Chapter 8 The Central Belt — continued. Black shale bands in the area between the Annan and the Nith

The Glenkiln Section. — The section in the Glenkiln Burn about three-quarters of a mile above Kirkmichael Manse, Dumfriesshire, [NY 00319 88672] has been fully described by Professor Lapworth in his paper on "The Moffat Series". From this section the lowest division of the series derives its name, because it yields the characteristic fossils of the group in greatest abundance.

From the accompanying plan (Figure 25) and horizontal sections it will be seen that the original sequence of the strata has been much disturbed by faulting. A still further disadvantage appears in the fact that as the observer ascends the stream from the Manse he first finds an exposure of the Lower Hartfell black shales, which, owing to a blank in the section, are not in visible continuity with other strata to the south. The Hartfell black shales at the latter point form an inverted syncline dipping to the north-west. At the edge of the south limb of this fold and on the left bank of the burn there is an exposure of grey and black shales which contain the following characteristic forms of the Climacograptus Wilsoni zone in excellent preservation (3II, (Figure 26)):

Climacograptus Wilsoni (Lapw.)

Climacograptus Schärenbergi (Lapw.)

Climacograptus peltifer (Lapw.)

Dicranograptus ramosus (Hall.)

Diplograptus foliaceus (Murch.)

Corynaides calycularis (Nich.)

Overlying the foregoing strata and occupying the centre of the trough some flaggy shales have supplied the following assemblage of fossils:

Climacograptus caudatus (Lapw.)

Climacograptus bicornis (Hall.)

Climacograptus tubuliferus (Lapw.)

Curynoides calycularis (Nich.)

Diplograptus foliaceus (Murch.)

Diplograptus perexcavatus (Lapw.)

Lusiograptus margaritatus (Lapw.)

Dicellograptus moffatensis (Carr.)

Dicranograptus ramosus (Hall.)

Dicranograptus Nicholsoni (Hopk.)

These fossiliferous shales are immediately followed by those forming the Climacograptus Wilsoni zone, on the north limb of the syncline, which there dip to the north at an angle of 80°. At this point the section is of importance, as it shows a gradual passage downwards into bands of chert with radiolaria, and mudstones. Indeed the evidence of the intercalation of radiolarian mudstones and cherts at the base of the Climacograptus Wilsoni zone, furnished by this stream, confirms the conclusion already arrived at from a consideration of the typical sections in Dobb's Linn and at Hartfell Spa. The beds of the Climacograptus Wilsoni zone here consist of grey calcareous ribs weathering with a brown rusty colour, and dark or black shales, the latter yielding the typical graptolite of the zone in fine preservation. The following measurements of the beds in descending order were here taken as the observer passes up stream:

At this point there is a blank in the section for a short distance, but soon cherty beds appear, followed by a band of black shales six inches thick, and by grey-blue mudstones, shales, and cherty ribs with calcareous seams. On the south bank, opposite the mouth of the little tributary of the Glenkiln Burn, black shales or mudstones dip to the north-west. They are for the most part very barren of fossils; but in certain seams they furnish specimens of Diplograptus foliaceus, Corynoides calycularis, and Climacograptus. In the bed of the stream, between the foregoing exposure of black shales on the south bank and the fine development of Glenkiln black shales at the mouth of the small tributary, we find grey cherty bands with dark or black seams, resembling those which underlie the Climacograptus Wilsoni zone further down stream. Indeed, it is not improbable that they may be the same beds repeated by folding, and that the two bands of black shales associated with them may be "outliers" of a portion of the Lower Hartfell Shales. The precise horizon of these black shale bands, however, is as yet undefined.

At the foot of the small tributary the grey cherty bands in the bed of the main stream are separated from the Glenkiln Shales by a fault, which is probably of no great importance. The black shales of the Glenkiln division are here admirably exposed, and yield the following characteristic assemblage of fossils:

Didymograptus superstes (Law.)

Didymograptus serratulus (Hall.)

Caenograptus gracilis (Hall.)

Caenograptus pertenuis (Lapw.)

Caenograptus surcularis (Hall.)

Thamnograptus typus (Hall.)

Dicranograptus formosus (Hopk.)

Dicranograptus Nicholsoni (Hopk.)

Dicranograptus ramosus (Hall.)

Dicellograptus patulosus (Lapw.)

Dicellograptus intortus (Lapw.)

Dicellograptus moffatensis (Carr.)

Dicellograptus sextans (Hall.)

Glossograptus Hincksi (Hopk.)

Climacograptus bicornis (Hall.)

Climacograptus peltifer (Lapw.)

Climacograptus caelatus var. antiquus (Lapw.)

Climacograptus Schärenbergi (Lapw.)

Cryptograptus tricornis (Carr.)

Diplograptus euglyphus (Lapw.)

Diplograptus foliaceus (Murch.)

Diplograptus Whitfieldi (Hall.)

Lasiograptus bimucronatus (Nich.)

Acrotreta Nicholsoni (Dav.)

These Glenkiln Shales are succeeded on the north side, in the tributary streamlet, by grey mudstones, which, from their lithological characters, are probably the Barren Mudstones of the Upper Hartfell group. If this correlation be correct, then the mudetones must be faulted against the Glenkiln Shales to the south. These mudstones are inclined to the north for a distance of eighty yards, and by means of another dislocation they are brought into contact with greywackes and shales containing black shale seams of Llandovery age.

Resuming the section in the Glenkiln Burn, the observer finds another exposure of Glenkiln Shales about 100 yards up stream from the foot of the tributary rivulet, at a point where the Glenkiln Burn takes a bend to the north. Here, on the south bank, the Glenkiln Shales appear, and yield graptolites in an imperfect state of preservation. Northwards they are followed by grey Barren Mudstones, the latter being succeeded by greywackes and shales exposed continuously for a distance of 200 yards up the stream, where the Glenkiln Shales reappear. Two thin seams of silky shales are found in the midst of these greywackes and shales, yielding Rastrites maximus, M. exiguus, &c. (Figure 27).

This higher exposure of Glenkiln black shales, charged with its characteristic fossils, is truncated by faults to the north and south. In the latter direction it is brought into conjunction with the Tarannon greywackes and shales, while on the north side it is thrown against the members of the Lower Birkhill group, which are there highly contorted. Owing to the faulting and contortion the black shales and mudstones of the Birkhill division are very shattery, but notwithstanding this feature the following forms have here been obtained from various sub-zones of the highest group of the Moffat series (Figure 27).

Diplograptus acuminatus (Nich.)

Diplograptus tamariscus (Nich.)

CUrnaeograptus normalis (Lapw.)

Monograptus tenuis (Portl.)

Monograptus attenuatus (Hopk.)

Monograptus lobiferus (M'Coy.)

Monograptus leptotheca (Lapw.)

Monograptus Hisingeri (Carr.)

Monograptus cyphus (Lapw.)

Monograptus spiralis (Geinitz.)

Monograptus spinigerus (Nich.)

Rastrites peregrinus (Barr.)

Petalograptus folium (His.)

Peltocaris aptychoides (Salter.)

Discinocaris browniana (Woodw.)

Discinoid shell.

These Birkhill Shales are followed in normal order by greywackes and shales, in the midst of which occurs a thin band of shales yielding Rastrites maximus. Still further up stream, at a prominent bend, two thin seams of dark silky shales afford fine examples of Rastrites maximus, Monograptus exiguus, M. priodon, Retiolites perlatus. It is probable that the higher of these fossiliferous seams in the coarser sediments yielding M. exiguus, M. priodon, &c., may be of Tarannon age (4m "l, (Figure 25)).

