part I] GAULT AND LOWER aEEE]S^SA]S^D JS^EAll LEIGHTOIS^. 



53 



rough determinations are poorly representative of the fauna, and 

 the list could certainly be much extended: — 



'Ammonites rostratus and vars.' (many); 'A. auritus and vars.' (both in 

 nodules and soft clay); 'A. varicosus' (few); 'A. splendens and vars.'; 

 ' A. near coelonotus ' ; ' A. studeri ' ; 'A. lautus ? ' ; and others ; ' Karaites ' ; 

 * Belemnites minimus' (many). ' Inoceramus concentricus ' (both in nodules 

 and soft) ; ' I. subsulcatus ' (one specimen in black phosphate) ; ' I. sulcatus ' 

 (nodules and soft); ' Nucula pectinata ' (soft); 'Plicatula' and ' Ostrea ' ; 

 ' Dentalium ' (many) ; ' Scalaria,' ' Solarium,' and other univalves ; ' Penta- 

 crinus ' (in patches). 



IV. CLASSIFICATIOlSr, SxETJCTUEE, AjS^D CONDITIONS 



OF Deposition. 



The sequence of beds exposed in the sections described may be tabulated 

 in downward order as follows : — 



Formation. 



Post- \.ry. 



Glacial. 5^^-) 

 Glacial 



Thickness 

 in feet. 



1 to 4 



/y N C Boulder-clays 

 ^ '' X gravels. 



Gault 

 (part of). 



Composition, Localitij 



Soil, dovvnwash and ' creep.' All sections. 



with associated and later Absent in some"! 



places : l)est seen 



^•Wfl^^r-'^^"'Hoto20 

 pit (fig. lo) and f 



Littleworth (p. [ 



39). J 



f Upper Gault, lowest part only: pale blue-~^ Harris's (fig. 3),^ 



I grey marly clay, with numerous corroded | Heath House (p. 



(5)<J phosphatic nodules (5a) at or near the base. |> 27) and Grove- 



I I buiy brickyard 



L . J (p. 34). J 



C Lower Gault ; dark grey-blue clays with ) 



( 4 ) ^ small brown-coated nodules ; generally > All sections. 



becoming gritty near tbe base (4a). } 



Oto 6 

 (seen) 



up to 18 



Basement,„,^i 

 beds. ^"^'^ 



South of 

 Lei gilt on. 

 Grittj^ glauconitic 

 clay and loam (3b) 

 with occasional 

 worn fragments of 

 ironstone; sparsely 

 studded with fos- 

 siliferous gritty 

 phosphatic nod- 

 ules. 



North of Leighton. 



Similar material more 

 coarsel}^ gritty (3 b) 

 associated with, and 

 in places thinning out 

 upon or under (3 a) a 

 band of irongrit- 

 breccia with f erricrete 

 ' pans ' and lenticles 

 (3) ; and with calcrete 

 patches thickening 

 locally into lumps or 

 tables of fossiliferous 

 limestone. 



Lower 



Green- 



sand 



Series 



(part of). 



L 



Uneven surface of erosion. 

 " ( 2 ) The Silty beds : regularly bedded ashj'-grey 

 silts, carbonaceous and ferruginous loam 

 and clay, and some sand. 



Plane of erosion. 



( 1 ) Leighton Sands : strongly cross-bedded"^ 

 ■{ coarse sands. North of Leighton : 



almost purel}'' siliceous 'Silver Sand ' with 

 local patches of ferruginous staining and 

 induration (Ix). South of Leighton: 

 less pure, speckled, brownish or greyish 

 sands, rarely showing staining or indu- 

 ration. ^ 



South— "^ 



Grovebury pits 



(fig. 17, p. 33) 

 Intermediate — 



Chamberlain 



Barn pit (fig. 16) 

 North- 

 All Shenley pits ; 



Poplars (fig. 14), }>1 to 5 



Claridge's (fig. 



15), and Heath 



House pits : also 

 West— at South- 



cott (p. 38), 



Littleworth (p. 



39), and Long 



Crendon (p. 40). J 



Present in some^ 

 Shenley sections | 

 and northwards ; J>0 to 12 

 absent south- | 

 wards. J 



All the pits around 

 Leiffhton. 



