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MACNAIR—LIMESTONES IN THE DISTRICT. 37

No. V.—THE STRATIGRAPHY OF THE LIMESTONES LYING IMMEDIATELY ABOVE THE CALCIFEROUS LAVAS IN THE GLASGOW DISTRICT. By PETER MACNAIR, F.R.S.E., F.G.S., and HARRY R. J. CONACHER.

[Read 13th March, 1913.]

THE group of sediments under discussion is that commonly known as the Lower Limestones, with the addition of those which occupy the space between the base of the Hurlet Seam and the top of the lavas, that is, from the Hosie Limestones at the top to below the Hollybush. These limestones crop out practically all around the basin in which Glasgow lies, and are seen in burn sections, quarries, and railway cuttings along the base of the hills of Calciferous lava which form its rim. The strata below the Hurlet Seam are grouped by the officers of the Geological Survey with the Calciferous series, but as there is no essential break at this horizon in our district such as exists in the Lothians, we propose to deal with all these beds as one series. The district dealt with may be defined as including Hurlet, Howood, Paisley, Bridge of Weir, Duntocher, Bearsden, Campsie, Kilsyth. The literature of the subject is meagre. There are references in the Geological Survey's publications dealing with Sheet No. 31 of their 1-inch Geological Map.1 In the Transactions of our Society there is a paper by Mr. Hugh M'Phail dealing with the -Paisley District;2 there is Dr. Young's paper of 1860 on Campsie and the Glasgow District;3 and there is the Memoir of the Geological Survey, published in October, 1911.4

1 Memoirs of the Geological Survey, . Explanation of Sheet 31 (1879). 2 On the Carboniferous Sections of the Levern Valley, . Glas. Geol. Soc. Transactions, vol. iii., p. 254. 3 On the Geology of the Campsie District. Trans. Geol. Soc. Glas.9 vol. i., p. 1, 1863. 4 Memoirs of the Geological Survey of Scotland. The Geology of the -Glasgow District, 1911. Downloaded from http://trngl.lyellcollection.org/ at West Virginia University on July 11, 2015

38 TRANSACTIONS GEOLOGICAL SOCIETY OP GLASGOW.

Prior to the issue of the last-named publication, no definite co-relation of the beds under discussion had been published.. It was while going over the ground with that book in hand that we came on the points which we now bring before you. Hurlet District.—In the Memoir, the following horizons are recognised and described in the district, and may be examined at the localities named: — Hosie Limestone—River Levern at Barrhead. Blackhall Limestone—Jenny's Well, Paisley, and Levernside,. Crookston. Hurlet Limestone—Not now seen, except at Arkleston Cutting,. north-east of Paisley. Blackbyre Limestone—Railway Cutting at Barrhead. Hollybush Limestone—Hollybush Quarries, and Hawkhead Dam. With regard to the Hosie Limestone at Barrhead, we are unable to offer any opinion or criticism of this identification. The Blackhall Limestone, as seen at Jenny's Well (first described by Mr. John Smith in vol. xii. of our Transactions)r shows definite and constant characters which enable it to be reoognised with certainty throughout the district. It is in several beds, the top one marine, the lower fresh water, and contains a parting of entomostracan oil shale. It can be seen to overlie a series of clay-band ironstones, which, again, are above the Hurlet Seam, as shown by old workings. The Blackbyre Limestone, as seen in the railway cutting at Blackbyre Farm, is also in several beds, the upper composed of small encrinite fragments, and the lower slabby and crowded with small producti and containing occasional plant remains. The Hollybush Seam is accessible with difficulty in the old quarries at Hollybush and below high-water level in the Hawk- head Dam. In both localities its most striking characteristic is the abundance of large producti (giganteus, latissimus, and semi-reticulatus), and branching and solitary corals. The stratigraphical relations of the Blackbyre and Hollybush Limestones cannot be certainly seen in the type district, but the positions assigned to them in the Memoir are confirmed by neighbouring sections, which are now described for the first time. Downloaded from http://trngl.lyellcollection.org/ at West Virginia University on July 11, 2015