Glancing for a moment at the horizontal sections (Figure 26), (Figure 27), which illustrate the structure of the highly faulted exposures in the Glenkiln Burn, one may see how their present complicated relations may be satisfactorily accounted for on the supposition that they originally formed two anticlines and synclines, subsequently truncated by faults. About five miles to the north-east of the section just described, there are several exposures of the black shale series in the Duffkinnel Water near Raehills, and in the Linholm Burn above Glenhall.

Duffkinnel Water. — [NY 06379 94882] Ascending the stream from Duffkinnel foot, we find brown crusted flags, greywackes, and shales inclined to the north-west at an angle of about 30°. About 300 yards from the mouth of the stream black shales appear on the west bank, much crumpled and shattered and thrown into sharp folds, from which no determinable fossils were obtained. These strata are succeeded by an exposure of the Barren Mudstones, followed by black shales dipping towards. the north. Still higher up on the east bank of the stream black shales appear, much smashed and broken, but yielding a few fossils of the Lower Hartfell group. Crossing two thin felsite dykes, we find the Barren Mudstones, followed by greywackes and shales pierced by a dyke of felsite.

These strata are succeeded by a fine development of the Lower Birkhill group, in which the flaggy black shales of the Diplograptus vesiculosus zone are conspicuously seen in a cliff on the west bank. From this exposure the following fossils were obtained:

Diplograptus vesiculosus (Nich.)

Diplograptus acuminatus (Nich.)

Dimorphograptus elongatus (Lapw.)

Monograptus attenuatus (Hopk.)

Monograptus gregarius (Lapw.)

Monograptus tenuis (Portl.)

Climacograptus rectangularis (M'Coy.)

Climacograptus sp.

Above these flaggy black shales come thin fissile black shales and clays yielding a group of fossils characteristic of the higher members of the Lower Birkhill group:

Monograptus lobiferus (M'Coy.)

Monograptus leptotheca (Lapw.)

Monograptus triangulatus (Hark.)

Monograptus attenuatus (Hopk.)

Monograptus tenuis (Portl.)

Monograptus gregarius (Lapw.)

Monograptus cyphus (Lapw.)

Monograptus spiralis (Geinitz.)

Diplograptus tamariscus (Nich.)

Diplograptus confertus (Nich.)

Climacograptus normalis (Lapw.)

Climacograptus sp.

Rastrites peregrinus (Barr.)

Rastrites hybridus (Lapw.)

A few yards to the north of this exposure of the Birkhill Shales, purple and red shales and flags are seen in the stream, which continue north to the footbridge. Though this lower section of the black shale series in the Duffkinnel Water cannot be said to be satisfactory, yet the evidence points on the whole to the conclusion that the members were arranged originally in an isoclinal arch, dipping to N.N.W. The northern limb of the arch is tolerably complete, the various zones from the top of the Lower Birkhill group to the Hartfell black shales being visible. It is clear, however, that a part of the southern limb is absent.

About half a mile to the north of the foregoing section there is another exposure of the Moffat series in the Duffkinnel Water, a few yards above a small cottage named Glenhall. As the section is not continuous, the physical relations of the black shales cannot be determined, but from the following list of fossils gathered from this isolated outcrop, it is clear that they belong to the Birkhill group:

Monograptus argutus (Lapw.)

Monograptus attenuatus (Hopk.)

Monograptus communis (Lapw.)

Monograptus gregarius (Lapw.)

Monograptus cyphus (Lapw.)

Monograptus leptotheca (Lapw.)

Monograptus lobiferus (M'Coy.)

Monograptus Sandersoni (Lapw.)

Monograptus spinigerus (Nich.)

Monograptus tenuis (Portl.)

Monograptus triangulatus (Hark.)

Monograptus spiralis (Geinitz.)

Diplograptus tamariscus (Nich.)

Diplograptus confertus (Nich.)

Cephalograptus cometa (Geinitz.)

Petalograptus folium (His.)

Petalograptus palaeus (Barr.)

Rastrites peregrinus (Barr.)

Rastrites hybridus (Lapw.)

Climacograptus normalis (Lapw.)

Climacograptus or Diplograptus with double rootlets.

Dawsonia campanulata (Nich.)

Retiolites, sp.

Peltocaris aptychoides (Salter.)

Discinocaris browniana (Woodw.)

Discinocaris gigas (Woodw.)

Linholm Burn. — [NY 05809 95782] About 200 yards above Glenhall the Duffkinnel Water is joined by the Linholm Burn on the north bank, in which there is a good exposure of the higher members of the Moffat series, belonging almost exclusively to the Birkhill group. The section begins at the footbridge near the mouth of the burn, and continues for about 200 yards up the stream.

At the footbridge on the east bank of the stream black shales and clays dip northwards at 85°, which, from the accompanying list of fossils, evidently belong to the higher zones of the Lower Birkhill group:

Rastrites peregrinus (Barr.)

Monograptus attenuatus (Hopk.)

Monograptus tenuis (Portl.)

Monograptus triangulatus (Hark.)

Monograptus cyphus (Lapw.)

Diplograptus tamariscus (Nich.)

Petalograptus folium (His.)

Climacograptus normalis (Lapw.)

Further up the stream on the left bank we encounter black and grey mudstones yielding Cephalograptus cometa, followed by black and grey shales, from which specimens of Monograptus spinigerus were obtained in fine preservation.

From this point northwards to where the section of the black shale series ceases, we find exposures from which forms belonging partly to the lower division and partly to the upper division of the Birkhill group have been obtained. Close to the northern limit of the section the Cephalograptus cometa zone reappears. Hence it is probable that the Moffat series in this section may have originally formed two or more minor anticlines. This supposition is confirmed by the evidence from the Duffkinnel and Broadshaw Waters along the same line of strike to the south-west. In the latter sections three well-marked anticlines occur in the overlying greywackes and shales. There can be little doubt that these are merely the prolongations of the axial folds which in the Linholm Burn are represented in the Birkhill group. This feature is worthy of note, because it helps us to realise the extent of the plication of the Tarannon formation, where the isoclinal folding cannot be demonstrated by the occurrence of the black shale series.

District of Wee Queensberry Hill. — [NX 98478 97854] In the extreme north-west corner of Sheet 10, several sections of the Moffat series are exposed in the head waters of the Ae, one of which is of special interest from the clear relations of the strata and from the excellent preservation of the fossils. These exposures occur in the Pishnack [NX 98672 96758] and Bran Burns [NX 97458 96649], draining the slopes of the Wee Queensberry Hill and flowing into the Water of Ae.

The best section is exposed in the lower part of the Pishnack Burn, beginning not far above the point where it joins the Water of Ae. Ascending the stream from the foot, we find greywackes and shales of the Tarannon formation having a dip to the north-west, succeeded by a considerable development of grey and greenish shales, with occasional bands of yellow decomposing greywacke. From the accompanying plan (Figure 28) and horizontal section (Figure 29), the position of the various sub-divisions of the black shale series will be seen at a glance. Beyond the green crumbly shales no rock is exposed for a few yards, but soon a fine display of black shales is encountered, followed by alternations of black shales and clays. In one of the black shale bands, yielding fossils in profusion and in good preservation, the following species were found:

Monograptus argutus (Lapw.)

Monograptus attenuatus (Hopk.)

Monograptus communis (Lapw.)

Monograptus leptotheca (Lapw.)

Monograptus lobiferus (M'Coy.)

Monograptus Hisingeri (Carr.)

Monograptus spinigerus (Nich.)

Monograptus Sandersoni (Lapw.)

Monograptus spiralis (Geinitz.)

Monograptus tenuis (Portl.)

Monograptus triangulatus (Hark.)

Diplograptus tamariscus (Nich.)

Diplograptus sp.

