158 



PROF. T. T. GROOM ON THE GEOLOGICAL [Feb. I9OO, 



Fig. 12. — Theoretical section of 

 a shaft at West Malvern. 



Specimens of 3, 4, & 5 are still to be seen in the collection of 

 the Malvern Field Naturalists' Club, and owing to the kindness of 

 Mr. H. D. Acland and of Mr. W. Edwards, the Curator, I have been 

 able to examine them. The Black Shale is indistinguishable from that 

 seen near White-leaved Oak in the Southern Malverns, but no fossils 

 are visible in the specimens preserved. The fossils, I understand from 

 Mr. Mackie, were sent to Cambridge. It is hoped that a precise 

 determination of* the species may in the future show whether they 

 belong to the zone of SjjJiaerojrfitJialmns, or to some other zone, not 

 represented in the Southern Malverns. No. 4 is a greenish grit, 

 essentially resembling portions of the lower part of the May Hill 

 Sandstone : it contains numerous, rather large, angular and rounded 

 quartz-pebbles up to a couple of inches or more in diameter. These 

 resemble the pebbles that occur in the conglomeratic May Hill and 

 Cambrian beds of the district, and differ from the sedimentary Cam- 

 brian quartzite. No. 3 consists chiefly of purple and greenish grit, 

 containing angular or partly rounded fragments of quartz, felsite, and 

 other rocks, the largest of which measured about an inch across. One 

 side of the specimen is composed of light green material resembling 

 one of the green, fine-grained, sandy bands alternating with some of 

 the purple May Hill Sandstones and Grits. I have no hesitation 



in referring Nos. 3 & 4 to the 

 lower, or purple, part of the May 

 Hill Sandstone, and presumably 

 No. 2 will come into the same 

 category. 



The occurrence beneath the Black 

 Shales of beds similar to Nos. 2 

 & 3 is very striking and sugges- 

 tive, and can be hardly explained 

 except on the hypothesis that the 

 original relative positions of the 

 Black Shales and lower sandstones 

 have been reversed. Originally the 

 latter may have rested on the 

 former, being now simply inverted ; 

 but in all probability the Black 

 Shales have been thrust on to the 

 sandstone (see fig. 12). The thrust 

 may well be the same as that which 

 has brought the Archaean rocks of 

 Cowleigh Park on to the purple- 

 May Hill Sandstones. With the 

 object of testing this hypothesis I 

 endeavoured to ascertain by enquiry 

 the direction of the dip of the beds 

 in the well, and was informed by Prof. Hughes that the Black Shales 

 dipped north-eastward, precisely the direction required by the 

 hypothesis ; were no such thrust-plane present, one might expect 



Shaft. 



f 



[Scale : 1 inch = 100 feet.] 

 1 = Hill- debris. FF= Faults. 



2 ] 



3 [ =May Hill Sandstone. 



4J 



5= Black Shales. 



6= May Hill Sandstone. 