MACNAIR—LIMESTONES IN THE GLASGOW DISTRICT. 39"

Nethercraigs.—At Nethercraigs, south of Paisley, there is a small syncline, truncated to the south by the fault which brings up the lavas of the Ferneze Hills, and in this basin— no more than half a mile across—we see the Hurlet Lime stone y the Blackbyre, and the Hollybush. The Hurlet Limestone, which at Hurlet is stated to be no more than 4 to 5 feet thick, has here increased, by the addition of limey shales, to about 30 feet. This is a surprising phenomenon, but it is also seen to occur at Howood, in the G-ryfe, and at Campsie. The

Fig. 1.—Plan and Section across Limestones at Nethercraigs, Paisley. (a) Strata below Hollybush Limestone; (b) Hollybush Limestone; (c) Hollybush Sandstone ; (d) Blackbyre Limestone; (e) Ashy muds with limey nodules; (/) Hurlet Limestone. alum shale and coal, which usually underlie the encrinital Hurlet Limestone, are not seen here, but a very characteristic brecciated limestone bed with ashy mud, recognised by us in the same position at Howood, Bridge of Weir, and Campsie, is well displayed in old quarry section and in the neighbouring burn. Below it comes a thickness of sandstone whose lower boundary is a line of unconformity, which is also seen in the Campsie district. The Blackbyre Limestone comes in at this Downloaded from http://trngl.lyellcollection.org/ at West Virginia University on July 11, 2015

40 TRANSACTIONS GEOLOGICAL SOCIETT OP GLASGOW. point and is, as elsewhere, a typically marine deposit. The beds underlying it are seen in the burn section to consist mainly of sandstone with thin coal (the "Lady Anne"), and then comes the Hollybush Limestone. This seam is not well seen m section, but it contains the typical large producti and corals. At Nethercraigs the burn section goes only a short distance below the Hollybush, showing nothing but sandstone, but at Hollybush we get a glimpse in burn and railway sections of volcanic muds and oolitic beds which seem every­ where to occupy a position immediately above the lavas. There are also some ironstones containing plant remains. Howood.—In old quarries here, and in a burn section at Meikle Corseford, we find the Hurlet Limestone exhibiting the Nethercraigs characteristics and immediately underlain by a shale and coal. Some parts of the shale contain a marine fauna (producti, &c), while others are matted with a lamelli- branch which appears to be Cypricardia (Sanguinolites) tricostata? The peculiar brecciated limestone is seen in the burn, and it here contains a few marine fossils, and is overlain by an ashy bed with nodules, like that of Nethercraigs. The equivalent of the Blackbyre Seam is also exposed, but differing somewhat in character from that of the type. Below it sandstone appears, overlying limey beds which are crowded witE giganteid producti and lithostrotion, which we regard as the equivalent of the Hollybush. Unfortunately the section gives no certain information beyond this point, and the boundary fault comes in. The modification of the characters of the Blackbyre Lime­ stone seen in this section is interesting as confirming the identification of the small, isolated exposure of limestone seen in the railway cutting at Auchinback, east of Barrhead, providing a link in the transition of this bed from the characters seen in the type section to those prevailng at Thorntonhall and in north Ayrshire. Bridge of Weir.—In the Gryfe, to the north-east of Bridge of Weir, there is an excellent section which, with but one important gap, is complete from the top of the lavas to the top Hosie Limestone. Beginning at Bridge of Weir and working down stream, there is an interesting section of muds and conglomerate of lava pebbles lying in hollows on the Downloaded from http://trngl.lyellcollection.org/ at West Virginia University on July 11, 2015

MACNAIR—LIMESTONES IN THE GLASGOW DISTRICT. 41

eroded lava surface. Above this comes ashy fireclay, with rootlets, irregular coal, and greenish sandstone. A horizon of fossiliferous nodules and shales then comes in, which is found to develop into a fairly compact limestone in places, crowded with large producti and branching corals. It can be examined at intervals along the banks of the Gryfe from the cottage on the west bank to the ford. At the latter place the