Climacograptus normalis (Lapw.)

Petalograptus ovato-elongatus (Kurck.)

Diplograptus confertus (Nich.)

Dawsonia campanulata (Nich.)

Lingula sp.

Obolella sp.

Discinoid shell.

Sponge-like markings.

From the foregoing list it is apparent that these black shales and clays belong to the middle zones of the Birkhill division.

Next in order comes an excellent exposure of flaggy black shales yielding characteristic specimens of Diplograptus vesiculosus, together with Monograptus gregarius, M. lobiferus, M. attenuatus, Dimorphograptus elongatus.

On the opposite bank of the stream there is an anticlinal fold in black shales in which Diplograptus acuminatus was detected.

A few yards higher up the observer is confronted with a prominent exposure of the Barren Mudstones, forming a cliff on the left bank of the stream. A small fault evidently intervenes between the black shales at the base of the Birkhill group and the Barren Mudstones, because both occur in the same line of strike, but it has little effect on the relative position of the beds. In a band of bleached shales was found Dicellograptus anceps, proving the horizon of the Barren Mudstones (3').

A short distance up the stream bleached black shales are encountered yielding the following fossils characteristic of the Hartfell black shales: Climacograptus caudatus, C. tubuliferus, Diplograptus perexcavatus (3II, (Figure 28), (Figure 29)).

Unfortunately, a portion of the section of the Moffat series is concealed at this point owing to a thick covering of superficial deposits, but not far to the north black shales again appear containing Diplograptus vesiculosus and D. acuminatus in a fine state of preservation. With the Diplograptus vesiculosus zone is associated a band of black grit. Beyond this point the solid rocks are buried underneath the drift for a little distance.

From the evidence supplied by this section, it is clear that the members of the black shale series are here arranged in an anticlinal fold, the lowest beds in the core of the arch being the Hartfell black shales. The strata, with the exception of the sharp anticline in the Diplograptus acuminatus zone south of the Barren Mudstones, are all inclined to the N.W. Hence it follows that the arch is an isocline and the southern limb is inverted. The section further shows how dark grits are associated with one of the prominent lower zones of the Birkhill group — a feature which is prevalent in some of the folds in the ground to the north-east in Sheet 16.

About 700 yards from the mouth of the Pishnack Burn, at a point where it takes a sudden bend to the south-west [NX 98899 96782], it is joined by a small streamlet on the east bank. In this streamlet, just above an angle in its course, about 60 yards from the Pishnack Burn, there is an interesting exposure of the black shale series on the west bank, where the strata form a sharp anticline. In the centre of the arch the black shales, which are associated with clays and mudstones, contain fossils characteristic of the Upper Birkhill group, and to these succeed black shales and clays belonging to the Monograptus spinigerus zone. The Rastrites maximus zone is probably represented by the greywackes and shales immediately overlying the black shale series.

At the head of the Pishnack Burn, on the southern slope of the Wee Queensberry Hill, at a height of about 1300 feet above the sea, black shales reappear belonging to the Birkhill group. In a scar on the eastern slope, about 30 yards above the stream, there is an arch in grey mudstones with black shale seams yielding Monograptus lobiferus. Not far above this point there are several exposures of folded black shales and clays, in which were detected the following fossils: Cephalograptus cometa, Peltocaris aptychoides, Monograptus cyphus, M. triangulatus, M. leptotheca, M. Sedgwicki, Rastrites peregrinus, Climacograptus normalis &.

These black shales and clays can be followed along a hollow named the Cat Slack, towards the south-west, in the direction of the Bran Burn, bounded by crags of grit on either side.

Descending the Bran Burn, it is joined by a small stream on the east bank not far below the point where it enters Sheet 10 [NX 97973 96027]. At the mouth of this streamlet another anticline in the Tarannon greywackes and shales reveals various zones of the Birkhill group, as is evident from the fossils obtained from the black shales: Monograptus spinigerus, M. tenuis, M. triangulatus, Diplograptus tamariscus, Climacograptus normalis.

The foregoing sections of the Moffat series in the district of the Wee Queensberry Hill are chiefly confined to members of the Birkhill group. Only in the lower section of the Pishnack Burn do we reach the horizon of the Hartfell black shales, and in no instance have the representatives of the Glenkiln group been observed. Where the sections are continuous, even though the axial folds be isoclinal, it can be demonstrated that the lowest zones occupy the centre of the anticlines, succeeded by the higher zones on either side.

Crook Burn, Tributary of the Daer Water. — [NS 98333 03280] As the observer passes northwards to the tributaries of the Clyde, he finds evidence bearing on the modification of the representatives of the Birkhill Shales. For example, in the Crook Burn, which rises on the north slope of Queensberry Hill and joins the Daer Water at Kirkhope shepherd's house, there are two exposures of bands belonging to the Moffat series. The more southerly occurs in a rivulet on the east side of the Crook valley, one mile south of the shepherd's house of Whiteholm. Ascending this streamlet, we find contorted black shales which have supplied the following assemblage of fossils, characteristic mainly of the basal zone of the Birkhill group:

Diplograptus acuminatus (Nich.)

Diplograptus tamariscus (Mich.)

Dimorphograptus elongatus (Lapw.)

Climacograptus, sp.

Monograptus tenuis (Portl.)

Monograptus attenuatus (Hopk.)

Dawsonia campanulata (Nick.)

These black shales are underlain by Barren Mudstones dipping to the north-west, but their relations to the surrounding strata are not visible.

A marked change supervenes in the strata as they are followed down the valley for a distance of three-quarters of a mile. In the banks of the stream black micaceous sandy shales are interleaved in grey shales, which alternate with bands of grit about six inches thick, the whole series dipping to the north-west. The following forms were collected from the thin dark films in the coarser sediments: Monograptus Sandersoni, M. lobiferus, Diplograptus tamariscus, and Climacograptus.

Still further north, beyond highly folded grits, greywackes and shales, dark films, in which graptolites occur sparingly, appear in a zone of slates traceable from the Caledonian Railway one mile south of Elvanfoot, along the southern base of the Lowther Hills to the Dalveen Pass. They are associated with greywackes and occasional grits. In a slate quarry, by the side of the road leading to Dalveen Pass, opposite the junction of the Daer and Portrail Waters, specimens of Climacograptus and Diplograptus were obtained. These beds are regarded as marking the northern base line of the Llandovery and Tarannon Rocks in this part of the tableland.

Black shale bands in the area between Nithsdale and the River Cree

In the belt of hilly ground between Nithedale and the valley of the Ken, the axial folds revealing representatives of the Moffat series within the Tarannon area lie mainly along_, a belt of ground extending from the valley of Glenessland, in the parish of Dunscore, by the Urr Water near Corsock to the Barend Burn near Loch Ken.

In the basin of Glenessland the black shale series appears on three folds at no great distance from each other.

Bogrie and Castramon. — [NX 80906 84978] The most northerly of these folds runs along a line stretching from the Bogrie Burn north of the Bogrie Tower to the Castramon Burn [NX 82091 84590]. Beginning with the section in Bogrie Burn (Figure 30), we find a sequence from the Hartfell black shales through the Barren Mudstones to the Birkhill Shales, the strata of which are vertical, or nearly so, being arranged in an anticlinal fold with the Hartfell Shales in the centre. The latter are well exposed in the core of the arch, followed by the Barren Mudstones on either side. The Hartfell black shales near their southern limit, close to the Barren Mudstones on the south limb of the fold, contain the following forms:

Climacograptus caudatus (Lapw.)

Climacograptus bicornis (Hall.)

Diplogrceptus foliaceus (Murch.)

Dicranograptus ramosus (Hall.)

Dicellograptus, sp.

