CHAPTER XXVI.

THE AND NEIGHBOUR­ HOOD-LOWER PALlEOZOIC TIMES.

By J. E. MARR, Sc.D., F.R.S., F.G.S.

INTRODUCTION.

NDER this title are included three districts which have at U different times been visited by the Geologists' Association, namely, the Lake District in r88r and again in 1900, Edenside in 1890 and 1907, and West Yorkshire in 1882. The tract to be hereafter described forms a rough rectangle, with the larger axis extending about IS° west of north and east of south, the length of this axis being about eighty miles, while the width of the rectangle averages about sixty miles. The northern part of this tract is the boundary between Cumberland and Scotland, from the Solway to the border of Northumberland; the eastern side may be taken along a line from this point, trending some­ what east of south, parallel with the west side of the north por­ tion of the Pennine Chain, but carried east of the watershed of that chain to the neighbourhood of Knaresborough, thus taking in the ground visited by the Association in 1882. For the southern boundary we may take a line from Knaresborough to the northern margin of the Lancashire coal-field, thus including the folded Lower Carboniferous rocks south of the Craven Fault, while the western side extends from the coal-field, across More­ cambe Bay, along the western coast of Cumberland to the mouth of the Solway. It is not proposed to treat of the geology of the whole of this. rectangular tract in detail, but a reference to the general struc­ ture of the whole is requisite to the right understanding of its parts. The dominant geological and physiographical feature of this region is the northern end of the Pennine uplift. The terms "range" and "chain," applied to this upland region are mis­ nomers. The Pennines consist of an uplifted "block" tilted downward towards the east, so that the general slope of their component strata is eastward. Along the area under considera­ tion the block is mainly limited by a fault-system on the east side, but farther south becomes a hog-back. The structure of the eastern side of the block is compara­ tively simple. The strata slope gently eastward, and the ground slopes in the same direction from the watershed, but less LAKE DI S TRICT-LOWER PALlEOZOIC. rapidly, so that the newer Carb oniferous rocks occur, on the whole, to the east side of the Pennine upl ift. To wards the plain of York these strata are succeeded unconformably by the Permo­ Triassic rocks. T he junction of Permian and Carboniferous rocks on this side TUns with considerable regularit y from north to south , so that the country east of the Pennine watershed forms in the main the eastern limb of an uplift, with an unconformity occurring at the base of the Permian deposits. If the Pennine uplift were an ordinary anticline, we should expect the reappearance of the Permo-Triassic rocks on its western side, and they do appear there. T he simplicity of structure charac­ teristic of the eastern side is here, however, replaced by extreme complexity. Westward of the main watershed the Pennine block is ter­ minated by the fault-system, and the generally sunken part west of the faulted ground is marked by much minor folding, which causes the Permo-Triassic rocks to appear locally in the troughs, while intervening ridges and domes are marked by th e present existence of high ground composed of pre-Permian strata. Of these uplifted tracts by far the most important is the Lake District dome. T o the south-east of that dome is that of the H owgill , and the fells to the eas t of them. South of this is the imperfect dome of th e Carboniferous Fells of the country east of Preston and Lancaster , and, still farther to the south, another imperfect dome of the Lancashire coal-field. The eastern ends of these domes ab ut against the main Penni ne uplift, and the main outcrop of the Permo-Triassic rocks sweeps in sinuous curves around the western side of the domes, though where th e depressions on parts of the easterly ma rgins ar e mark ed, out­ crops of Permo-Triassic rocks occur there also. Beginning in the north, we find the Permo-Triassic rocks of the Eden Valley between the north-eastern margin of the Lake District and the Pennine uplift . These rocks sweep westward from the Eden Vall ey across the Carlisle Plain to Maryport on the Cumbrian coas t, where they pass under the sea to reapp ear farther south at St. Bees' H ead whence they extend along the Cumbrian coast and up Morecambe Bay, and then southward to the west of Lancaster and Preston. An outlier of Permi an rack occurs near lngleton between th e H owgill and Lancaster uplifts, and other outliers farther south between this uplift and that of the Lancashire coal-field. The main outcrop turns south-west at Preston, around the western margin of the Lancashire coal­ field, and then turns sharply eastward on the north side of the great semi-circular depression, forming part of the Cheshire plain, to the south of Manchester. Much of the uplifted ground shows Carboniferous rocks at the surface, but where the uplift has been marked, and denuda­ tion great, Lower Palseozoic rocks app ear. The principal mass 4° 626 GEOLOGISTS' ASSOCIATION JUBILEE VOLUME. of these rocks forms the centre of the Lake District, and is con­ tinuous into the Howgill Fells and adjoining region. A minor mass occurs along the fault-fracture east of the Eden Valley depression, with an isolated outcrop exposed by denuda­ tion in Teesdale, and several inliers occur along the northern side of the Craven Fault. With the exception of the main mass, the presence of these Lower Palzeozoic rocks at the surface is determined also by faulting. We have above referred to some of the faults, and as these faults are of very great importance as affecting the geology and the physical geography, it will be well that we should at once note their positions, leaving further description until later. The sketch-map (Fig. I IS) shows the distribution of the main faults, and the general situation of the New Red Sandstone, Carbon­ iferous and Lower Paleeozoic rocks. On the map is also inserted the position of the chief uplifts, which we shall speak of as the Lake District, Howgill Fells, and Central Fells uplifts. The Lancashire coal-field uplift is beyond our district. The complexity of geological structure of the Pennine area and surrounding tracts is echoed by a like complexity of the drainage. The Pennine uplift, as we have seen, is not a simple anticline with a fairly straight axis, but is a block uplift, com­ plicated by smaller uplifts on its western side. At the extreme north end of the Pennine uplift in our district, and at its extreme southern termination outside the limits of the district, the drain­ age is comparatively simple, the rivers rising on a fairly straight watershed determined by the axis of the uplift, but between these ends the watershed is very irregular, running from the main axis of the Pennine uplift to the centres of some of the subsidiary uplifts. In their lower courses the rivers rising on the various uplifts find their way over the low ground separating these uplifted tracts. The Eden rises on the Carboniferous rocks of the Howgill uplift, but its waters soon flow into the depression between the Pennine uplift and that of the Lake District, and continue in this depression to the sea, receiving tributaries from the high lands of each of these uplifts. The Kent rises on the Lake District uplift. but its lower course is between that uplift and the Howgill Fells uplift. The Wenning and the lower part of the Lune flow along the depression between the Howgill uplift and that of the Central Fells. and receive tributaries from each of these uplifted tracts, while the Ribble, rising on the Carboniferous rocks of the Howgill Fells uplift, flows in the lower part of its course between the uplift of the Central Fells and that of the Lancashire coal-field, again receiving tributaries from each of these. With this preliminary account of the physiography of the tract, we may now proceed to a more detailed study of its geology. FIG. JI3.-SKETCH MAP OF PARTS OF CUMBERLAND, WESTMORLAND, LANCASHIRE, AND YORKSHIRE.-J'. E. Man'.

