J. O. Goodchild — -the Coniston Limestone Series. 295 



II. — Notes on the Coniston Limestone Series. 



By J. G. Goodchild, F.G.S., 



H.M. Geological Survey. 

 Communicated by permission of the Director for Great Britain. 



MR. MARK'S valuable communication on the Coniston Limestone 

 Series, which appeared in the March Number of this Magazine, 

 is sure to be welcomed as an excellent summary of the geology of 

 this interesting group of rocks. It contains a digest of most of the 

 published work relating to the Coniston Limestone Series, and also 

 many new facts and arguments drawn from Mr. Marr's own obser- 

 vations in the field. 



The stratigraphy of some of the areas referred to in the paper 

 presents very considerable difficulties, and therefore requires very 

 detailed observations before any definite conclusion can be drawn 

 from the facts. This is perhaps the reason why so many observers 

 have differed in their interpretation of the evidence. In the areas 

 adjoining the Pennine-Craven Fault especially the geology is so 

 complicated that many square miles of country might be described 

 as consisting of a gigantic fault-brecia, whose constituents appear to 

 defy any attempt at identification. The officers of the Geological 

 Survey had to go over a large part of this faulted area again and 

 again, long after every available piece of evidence within the area 

 itself appeared to be exhausted. All this requires much time. But 

 one result of such repeated revisions of the more difficult parts is 

 that those who have gone so many times over the ground gain 

 obvious advantages over those who happen to be less fortunate in 

 such matters. 



Under the circumstances, therefore, Mr. Marr will hardly be 

 unprepared to find that, in minor points of detail relating to the 

 rocks under notice, some of his predecessors have arrived at con- 

 clusions different from his own. That is so in the present case ; 

 and I avail myself of the Director's permission to call Mr. Marr's 

 attention to one or two such, in the hope that the corrections may 

 be of service to him in his future work over the same ground. 



Tlie Bala Rocks of the Cross Fell Inlier. — The highest members of 

 this series have already been adequately described by Messrs. Marr 

 and Nicholson (Q.J.G.S. vol. xlvii.), so that there is no need to 

 discuss any special point in connexion with them here. For field 

 purposes it suffices to separate these rocks into a (1) lower series 

 consisting of calcareous shales, and containing a fauna proper to 

 pelitic rocks of this age. (2) An upper, mainly calcareous series, 

 with the fauna such as might be expected to occur in the clearer 

 waters where limestone was in process of formation. Any local 

 change from argillaceous to calcareous is, as might be expected, 

 accompanied by a corresponding change in the fossils. The lower 

 series of shales graduates upward into the calcareous series. The 

 limestone of Keisley belongs, I believe, to a higher part of this 

 calcareous series than has been left by pre-Silurian denudation else- 

 where in the area under notice. It is faulted in all round. 