Lasiograptus margaritatus (Lapw.)

Corynoides calycularis (Nich.)

About five feet from the foregoing locality, on the east bank, further up stream, abundant specimens of Diplograptus foliaceus were found crowding the surface of the black shale seam.

On the opposite or west bank, four yards up stream, the following forms were collected from the black shales:

Diplograptus foliaceus (Murch.)

Cryptograptus tricornis (Carr.)

Climacograptus bicornis (Hall.)

Dicranograptus ramosus (Hall.)

Diceilograptus, sp.

Leptograptus, sp.

On the north limb of the fold the Harden black shales are succeeded by the Barren Mudstones, which occupy the course of the stream for a distance of 16 yards, displaying the typical characters of this sub-division in the Moffat region. These are overlain by black shales, which at the junction furnish Climacograptus, Diplograptus tamariscus, Dimorphograptus elogatus, Monograptus, and are followed by black shales of the D. vesiculosus zone and bands yielding M. gregarius. These Lower Birk hill shales are here overlain by grey shales and greywackes.

Returning now to the south limb of the fold, the observer may note that thin layers of chart with radiolaria are associated with the Barren Mudstones in contact with the Hartfell black shales. This association probably indicates a recurrence of clear-water conditions similar to those which prevailed in Upper Arenig time. Again, near the base of the Barren Mudstones, a thin seam of black shales, two inches thick, occurs, yielding Dicranograptus, Dicellograptus, and Climacagraptus. From this outcrop southwards to the Birkhill Shales, a distance of 36 yards, the space is occupied by Barren Mudstones which are evidently repeated by folding. Near the top of this sub-division a thin seam of dark or black shale occurs, and close to the junction with the overlying Birkhill group an intrusive dyke makes its appearance. From the Birkhill Shales on the south limb of the arch the following forms were collected:

Diplograptus confertus (Nich.)

Diplograptus vesiculosus (Nich.)

Diplograptus tamariscus (Nich.)

Climacograptus normalis (Lapw.)

Climacograptus innotatus (Nich.)

Monograptus tenuis (Portl.)

Monograptus attenuatus (Hopk.)

Monograptus leptotheca (Impw.)

Monograptus gregarius (Lapw.)

These strata are succeeded by greywackes and shales, which, at the sharp bend in the stream to the south-west, contain a fold of black shales yielding Diplograptus tamariscus and Climacograptus normalis.

About 100 yards south-west from the junction of the Castramon Burn with the Shillingland Burn, and on the southeast side of the stream, a heathery knoll of black shales about 15 yards long shows the junction of the Hartfell black shales with the Barren Mudstones. The latter occur on the south-east side of the knoll, and by stripping off the heathery covering the junction line can be laid bare at the north-east corner. From the band of black shales in contact with the Barren Mudstones, Pleurograptus linearis was collected. The following forms were obtained from this exposure:

Pleurograptus linearis (Carr.)

Diplograptus quadrimucronatus (Hall.)

Diplograptus foliaceus (Murch.)

Leptograptus capillaris (Carr.)

Leptograptus flaccidus (Hall.)

Climacograptus, sp.

Dicranograptus, sp.

Dicellograptus Forchhammeri (Geinitz.)

The Hartfell black shales seem to form the core of the arch, for as we proceed south-westwards the Barren Mudstones appear on the north limb near the Castramon Burn with a north-west dip.

Mark Cleuch. — [NX 80021 83523] About a third of a mile to the south of the axial fold just referred to, the Moffat Shales reappear in the Mark Cleuch, one of the tributaries of the Glenessland Burn, which rises on the north slope of the Craigdasher Hill. At the south limit of the alluvium, and about 200 yards from the foot of the burn, sandy shales and greywackes occur on the east bank, to which succeed blue-grey shales dipping up stream at about 70°. In the bands about two feet from the greywackes the following forms were collected in splendid preservation:

Monograptus gregarius (Lapw.)

Monograptus triangulatus (Hark.)

Monograptus Sedgwicki (Portl.)

Monograptus Hisingeri (Carr.)

Monograptus lobiferus (M'Coy.)

Monograptus attenuatus (Hopk.)

Monograptus tenuis (Portl.)

Monograptus Sandersoni (Lapw.)

Diplograptus tamariscus (Nich.)

Diplograptus confertus (Nich.)

Petalograptus palmaeus (Barr.)

Rastrites peregrinus (Barr.)

Climacograptus normalis (Lapw.)

Discinocaris browniana (Woodw.)

Dawsonia campanulata (Nich.)

The foregoing assemblage would seem to indicate that the highest visible zone at this locality is that of Monograptus gregarius. The beds at this exposure consist of alternations of grey clays and black shales, resembling the normal types of this zone in the Moffat region.

Following the stream upwards, we find on the left bank, beyond the stone fence, blue shales and greywackes with black shales, the latter yielding fragments of graptolites. A few yards further up on the east bank, alternations of black shales and grey clays are exposed with blue shales. These contain the fossils of the M. gregarius zone, and are succeeded by the shales of the D. vesiculosus zone, visible on the right bank up stream, from which the following species have been obtained:

Diplograptus vesiculosus (Nich.)

Diplograptus confertus (Nich.)

Climacograptus normalis (Lapw.)

Monograptus gregarius (Lapw.)

Monograptus attenuatus (Hopk.)

Monograptus tenuis (Portl.)

Monograptus leptotheca (Lapw.)

South-westwards, on the right bank, an arch of the Barren Mudstones appears, overlain by the Birkhill black shales. The beds of the D. vesiculosus zone, visible on the top of the cliff, have here been slightly hardened by various intrusive dykes.

The most southerly exposure in the bed of the stream yields an assemblage of graptolites characteristic of the Monograptus gregarius zone:

Monograptus gregarius (Lapw.)

Monograptus lobiferus (M'Coy.)

Monograptus leptotheca (Lapw.)

Monograptus attenuatus (Hopk.)

Monograptus tenuis (Portl.)

Climacograptus normalis (Lapw.)

Diplograptus tamariscus (Nich.)

Dawsonia campanutata (Nich.)

From the foregoing description it is apparent that the members of the Moffat series are here arranged in an axial fold, the centre being occupied by the Barren Mudstones, succeeded by the Lower Birkhill Shales on both sides of the fold.

Nether Whiteside. — About half a mile to the southeast of the line of strike of the foregoing band, the Moffat Shales reappear along another anticlinal arch, the exposures being restricted to two localities — one to the east of Nether Whiteside Farmhouse, and the other on the same strike on Whiteside Moor.

About 450 yards to the east of Nether Whiteside Farmhouse [NX 81771 84232] an isolated exposure lies at the northern base of the slope of Nethertown Moor. Here the radiolarian cherts appear associated with black shales yielding Didymograptus superstes, Climacograptus bicornis, Diplograptus foliaceus, &c. By means of fragments in the soil the black shales can be traced across the Nether Whiteside Moor to a point about a quarter of a mile S.S.E. of Upper Whiteside [NX 80964 82781], where alternations of black shales and grey clays appear, yielding the following forms:

Monograptus gregarius (Lapw.)

Monograptus tenuis (Portl.)

Monograptus leptotheca (Lapw.)

Monograptus triangulatus (Hark.)

Diplograptus tamariscus (Nich.)

Diplograptus confertus (Nich.)

Rastrites peregrinus (Barr.)

Dawsonia campanulata (Nich.)

