A HISTORY OF WARWICKSHIRE 



found to form elevations, just as the knots in the planking of an old 

 floor always stand up above the general surface. We accordingly find 

 that the hard quartzites and diorites of the Cambrian rocks occupy the 

 ridge extending from Nuneaton to Atherstone ; the durable pebble-beds 

 of the so-called Permian rocks produce a well-marked feature at Corley 

 (625 feet above sea-level) ; while the Bunter pebble-beds and Keuper 

 building-stones generally give rise to picturesque wooded scarps. 



We shall now proceed to a consideration of the various sheets of 

 rock which have built up the earth-crust of our district, commencing 

 with the lowest and oldest visible layer. 1 



ARCH^AN 



On the north-eastern borders of the county, in the neighbourhood 

 of Nuneaton, occurs a narrow strip of volcanic rocks, the Caldecote 

 Series, which have been shown within the last few years to be of 

 Archasan (i.e. pre-Cambrian) age. In the Geological Survey map 2 and 

 accompanying memoir 3 the rocks in question were called * greenstone ' 

 and were regarded as probably intrusive, like the diorites in the over- 

 lying Cambrian rocks, and were not assigned to any definite age. The 

 discovery by Professor Lapworth in 1882 of Upper Cambrian fossils in 

 the black shales of Stockingford restricted the age of the Caldecote rocks 

 to the Cambrian and pre-Cambrian periods. These discoveries were 

 embodied by Mr. A. Strahan in a revised issue of the Survey map in 

 1886, in which the Caldecote Series tuffs, quartz-porphyry, and 

 diabase were separately distinguished, but were classed as ' igneous ' 

 without being assigned to any definite period. 



The recent determination of a Lower Cambrian fauna in the Harts- 

 hill Quartzite itself (see Table, p. 3), together with the lapse of time 

 suggested firstly by the contrast between the general lithological character 

 of the quartzite and that of the underlying Caldecote Series, and 

 secondly by the occurrence of abundant detritus of the latter in the 

 basement beds of the quartzite, make it practically incontestable that the 

 Caldecote rocks are pre-Cambrian in age. 



The outcrop, less than a quarter of a mile wide, commences near 

 the Midland Railway station at Nuneaton, and can be traced by small 

 occasional exposures in a north-westerly direction for nearly two miles. 

 The beds pass unconformably under the Cambrian rocks on the west, 

 and are faulted against and unconformably covered by the Trias on the 

 north-east. As was first recognized by Professor Lapworth, 4 they con- 



1 For the chief publications relating to the geology of Warwickshire the reader is referred to a 

 List of Works on the Geology, Mineralogy, and Paleontology of Staffordshire, Worcestershire, and 

 Warwickshire, by W. Whitaker, in the Report of the British Association for 1885 ; to the Geological 

 Record, edited by W. Whitaker, for 1874-84; and to Professor Blake's Annals of British Geology 

 for 1890-3. Some later papers will be found in the 'Geological Literature added to the Geological 

 Society s Library, published annually, also in 'A Sketch of the Geology of the Birmingham District,' 

 by Professors Lapworth and Watts and Mr. W. J. Harrison, Pne. Geol. Assoc. xv. (1898), pp. 313-416. 

 Old Sen* 63 S.W. (,8 SS ). Howell, The Warwickshire Coalfield (i^, 1 7. ' 



Geol. Mag. (1882), p. 563 ; (1886), p. 3,9 ; and Proc. Geol. Assoc. xv. (1898); 330. 



4 



