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SKETCH OF THE GEOLOGY OF THE CAEADOO 

 AND ITS NEIGH BOUEHOOD. 



[By Professor C. Lapworth, LL.D., F.R.S., F.G.S.] 



The Caradoc is part of a long wedge of very ancient rocks lying between two 

 mighty faults which stretch along on opposite sides of the Caradoc range from 

 the neighbourhood of Ulil Radnor, away past Horderley, Ragleth, Lawley, the 

 Wrekin, and Lilleshall towards the Peak in Derbyshire. This long wedge, of 

 which the Caradoc hill itself forms a part, has been thrust up between the two 

 faults from a great depth in the earth's crust, throwing ofif on the west side the 

 Cambrian formation of the Longmynds, and, on the east, the newest Ordovician 

 formation, known as the Bala, or Caradoc. Between these two great faults along 

 the Caradoc range, we find patches of the oldest volcanic rock of Britain, namely, 

 the mighty masses of ashes and lavas of which the Caradoc, Lawley, and 

 Wrekin are built up. These form the so-called Uriconian rocks of Callaway, 

 and are believed by many to be of Archaean age, much older than the Cambrian 

 and the Lingula rocks, and to be of the same age as the Huronian system of 

 America, even if they do not include representatives of the Laurentian itself, as 

 at Primrose Hill near the Wrekin. That these ancient volcanic rocks are older 

 than Upper Cambrian is quite clear ; but their Archaean age remains, as yet, 

 totally undemonstrated. They are well shown in the great pink and pinkish 

 yellow rocks south-west of the Caradoc summit, and form all the main mass of 

 the Cardington Hills. On the Caradoc itself they are cut through by dykes and 

 veins of dark basalt, of very much later age. On the top of these Uriconian 

 ashes and lavas (Rhyolites, as they are called) lie the Upper Cambrian rocks of 

 Little Caradoc. The lowest of these is a quartzite, which runs nearly to the 

 summit of Caradoc itself, and forms the main mass of Little Caradoc. In the 

 quarries at Comley a green sandstone rests on this quartzite, containing 

 fossils, and believed to be the same rock as the Holly -bush Sandstone of the 

 Malvern Hills. In the deep hollow east of Comley are seen the thin bedded 

 shales known as the Shineton Shales, which have afforded Upper Cambrian 

 fossils. On the west side of the Caradoc, where we should naturally expect these 

 Upper Cambrian rocks again, we find no traces of them whatever. The great 

 fault at the base of the hill has there split in two, and let down a long wedge of 

 the Silurian rocks, proving that these Silurian beds must once have covered the 

 whole region, and showing that the rocks of that wedge must (according to 

 Professor Ramsay) have been dropped down by the fault a depth of at least 2,000 

 feet. West of the great fault, we find the valley of Church Stretton dug out of 

 soft lower Cambrian shales, and the Longmynd itself made out of the ancient 

 barren Cambrian rocks, in which no true fossil has yet been detected. Far off to 

 the west near Pontesbury we find the Shineton shales again, and on them rest the 

 Quartzite beds of the Stiper Stones, which lie at the base of the great Ordovician 

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