Fig. 2—Plan and Section along the Gryfe, from Bridge of Weir to Crosslee. Lettering same as tables in text (see page 42).

nodular phase is well seen. This limey horizon overlies a thin coal. A sill penetrates the strata, and the sequence is obscured by small disturbances which run parallel to the line of section. From the ford to the turn in the stream at the old limestone workings, there are no exposures, but below water level at the sharp bend, the nodular green limestone can be seen, contain­ ing corals and encrinites. The coal and alum shale are not now exposed, but fragments can be picked up in the bings. The evidence for identifying this seam as the Hurlet is fairly Downloaded from http://trngl.lyellcollection.org/ at West Virginia University on July 11, 2015

42 TRANSACTIONS—GEOLOGICAL SOCIETY OF GLASGOW. complete, and as already mentioned, this section also displays the augmentation of its thickness by the addition of limey shales, while the more typical encrinital part, 4 to 5 feet thick, has been worked out. The gap in this section occurs below the nodular green bed, just described, and we believe that at this point the Blackbyre Limestone exists, which opinion is confirmed by the evidence of the following bore put down at Goldilee and quoted in the Transactions of the High­ land and Agricultural Society : —

BORE AT GOLDILEE, BRIDGE OF WEIR, RENFREWSHIRE. CORRELATED WITH THE HURLET SECTION.

Feet. Inches. Clay, - - 12 0 Flag, - 20 0 Limestone, - 7 g Hurlet Limestone. Till, - 1 0 /Alum Shale. Coal, - 2 6 e Hurlet Coal. Fire-clay, 5 d Ashy Muds with Limey Nodules. Limestone, - 4 c Blackbyre Limestone. Fire-clay, 2 Black Till, - 19 ^ Coal, - 10 } b Equivalent of Hollybush Sandstone. Grey Till, - 13 J Greenstone, - 5 Intrusive Sill. Grey Till, - 5 a Hollybush Limestone. Freestone, 5 Coal Till, - 9 Coal, - 1 3 Fire-clay, 5 Whinstone, - Lavas.

The limey beds, containing large producti and corals, we correlate with the Hollybush Seam. Proceeding with the stream, a small fault is crossed, which brings down the top of the Hurlet, and then the shales and ironstones, with a thin coal, are met. These are overlain by a very interesting series of strata, of which we give a detailed section—

18" encrinital limestone. 14" strong shale. 12" shale or fireclay with stigmaria and entomostracan shale. 12" entomostracan limestone. 12" shale. 4" coal. Shale with ironstones (containing Lithostrotion in places) and coal. Downloaded from http://trngl.lyellcollection.org/ at West Virginia University on July 11, 2015

Trans. Geol. Soc. of Glasgow. Vol. XV., Plate V

Fig 3. Plan and section across the South Hill of Campsie from Craigenglen to Baldow Glen, Lettering same as Table in text, see page 45. Downloaded from http://trngl.lyellcollection.org/ at West Virginia University on July 11, 2015

MACNAIR—LIMESTONES IN THE GLASGOW DISTRICT. 43

There can be no doubt that this represents the Blackhall Limestone with some interesting variations. Above these strata comes a fresh series of shales with iron­ stones, some of which contain entomostraca and almost develop into limestone, and then we reach the two encrinital bands of the Hosie, with shale containing Posidonomya corrugatcfi (marked i in section). We consider that the Nethercraigs, Howood, and Gryfe sections together afford important evidence bearing upon the co-relation of the Hurlet section with those in the north of Ayrshire. Thus it seems to us that the lower division of the main limestone, as seen at Broadstone, Beith, and elsewhere, with its underlying coal is the equivalent of the Hollybush seen in the three Renfrewshire localities. The fragmental deposits lying between the lower and upper divisions of the main limestone of Ayrshire, as seen at Broadstone, is the representative of the Hollybush Sandstone; while the upper division of the main limestone, as seen at Dockra, is the equivalent of the Blackbyre Limestone, the position of this limestone being fixed over a large part of the north of Ayrshire by the capping of ashy muds with limey nodules, which, we have shown, is so characteristic of this horizon in the Renfrew­ shire sections. The Hurlet in the north of Ayrshire has dwindled to less than its thickness in the type section, and the top of the Lower Limestone Series is marked by beds of limey shale with Posidonomya corrugata, which have a very striking resemblance to the shales and limestones of Calder- wood Glen. We hope, however, to deal with this matter in more detail next session. Crossing now to the north side of the Clyde, we take the Campsie district first, because there we find the clearest sections. There are no sections so complete as that on the Gryfe, but, in the numerous small burns, exposures occur which can be pieced together. In the Memoir it is stated that the Hollybush Limestone is not seen north of the Clyde, but we

