Page:VCH Cornwall 1.djvu/89

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GEOLOGY which are formed of alternate bands of limestone and shale extending from the foreshore to the top of the cliff for a distance of 350 yards. The limestone bands vary from 2 inches to 2 feet thick, weather a yellowish grey, and form a marked contrast with the dark shale ; there are from sixty to seventy distinct beds of each dipping at a low angle under the greenstone. The blue and grey slates on both the north and south banks of the Camel yield fossils of small interest, and amid these slates are other beds 2 miles in extent of purple and green variegated slates with a general southerly dip which have hitherto yielded no fossil of any kind. North of these occasional fossiliferous beds of slate occur ; the most interesting of which is in Epphaven Cove in Port Quin Bay. This has recently yielded a small starfish, Opbiurina (?), besides some tiny pyritized thorn-like organisms at present undetermined. Mr. S. R. Pattison, 1 writing on the geology of the Tintagel district in 1847, says that fossils between Boscastle and Port Isaac were found in and near the good slate and in an earthy bed among the slates. He records Fenestella at Bossiney, Spirlfera gigantea and S. disjuncta and crinoids at Tintagel, Delabole, Lesnewth and Trevivian, and Terebratula and Ortboceras at Tintagel. He adds : ' Fragments of Spiriferce may be seen in the roofing and flooring slates of all the quarries from Grower to Delabole.' Good specimens of much flattened Spirifers are still con- stantly found in the Delabole quarries. Sir Henry De la Beche in his Report gives a sketch of the junction of the Devonian and Carboniferous rocks as seen from a boat outside the harbour of Boscastle. He writes thus : 'Proceeding now to the southern boundary line of this (Carboniferous) system ... we find that the upper series rests upon the lower near Boscastle, in a bay between the Meachard Rock and Short Island. Here though the one rests con- formably upon the other, as represented (plate 4, fig. i), there is no passage of the one system into the other. On the contrary, there is a marked line between the carbonaceous slates and arenaceous rocks above and the clay slates passing into roofing-slate beneath.' About a mile north of this junction line, the crest of Fire Beacon Point, a very conspicuous landmark 469 feet above sea level, is composed of a cherty rock showing casts of radiolaria. The foldings of the in- tervening beds of grit and shale are numerous, but cannot be on a large scale, as the chert appears nowhere else on the north coast. As we follow the coast northwards the foldings and contortions increase in size and complexity till we reach the extraordinary sections for which the ' Northern Door ' and ' Millook ' are so notable. Further north General McMahon in writing of Bude says that in some places the contortions and convolutions are too complicated for verbal description . . . Beds are not only doubled up and folded on themselves, but they are crushed, ruptured and severed from each other in a way that has, in places, reduced them to the condition of a Chinese puzzle. The conclusion he arrived at after a microscopical examination of the rocks, was that the 1 Trans. R. Geol. Soc. Com. vii. 3-12. I 41 6