Water of Urr. — As the observer passes towards the southwest from Glenessland, he encounters in the Water of Urr, from Nether Glaisters to near Crogo Tower, a series of folds that reveal the members of the Moffat series. Beginning with the section of the southmost axial fold, displayed on the west bank of the stream, about 300 yards north-west of Crogo Tower [NX 75728 77658], he finds the representatives of the Moffat series arranged in the form of an arch with the Barren Mudstones in the centre. On the south limb of the fold, where a footbridge crosses the stream, the Lower Birkhill Shales succeed and afford the following forms:

Diplograptus acuminatus (Nich.)

Diplograptus vesiculosus (Nich.)

Diplograptus tamariscus (Nich.)

Diplograptus confertus (Nich.)

Dimorphograptus elongatus (Lapw.)

Dimorphograptus Swanstoni (Lapw.)

Monograptus attenuatus (Hopk.)

Monograptus Sandersoni (Lapw.)

On the north limb of the fold, at the northern limit of the shales, the following fossils were collected:

Monograptus gregarius (Lapw.)

Monograptus Sandersoni (Lapw.)

Dimorphograptus Swanstoni (Lapw.)

Dimorphograptus elongatus (Lapw.)

Climacograptus normalis (Lapw.)

Diplograptus confertus (Mich.)

About 300 yards further north, near a cottage by the side of the Urr, an isolated exposure of the black shales yielded specimens of Dimorphograptus Swanstoni, Climacograptus normalis, &c.

When the stream is ascended to a point near the old mill of Crogo — about 100 yards south of the mill, now in ruins — a fine exposure of the Moffat series, with the Barren Mudstones in the centre, is met with, followed on the north side by the Lower Birkhill Shales. Here the D. vesiculosus zone is well seen, fine specimens of that zonal form being obtainable, together with Dimorphograptus Swanstoni, D. elongatus, Monograptus tenuis, Climacograptus normalis.

Along the strike of this outcrop, in knolls among the fields to the north of the farmhouse of Upper Bar, numerous exposures may be noticed of the Barren Mudstones and Birkhill Shales, and in one or two instances of the Hartfell Black Shales.

When the Urr is followed northwards for about a third of a mile to a bend where a streamlet from Knocklearn Farm joins the river from the west, the Moffat Shales are seen to reappear.

Here a small exposure of Barren Mudstones is followed by black shales, which, visible at the edge of the river, contain Climacograptus normalis, Diplograptus tamariscus, Diplograptus acuminatus (?), and siculae of graptolites.

About six yards down stream on the same bank the following forms were obtained from a black shale band: Diplograptus foliaceus, Climacograptus bicornis, Climacograptus with three spikes, Retiolites (Neurograptus) fibratus, Diplograptus quadrimucronatus, and Leptograptus flaccidus. Here were found in profusion, in the black shales, arms of Dicellograptus and Diplograptus socialis (?) (Lapw.)

The foregoing assemblage of fossils undoubtedly belongs to the Hartfell group.

Crossing the river and proceeding northwards along the east bank, we meet with a fine development of the Barren Mudstones and Birkhill Shales, the former occupying the core of the arch. On the south limb of the fold the Lower Birkhill Shales dip towards the north-west at high angles and have furnished the following assemblage of graptolites:

Diplograptus acuminatus (Nich.)

Diplograptus vesiculosus (Nich.)

Diplograptus tamariscus (Nich.)

Monograptus attenuatus (Hopk.)

Climacograptus normalis (Lapw.)

Dimophograptus Swanstoni (Lapw.)

Dimophograptus elongatus (Lapw.)

This locality is of special interest because it furnishes beautiful specimens of Dimorphograptus Swanstoni. The fine specimen in the Geological Survey Collection was here obtained.

On the north side of the arch the Birkhill Shales are again met with, having a general north-west dip.

The most northerly exposure of the Moffat Shales occurs at a bend on the west bank of the Urr, due west of Nether Glaisters, where the relations of these strata to other rocks are not visible. Here they enclose:

Dimorphograptus Swanstoni (Lapw.)

Dimorphograptus group of above.

Climacograptus normalis (Lapw.)

Diplograptus confertus (Nich.)

Monograptus Sandersoni (Lapw.)

Monograptus gregarius (Lapw.)

About half a mile to the east of the river Urr at Crogo Tower, in the Auchenhay Burn, which joins the Knarie Burn, a tributary of the Urr, a small outcrop of the Birkhill Shales occurs in a wood about a quarter of a mile to the north of its junction with the Knarie Burn and below Fordhouse. The species in the following list were collected from this locality:

Monograptus Hisingeri (Carr.)

Monograptus cyphus (Lapw.)

leptotheca (Lapw.)

Monograptus tenuis (Portl.)

Monograptus lobiferus (M'Coy.)

Monograptus Sedgwicki (?) (Portl.)

Monograptus attenuatus (Hopk.)

Monograptus gregarius (Lapw.)

Diplograptus tamariscus (Nich.)

Diplograptus confertus (Lapw.)

Diplograptus acuminatus (?) (Nich.)

Petalograptus palmaeus (Barr.)

Dimorphograptus Swanstoni (Lapw.)

Climacograptus normalis (Lapw.)

Dawsonia campanulata (Nich.)

Crogo Burn, Auchenvey. — [NX 73519 77434] On the west side of the Urr an important tributary of that stream, named the Crogo Burn, about two miles north-west of Corsock, shows a section of the Birkhill group. Here, at a point a few yards east of where the stream is crossed by the road from Corsock to New Galloway, the shales yield Diplograptus confertus, Climacograptus normalis, Diplograptus vesiculosus, Monograptus gregarius, M. tenuis, M. attenuatus.

Towards the north-east this axial fold is traceable at intervals for nearly a mile by means of isolated exposures; towards the south-west it can be followed for about half a mile along the east border of the Auchenvey Plantation, the Barren Mudstones appearing not far to the south-west of the New Galloway Road.

Barend and Auchenvey. — Between the valley of the Urr and Loch Ken the Moffat Shales reappear on an axial fold which extends along part of the course of the Barend Burn [NX 70715 74500] to the Auchenvey Hill [NX 73121 76627], a distance of upwards of three miles. Like the bands previously described, the members of the Moffat series are arranged in the form of an arch or a series of compound folds, usually inverted and broken by faults. At one or two points in the course of this band the Hartfell Shales appear; there is also a fine development of the Barren Mudstones and the overlying Lower Birkhill Shales.

The best section in the course of the Barend Burn, showing the sequence from the Barren Mudstones through the Birkhill group to the overlying greywackes and shales, is to be found at a point half a mile to the north-east of the Barend Farmhouse. Here the stream, for a distance of nearly 300 yards, runs in a south-easterly direction at right angles to its normal course. For part of this distance it flows through a rocky gorge, displaying a fine section of several members of the Moffat series. Where the stream issues from the ravine the Barren Mudstones appear, having at one point a south-east dip. Ascending the gorge we find the Birkhill Shales in normal sequence on the north limb of the arch, the D. vesiculosus zone being at once recognised by its flaggy character, as in the Moffat region. At the waterfall the following species were collected:

Diplograptus vesiculosus abundant.

Diplograptus tamariscus (Nich.)

Diplograptus confertus (Nich.)

Diplograptus acuminatus (Nich.)

Dimorphograptus elongatus (Lapw.)

Dimorphograptus Swanstoni (Lapw.)

Monograptus tenuis (Portl.)

attenuatus (Flopk.)

Climacograptus normalis (Lapw.)

To these strata succeed alternations of black shales and grey clays: from the former were obtained fine specimens of Rastrites peregrinus, together with Monograptus gregarius and Climacograptus normalis. These shales pass upwards into sandy shales and greywacke. On the north limb of the fold it is evident that there is a continuous sequence from the Barren Mudstones to the greywackes and shales overlying the Birkhill Shales.