Lias. New Red Sandstone.

Carboniferous. Lower Palzeozoic. P-P. Pennine Fault. D-D. Dent Fault. C-C. Craven Faull. The Lake District uplift is in the centre, that of the Howgill Fells to the south-east of the Lake District, and that of the Central Fells south-west of the Craven Fault, C-C. 628 GEOLOGISTS' ASSOCIATION JUBILEE VOLUME.

In studying the geology it will be convenient to treat of the rocks in the order of their age, considering so far as possible the various changes in the way of deposit, erosion, earth-move­ ment, volcanic activity, and metamorphism as we proceed with our description.

THE LOWER P ALlEOZOIC ROCKS. The rocks of Lower Palseozoic age are all, as before stated, chiefly developed in the Lake District, and we will at the outset consider their development there, afterwards noting the more im­ portant features of the subsidiary exposures. (A) The Lake District.-The continuous tract of Lower Palseozoic Rocks which forms the true Lake District also extends into the Howgill Fells and to other fells south of the Howgills, between Sedbergh and Kirkby Lonsdale. The general strike of these rocks is about east-north-east to west-south-west, and they occupy a tract of country with a longer diameter of over 40 miles at right angles to, and about 32 miles parallel with that strike, the outline of the area being roughly that of a balloon, with the top facing north-north-west, and the" car" being formed of the tract of the Howgills and neighbourhood. The general order of succession of these rocks was first pub­ lished by Jonathan Otley in a letter in the" Lonsdale Magazine" for 1820, p. 433, but the detailed succession was subsequently determined by many geologists, among whom we may primarily mention Adam Sedgwick, and after him Professors Harkness and Nicholson, and the Officers of the Geological Survey. The following table gives the order of succession of the strata, with approximate thicknesses: EQUIVALENTS IN NAME OF DIVISION. THICKNESS. WALES, ETC.

rKirkby Moor Flags to r,50o ft. Upper Ludlow. IBannisdale Slates about 4,000 ft. Aymestry Lime- stone and Lower :i Ludlow. ~ I ~ ~ Coniston Grits. . to 4,000 ft. } Lower Ludlow. Gl IUpper Coniston Flags about 1,5°0 ft. I ILower Coniston Flags 1,000 ft. Wenlock. lStockdale Shales 250 ft. Tarannon - Llan- dovery. LAKE DI STRICT-LOWER PALlEOZOIC.

EQUIVALENTS IN NAME OF D IVISIO N. THICKNESS. WALES, ETC.

rConiston Lim estone. 2 0 0 - 1 , 000 ft. Carad oc (and Up per Bala). i::: l ~ ~ Borrowdale Series 10,000- 20,000 ft. Llandeilo. 0 1 ~ ISkiddaw Slates. many thousand Arenig, T rema- O feet. doc (?) and l earlier beds (?) T he general conception of the arrangement of these rocks in the formof an anticline whose axis runs inaneast-north-east to west­ south-west direction through will suffice to explain the general distribution of the rocks. The lowest strata-the Skiddaw Slates--dip away from this axis, but as the Lower Palseozoic Rocks are quickly covered by an unconformable series of Carboniferous strata on the north , little save the Skidd aw Slates and one group of the succeeding Borrowdale series is exposed to the north of the axis. On the south side it is different , and there we get a complete development up to and including the Kirkby Moor Flags.

