Vol. 68.] SUCCESSION IN THE NORTH-WEST OF ENGLAND. 405 



Burrells, the limestones are occasionally fossiliferous, but no 

 examples of Cijatliaxonia, which is so characteristic of the D^ beds 

 of the Midland area, have been found, nor any of the forms usually 

 met with at that horizon. The upper limestones are here highly 

 magnesian, and the dolomitized fragments in the Permian Brock- 

 rams at Burrells may well have been directly derived from these 

 magnesian limestones. 



The Ravenstonedale District, 



The rocks in this district form the southern continuation of the 

 Shap sequence.^ The district includes all the Carboniferous rocks 

 which lie between the North-Eastern Railway and the Dent 

 Pault. The lower beds dip fairly uniformly north-eastwards at 

 about 15° : decreasing somewhat on the east of the water-parting, 

 but increasing again in the neighbourhood of Kirkby Stephen. 

 The total thickness of Carboniferous rocks exposed in the district is 

 between 3000 and 3500 feet. The lowest beds are well seen between 

 the base of the Howgill Fells and Ashfell Edge, while the higher 

 beds form the dip slope between Ashfell Edge and Kirkby Stephen ; 

 here, in places, the dip almost coincides with the slope of the ground, 

 80 that the NematoplinUam-minus Beds, the Bryozoa Band, and the 

 Lower DibunophyUum Sub-zone occupy a considerable extent of 

 country on the east of the water-parting. The highest beds near 

 Xirkby Stephen cannot, however, lie far below the base of the 

 Upper DibunoiDliyllum Sub-zone. The district is traversed by a 

 series of nearly north-and-south faults which, nevertheless, do not 

 affect the general interpretation of the succession. The section 

 (PI. LYI, fig. 2) gives a general idea of the sequence in this 

 •district. The important points to be noted in a comparison of 

 this development with that in the Shap District are : — 



(1) The presence of a fossiliferous series of deposits in Pinskey Gill, which 

 underlie tlie Shap Basement Conglomerate and represent older beds 

 than any found elsewhere in the ai-ea, and moreover contain an unique 

 fauna. 



.(2) The increased thickness and consequent greater importance of the 

 members of tlie series lying below the Ashfell Sandstone. 



(3) The distinctly later period at which the sandstone phase (represented in 



the north by the Orton Sandstone and in the south by the Ashfell 

 Series) begins in the Ravenstonedale District. Thus the base of the 

 Gastropod Beds in l\irn Sike, close to the Dent Fault, lies about 350 

 feet below the base of tiie Ashfell Sandstone ; whereas the same horizon 

 at Shap (in the Docker-Beck section above Water's Farm) lies 60 feet 

 above the base of the corresponding Orton Sandstone. 



(4) The change in the petrological and pal^ontological characters of the 



Lower Dibunoplii/Uum Sub-zone, which is here represented by a shalv 

 ai-gillaceous limestone and is characterized by the genend absence ok' 

 Dibunophyllids and Ci/athophyllum murchisoui, also by tlie presence, 

 in \i% VL^\iQY ]^oy{'\ox\, oi I'Q&is o^ LithosirotLonjimceum which are else- 

 wliere characteristic of the base of the Upper Dlbuno'phyUum 

 Sub-zone. 

 (r>) The absence of the Upper DibunophyUum Sub-zone, due to the overlap 

 of the Permian beds on the Lower Bihunophylhim Sub-zone in the 

 neighbourliood of Kirkby Stephen. 



1 Geol. Mag. dec. 5, vol. iv (1907) pp. 70-74. 