At the mouth of the gorge the section is obscured for a short distance, but at the point where the Barend Burn resumes its normal south-west course the black shales occur. To the south of the line of strike of the foregoing arch isolated exposures of the Barren Mudstones and the Birkhill Black Shales appear in the course of the stream, and in- the fields towards the farmhouse of Barend. Further to the south-west, below the farmhouse, the cherts appear on the south-east bank of the burn associated with black shales, but they are so much bleached that it is difficult to determine their horizon from the fragments of graptolites obtainable from the shales.

To the north-east of the fine section in the gorge of the Barend Burn, above described, the Moffat series can be traced for about 1¼ miles to the watershed between the Barend and Auchenvey Burns, forming compound folds which reveal the Barren Mudstones and Birkhill Shales, and in some instances the Hartfell Shales.

Still further to the north-east, the Auchenvey Burn presents an interesting, though not continuous, section of the Birkhill and Hartfell Black Shales. At the ford, where a hill path crosses the stream, an exposure of Hartfell Shales has yielded Retiolites (Neurograptus) fibratus, Dicellograptus Forchhammeri, D. Morrisi, D. elegans, Leptograptus flaccidus, Climacograptus, Diplograptus foliaceus.

Down stream towards the south-east there is a blank in the section, but towards the north-east, along the strike of the beds, the Barren Mudstones appear at no great distance from the burn. On the south-east limb of the fold the Birkhill Shales are visible on the east bank, where they are brought into contact with the greywackes by means of a fault. On the north-west side of the arch the Birkhill Shales reappear and yield the following forms: Monograptus gregarius, M. tenuis, Diplograptus vesiculosus, Climacograptus normalis, and siculae of graptolites.

To the north-east, on the Auchenvey Hill, the prolongations of the band above described reappear. At one point on the hilltop blocks of radiolarian chert can be traced along the line of strike, evidently indicating that the chert zone is there in situ. To the north and south of this band the Moffat series comes to the surface along several folds, representing the Hartfell Shales, Barren Mudstones, and Birkhill group.

We must now refer to certain exposures of the Moffat series where the strata having either not yielded graptolites at all or only indeterminable fragments, their horizon cannot be definitely determined by palaeontological evidence. But as they occur within the area of the Tarannon Rocks they may with probability be referred, in part at least, to the Birkhill group. One of these exposures occurs by the side of the road near Barlay, about 2½ miles E.S.E. of Balmaclellan. Others may be seen on the Benan Hill within the contact zone of the New Galloway mass of granite. Others, likewise within the contact zone, in the Knocknairling Burn [NX 61471 77389]? and on the Knocknairling Hill are traceable to the granite junction.

Glen Burn and Skeoch. — In the south-east part of Sheet 9 of the Geological Survey Map an important band of the Moffat series appears in the Scar Burn, near Skeoch Farmhouse [NX 86381 77928], and can be traced still further to the south-west along the course of the Glen Burn for upwards of a mile.

In the Scar Burn [NX 85906 77989], about a quarter of a mile west of Skeoch Farmhouse and about half a mile up stream from the point where it joins the Old Water, the black shales crop out. Further down the stream brown flags and shales, with occasional greywackes dip towards the north-west at high angles. These are underlain by blue, grey, and black shales alternating with grey clays, which have yielded Climacograptus normalis, Monograptus gregarius, M. Sandersoni, M. leptotheca, M. tenuis, Dimorphograptus Swanstoni, Dawsonia campanulata. A few yards down stream on the east hank flaggy black shales occur of the D. vesiculosus zone, which yielded D. vesiculosus, Dimorphograptus elongatus, Monograptus tenuis, Diplograptus tamariscus.

These strata are followed still further down stream by the Barren Mudstones, when a blank occurs in the section, the strata next met with being grey flags and shales.

Glen Burn. — [NX 83413 76170] Ascending this stream to a point about 500 yards west from Glen Burn (Figure 31), black shales are found in the channel of the burn and on the north-west bank, from which the following assemblage of fossils has been collected: Leptograptus capillaris, Pleurograptus linearia, Climacograptus, Dicellograptus, Diplograptus foliaceus, &c. South of this exposure a fine development of Barren Mudstones occupies the burn section for a distance of about 100 yards, followed by black shales, probably on the horizon of the Lower Birkhill division, though no fossils were obtained to prove their position. Still further west the Barren Mudstones reappear, and are succeeded on the south limb of the fold by the Lower Birkhill Shales, yielding Diplograptus acuminatus, D. vesiculosus, Dimorphograptus elongatus, Climacograptus, &c. Thereafter the stream traverses the overlying greywackes and shales for several hundred yards as far as the margin of the Glen Plantation, but the arch in the Moffat series can be traced along the northern bank. In the plantation, the observer can trace the arch in the Moffat series for a distance of about 700 yards. As the course of the stream is more westerly, he soon reaches the Birkhill Shales exposed on the south limb of the fold, where they furnish specimens of Dimorphograptus, Diplograptus vesiculosus, D. tamariscus, Climacograptus normalis, Monograptus tenuis, M. attenuatus. For some distance up stream the centre of the fold is occupied by the Barren Mudstones, while the overlying Birkhill Shales are exposed on both limbs at occasional bends in the stream-course. At a point in the wood S.S.E. of Glen Farmhouse, and about 200 yards east from the west margin of the wood, black shales appear on the south-east bank associated with radiolarian cherts and ashy mudstones, From the following list of fossils obtained from this locality it is evident that the strata represent the Glenkiln Shales:

Thamnograptus, sp.

Caenograptus pertenuis (Lapw.)

Leptograptus flaccidus (Hall.)

Climacograptus bicornis (Hall.)

Climacograptus Schärenbergi (Lapw.)

Cryptograptus tricornis (Carr.)

Dicranograptus formosus (Hopk.)

Dicellograptus sextans (Hall.)

Dicellograptus moffatensis (Carr.)

Dicellograptus patulosus (Lapw.)

Climacograptus peltifer (Lapw.)

Diplograptus foliaceus (Murch.)

Siphonotreta micula (M'Coy.)

For a short distance westwards the radiolarian cherts and ashy mudstones appear at intervals. Leaving the plantation and crossing the alluvial flat S.S.W. of Glen Farmhouse, the observer will notice another exposure of the Arenig cherts and spotted ashy mudstones or tuffs resembling those south of Trowdale Wood in the valley of the Urr. Further to the southwest, in the direction of Larghill Bridge, the Arenig cherts and ashy mudstones can be traced on the rising ground south of the road, and the black shales associated with them are visible in a quarry at the road-side. Near Larghill Bridge [NX 81689 74492], in a little tributary of the Brooklands Burn, south of the road, black shales appear on both sides of an arch of Arenig cherts and volcanic tuffs about 100 yards broad. The black shales are much crushed, but those on the north side of the anticline have yielded Climacograptus caudatus, Dicellograptus moffatensis, D. flexuosus, Diplograptus foliaceus — forms which evidently indicate a Hartfell horizon. The Arenig cherts are visible west of Larghill Bridge, but the strata are buried in this direction under a covering of drift and peat.

Trowdale, Crossmichael, and Lawrieston. — [NX 76302 69211], [NX 73005 66919], [NX 68157 64818] Along a line extending from Tottlehams Burn and Trowdale Glen by Crossmichael to Lawrieston, exposures of the Moffat series may be observed (Sheet 5 of Survey Map). Though nearly in the same line of strike, these outcrops occur on separate folds. The most important of them are those of Trowdale Glen, Tottlehams Burn, and adjoining fields, in the valley of the Urr, about four miles north of Castle-Douglas, which will be first described.

