GEOLOGY 



sist of sheets of volcanic breccia, tuffs, and volcanic grits, with a few 

 intrusive dykes of basic rock. 



The lowest beds of the series are some coarse breccias met with in 

 a disused road near the Anchor Inn. The more compact tuffs with the 

 aspect of brecciated quartz-felsites are exposed in Mr. Abel's Long 

 Quarry immediately south of Hartshill Grange, and remarkably fine- 

 grained tuffs are to be seen in the sides of an old tunnel 100 yards west 

 of Caldecote Hill House, where, according to Mr. Strahan, the bedding 

 planes dip at 25 to 30 in the same direction as those of the overlying 

 quartzite, that is, about south-west. 



An intrusive basic rock, a porphyritic basalt according to Professor 

 Watts, 1 takes the form of a dyke which intrudes upon and partly over- 

 lies the ashes, and is exposed in an old paving-cube quarry known as the 

 Blue Hole, about a quarter of a mile east of Caldecote Windmill. The 

 rock into which it intrudes has the appearance of a quartz-porphyry, 

 but Professor Watts, who describes it as the ' quartz-felspar rock,' is 

 inclined to regard it as a tuff.* A similar and possibly the same dyke 

 of porphyritic basalt traverses the ' quartz-felspar rock ' at the entrance 

 to Mr. Abel's quarry near Hartshill Grange. 



Professor Lapworth is of opinion that the Caldecote rocks are 

 theoretically paralleled with the Upper Longmyndian and Uriconian 

 groups of Shropshire. 3 



From the foregoing details it will be seen that the earliest and 

 lowest Warwickshire deposits were produced by the agency of volcanoes. 

 Exactly where these were situated it is as yet impossible to say, but in 

 the Charnwood district, a few miles to the north-east, there are con- 

 siderable masses of somewhat similar volcanic materials, though it is 

 thought that these are of an earlier date ; here, according to Professor 

 Bonney, we have the site of a volcanic cone or group of cones which 

 threw out dust and fragmentary materials into adjacent shallow lakes 

 or lagoons. 4 It seems likely that at this time the area which is now 

 Britain was occupied by an archipelago of small volcanic islands. Such 

 conditions were not perhaps highly favourable to the existence of 

 living beings in the surrounding waters ; nevertheless life was not 

 entirely absent, for a few fossil worm-burrows have been discovered 

 in some of the Charnwood rocks, though none has yet been met with 

 in the Caldecote beds. 



CAMBRIAN 



After a while this low-lying tract of volcanic islands subsided 

 beneath the waters and was in part covered by several thousand feet of 

 Cambrian sands and muds. These, the lowest rocks in which fossils 

 occur in any abundance, are found to overlie the Archaean rocks in the 



1 Pnc. Geol. AIIOC. xv. (1898), 391. 



* Watts, op. cit. p. 392. See also Rutley, Geol. Mag. (1886), p. 557 ; and Waller, ibid. p. 322. 

 8 Lapworth, Pnc. Geol. dsioc. xv. (1898), 327. 



* A. J. Jukes-Browne, The Building of the British Isles, ed. 2 (1892), pp. 29-32. 



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