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. 

 (Concluded from p. 62.) 



C. Identification of the Strata between the " Silver-sands " 

 AND THE Inverted Mass in Mr. Harris's Pit. 



AN examination of the sections at and near Shenley Hill, 

 described above, thus provides the means for a complete inter- 

 pretation of the puzzling stratigraphical relationships seen in Harris's 

 Pit. The inverted Upper Gault and basal Cenomanian limestone 

 masses have already been identified zonally : the sand-beds dis- 

 tinguished as G and F by Mr. Lamplugh and those parts of his 

 bed D which are not of Cenomanian age remain to be correlated. 

 The well-bedded, impure, fine sand (G), overlying the " silver- 

 sands ", may be recognized as a thin and probably denuded repre- 

 sentative of the 6 ft. bed of streaked and carbonaceous sand 

 underlying the tardefiircata bed at Miletree Farm (No. 8). The 

 overlying stratum F, a coarser and less well-bedded greenish 

 clayey sand, is here and there rather abruptly separated from 

 bed G, but in other places formS an upward continuation of it. 

 The two may be considered to form part of one deposit. The coarser 

 sand of F occurs as small shallow banks, which are discontinuous 

 in places ; when it is absent the next higher bed, forming part of 

 bed D of Mr. Lamplugh (the part designated D^ in Fig. 2), is then in 

 contact with bed G, which in one place where such a relationship 

 was seen was reduced to 4 inches in thickness. 



The sandy beds G and F, of pre-tardefurcata age, form the highest 

 member of the Lower Greensand present in this section. They are 

 overlain immediately by the unconformable basal bed of the Upper 

 Gault, with which we have become familiar in neighbouring sections. 

 For convenience we refer to this bed at Harris's Pit as D^. We have 

 seen that its development, wherever it is normally overlain by the 

 Upper Gault Clay, is that of a continuous basal bed of mixed com- 

 position, variable in thickness, and with uneven lower surface. 

 At Harris's Pit it shows less continuity and greater irregularity in 

 its mode of occurrence. The clay which normally overlies it, with 

 the exception perhaps of a few little isolated traces, had been locally 

 removed by denudation before the overturned mass of strata became 

 deposited in this place. The remnants of the basal bed itself, which 

 formed the floor upon which the inverted strata came to rest, may 

 owe some of their present irregularities to the same denudation ; 

 but the confused aspect of the bed is doubtless to be ascribed in 