6 See Trans. Geol. Soc. Glas.f vol. xiv., part iii., page 309, " On the Dis­ tribution of Posidonomya corrugata, Ether. Jun., in the Carboniferous Limestone of the Glasgow District," by Peter Macnair, F.R.S.E., F.G.S., and Harry R. J. Conacher. Downloaded from http://trngl.lyellcollection.org/ at West Virginia University on July 11, 2015

44 TRANSACTIONS—GEOLOGICAL SOCIETY OF GLASGOW. believe its exposures there are more plentiful than those of any other beds. South Brae of Campsie.—In Craigen Glen there is a section of a series of shales which are famous for the variety of their fossils. These beds are correlated by the Survey with the Blackbyre Seam (Productus Shales), but we are of opinion that they represent the Hollybush horizon. The section, beginning at the base, shows an oolite in fireclay-like beds overlain by sandstone containing a thin coal. The limey shales contain several bands of calcareous ironstone nodules, which were formerly mined; these nodules, as well as the shales, contain producti and corals which, in some cases, have been completely removed by percolating water, leaving very striking casts of the calcareous parts of the organism. The section passes up into sandstone and fireclay apparently underlying the Hurlet, whose position is traceable, but the section at this point is obscure. In Glen Wynd, immediately to the west, the Craigen Glen shales can be identified passing under sandstone which is overlain by a limestone, consisting of beds of small producti, with plant remains, and an encrinital upper part. These characters at once suggest the Blackbyre Limestone of Barrhead, and it also has an unconformity above it, as noted at Nethercraigs. Above this unconformity is a peculiar deposit, weathering with a characteristic red crust; if sampled near its base it is found to be a hard sandstone with rootlets and spirorbis, but the upper portions are distinctly limey, and in other sections it is found to be a calmy limestone with many entomostraca. It can be examined to advantage at the Linn of Baldernock, where thin shale bands subdivide it, as is also the case elsewhere. In Glen Wynd this limestone is not well seen, and the succeeding strata are also either worked out or hidden from sight, with the exception of a black shale, baked by a sill of white trap, whose identity is betrayed by its fauna as the alum shale of Lennoxtown district. North-west of Glen Wynd a small pine wood is fronted by extensive signs of old workings, and at one point, where a small burn falls into the old waste, a few feet of an encrinital limestone, with a few small producti, is seen overlain by black shales with small ironstones. These old workings, with occasional exposures of Downloaded from http://trngl.lyellcollection.org/ at West Virginia University on July 11, 2015