I. Skiddaw Slales.-The rocks of this division are found in an area of a rough, semi-elliptica l form north of a line drawn from the [Qat of Ulleswater to near Egremont, but a th in strip occurs on the east side of the district between Bam pton and Shap, and a considerab le development is found in Black Combe at the south-west extremity of Cumberland, while another tract is seen on the east side of the Duddon estua ry. T he rocks are chiefly argillaceous, consisting in their present condi tion of roughly-cleaved, glossy blac k or grey slates, but ma ny grit band s of varying degrees of impo rtance occur; one of them of considerabl e coarseness on the Skiddaw fells is termed the Skiddaw Grit, and thicker though finer grits are abu nda nt on '.the s west of Derwentwater and Bassenthwaite. The positions of the grits in the series have not been clearly ascer­ tained. Near the summit of the series are found contempora­ neous volcanic rocks seen near Scale Force, Crummock, close to Grange in Borrowdale, and in the tract near Shap, These are andesitic lavas and ashes, and mark the incoming of the volcanic conditions found during the accumulation of the succeeding rocks of the Borrowdale Series. The fossils of the Skiddaw Slates are chiefly graptolites, with a few trilobites and other organisms. They occur mainl y in definite bands, now consisting of more earthy beds th an the main ,mass of the Slate series. Such ba nds occur in Keld and Thorn­ ship becks, near Shap j Aik beck, Ulleswater j near Troutbeck j 630 GEOLOGISTS' ASSOCIATION JUBILEE VOLUME.

Mosedale and Saddleback ; Skiddaw and the east side of Bassen­ thwaite; Hodgson H ow, , Out erside, the Pass , and Grizedale Pike, near ; and Mosser, near Cocker­ mouth. Whether these beds are of the same age as the black , glossy, unfossiliferous slates, or whether they are newer bed s folded as synclines among these slates, yet remains to be ascer­ tained. Most of the slates were probably formed at no great distance fro m the land. T hey contain much quart z and detrital mica in pla ces, but many of the fossiliferous beds are probably of deeper water character. An account of t he grapt olitic zones of the Skiddaw Slates by Miss G. L. Elles will be found in the Quarterly J ournal of tlte Geological S ociety, vol. liv (1898), p. 463.

