Page:Encyclopædia Britannica, Ninth Edition, v. 10.djvu/365

Rh PERML-N.] PERMIAX. BRlTAIN.——Ill England the Coal-measures are unco1i- furmably overlaid by a series of red sandstones, conglo- merates, breecias, and niarls, which at one time were grouped in one great formation as the New Red Sandstone, in coiitra- distinction to the Old Red Sandstone lying below the Car- boniferous system. They were likewise known as the Poikilitie series, from their mottled or variegated colours. They are now divided into two systems or groups of forni- .-itions, the lower half being included in the Palreozoic series under the name of Permian (after Perm, a Russian province where they are well displayed), and the upper half being relegated to the Secondary series, and termed Trias. The Perniian system in England consists of the following subdivisions :— _'. of Eiigland. of England. 3 Red sandstones, clays, andI_ 3' l"l'Pm“" ( gypsum ..: ................. .. 5 600 ft 50-100 ft We--'-E :ll::{?’£‘:f;1‘$;‘TTTi‘.????.‘f?..:::::::: 10—30 ~ 600 » {Red and variegated sand-] stone ........................ .. Reddisli-brown and purplel 1. Lower...{ sandstones and inarls,w1th} 3000 ,, [ calcareous conglomerates! 1 00-250, , and brcccias of volcanic rocks. ........................ .. From the thicknesses here given, it is evident that the l’erniian rocks have a very cliﬁ"erent development on the two sides of England. On the east side, from the coast of Northumberland southwards to the plains of the Trent, they consist chieﬂy of a great central mass of limestone. But on the west side of the Peniiine Chain, and extending southw-arrls into the central counties, the calcareous zone disappears, an] we have a great accumulation of red, arenaeeous, and gravelly rocks. L9~.ve2'.—This subdivision attains its greatest development in the vale of the Eden, where it consists of brick-red sand- stones, with some beds of calcareous conglomerate or breccia, l.)cilly known as “brockram,” derived from the waste of the Carboniferous Limestone. These red rocks extend across the Solway into the Valleys of the Nitli and Annan, in the south of Scotland, where they lie unconforniably on the Lower Silurian rocks. Their brecci-as consist of frag- ments of the adjacent Silurian greywackes and shales, but near Dumfries some calcareous breccias or “brockrains” occur. These brecciated masses have evidently accumulated in small lakes or narrow fjords. Much further south, in Statfordsliire, and in the districts of the Clent and Abberley Hills, the brccciated conglomerates in the Permian series attain a thickness of 400 feet. They have been shown by R-imsay to consist in large measure of volcanic rocks, grits, slates, and limestones, which can be identiﬁed with rocks on the borders of Wales. Some of the stones are 3 feet in diameter and show distinct striation. The same writer has pointed out that these Permian drift-beds cannot be dis- tinguished by any essential character from modern glacial drifts, and he has no doubt that they were ice—borne, and, consequently, that there was a glacial period during the accumulation of the Lower Permian deposits of the centre of England. Like red rocks in general the Lower Permian beds are almost h.irren of organic remains. Such as occur are indicative cliiclly of terrestrial surfaces. Plant remains occasionally appear, such as C'nwlcrpz'£cs (supposed to be of marine growth), Lrpidodcndron clila/atmn, Oalamitcs, Stcrnbciyia, and fragments of coniferous wood. The cranium of a labyrintliodont (Dasy/ccps) has been obtained from the Lower Permian rocks at Kciiilwortli. Foot- prints referred to members of the same extinct order have been observed abundantly on the surfaces of the sandstones of Dumfrics- shire, and also in the vale of the Eden. J[id¢lle.