BOTTLDER-CLAYS OF LINCOLNSHIRE. 



125 



entire absence of even ditch-sections prevented my coining to any 

 conclusion on this point. 



The appearances at these three localities being not unfavourable 

 to the supposition that the brown clays passed into chalky clay, 

 taken together with the fact of the former clay occurring at so 

 great a height on the "Wold as nearly 400 feet, inclined me to the 

 belief that there was no great separation in time between the 

 formation of the two series. It was not, therefore, till last year 

 (1883) that I recurred to the opposite opinion, in consequence of 

 finding evidence on the west side of the Wolds which forced me to 

 regard the brown clays of that district as belonging to a much more 

 recent period than the blue and chalky clays. This evidence may 

 be briefly recapitulated as follows : — 



1. The position of the red-brown clays near Brigg resting against 

 ridges of Jurassic clay, which are capped by outliers of Chalky 

 Boulder-clay (as in fig. 3), the two clays being very different in 



Fig. 3. — Section througJi Low Barf, S.E. of Brigg. 

 (Horizontal scale : 2 inches to a mile.) 



d d 



a. Alluvium. b. E,ed Clay, c. Chalky Clay. d. Oxford Clay. 



appearance, and the former occupying valleys which appear to have 

 been eroded out of a surface composed of Oxford Clay overspread 

 by a sheet of Chalky Boulder-clay. 



2. The fact that a red-brown clay of similar type actually rests 

 upon a continuation of the older Boulder- clay in the district between 

 Market Basen and Langworth. 



3. The manner in which the mottled clays separate themselves 

 from the blue Boulder-clay and from a terrace or narrow tract along 

 the western border of the Fenland, between it and the highland, 

 just as they do between the marshland of East Lincolnshire and the 

 Chalk Wolds. 



To these considerations may be added the following : — 



4. The actual superposition of the mottled clay on the blue 

 Boulder -clay at Boston. 



5. The relative positions of the two clays along the north border 

 of the Pens by East and West Keal, where the Brown Clay is 

 banked against the slope of hills capped with Chalky Boulder-clay*. 



6. The fact that, while both Boulder-clays are found at the same 

 level south of Bevesby, they each retain their distinctive colours 

 and characters and occur in separate areas. 



* See Section in Quart. Journ. Geol. Soc. vol. xxxv. p. 405. 

 Q.J.G.S. No. 162. L 