On the west bank of the Urr, in the fields immediately to the south of Trowdale Glen, the lowest beds are exposed. These consist of radiolarian cherts, mudstones, and shales, associated with fine felsitic tuff: They are inclined to the northwest at high angles, and plunge underneath the band of Glenkiln–Hartfell black shales exposed in the Trowdale Glen. Acre is one peculiar band of shales, which breaks under the hammer into pencil-shaped fragments, exposed in a small hollow about 120 yards to the south of Trowdale Glen in the midst of ashy mudstones and cherts. It is highly probable that this band and others associated with it may yield Arenig graptolites, though a careful search has hitherto failed to bring them to light. The volcanic tuff is well seen in knolls close to Trowdale Wood, and it likewise forms a prominent feature in the wood to the south of the Glenkiln black shales. The lithological character of this rock is interesting. The common variety is a dull pinkish-grey rock, which on weathered surfaces has a yellowish tint. It has a curious speckled appearance owing to the presence of pink or yellow spots in a grey matrix. Sometimes the rock is compact, has a uniform colour, and breaks with a conchoidal fracture.

The intercalation of some of tuese felsitic tuffs between the Glenkiln black shales and the radiolarian cherts seems to indicate the continuance of volcanic conditions in that area in Llandeilo time. Abundant evidence has been obtained of similar phenomena during the re-examination of the volcanic area south of Ballantrae.

In the section in Trowdale Glen (Figure 32), the Glenkiln black shales occur near the entrance, and may be followed along the south bank for a short distance up stream. They consist of black flinty ribs, with black shale partings, passing upwards into the Hartfell black shales, which are in turn overlain by the Barren Mudstones, forming the north cliff in the lower part of the glen. The black shales in the ravine have yielded the following fossils:

Didymograptus superstes (Lapw.)

Caenograptus gracilis (Hall.)

Caenograptus nitidulus (Lapw.)

Caenograptus pertenuis (Lapw.)

Diplograptus Whitfieldi (Hall.)

Diplograptus foliaceus (Murch.)

Clathrograptus cuneiformis (Lapw.)

Cryptograptus tricornis (Carr.)

Climacograptus caelatus var. antiquus (Lapw.)

Climacograptus bicornis (Hall.)

Dicellograptus patulosus (Lapw.)

Dicellograptus moffatensis (Carr.)

The Birkhill Shales are not visible in the Trowdale Glen to the north of the Barren Mudstones, but a small exposure of them is seen on a footpath about half a mile east of Balgerran Farmhouse, in the strike of the Trowdale band, which has yielded fragments of Dimorphograptus.

From the foregoing description it is apparent that the strata in the neighbourhood of Trowdale form the northern limb of a fold, the lowest beds being the radiolarian cherts and volcanic tuffs, and the highest, some member of the Birkhill black shales. Southwards towards the Mountskip Plantation, however, the relations of the strata are disturbed by faults. The southern limb of the fold cannot be traced. Greywackes of Tarannon age rapidly follow the cherts in the field to the south of Trowdale Glen, and are also visible in a burn in the Mountskip Wood [NX 76422 68280]. It is clear that a fault must intervene to bring these different zones in contact with each other. Again, in the burn in this plantation, about 200 yards west from the Castle-Douglas Road, a small exposure of black shales has supplied the following Glenkiln forms:

Didymograptus superstes (Lapw.)

Lasiograptus bimucronatus (Nich.)

Cryptograptus tricornis (Carr.)

Dicellograptus moffatensis (Carr.)

Dicellograptus patulosus (Lapw.)

Dicellograptus divaricatus (Hall.)

The relations of these shales to the surrounding rocks are not visible. Above the forkings of this burn, in the south branch, the Barren Mudstones are met with; but this exposure is also isolated. The nearest visible frocks consist of Tarannon greywackes and shales, the horizon of which is clearly defined by certain fossils found in a small quarry on the north side of Mountskip Plantation, and about 500 yards south of Trowdale Glen. Here a dark band yielded the following forms:

Aptychopsis minus (Barr.)

Petalograptus palmaeus (Barr.)

Monograptus exiguus (Nich.)

Monograptus turriculatus (Barr.)

Monograptus tenuis (Portl.)

Monograptus attenuatus (Hopk.)

The presence of Monograptus exiguus and some of its associates indicates a higher horizon than the Rastrites maximus band at the top of the Birkhill group.

Tottlehams Burn. — [NX 76901 69395] In the extension of this band in a north-east direction, the radiolarian cherts and mudstones are not visible in the Urr, owing to the alluvial covering (Sheet 5 of Survey Map). But at the mouth of the Tottlehams Burn a fine exposure of the Barren Mudstones may be seen in the river.

A few yards below the junction of this stream with the Urr, a band of black shales, yielding Climacograptus Schärenbergi, Dicranograptus, &c., occurs in the mudstones, possibly representing a part of the Hartfell black shales in an isoclinal fold. There the strata dip in a uniform direction towards the northwest at high angles.

In the Tottlehams Burn the Barren Mudstones present the characteristic features of the zone. They contain nodules composed of oxides of iron and manganese, the latter ore predominating. From an examination of one of the cores of these nodules by Mr. Teall, it appears that it is a carbonate of manganese and iron. It is traversed by a vein, black in the piddle, brown at the margins, fading off gradually into the surrounding rock. There are also peculiar structures, probably organic, in this rock. From these data he infers that the rock was originally a limestone, that it was subsequently changed to a carbonate of manganese and iron, and finally that the carbonate was decomposed under oxidising conditions so as to give rise to the nodular masses of the oxides of the two metals.

At the mill, alongside of the public road, the Glenkiln–Hartfell black shales appear in the burn and the mill-lead, rising from underneath the Barren Mudstones. The following fossils characteristic of these groups were here obtained:

Caenograptus gracilis (Hall.)

Caenograptus pertenuis (Lapw.)

Didymograptus superstes (Lapw.)

Diplograptus foliaceus (Murch.)

Climacograptus Schärenbergi (Lapw.)

Climacograptus caudatus (Lapw.)

Retiolites (Neurograptus) fibratus (Lapw.)

Dicellograptus Forchhammeri (Geinitz.)

The Barren Mudstones are seen in the mill-lead for about 80 yards above the mill. From the mill pond, for a distance of 500 yards up stream, the rocks are concealed by boulder clay; but at the eastern edge of the Tottlehams Wood, the Barren Mudstones appear on the south bank of the stream, succeeded on the south by a small exposure of the Birkhill Shales, which contain, amongst other forms, Diplograptus acuminatus, Climacograptus normalis, &c. On the north-east side of the stone fence crossing the burn at the point where the stream-course changes and bends towards the north, a small exposure may be seen of black shales charged with Climacograptus caudatus, Diplograptus, and Dicellograptus moffatensis, characteristic of the Lower Hartfell group. They are followed by Tarannon greywackes to the south, so that a fault must here come between these zones. They must be truncated also by a north and south fault, which brings them in contact with the Barren Mudstones and Birkhill Shales just described.

From the prominent bend in the Tottlehams Burn just referred to, north-eastwards by Corsehill and Barmofitty, the members of the Moffat series are traceable for a distance of about half a mile, partly by means of rocky knolls peering through the drift. The bands of felsitic tuff with cherts and mudstones inclined to the north-west at high angles can be followed in isolated exposures to the fields west of Barmofitty Farmhouse. On the north side they are succeeded by the Glenkiln–Hartfell black shales visible in the Tottlehains Burn and in the fields south-west of Corsehill. On the south side of the fold black shales are well exposed on a knoll about 150 yards north of the east end of Tottlehams Wood, with graptolites of the Glenkiln horizon, in abundance and excellent preservation. Here the black shales are repeated by folds, and the grey radiolarian cherts are brought to the surface in two sharp anticlines. The following fossils were here collected (Figure 33):

Caenograptus gracilis (Hall.)

