3G ME. Ct. w. LAMPLrGii OX THE junctiojS^ OF [vol. Ixxviii^ 



Thickness in feet^ 

 3b. The fossilifevous bed : gritty clay with small polished pebbles (up 

 to \ inch in diameter), and streaked with gritty loam and rusty 

 weathered glauconite ; small nodules (up to 6 inches in diameter) 

 of dark gritty phosphate are scattered rather plentifully through 

 the band, although with a few ferruginous nodules and worn 



fragments of ironstone 2 — 3 



Nos. 3 and 4 become thicker towards the south. 



1. Coarse current-bedded greyish sand, with many dark coffee- 

 coloured grains in streaks ; some indurated calcareous lumps (up 

 to 1 foot in diameter) occur (lb) immediately below the sharp 

 junction with 3b seen to about 20 



Among the ammonites wliich I obtained from the nodules ii> 

 this section, Dr. F. L. Kitchin identified LeymerieUa regularis- 

 (Bruguiere) and L. tardefiircata (d'Orbigny). 



A further exposure of the same beds was open for a short time 

 recently in ' Webster's pit,' on the east side of the road, 200 3'ards. 

 south of the railway-crossing, on the site marked ' Brick Works ' 

 in the G-inch Ordnance map. The section corresponded to that 

 seen in tlie adjacent Spinney pit ; it was partly obscured when I 

 visited it early in 1920, and has since been all hut obliterated. It 

 was, however, seen clearly in Ma}^ 1919 by Dr. Kitchin & 

 Mr. Pringle, from whose published account (Geol. Mag. 1920^ 

 p. 52) the following details are taken : — 



Section in Webster's pit,' May 1919 [fide Kitchin & Pringle]. 

 Surface, 290 feet CD. 



Feet, inches.. 



(Z) 'Soil' 1 



(4) ' Greenish-giey stiff lumpy clay wilh a iew smooth-skinned 

 nodules. Numerous fragments of ammonites of the 



i7iter?'njotus-ty'pe occur mainly in the form of casts '.. abt. 4 



/ . N ( ' Brownish sandy chi}' with streaks of glauconite ' 1 to 2 



^ '^^I'Thin band of dark-grey clay' 2toa 



(3 b) ' Dark-brown well-bedded sandy clay with numerous rounded 

 quartz-grains and pebbles. Pale-coated dark gritty phos- 

 phatic nodules of irregular shape (up to 6 inches in diametei'), 

 their surfaces studded wilh quartz-grains, occur sporadically 



throughout ' abt. 4 



(1) 'Dirty brownish-white faUe-btdded sand with bands and 



masses of iron-grit in the lowest 5 feet,' etc.. seento 9 



The authors mention the following ammonites as having beeii 

 obtained by them from the nodule-bed (8 b) of the two pits, this 

 and Pratt's: — Desmoceras aff. heiidanti (Brongniart), Donvillei- 

 ceras mammillafiim (Schlotheim), LeymerieUa regularis (Bi'u- 

 guiere), X. tardefiircata (d'Orbign}^), and Sonneratia diitem- 

 pJeana (d'Orbigny). 



The Grovebury sections, as a whole, differ from those north and 

 north-east of Leighton in the absence of a definite band of iron- 

 stone-breccia and pan, and m the fuller development of the gritty 

 beds with phosphatic nodules at the base of the Gault. The 

 Chamberlain Barn section (fig. 16, p. 30), with its thin and 

 diffused breccia, affords the intermediate link; and the presence of a 

 few worn fragments of iron-grit, and of an occasional concretionary'^ 



