ORIGINAL ARTICLES. 



On an Inverted Mass of Upper Cretaceous Strata near 

 Leighton Buzzard, Bedfordshire ; and on an Overlap 

 of the Upper Gault In that Neighbourhood. 



By F. L. KiTCHiN, M.A., Ph.D., and J. Pringle, F.G.S. 

 (Contimied from p. 15.) 



B. Comparison with other Sections in the District- 

 I. Sections near LeigJiton Buzzard. 



WE owe to Mr. Lamplugli a description of the lowest beds of the 

 Gault and their junction with the Lower Greensand, as seen in 

 sand-pits on the south side of Leighton Buzzard.^ Mr. Lamplugh 

 proved the presence of the fauna of the mammillatus zone and 

 found that the fossils preserved in the gritty phosphatic nodules 

 of the lowest bed above the false-bedded sands include Douvilleiceras 

 mammillatum (Schloth.) and the characteristic Desmoceras usually 

 associated with it.^ 



In May of last year an excellent section, comprising Lower Green- 

 sand and Lower Gault, was shown in a sand-pit (Mr. Webster's) 

 about 200 yards south of Billington Crossing (No. 1) on the Leighton 

 Buzzard-Dunstable railway (L. & N.W.E,.). This old excavation 

 was reopened at the end of 1918 and has now been abandoned. At 

 the time of our visits the beds exposed were as follows : — 



ft. in. 



Soil 10 



Gault Greenish-grey stiff lumpy clay -with a few smooth 



with skinned nodules. Numerous fragments of 



interruptus ammonites of the interrupt us -type occur mainly 



fauna "| in the form of casts . . . about 4 



Brownish sandy clay with streaks of glauconite . 1-2 



*^Thin band of dark-grey clay .... 2-3 



Passage-bed to ^^ Dark- brown well-bedded sandy clay with numerous 



Gault, I rounded quartz-grains and pebbles. Pale-coated 



with I dark gritty phosphatic nodules of irregular shape 



iardefurcata \ (up to 6 inches in diameter), their surface studded 



fauna with quartz-grains, occur sporadically through- 



V. out ...... about 4 



rDirty brownish-white false-bedded sand with 



I bands and masses of iron-grit in lowest 5 feet. 



Lower < Numerous thin brown rusty streaks occur 



Greensand parallel to bedding-planes ; the sand paler in 



I colour at the top .... seen to 9 



1 G. W. Lamplugh, " Report of an Excursion to Leighton Buzzard " : 

 Proc. Geol. Assoc, vol. xxvi, pt. v, 1915, p. 310. 



" Specimens of the Desmoceras were submitted to one of the present writers 

 and were identified by him ; but he is not responsible for the name under 

 which they were cited in Mr. Lamplugh's report (op. cit., p. 310). Forafurther 

 account of the species see A. J. Jukes- Browne, The Cretaceous Eocks of Britain, 

 vol. i, " The Gault and Upper Greensand of England " (Mem. Geol. Surv. ), 1900, 

 p. 443 ; also G. W. Lamplugh & F. L. Kitchin, On the Mesozoic Rocks in 

 some of the Coal Explorations in Kent (Mem. Geol. Surv.), 1911, p. 100. 