——Tliis subdivision is the chief repository of fossils in the Permian system. Its strata are not red, GEOLOGY 351 but consist of a lower zone of hard brown shale with occasional thin limestone bands (Marl Slate) and an upper thick mass of dolomite_Iagnesian _Liinestone). ’lhe latter is the chief feature in the Permian develop- ment of the east of England. It corresponds with the Zcchstein of German as the Marl Slate does with the, . Y’ . . . . Ixupfer—schiefcr. It is a very variable rock in its litho- logical characters, being sometimes dull, earthy, ﬁne- grained, and fossilifcrous, in other places quite crystal- line, and composed of globular, reniform, botryoidal, or other irregular concretions of crystalline and frequently internally radiated dolomite. Though the Magnesian Limestone runs as a thick persistent zone down the east of England it is represented on the Lancashire and Cheshire side by bright red and variegated sandstone covered by a thin group of red inarls, with numerous thin courses of limestone, containing Sr.-ln'zoclus, ];’«_(l.'evcllia, and other characteristic fossils of the Magnesian Limestone. The middle Permian division has yielded about 100 species belonging to 46 genera of fossils-—a singularly poor fauna when contrasted with that of the Carboniferous system below. 'lhc bracliiopods (9 genera, '21 species) include I’ro0’iIctzfs Iz.o7'ri(lus, C'amarophorz'a multiplicala, C. Schlothcimzz,.S'h'op7¢aIosza Goldfussz, Lin ula Crcdncri and Tcrclmatula clonmta. The lainelhbranchs U 2 J _ _ number 16 genera and 31 species, among which Schzzodus Schle- t/w2'mz't', Bakcccllza tumicla, B. antiqua, B. ceratophaga, 1113/til us squamosus, and Area striata are characteristic. The univalvcs are represented by 11 genera and ‘.26 species, including Plcm°o(omarz'a and Turbo as common genera. F islics have been obtained chieﬂy in the marl slate to the number of 21 species belonging to 8'genera, of which Palwoizisczts is the chief. These small ganoids are closely related to some which haunted the lagoons of the Carboniferous period. Uppe-r.—Murchison and Harkness have classed as Upper Permian certain red sandstones with thin partings of red shale, and an underlying band of red and green marls and ' ' )Sl1l11. These rocks seen at St Bees near Whitehaven 931. . ’ . ’ . ’ restipg on a magnesian limestone, have not yet yielded any fossi s. CONTINENTAL EURoPE.—The two types of the Permian system presented by the east and west sides of England reappear in different areas on the mainland of Europe. The eastern or Durham type is found in enormous masses of strata ﬂanking the Harz Moiiiitaiiis, also in Tliuringia, in Saxony, and in Bohemia. The western or S-alopian type is found over many thousands of square miles in the north and east of Russia. The German geologists, recognizing the remarkable two- fold eliaracter of its rocks, _have called this system “ Dyas,” and have proposed to retain the term Permian to express the more simple type, such as is found in Russia and western England. They group the members of their Dyas as follows :—— ( Anhydritc, gypsum, rock-salt, marl, dolomitc,_fetid shale, and limestone. The amorphous gypsuin is tlief ﬁne; 554 member of this group; the limestone is sometimes u o 5 bitumen. I3 Crystalline granular (llauch-zcacl:c) and ﬁne sandy (Asclu; 5 « dolomite (6 to 65 feet). 4? Zechstein, an argillaccous tliin-bedded compact limestone -5; 15 to 30 (sometimes even 90) feet thick. L3 Kn 1fCI‘-SCl1fl_CfL‘I‘-1 alblack bituminous shale not more than a rout 2 cet t do i. Zcehstcin, conglomerate, and calcareous sandstone. D ( Upper.——C‘onglomerates (quartz-porphyry conglomerate) and 2 sandstone, with associated melaphyres and tuffs. ,2’ _§ { bands of quartz-congloineratc and earthy limestone. Mela- E 5 pliyre and porphyrite masses intcrcalatcd. _ pg LLowe1r.——Slialy sandstones, shalcs (with bituminous bands), am cong omeratcs. The name “ Rothliegcnde” or ‘ ‘ Rothtodtliegcndc" (red-layer _cr red-dead-layer) was given by the miners because their orcs_ dis- appeared in the red rocks below the copper-bearing Kupfcr-sclnefcr. The coarse conglomerates have been referred by Ramsay to _a glaclal origin, like those of the Abberlcv Hills. One of the most interest- ing features of the formation is the evidence of the contemporaneous
 * 3 5.. Middlc.—Red clays, shales, and fine slialy sandstones, with