2 . Borrowdale S eries.-The main development of the rocks of this group is south of the Skiddaw Slates, and between them an d a line drawn from Shap Wells to MilIom, with a subsidiary patch on the east side of the Duddon estuary; but a band runs in an arc from near Troutbeck Station to Cockerrnouth, on the north side of the main mass of Skiddaw Slates. The following sequence has been ascertained by Mr. Alfred H ark er and the writer : Coniston Limestone. Shap Rh yolitic Group. Shap Andesitic Group. BORROWDALE Scawfell Ash an~ Breccia Group. SERIES -,f Sty H ead Garnetiferous Group. . l UIIeswater Basic Andesitic Group = Eycott Group. F alcon Crag Group . Skiddaw Slates. A map of the above-named authors in the PROCEEDINGS of the Geologists' Associat ion, vol. xvi, facing p. 526, gives the general distribution of these rocks. T he rocks of the garneti­ ferous series are there indicated as doubtfully intrusive, but the researches of the late Mr. E. E. Walker proved the contempo­ raneous origi n of the bulk of these garneti ferous rocks, though some are intrusive, and garnets are found in many of the other divisions, though rarely of lar ge size. The work of Mr. W. M. Hutchings points to the probable existence of microscop ic garnets in rocks of each one of the series. The lowest group is- named aft er Falcon Crag, near Derwent­ water. This spot was taken by the late Clifton Ward as a typi cal section of the Borrowdal e volcanic series. (See Ward, Mem. Geol. Survey, "The Geology of the Northern P art of the En glish Lake Distri ct," pp. 13-19.) The Falcon Crag group occupies the tra ct of country bet ween Borrowdale and the Vale of St. John. The rocks are folded into LAKE DISTRICT-LOWER PALlEOZOIC. 631 a shallow basin with a ~ il an anticline on the .'5 ?i south side. The !' is composed of ;: group .... '" p":,,, ?' lavas, mostly thin and tr: u: ~ o I generally vesicular, ..:< n :; 0 ;:~ < r :-:: C ." with intercalated ~ "U> (-. ~ ~ :> ;::: 0 '"' ;:. ashes. It contains c, ~5 % :..- " ~ it few thin highly- Cl 'J . ~.'"' 0- 3' ir. contorted bands of :: r." ;:;. ::: s," ~ sediment of the Skid- l! Cl c; § ;: '" c; Ul daw Slate type inter- ~ ~ c: g 1> '" 0 ~ calated among the ;;; "'"' ;:: ;:: ~. ~ volcanic rocks in Cat o '". '"....0 Cl Gill, at the base of ~ .; Falcon Crag. ~ ~ Vl'" The lavas are 0 c: generally of inter- It,l ~ .; mediate composition, with a silica percent- :-:l ~ age of 59 to 61, but i Iff 0 more basic flows ~ /of ." occasionally occur. ~ o They are pyroxene- 5!-~ '" " o . "::; andesites, containing "e- C» .... ,, :;: either hypersthene, :- :- ~ t i '"~ :"' !" '" :; .; augite, or both of u: g- ::; :r.- ""= ;:. these minerals. The ;:;" .; ~ a~" ~ g if ~ rocks of this group ~ ~ :: '" ~ :::: ~ .;" have undergone but o: ~ ~ 0 r;" little change as the a~" t;;l .; !! ~ ~" :: ;;; = result of subsequent :::: :::: o :n r: c. movements. g'"' c- '" g'"' :..- !'" % Vl ;,- 0 The second group -: :r.- a c " .; is the sole representa- ;,- t !'!.'"' " tive of the Borrowdale ~ r; 5 ":::: '-': ::1 Cl 'l, series on the north Vl ~ "tr: ~ 0 ::I side c: of the Skiddaw ~ 0 r;" ~ c; ." Slates j there the U> rocks g o have long been c," o known as the Eycott "c. ::: r. Ul Hill group, a name c ~ .; a 0 applied to them "U> z by Clifton Ward. g fr. (illonthly M icroscopi- ;,- ~ ir: cal ] ournal, vol. xvii, ;; ~ !'l 18 U> s () ~ 77, p. 239·) ~ 0 ;;;- § ~. In that tract of ~ g ~ ). !" 632 GEOLOGIST S' ASSOCIATION JUBILEE VOLUME. country the rocks have undergone little alt eration subsequent to their formation, save as the result of weathering action. H ere again we find an alternation of lavas and ashes. The lavas -are more basic than those of the preceding group, containing only 51 to 53 per cent. of silica. The pyroxene constituent is often hypersthene. Near the base of the group ar e some remark able lavas with large phenocrysts of bytownit e felspar, often more than an inch in diameter. The rocks of the more central part of the district have usually undergone much subsequent change as the result of pressure and occasionally also of heat, which has to some extent destroyed th eir original characters, and accordingly for many years the existence of equivalents of the Eycott rocks in this central tract was unsu spected. To the north of H aweswat er, however, the rocks are slightly altered, and there the charac­ teristic bytownite ph enocrysts are abundantly developed. We have accordingly been able to show that these basalts (or basic andesites) are widely distributed over the district as indicated on the above-mentioned map. In this group is the fine-gr ained ash band of Honister, which is extensively worked for roofing­ slates. The Sty Head garnetiferous group is largely developed as a ring around the rocks of the next group, where they form the centre of the Scawfell syncline, but another marked development is found around H aweswat er, and these rocks certa inly occur in the H elvellyn range, though they are not inserted upon our rough map. The group has been described in some detail in a paper by the lat e E. E . Walker. * The rocks consist of lavas, ashes, and breccias, and although garnets of fairly large size are very frequent, they are by no means universall y distributed j and, moreover, such garnets occur, though less abundant ly, in other groups, as in the Falcon Crag an d! Ull eswater groups. The rocks frequentl y show a streaky stru cture, which, as shown by Walker, is produced in more than one way. The composition of these rocks varies considerably, according as they approach to the andesites on the one hand or the rhyolites on the other. Many of the streaky rocks show an intermixture of andesitic and rhyolitic material. Such rocks have silica per­ centages varying from 63 to 69. The available evidence suggests a metamorphic origin for the garnets rather than that they are original constituents. The Scawfell ash and breccia group succeeds the garnetiferous Sty Head group in the centre of the Scawfell syncline. Another development forms the sum­ mit of the Helvellyn ran ge, and send s offshoo ts to­ wards Ulleswater and Haweswater, This is traceable south- • Quart . [ ou rn , Geol , S oc., vol. Ix (1904), p . 70. LAKE DISTRICT-LOWER PALlEOZOIC. ward into a mass which runs as a narrow band from Mosedale, near Shap, to the Coniston Fells, widening towards the latter locality. The beds consist chiefly of ashes and breccias, tne former being often banded with extraordinary regularity, owing to the interstratification of bands of ash of different degrees of coarseness, the finest having been originally volcanic dust. Lavas are rare. The rocks of this series occur in two very different states, owing to the subsequent alteration of different character. The ashes and breccias of the Scawfell tract are often very flinty owing apparently to heat-action, while those of the Mose­ dale-Coniston band, having been changed by pressure, are well­ cleaved slates, largely quarried for roofing purposes. In 1907 I found in a slate quarry near Hole Rake, Conis­ ton, a grey crystalline limestone associated with the slates of this group. It was much folded, and I could find no organisms therein, but it appeared to be a true sediment. If so, it is the only ordinary sediment which has yet been found in the heart of the Borrowdale series. It resembled some of the beds of the Coniston Limestone, but it is hard to suppose that it is a member of that group folded into the Borrowdale rocks. The Shap andesites succeed the slate group. They extend from the Shap Granite to the Coniston Fells. They consist of thin vesicular lavas with ashes and breccias, and recall the Falcon Crag rocks, being, like them, of intermediate composi­ tion. The Shap rhyolites occur above the andesites, and lie to the south of those rocks. The flows are again mixed with fragmental bands. To sum up the characters of the lavas, the order of outpour- ing appears to have been as follows: Intermediate andesites (Falcon Crag Group). Basic andesites (Ulleswater and Eycott Group). Andesites, rhyolites, and a mixture of the two (Sty Head Group). Intermediate andesites (Shap Andesite Group). Rhyolites (Shap Rhyolite Group).

