30 



ME. G. AV. LAMPLrGH OX THE JUXCTIOX OF [vol. Ixxviii, 



Fig. 16. — Section on tlie north-west side of tlie tramway -cuttincj 

 into Chamherlain Barn ;pit, Leigliton Buzzard; Octoher 

 Utli, 1920. Surface, alout 315 feet O.B. 

 W.N.W. _ E.S.E. 



! -" J z. 



... ... . . ^:=^._^^r— -.^r— '*^- 



Scale: Vertical 



Horizontal reduced i 



1 to2 



to 



ThicTcness in feet. 

 Z. Soil, rather sand}', with a few flints, drift - pebbles, and 



weathered gritt\' nodules about 1 



■la. Weathered brownish claj', with grit and cracked phosphatic"^ 

 nodules: some 'race,' but not abundant; no bedding in the ( 

 upper part ; streaks of bl\;e clay and grittj' claj' towards t 

 the base, with nodules, less gritt\' than those below. J 



3 b. (v) Gritt}' brown unstratified loam, with polished grit and"^ 

 l3-dites (up to 1 inch in diameter), some lumj)s of conglo- 

 merate, and gritty grej'-coated fossiliferous phosphatic 



nodules, black internally 6 inches 



(iv) Bluish grittv clav, with similar nodules 4 inches [ o f j, 



(iii) Gritty loam", as above 3 inches ^ 6 to 4> 



(ii) Bluish gritty clay, as above 2 inches 



(i) Gritty loam, as above, with lumps of conglomerate and 

 gritt}' phosphatic nodules, the latter less plenliful than 

 in the top loam (v) 24 inches J 



3. Bubbly iron-grit breccia ; with ironstone in worn slabs,~] 

 fragments, and flakes up to 15 inches long; some worn } 

 hematitic ' boxstones,' hollow inside or containing a little 

 coarse sand; worn lumps of pebble-conglomerate: a few [ 

 grittj^ phosphatic nodules ; and rare quartzite and other j 

 pebbles (up to 4 inches in diameter.) 

 Base uneven and pockety, with some patches of gritty loam ' 

 (3 a) in hollows below the breccia. J 



1. Cross-bedded Sands ; with reefs of cross-bedded iron-grit and~^ 

 crimson-coated hematitic boxstones, some lined internally 

 with quartz-crystals. At the top, immediately' under the 

 breccia, a band (lb) of concretions of irregular shapes, [> 8 + 

 sandy externally, but often having hard horny pale-grej' or 

 mottled pinkish phosphatic cores, as at Groveburv (p. 33); | 

 no fossils found in these, except sponge-like markings. J 



The fossils from the phosphatic nodules in 3 b include ' Ammon- 

 ites mammillatus,' • regularis ' (the most abundant), ' tardefur- 

 catus,' the small form called ' beudanti,' and others ; many 

 brachiopods, lamellibranchs and gasteropods ; a few echinoderms ; 

 some lobster- like crustaceans, etc. (p. 50). 



These well- characterized fossiliferous nodules occur through all 

 the beds exposed above the iron-grit breccia, as well as, more rarely, 

 in the breccia itself. They are widely-spaced and never clustered, 

 but display a slight tendency towards a linear arrangement ; and 



