42 MR. G. W. LAMPLrGH O'S THE JUNCTIOIS^ OF [vol. IxxVlii,, 



Davies, who published, in 1899, the following description of it in. 

 his excellent paper, ' Contributions to the Geology of the Thame 

 Valley ' (Proc. Geol. Assoc, vol. xvi, p. 22). 



'Section at Southern Windmill, Long Crendon.' 

 (A. M. Davies, 1899.) 



Feet, inches.. 

 ' Gault.' ' Claj'' with Inoceramus concentricus, Belemnites minimus, 



and foraminit'era 8 



f Sand, with pebbles of quartz and lydite, and ironstone 



'PSTnf -I concretions containing calcite 1 6 



Ironsands.'i [ ^^reen sandy clay 1 6 



I Ironstone b 



l^' Bluish clay, black at base 6 



' Purbeck.' ' Limestone with clay-veins ' 4 6 



With other details, down to Portland limestone. 



In a later paper Dr. Davies mentions that in the Gault here he 

 ' failed to find ammonites, though foraminifera were plentiful ' 

 (GeoL Mag. 1899, p. 161). 



I first visited the spot myself in June 1902 ; but by this time 

 the deeper part of the section had become obscure, and I saw the- 

 base of the Gault only where the cover was comparatively thin- 

 and the beds much weathered. The following details are from 

 m}^ sketch and section of the best exposure ^ : — 



Long Crendon pit, in field north of South Windmill; 



June 22 n d, 1902. 



Thickness in feet.. 



Clay (weathered Gault) : thicker on the east side of the pit, now over- 

 grown seen 2 



Ferruginous claye.y stuff, sprinkled with lydite and other pebbles 



(up to f inch in diameter) i to 2 



In another exposure 15 j'ards farther east, the band has thickened 

 to 2 feet, is more sandy, and at the bottom is full of lydites in a 

 clayey base. 



Grey and ferruginous clay, with a band, about midway, of large tabular^ 

 clay-ironstone septaria with concentric coating : in the lower part a [ 

 white streak occurs, with small organisms ; and at the bottom a wedge )» 2 to 2f 

 of grey clay with white fragments, like the earthy Purbeck breccia 

 at Stone J 



Limestone : uppermost 6 inches broken up and ' pebbly '-looking seen to 4 



Like the previous observers, I regarded the gritty ' ferruginous- 

 clayey stuff ' as Lower Greensand, but was (and am still) inclined 

 to assign the underlying grey clay with tabular clay-ironstone to 

 the Purbeck. 



This area is well outside the region of thick Glacial drift, which 

 terminates rather abruptly in steep-featured ground north of" 

 Aylesbury, 7 or 8 miles farther east. It is very generally veneered, 

 however, with a surface-wash of flinty gravel or loam, containing- 

 a few quartzite and other stones along with the flints. 



The ferruginous breccia at the base of the Gault appears to- 



^ It is necessary to give all available particulars regarding this section, as- 

 I believe that it is questioned whether the fossiliferous gritty limestone- 

 lumps found by Mr. Rhodes occurred below the Gault. 