2A. T'Iie Intrusive Rocks of the Borroiodale Series.-The area under description contains many intrusive rocks of different ages, from Ordovician to Tertiary. It will give a better idea of the sequence of events if we treat of these rocks not as a whole, but according to age, taking each group in that part of the paper which treats of the age at which the intrusive rocks were certainly or probably injected. Accordingly in this place will be noticed those igneous rocks which are intrusive in the rocks of the Skiddaw Slates and Borrowdale Groups, and 634 GEOLOGISTS' ASSOCIATION JUBILEE VOLUME. were probably injected before the deposition of the sediments succeeding the Borrowdale Rocks. E. E. Walker, in the paper cited, describes a number of dykes and sills of garnetiferous rock, which show relationship as regards composition to the contemporaneous rocks of the Bor­ rowdale Series, and are probably therefore of the same period, though of course later than the rocks into which they have been injected. These appear to have been produced as the result of the differentiation of one magma, and evidence of such differentiation is given in the case of the irregular laccolite or sill which crosses the Langstrath Valley. Furthermore, some of these minor intrusions of varied com­ position are shown to occur as offshoots of the Eskdale granite and Ennerdale granophyre, which would indicate that these Jocks also are of the same general age j which may also be said of the St. John's Vale intrusion. These rocks vary in degree of acidity from diabases to quartz­ felsite j the well-known dykes of Armboth Fell and Helvellyn are of the latter class. The larger igneous masses were described by Clifton Ward in his papers on "The Granitic, Granitoid, and Associated Rocks of the Lake District."* The Ennerdale granophyre has been the subject of a special paper by Mr. Rastall, t while the minor sills, dykes, and laccolitic intrusions are discussed in E. E. Walker's paper. In these papers also some reference is made to the metamorphic phenomena produced by these igneous masses. It will be convenient here to notice that the celebrated vein of graphite in Borrowdale occurs along the junction of two of these intrusive igneous masses as described by Clifton Ward.:t The graphite occurs in nodules in vein stuff composed largely of quartz and decomposed igneous rock. Its origin has yet to be satisfactorily explained. Some of the metalliferous veins of the district may be of Ordovicia~ age. A vein containing copper pyrites and galena is metamorphosed by the Shap Granite, and is therefore earlier in age than that rock. Other metalliferous deposits of the dis­ trict are clearly later. The Skiddaw Slates and Borrowdale Volcanic Rocks con­ tain many veins of galena, copper pyrites, and hrematite, and occasionally of cobalt, antimonite, and zinc blende, with rarer minerals. Accounts of the mines will be found in Clifton Ward's Memoir; in a treatise on "Mines and Mining in the English Lake District," by Mr. J. Postlethwaite (r889) j and in a paper on

• Quart. [ou rn, Ceol. Soc., vol. xxxi (1875), p. 568, and vol. xxxii (1876), p. I. t Quart. Journ. Geol. Soc" vol. Ixii (1906), p. 253- t Mem. Geot. Su,vey, "Geology of the Northern Part of the English Lake Dis­ trict," p. 60. LAKE DISTRICT-LOWER PALlEOZOIC. 635 "The Mineral Veins of the English Lake District," by J. D. Kendall.*

3. The Coniston Limestone Scries.-The rocks of this series extend from Shap Wells in an east-south-easterly direction to Coniston Waterhead, where the strike changes and they are continued to the south-west as far as Millom. On the east side of the Duddon estuary they extend from Soutergate to a point north of Dalton-in-Furness. Isolated exposures occur on the east side of the Dent Fault in the valleys to the east and north­ east of Sedbergh. There is also an isolated patch in the extreme north-east of the district, in the Caldbeck Fells. In no case.has the exact relationship of these beds to the volcanic group below been determined. In the Edenside tract (to be noticed later) the following divisions have been made by the writer in a paper which gives a summary of our knowledge of the strata of the series: t I Ashgill Shales. ( Ashgill Group •" Stauroapha/us Limestone. CONISTON ' Applethwaite Beds. LIMESTONE ) Conglomerate. ~ Sleddale Group SERIES. '1 Stile End Beds with Yarlside Rhyolite above. ~ Roman Fell Group Corona Beds.