MACNAIR—LIMESTONES IN THE GLASGOW DISTRICT. 45 the limestone, can be traced practically right round the hill, and at Boyd's Burn and Culloch Slap work is still going on. For a short distance to the south of the wood just mentioned the tirring of old opencasts encumbers the ground, but above an old mine mouth in the former bed of the stream we see again the sandy base of the Baldernock Limestone, with its line of unconformity, and it is possible to recognise below it the same beds as seen in Glen Wynd. The structure in this glen (Borraston) is complicated by a number of small faults, which repeat part of the sequence. At Baldernock Linn, or higher in the burn which forms it, the following section is exposed: — Black shale with small ironstone nodules. Thin limestone, with small encrinites, &c, and pebbles of dolomite. (Shields bed). Black shales with small ironstone nodules. t\ -i • » • i ~ - vj •Encrinitam t EN. l i Limestone. 1 Dolerite intrusion here, seen in bed Black Shale. V cu •> . *.A ,of burn and in old quarry. Entomostracan Limestone. Sandy Limestone. Unconformity. Shales with plant remains and Lingula. Encrinital Limestone. This section is much distorted by the dolerite intrusion near the linn, and a small dyke and sill of white trap also appear higher up. West of here, and near to the Auld Wives' Lifts, the sill is again seen, with fragments of limestone, &c, sufficient to identify it, and its outcrop across the slope to the south-east is marked by the depression left by old workings. No doubt this is the locality referred to in "The Geology of Campsie" where the author speaks of an encrinital limestone passing under the Craigmaddie Sandstones; in reality it is thrown against them by a fault. Passing now to the north face of the South Brae, we get several glimpses of our encrinital limestone—sometimes accom­ panied by the sill—in old workings. At Culloch Slap (above Lennoxtown), where work is still going on, we see that this limestone, 4 to 5 feet thick, overlies alum shale, coal, and Downloaded from http://trngl.lyellcollection.org/ at West Virginia University on July 11, 2015

46 TRANSACTIONS—GEOLOGICAL SOCIETY OP GLASGOW. entomostracan limestone, and in Baldow Glen we see the position of these strata in the sequence. Beginning at the road to Lennox Castle, we see, in ascending order,

a Sandstones. b Fossiliferous limey shales, with nodules and some more solid beds Productus giganteus (Craigen Glen beds). (Hollybush.) c Sandstones and fire-clays. d Limey shales crowded with small Producti and two posts of limestone composed of small encrinite fragments (Glen Wynd beds). (Blackbyre.) e Shale with Lingula. f Unconformity. g Sandy Limestone. h Entomostracan Limestone (Baldernock). i Fireclay. j Gap. (Campsie Main Limestone worked out.) (Hurlet.) Jc Black shales with small ironstone nodules. I Limestone band with dolomitic pebbles, encrinites, &c. (Shields bed.) m Black shales with large C.B. ironstones at top. n Limestone, in five beds, top one encrinital, others entomostracan and red crusted, partly oolitic, shale partings, one an oil- shale (Baldow). (Blackhall.) o Shale with nodules (Posidonomya becheri bed at base).

The rest of this section shows only black shale and ironstone nodules. It is stated by the miners that in some parts of this district there is a 14-inch coal below the entomostracan limestone {Baldernock Limestone), but we have seen no trace of this. In the new Memoir, reference is made to a blue limestone cropping out in this glen, now no longer visible. This we suppose to be the limey shales, &c, which have yielded Productus giganteus. The exposure is very small and obscured by drift, but we identify it as the representative of the Craigen Glen shales, and we feel no doubt also that the productus shales with encrinital beds are the same as those seen in Glen Wynd. The upper part of the Baldernock Limestone here contains a nodular brecciated band with rootlets, whose appearance at once suggests that already described from Thorntonhall, Gryfe, and Nethercraigs. In Baldow, the Hurlet Coal and Limestone are not seen, and the alum shale is barely visible, but all can be examined in neighbouring workings. In €ulloch Slap and Boyd's Burn the alum shale contains numerous Downloaded from http://trngl.lyellcollection.org/ at West Virginia University on July 11, 2015

