kings Sutton, and for building stone and road metal almost 

 everywhere where it occurs near to the surface. 



The Transition Bed 



At or near the close of the Middle Lias period there appears to 

 have been a pause in the terrestrial movements we have chronicled in 

 previous pages, during which time little or no sedimentation took place, 

 for attrition of the rock-bed itself may have yielded the small thickness 

 of grey marl usually found resting upon it. The striking similarity in 

 character, thickness, and fossil contents of the Transition bed over a large 

 part of Northamptonshire and some neighbouring counties, indicates 

 uniformity of conditions, including depth, hence a few pages back we 

 took this horizon as a datum for calculating subsequent earth movements. 

 The time taken up by the period we are considering was no doubt a 

 fairly long one, for the fauna of the bed is a mixture indicating a decline 

 of Middle Lias forms and an influx of Upper Lias ones, hence the term 

 ' Transition Bed ' given to it by Mr. E. A. Walford.^ Ammonites acutus 

 is characteristic, and several of the interesting gasteropods found in it 

 might be so regarded for this district. 



The Upper Lias 



Before the Transition period much or the whole of Northampton- 

 shire was embraced in the north-westerly rising area, after it in the sink- 

 ing (south-easterly or general ?) area. Then followed, on a smaller scale, 

 a remarkable repetition of Lower and Middle Lias phenomena. As the 

 near land disappeared, and the shore line receded, in succession were 

 formed paper shales with much vegetable matter, and fine-grained fish 

 and insect limestones, then calcareous clays with argillaceous limestones, 

 (but only two or three) ; next purer clays with isolated cement stones. 

 Towards the close (corresponding to the change from Lower to Middle 

 Lias, p. 11) we find a layer of water-worn nodules and rolled fossils, some 

 covered with ostrea or serpu/ce, followed by micaceous sandy clays 

 containing an entirely new fauna mixed with the old, and in certain 



' W. D. Crick and C. Davies Sherborn, ' On some Liassic Foraminifera from North- 

 amptonshire,' Journ. North. Nat. Hist. Sac, vol. vi. p. 2o8. 



* Edwin A. Walford, ' On some Middle and Upper Lias Beds in the Neighbourhood of 

 Banbury,' Proc. IVarw. Nat. and Arch. Field Club (1878). 



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