Of the three groups, the lowest has been detected only in the Edenside tract. Along the main line of outcrop between Shap and Millom the Stile End Beds are easily traced between Shap Wells and Kentmere, owing to the intercalation of the Yarlside rhyolite between them and the Applethwaite Beds. As they strongly resemble the Applethwaite Beds, separation is difficult, in the absence of the rhyolite, as the beds of the two minor divisions strongly resemble each other, but there is some evidence of local unconformity between them. The whole of the Sleddale Group corresponds generally with the Bah Limestone and associated beds of North Wales, and is therefore of Caradoc age, many of the fossils being identical with those of the Bala Limestone. The subgenus Chasmops of the genus P haco-ps marks the beds of this group in our district. The group consists chiefly of calcareous shales with an inter­ mixture of much ashy material, the limestone beds being thin, inconstant, and usually impure. The rhyolite is often marked by a well-developed flow structure, and is frequently nodular and spherulitic, Contemporaneous volcanic rocks are also found in the Sled­ dale Group of the hills north-east of Sedbergh. The representative of the Sleddale Group at Drygill, in the

* T'r ans. Manchester Geol, Soc., vol. xvii, p- 292. t Geol; Mag. dec. 3, vol. ix (t892), p. 97. 636 GEOLOGISTS' ASSOCIATION JUBILEE VOLUME.

Ca ldbeck F ell s, is of interest as bearing on the nature of sub­ sequent earth movements. The beds are here more sha ly th an those of the main outcrop, resembling the beds of the same age in the Edensid e tract, there known as the Dufton Shales. T he Ashgill Group is well developed along the main line of outcrop and in the Sedbe rgh region. The basal calcareous member is separated from the calcareous beds of the Sleddale Group on palreontological grounds . It is usuall y thin , but swells out near Mill om into a knoll of white or pink crysta lline lime­ stone, like th at of Keisley, in th e Edenside tract, save that no fossils have yet bee n detected in it. T he Ashgill Shales are usually dark grey or blue calca reous shales, with a characteristic fauna. They are extensively cleaved in the districts south -west of Coniston and north of Dalton-in­ F urness; in these districts they furnish roofing slates. T he Ashgill Group is the equivalent of Prof. Sedgwick's U pp er Bala Beds above the Caradoc of North Wales. A discussion of the classification of these beds will be found in a pa per by t he writer.* In the Sedbergh district some peculiarities in the development of the beds of the Conisto n Lim estone Series are noticeabl e, especially in the country north-east of Sedbergh, where three knoll-like masses of the series occur, associated with sills of igneous rock. In these knolls representatives of the Sleddale and Ashgill Groups occur, and th e contemporaneous volcanic rocks, consisting of rhyolites and tuffs, occur between these two groups, and accordingly at a high er horizon th an th at of the latest lava of the Lake District proper, which is in the Sleddale Group. 4. The Stockdale S hales.- T hese beds form a thin strip south of the Coniston Limestone Series. They are divided into two groups, the lower, the Skelgill Beds, and the upper, the Browgill Beds. T he beds are almost entirely argillaceo us, though fine greywacke grit s occur in the upper group. The Skelgill Beds of the main outcrop are only about fifty feet thick, but were prob­ ab ly acc umulated slowly, as indicated by the great cha nges in the fau na between the base and summit. They consist of grey to sooty-black laminated mudstones, alternating with fine cal­ careous non-laminated mudst ones, the former characterised by the abundance of graptolites and paucity of other forms, the latter by absence of graptolites and inclusion of a few tril obites and other invertebrates. The lowest member rests conformably upon the Ashgill shales beneath . The Browgill beds are chiefly pale green mudstones, with a few thin dark graptolitic bands. The distribution of the graptolites in zones through the Stock­ dale Shales has long been known. The following zones occur :

• Geol, M.'lg., dec. 5, vol. iv (1907), p. 51. LAKE DI STRICT- LOWER P ALlEOZOIC.

Zone of Cyrtograptus sr-r« (hitherto found in the 13ROWGILL Sedbergh dist rict only). BEDS. { " M onograptus turriculatus, " M onograptus crispus. " Rastrites max imus (in the Sedbergh area only). M onograptus spinigerus , S KE LG ILL " Monograptus conuolutus, B EDS. " Monogra ptus argenteus, " M onogr aptu s fimbriatus. " D imorphogra ptus conf ertus. " Ceph alogr aptu s acuminatus, " A full account of these beds will be found in a paper by the late Prof. Nicholson and the writer. * In that pa per the various zones are correlated with their equivalents elsewhere. The Skelgill Beds corresp ond with the Llandovery Rocks of Siluria, and the Birkhill Shales of the Southern Uplands of Scot­ land and the Browgill Beds with the Tarannon Shales of Siluria, and the Gala Beds of the Southern Uplands. The Stockd ale Shales are well developed in the Sedbergh area, where they are thicker than in the central Lake District tract. Several exposures occur, of which the section of Backside Beck is the most complete, and, indeed , is in many respects th e fi nest development of these beds found in the North of England. A good account of these beds in the Sedbergh area by Dr . St rahan will be found in a Memoir of the Geological Survey. t