MACNAIR—LIMESTONES IN THE GLASGOW DISTRICT. 47 limestone nodules which closely resemble, when seen lying broken and weathered, the Baldernock Limestone, but they contain no entomostraca, but frequently a marine fauna, and are intricately brecciated like septarian nodules, which indeed they are. The alum shale contains a varied fauna; at Culloch Slap, Boyd's Burn, and Glen Wynd beds occur which are crowded with Leppodomus costellatus, while others bear only Lingula, small Producti, or Bellerophcm, and an occasional plant print (Sph&nopteris?), and in parts fish remains and ento­ mostraca are abundant.7 At Boyd's Burn and Glen Wynd, and in old bings east of Craigen Glen, we have found an occasional Posidonomya corrugata (one specimen from each locality). In Baldow Glen, at the sharp bend above the Hurlet outcrop, there is well exposed the striking bed which we refer to as the " Shields Bed." This bed is seen with approximately the same features in the burn above Baldernock Linn, in diminished size in the burn at Flutcher, in the wood between Langshot and Newlands (in small burn at east side of wood), and in Glen Whapple (north-west of Upper Carlston). In the last-named locality it has become partly oolitic and sandy enough to contain annelid burrows. In the type locality (Shields Burn, Milton of Campsie), it is a 3- to 4-feet bed of sandy encrinital limestone; while it is constant in some form throughout this district, the distance above the Hurlet Limestone varies. The section of the Baldow Limestone in Baldow Glen is the best in the district, but it is also seen in Glen Whapple, where it has been wrought, and its position is marked by old workings and numerous fine fragments at the mouth of Craigen Glen, to which position it is brought by a fault. On the South Hill, no higher strata than the Hosie Sandstone •occur, and this is to be seen in one or two small, old quarries south of Clochcore and at Newlands.

7 In the alum shale which comes between the Cobbinshaw limestone and coal at Cobbinshaw and at West Mains there occurs an exactly similar fauna to that just described, and it is certainly very striking that in two places so widely separated there should be found such a close resemblance in the strata and their contents ; in both districts the descending sequence is encrinital limestone, alum shale, pyritous coal, fire-clay, and entomo- stracan limestone. Downloaded from http://trngl.lyellcollection.org/ at West Virginia University on July 11, 2015

48 TRANSACTIONS GEOLOGICAL SOCIETY OF GLASGOW.

North Brae of Campsie, &c.—Leaving the South Hill and crossing to Balgrochan, north of Lennoxtown, we find 4 to 5 feet of encrinital limestone capped by many feet of flaggy limestone, with pecten, productus, &c, and limey shales, a state of affairs similar to that at Nethercraigs, Gryfe, and Howood. Below this seam occurs the alum shale and coal, then the Baldernock Limestone, and a long section of the Glen Wynd Limestone is found in burns at Balgrochan and east of Bencloich Mains. In the burn at the latter place the Shields bed can be seen in its more typical form, and higher up the Baldow Limestone comes in. Above it at this point the shales contain an interesting fauna, not yet fully examined, including Posidonomya becheri (first noticed in this position by Mr. Reoch at Corrie Burn), orthoceras, and nautilus. This fauna we have also found in the same position in Baldow Glen and at Shields Cottage, but where the lime­ stone crops in Glen Whapple the shales are too much crushed by an adjacent fault to yield fossils. The Baldow Limestone is also exposed in the Bught Glen at Maiden Castle, where it is curious to note that the burn has sunk its ravine many feet right through that structure. In the burn east of Shields Farm we get our first sight of the Hosie Limestone, where it is of a cement-like nature in two bands about 8 feet apart, accompanied by black shales and one or two ironstone and kingle ribs. A few feet above the upper limestone the Posidonomya corrugafebeds occur in good form. The group is not again seen .early until we reach the Corrie district, but there the burn west of Burnhead gives an excellent section. Above the Hosie Limestone along the south face of the Campsie Hills between Corrie and Spouthead there occurs a. mass of sandstone alternating with shales and fakes, the alter*- nation being repeated several times with remarkable regularity. Near the top of the series there occurs a sandstone with annelid burrows and Spirophytan caudagalli and small encrinities, and the latter bed is also to be seen near Burnhead. At Corrieburn there is a very interesting section, which passes from the zone of the volcanic detritus, with rough conglomerates and fine muds to the strata above the Upper Downloaded from http://trngl.lyellcollection.org/ at West Virginia University on July 11, 2015

Trans. Geol. Soc. of Glasgow. Vol. XV., Plate VI.

