252 Bernard Smith — Green Keiiper Basement Beds 



It may seem ungracious to criticize where one is supplied with so 

 rich a store of valuable information, but there is an omission 

 to which atteTition may be directed, and that is the absence of any 

 reference wliatever to the petrology of Usu-san. It is certainly 

 desirable that a comparison should be made between the material of 

 the lava-domes 0-usu and Ko-usu and that wliich has been intruded 

 beneath the New Mountain ; samples of the intrusion may reason- 

 ably be looked for in the ashes ejected at the numerous craterlets. 

 In both cases the magma has given evidence of a rather unusually 

 high degree of viscosity, and it would be interesting, if possible, to 

 connect up this feature with some peculiarity of composition or 

 condition as revealed by the microscope. 



And now a point somewliat foreign to the main purpose of this 

 discussion may briefly be referred to. Usu-san falls into line with 

 iSkye and Mull in furnishing an instance of peripheral upheaval in an 

 igneous region. Although it is probable enough that the analogy thus 

 afforded is a false one, it is nevertheless one that will have to be 

 borne in mind by students who attempt an interpretation of the 

 curved anticlinal folds so well developed in the case of the two 

 Hebridean examples. Having broached the subject, it is only right 

 to point out that the independence and isolation of the New Mountain 

 of Usu-san is in striking contrast to the systematic grouping of the 

 folds either of Skve or of Mull. 



III. — The GrREEN Kecper Basement Beds in Nottingham shike and 



Lincolnshire.* 



By Bernard Smith, M.A., F.G.S. 



IN the recent memoir on the Geology of the Country around Ollerton"^ 

 a description is given of certain ' Green Beds ' which in that 

 neighbourhood form the base of the Keuper Waterstones and overlie 

 the Bunter Pebble Beds. 



The survey of the Nottinghamshire district being for the time 

 completed, it seems desirable to lay more emphasis upon the occurrence 

 of the Green Beds than has been possible in a sheet memoir. 



Their chief importance lies in the fact that they are easily 

 recognizable over a fairly large area and furnish engineers who may 

 be boring for coal or water with a safe guide to the proximity of the 

 surface of the Bunter Pebble Beds. By their aid also we are able to 

 check certain published records in which the dividing line between 

 Keuper and Bunter was perhaps not clearly recognized, and to prepare 

 a contoured map showing the dip of the Bunter surface beneath some 

 part of its overlying cover of younger rocks in Nottinghamshire and 

 Lincolnshire. 



In the Ollerton memoir the beds are described as follows : ^ "The 

 greenish clayey basement beds of the Keuper were first noticed by 

 W. T. Aveline, who, in 1861, drew attention to the 'alternations of 



^ With the permission of the Director of H.M. Geological Survey. 

 - Mem. Geol. Surv., 1911. 

 ^ Ibid., p. 26. 