5. L ower Coniston F lags-s-Brathay F lags.-The Browgill Beds pass up gradually into blue-grey laminated mudstones, usuall y well cleaved as the result of post Silurian earth move­ ments, and quarri ed for roofing slates on Applethwaite Com­ mon , Broughton Moor and elsewhere. The presence of large elliptical concreti ons in these beds is a. feature which they also possess in other British districts, and in several Eu ropean coun­ tri es. These beds, about 1 ,000 feet in thickness, represent the 'Wenlock Beds of Siluria, but the calcareous element is here abse nt. Few fossils, save grapt olites, occur. In the Silurian region and elsewhere several graptolite zones ha ve been deter­ mined, chiefly charac terised by spec ies of Cyrtogra ptus. Of these the lowest only, th at of C. murchisoni, has been found in the L ake District. This is due to the fact that the graptolites have hitherto only been found in a state fit for identificati on at the base of this group, where they have escaped cleavage owing to the presence beneath of the more massive greywacke grits at the top of the Stockdale Shales. Graptolites are often

• Q lla r!. Lourn , Geot, Soc .. vel. xliv (y888\, p.6.;t. t H "The G eology of the Country around Malle rs tang;' etc., p p . 28-34. 638 GEOLOGI STS' ASSOCIATION J UBILEE VOLUME. visible in higher beds, but all deta ils of structure have been obliterated. The beds are foun d in a belt south of that of the exposure of the Sto ckdale Sha les, and in several exposur es in the Howgill Fell s tract . The succession of fau nas in th e equivalents of th e Wenlock an d Lu dlow beds of th e L ake Di str ict is considered in a paper b y the writer. * 6. Upper Couiston F lags- Coldwell Beds.-The Brat hay Fl ags are immediately succeeded by a thin qu artzose grit whi ch has yielded no fossils, an d which I regard as the base of the Ludlow Beds. T his grit forms th e Lower Coldwell Beds. It is succeeded by well-bed ded calcareous flags, th e midd le Coldwell Beds with Ph acops ( D almannites) obtusicauda tus , Cardiola interrupta , Ortho­ cera ia, an d other fossil s. The fauna is distinctively of Lower Ludlow age. T hese flags pass int o laminated gritt y flags of con­ siderable thickness-the Uppe r Coldwell Beds. They contain an ab undant fauna, with ma ny graptolites . Miss Wood (Mrs. Shakespear) correlates these beds and the overlying Con iston Grits, which have much th e same faun a , though poorer in species, with her Lower Ludlow zone of Monograptus nilsoui.

7. Coniston Grits.- These beds consist of mas sive grit s of g reat th ickness with some shales. It is in the latt er that fossils have been foun d. ch iefly at Pennington's Qu arry, near Winder­ mere. The grits usuall y give rise t o a prominent feature in the landscape. North of Sedbergh a very coarse grit is found in this series, which Professor Hughes termed the Winder grit. In it he found Chonetes striatella, Dayia navicula, B eyrichia, Kloedeni, and ot her Lu dlow fossils.

8. Hannisdale Slates.-A thi ck group of stripe d grey laminated flagstones with some grits, obviously of shal low water chara cter. F ossils are rare, save towards th e t op. These beds are widely spread over the low ground of the southern part of the L ake Di stri ct. The greatest number of fossils have bee n foun d in th e strea ms on th e north side of the Howgill Fell s. Here is th e grapt olite Monograptu s leintioardinensis var. incipiens, in dicat ing that the se beds belong to the zone of 111. l eintwardinensis. Towar ds th e top th e Bannisdale slates become f airly ca l­ careous, and contain in places abundant fossils. Several starfi sh have been found in these passage beds, which have accordingly been termed the sta rfish-beds . They may represent th e Avmest ry L imest one of Siluria. -

., Grnt. ~' f(1 g . , de c . 3, "01. ix (r892), p. 534. L AKE DI STRICT-LOWER PALlEOZ OIC.

9· The K irkby M oor Flags are well developed in the district between Kendal and Kirkby Lonsdale, and are also found in a synclinal fold between Tebay and Staveley. They consist of greenish-grey calcareous sandstones and flagstones with an abun dant fauna, which has long been recogn ised as of Upper Ludlow age. The summ it of this series is not found, and accordingly we get no representatives of the passage beds between the Silurian and Old Red San dstone Rocks, like those which occur in Siluria.

