40 



Geology of Churehdown Eill, {Part I.) By Feedeeick Smithe, M.A., 

 F.Gr.S., Member of the Cirencester Natural History Society, ^c. Read 

 at Dumbleton, August lith, 1861. 



Op the principal hills standing aloof from the Cotteswold range, namely, 

 Bredon, Stanley, Dumbleton, Oxenton, Netting, and Churehdown, the 

 latter has been not unfrequently referred to by writers on the middle 

 division of the Lias system ; but although the name of Churehdown has 

 thereby become familiar to the geologist, there does not exist any fuU and 

 detailed description of it more succinct than that given in Murchison's 

 Outline (Ed. 2, by Buckman and Strickland, 1847). Indeed, one may 

 hazard the remark that this outlier has never been completely and 

 faithfully sectionized. I have, therefore, ventured to make the attempt, 

 and have here thrown together the observations of the last two weeks' 

 study of the uppermost portion that constitutes the capping of the hill, 

 and which reposes comformably upon the Marlstone of the Middle Lias ; 

 intending at a future time to investigate, seriatim, the remaining subjacent 

 deposits. It may be of assistance, by way of index, or as bringing the 

 subject in its entirety before the eye, to add an outline of the main 

 divisions of the Upper and Middle Lias sections received by European 

 geologists. In descending order, according to the characteristic Ammonites 

 prevailing during each period, we have 



1. The Upper Lias, containing the j J^ensis zone, .above 



° ( Uommunis ,... beneath. 



/ Spinatus, \ 



\ Margaritatus, f 



2. The Middle Lias, cojnprising the < Davosi, [ Zones. 



/ Ibex, I 



\ Jamesoni, / 



The Upper Lias may be briefly defined as a mass of shale upon a bed of 

 rock, and Churehdown possesses the lower beds only of this Upper Lias 

 mass. Beneath them we have exceptionally the zones of the lower 

 division just cited ; from the Spinatus to the Jamesoni beds. 



Here, though, in accordance with my plan, I shall treat only of the 

 Upper or Communis beds. It would be futile to pretend that Churehdown 

 HiU is a typical locality for this subdivision, either in the thickness of its 

 deposits, or in the strictness of their sequence ; stiU, though not claiming 

 for it in these respects the appellative of typical, it will repay any 



