554 PROP. E. J. GARWOOD ON THE LOWER CARBOXIPEROUS [DeC. I912, 



The Submergence of the Pennine Area. 



In considering the date of this submergence, much interest- 

 ing evidence is afforded by the Brownber Pebble-Bed, which lies 

 a few feet above the Thysanophyllum Band. In the first place, 

 this bed marks an important change which took place in the 

 physiographj' of the region. Hitherto the Carboniferous beds 

 had been deposited in shallow land-locked seas or lagoons, which 

 favoured the formation of dolomites and fostered the growth of 

 calcareous algse. The deposits laid down under these conditions 

 were characterized also by the absence of mechanical sediment and 

 freedom from wave- and current-action. During their deposition, a 

 land-barrier must have existed to the east of the Shap District in the 

 neighbourhood of the present Pennine range ; this is evident from 

 the absence from the Pennine area of any Carboniferous deposits 

 older than the Tliysanopliyllum Band. At the time, however, when 

 this band was being deposited a general submergence took place 

 over the Xorth- Western Province, and for the first time the 

 present site of the Cross-Fell range was covered by the waters of 

 the Carboniferous sea. This is shown, not only by the presence of 

 Thysanoplujllum at the base of the Carboniferous succession on 

 the south side of Poman Fell, but also by the occurrence of the 

 oolitic Brownber Pebble-Beds over the whole of the Shap and 

 Pavenstonedale Districts and the Poman-Fell area. This submer- 

 gence of the eastern land-barrier abolished the lagoon-conditions 

 which had hitherto prevailed, letting in the sea from the east 

 with the accompanying effects of wave- and current-action. The 

 distribution of the quartz-pebble beds is of importance in this 

 connexion, for the material of which they are principally composed 

 undoubtedly originated in the Cross-Fell area and travelled west- 

 wards. The original source of the pebbles is difficult to determine ; 

 but it seems probable that it may be traced to the quartz-veins 

 which occur in the Lower Pala30zoic rocks, especially in the 

 Skiddaw Slate Series of the Cross-Fell Inlier, and notably the 

 rocks of this age now exposed in Brownber Pike, which had been 

 plentifully injected with quartz-veins in pre-Carboniferous times. 



The eflect of wave-action is manifested by the rounding of the 

 quartz-pebbles, Avhile the presence of strong currents setting in 

 from the east is indicated by the sifting of the material and the 

 transport of the pebbles and sand over a large area to the west of 

 Appleby hitherto free from mechanical sediment. The markedly 

 false-bedded character of the pebble-beds and the fragmentary 

 condition of the shells which they contain further bear witness to 

 current-action. The pebbles are, on the whole, largest and most 

 abundant in the east of the area under Eoman Fell, and gradually 

 die away when we trace this horizon into the Western Districts. 

 In the intermediate area to the west of Kendal, the deposit is 

 represented under Scout Scar by the calcareous grit which closely 

 resembles the band that occurs at the same horizon at the base of 

 the series in Scordale Beck. 