Fig. 4. Plan and section across Limestones at Corrieburn, Kilsyth. Lettering same as Table in text, see page 49. Downloaded from http://trngl.lyellcollection.org/ at West Virginia University on July 11, 2015

MACNAIR—LIMESTONES IN THE GLASGOW DISTRICT. 49

Hosie Limestone. The details of the section as observed by us differ from those given in the Survey Memoir, and we set them out side by side below—

Survey Memoir. Present Authors. Black oily shale with Lingula. z Posidonomya corrugata beds and Limestone with Bellerophon (Hosie Lingula shale. Limestone). y Black limestone with Bellerophon. Strata with thick yellow sandstone x Black shales with Leptodomus (Hosie Sandstone). costellatus, Pinna, &c. Black shale with septarian ironstone w Limey shale. nodules. Marine fossils near base. v Black limestone with Bellerophon Limestone, partly marine with en- and Orthoceras. crinites, partly dolomitic and u Shale. oolitic with entomostraca (Black­ t Sandstone. hall). s Shale with nodules (P. becheri Strata—black shales and sandstones bed at base). with I.S. band. r Encrinital limestone with small Hurlet j Upper hard band, solitary corals. -r« , i Calmy band. Limestone. | / q Brown - crusted entomostracan Low rhardband limestone. Large growth forms of brachiopods p Sandstone, flaggy and ripple- and mollusca. marked, limey and oolitic in Strata with thin coal. parts. Coral limestone. 0 Limey shales with large encrinites Black shales, sandstone bands, iron­ and Polyzoa. stones and calcareous nodules; n Encrinital limestone (Hurlet). with alternations of purplish m Black shale with Leptodomus volcanic detritus and rolled costellatuSy and small ironstone fragments. Lingula in shales nodules. and volcanic muds. 1 Coal. Thick volcanic muds and con­ k Fire-clay. glomerates resting on lavas (pp. j Nodular green limestone with 15 and 24 of Memoir). corals. i Coral limestone, eroded in places (Hollybush). h Limey shales with Rhynconella and nodules containing corals and brachiopods. g Shale with ironstone. /Naiadites crassa bed. e Sphenopteris (?) bed. d Beds containing young of Naia­ dites crassa. c Shales grading down into volcanic mud with oolitic ironstone nodules. b Sandstone. a Muds and conglomerate. The Hurlet Limestone appears to be correctly identified here, and the overlying beds at once betray their identity, but below the coal there is difficulty. We are inclined to think that here the line of erosion, elsewhere noted above the Glen VOL. XV., PT. I. Downloaded from http://trngl.lyellcollection.org/ at West Virginia University on July 11, 2015

50 TRANSACTIONS—GEOLOGICAL SOCIETY OF GLASGOW.

Wynd Limestone, has cut out that seam, and that the coral limestone and the accompanying very fossiliferous beds are equivalent to the Craigen Glen shales. East of Corrie there are only one or two unimportant, isolated exposures of the Baldow Limestone at Berryhill, hints of it at Linns, while the Hosie is seen at Drumnessie. At North Bardowie, the Hurlet group can be traced by old workings, at Flutcher the Shields bed is seen, and at Dowans there is an excellent section of the Craigen Glen beds involved in a dolerite intrusion, the intervening strata being hidden. West of Milngavie, the Hurlet group is not seen, but old workings mark its outcrop. At Hardgate Quarry, in the burn at Duntocher Mill and at Auchentoshan and on and near the golf course at Lawmuir, are exposures of what is evidently the same calcareous series, containing corals and large producti. The character of these beds, their relation to the Hurlet outcrop, and the nature of the adjacent strata (sandstone with thin coal above and below), cause us to regard them as the equivalent of the Craigen Glen beds. From the foregoing, it will be seen that throughout the Glasgow district the limestones are remarkably constant in occurrence, and that those modifications which take place can be traced in their development from one locality to another, showing that the Blackhall, Hurlet, Blackbyre, and Hollybush Limestones of the type locality have their counterparts north of the Clyde in the district stretching from Kilsyth to Dun­ tocher in the Baldow, Campsie Main, Glen Wynd, and Craigen Glen beds respectively.