(B) Tlte Outlying L ower P ala ozoic R ocks of the S ettl e, Edensid e, and T eesdale D istricts. ( a) S ettle.- A general acc ount of the rocks of this tr act by Professor Hughes will be found in the Geological Maga zine, dec. r , vol. iv (1867), p. 346, and some further details in a paper by the present writer in the same Magazine (dec. 3, vol. iv (r887), p. 35). The rocks occur owing to the great Craven system of Faults bringing up old er rocks on its upthrow (north) side. They are developed in several valleys, namely, Doe Beck and its tributary near lngleton, Cla pham Dale, Austwick Dale, Ribblesdale, Malham, and Wharfedale. They are not exposed in the last­ named dale, but Mr. Dakyns gives evidence for their occurrence therein. The oldest rocks seen are largely developed in the valleys of Doe Beck and its western feed er, and to a less degree near Horton­ in-Ribblesdale. These are the lngleton green slates , consisting of green slaty beds with grits stan ding nearly vertically. They have often been correlated with the Borrowdale volcanic series from their general appea rance and because th ey are succeeded by the Coniston Lim estone series. They differ markedly from the Borrowdale Rocks, being detrital sediments derived from gneissose, schistose and other rocks, and their :J ge yet remains to be determined. It is possible that they are of pre-Cambr ian date. An account of these rocks bv Mr. R. H . Rastall will be found in the Proceedings of lite Y orkshire Geological S ociety YOI. xvi, p. 87· The beds' of the Coniston Limestone Series are seen in many sections, the best being at Norber Brow and in Austwick Beck and its tributaries. Equivalents of both the Sleddale and the Ashgill Groups occur. The Stockdale Shales are represented by a thin, impure lime­ stone (about four inches thi ck) in the bed of Austwick Beck. It conta ins numerous small tril obites like those found elsewhere in the Skelgill Beds. 640 GEOLOGISTS' ASSOCIATION JUBILEE VOLUME.

The equivalents of the Brathay Flags are also found in this district. The Lower Coldwell Beds may be represented by the Moughton Whetstones. The exact position of these has not been determined. The former identification by me of Monograptus uncinatus in these beds is not correct; and it is doubtful whether the graptolite which I claimed as Monograptus nilsoni is really that form. The Horton Flags contain the fauna of the Upper Coldwell Beds, and a set of grits on the east side of Ribblesdale, the highest Lower Palzeozoic Beds of this tract, may represent the base of the true Coniston Grits. (b) Edenside.-Details of the development of the beds in this area are given by Prof. Nicholson and myself in a paper, "On the Cross Fell Inlier."* An important memoir on the Keisley Limestone, by Mr. Cowper Reed, also occurs in the Quarterly]ournal, t and I have discussed the relationship of the Dufton and Keisley Beds in a paper in the Geological Magazine. t The Lower Palreozoic Rocks are found in a narrow strip running nearly north and south on the west side of the great scarp of the Cross Fell block, between the Alston Moor road near Melmerby on the north and Roman Fell on the south. On the east side of this inlier the Skiddaw Slates are chiefly developed, being separated from higher Ordovician and Silurian Rocks to the west by a fault, the Middle Pennine Fault. The Skiddaw Slates are much like those of the Lake District, high fossiliferous members of the group being found in Ellergill and still higher beds with intercalated contemporaneous volcanic rocks of intermediate composition on and in the neighbourhood of Wythwaite Top. Near Melrnerby, volcanic rocks of the Eycott Hill type of the Borrowdale Series are found. The main mass of the Borrowdale Rocks of Lakeland is not represented, for the fault just mentioned brings the volcanic rocks of the Shap Rhyolitic series against the Skiddaw Slates. The Coniston Limestone Series is well represented. The interesting features are (I) the occurrence of the variable series of calcareous and ashy sediments apparently succeeding the rhyolitic rocks with perfect conformity, and characterised by the occurrence of a rich fauna, including the type fossil Trematis corona; (2) the replacement of the somewhat highly-calcareous rocks of the Sleddale Division in Lakeland by an argillaceous group with thin impure limestones, the Dufton Shales; and C') the local expansion of the lower calcareous member of the Ash­ gillian Group at Keisley into the richly-fossiliferous Keisley Limestone. The Silurian Beds up to and including the Coniston Grit are represented, but call for no special remarks here.

... Quart. JOUT1:. Geol. Soc., vol. xlvii. (1891), p. 500. t Vol. Iii (1896), p. 407. and vol. Iiii (1897). p. 67. t Dec. S, vol. iii (1906), p. 481. LAKE DISTRICT-LOWER PALJEOZOIC.

(c) Teesdale.-In Upper Teesdale a fault known as the Bur­ treeford dyke runs across the Tees, and Lower Palreozoic rocks are found at Cronkley and Widdybank Farm on its west side. At Cronkley Pencil Mills, slaty beds have been worked for roofing slates, while in the neighbourhood of Widdybank con­ temporaneous volcanic rocks occur j the former have been referred doubtfully to the Skiddaw Slates, and the latter to the Rorrowdale series. but their true age remains to be determined. These beds were described by Messrs. Gunn and Clough.*

4 1