VOL. XVII. (i) EXCURSION— NUNEATON ii 



the present time subaerial denudation, by its differential action, is removing 

 the cloak of Triassic sediment that has for long hidden a sculptured upland 

 of an early age. 



From the high ground at Camp Hill there are extensive views over 

 a considerable part of the East Warwickshire Coalfield, which is marked by 

 innumerable chimneys ; over the low ground where Bosworth Field was 

 fought ; of the distant eminence of Bardon Hill— the highest point (850 feet) 

 of Charnwood Forest ; and the great valley of the Trent. 



The rocks composing this ridge have a prevalent south-westerly dip. 

 Therefore the oldest are found immediately to the west of the fault-line 

 already referred to, and are known as the Caldecote Series — pre-Cambrian 

 rocks. They comprise sheets of volcanic breccia, tuffs, and grits, with a few 

 intrusive dykes of basic rock. 



In the " Blue Hole," on the slope of Caldecote Hill, the Caldecote rocks 

 are exposed, and the predominant type is a dense bluish quartz-felspar-tuff, 

 which has been pierced by a very distinctive porphyritic basalt with numer- 

 ous plagioclase-felspar phenocrysts and blebs of quartz. In places, so fine 

 are the intrusions of this rock amid the tuff, that specimens of a very inter- 

 esting " mixture-rock " can be obtained. A precisely similar rock-association 

 is seen in the entrance-cutting to Abell's Quarry, a little over a mile to the 

 north-west of the " Blue Hole." Here the top-portion of the quartz-felspar 

 tuff has been weathered, apparently in pre-Cambrian times, into great 

 spheroids, one of which is six or seven feet across. 



Between the Caldecote rocks and the succeeding quartzites there is 

 no marked unconformity, but the noticeable difference between the lithic 

 structure of the two, comtiined with the presence of derived fragments of the 

 Caldecote rocks in the basement-beds of the quartzites, show how really 

 great must be the break. 



In this Nuneaton-Atherstone area the Cambrian rocks admit of the same 

 dual division that characterizes the system throughout our English Midlands 

 — bedded quartzites of a pale pinkish colour at the base, shales above. 



In this area, certain shale-bands amid the quartzites have allowed 

 of still further subdivision, while, piercing shales and quartzites alike, are 

 noticeable masses of diorite. 



Dr C. Callaway, who was unable to be present, sent the following paper, 

 which was communicated by the Hon. Secretary : — 



Previous to the eighth decade of the last century, the only rocks in the 

 Midlands which had received the name of Cambrian were the Charnwood 

 mass and the Longmynd series. These are now admitted to be pre-Cambrian. 

 True Cambrian strata in the Midlands were first identified in Shropshire 

 at Shineton, south of Shrewsbury. In certain shales exposed on a brook near 

 the Severn I found, in the early seventies, a fauna, chiefly trilobites, of 

 Upper Cambrian" age. In the same area there was a well-known formation 

 of similar shales, containing Ordovician fossils, and known as the Harnage 

 Shales. The two formations were often brought together by faults, and being 

 so similar in composition, had been lumped together as Caradoc (Upper 

 Ordovician, then called Lower Silurian). Strata underlying the Shineton 

 Shales rested upon the igneous rocks of the Wrekin, and were supposed to be 

 of " Lower Silurian " age. The lowest of these beds was a quartzite, the 

 crystalline structure of which was thought to be due to the metamorphic 

 action of the Wrekin mass, which was regarded as intrusive, and later than 

 the rocks on its flanks. 



While I was at work on the newly discovered Cambrian strata, Mr 

 AUport, of Birmingham, ascertained that the Wrekin rocks were not in- 

 trusive, but older than the flanking beds, and consisted of volcanic ashes and 

 lava-flows, whose age he left undetermined. It was therefore obvious that 

 they could not have metamorphosed the adjacent strata. What was the age 