Caenograptus surcularis (Hall.)

Caenograptus pertenuis (Lapw.)

Caenograptus nitidudus (Lapw.)

Didymograptus superstes (Lapw.)

Didymograptus serratulus (Hall.)

Lasiograptus bimucronatus (Nish.)

Diplograptus euglyphus (Lapw.)

Diplograptus foliaceus (Murch.)

Diplograptus mucronatus (Hall.)

Diplograptus Whitfieldi (Hall.)

Cryptograptus tricornis (Carr.)

Glossograptus Hincksi (Hopk.)

Climacograptus bicornis (Hall.)

Climacograptus caelatus var. antiquus (Lapw.)

Dicellograptus sextans (Hall.)

Dicellograptus patulosus (Lapw.)

Dicellograptus divaricatus (Hall.)

Dicellograptus moffatensis (Carr.)

Dicranograptus tardiusculus (Lapw.)

Dicranograptus ramosus

Clathrograptus cuneifomis (Lapw.)

Siphonotreta micula (M'Coy.)

In the prolongation of the Trowdale band in a south-westerly direction towards Kilnotrie and Crossmichael, only isolated exposures of the Moffat series protrude through drift. Along the strike of the outcrops south of Trowdale Glen, the radiolarian cherts, mudstones, shales, and volcanic tuffs are met with in fields about a third of a mile south-east of Balgerran Farmhouse, the general dip being to the north-west. On the north side of the fold these strata are succeeded by th Glenkiln–Hartfell shales, which, at an old mine about one-third of a mile E.S.E. of Balgerran, have yielded: Caenograptus gracilis, Clathrograptus cuneiformis, Climacograptus bicornis, C. caelatus var. antiquus, Diplograptus foliaceus, Dicellograptus moffatensis, Siphonotreta micula.

Again, on the south side of the cherts and mudstones, in a field north-west of Mountskip Plantation [NX 76449 68618], and not far to the north of the Monograptus exiguus band already referred to, soft black shales, which appear at the side of a streamlet, have supplied some characteristic Glenkiln forms, with others (Figure 32):

Didymograptus superstes (Lapw.)

Didymograptus nov. sp. with disc.

Caenograptus gracilis (Hall.)

Thamnograptus typus (Hall.)

Diplograptus euglyphus (Lapw.)

Diplograptus Whitfeldi (Hall.)

Diplograptus foliaceus (Murch.)

Cryptograptus tricornis (Carr.)

Climacograptus bicornis (Hall.)

Climacograptus caelatus var. antiquus (Lapw.)

Glossograptus Hincksi (Hopk.)

In consequence of a synclinal fold the Barren Mudstones appear to the south of this exposure, followed by the Glenkiln shales, charged with Caenograptus gracilis, Diplograptus Whitfieldi, D. foliaceus, Climacograptus bicornis, Dicellograptus, Lasiograptus bimucronatus, &c.

Westwards, at the Kilnotrie Farmhouse [NX 75000 67440], the cherts and volcanic tuffs crop out in the fields to the north of the steading, and may be followed west to a point south of Erncrogo Loch. They occur on a different anticlinal fold from that of the Trowdale band, though not far to the south of it. The Glenkiln–Hartfell black shales and Barren Mudstones occur on the north side of the anticline in the fields near Erncrogo Loch, and on the south side of the fields to the east of Kilnotrie. A few yards west of Kilnotrie Farmhouse [NX 75055 67325] the following Hartfell species were obtained: Climacograptus caudatus, C. bicornis, Diplograptus foliaceus, D. tricornis, Dicellograptus moffatensis. Again, at Crossmichael the black shales are visible near the south end of the village, while the felsitic tuffs appear on the slope north-east of this locality, but their relations to the surrounding rocks are not apparent.

Still further to the south-west, in the neighbourhood of Lawrieston [NX 68324 64819], the volcanic tuffs and radiolarian charts are to be seen at one or two localities, south of Bellymack Farmhouse, and about half a mile east of the village. Here they are associated with black shales, visible in a small burn east of South Quintenespie [NX 68612 64603] , charged with Didymograptus superstes, Lasiograptus bimucronatus, Cryptograptus tricornis, Climacograptus bicornis, Dicellograptus moffatensis, D. Forchhammeri, &c. The black shales likewise appear at the roadside a few yards west of Bellymack [NX 68949 64827].

About a mile to the south-west of the last-named locality, representatives of the Birkhill black shales come to the surface along an axial fold in the Tarannon greywackes and shales. From the assemblage of their fossils, it is apparent that members of the Lower Birkhill division are here met with, ranging from the Diplograptus acuminatus zone to that of Monograptus gregarius. In the stream, about fifty yards to the north of Dunnance Farmhouse, black shales are exposed, dipping to the north-west, from which the following fossils were obtained:

Diplograptus acuminatus (Nick.)

Diplograptus vesiculosus (Nich.)

Climacograptus normalis (Lapw.)

Dimophograptus (Lapw.)

Monograptus tenuis (Portl.)

Monograptus attenuatus (Hopk.)

Monograptus lobiferus (M'Coy.)

Dawsonia campanulata (Nich.)

In one of the branches of this stream, about one-third of a mile; south-west of Dunnance Farmhouse [NX 67064 63770], in the same line of strike, the black shales yielded:

Diplograptus acuminatus (Nich.)

Diplograptus tamariscus (Nich.)

Climacograptus normalis (Lapw.)

Monograptus tenuis (Portl.)

Monograptus attenuatus (Hopk.)

Monograptus leptotheca (Lapw.)

Monograptus jaculum (Carr.)

Monograptus triangulatus (Hark.)

Monograptus gregarius (Lapw.)

Monograptus lobiferus (M'Coy.)

Lingula striata (Sow.)

At this part of the stream-section the black shales are repeated several times by isoclinal folds inclined to the N.N.W. in conjunction with the Llandovery grits and shales.

Hensol Black Shale Band, River Dee. — [NX 67519 69865] Owing to plications of the overlying Tarannon grits and shales, the members of the Moffat series reappear about three miles to the north of the Lawrieston band, in the River Dee at Hensol House, close to its junction with the Ken. This exposure is of special interest, as the strata are arranged on the whole in a normal fold, the lowest beds occupying the core of the arch. On the north bank of the liver, at the bend a quarter of a mile below Hensol House, Barren Mudstones form the centre of the fold, succeeded on both sides by the Lower Birkhill Shales. At the top of the Barren Mudstones, on the south side of the arch, Dicellograptus anceps was obtained from black shales that have here been pierced by an intrusive dyke. A band of black grits is, on the south limb of the arch, associated with the Birkhill Shales, which are inclined to the south-east at high angles. In like manner, the Lower Birkhill zones dip away from the Barren Mudstones on the north side of the fold. The Birkhill Shales have here yielded the following forms:

Diplograptus vesiculosus (Nich.)

Diplograptus tamariscus (Nich.)

Dimophograptus elongatus (Lapw.)

Climacograptus normalis (Lapw.)

Monograptus tenuis (Portl.)

Monograptus attenuatus (Hopk.)

Monograptus gregarius (Lapw.)

Dawsonia campanulata (Nich.)

It is worthy of note that the highest zone represented here is that of Monograptus gregarius, as the Llandovery greywackes and shales immediately succeed in the railway cutting to the north. These members of the Moffat series can be traced down the river Dee for a short distance along the strike, and they are also visible in the railway cutting to the north. A small exposure of the Birkhill Shales occurs on another fold near the railway viaduct on the east bank of the Ken.

Not far from the granite boundary, in the north-west corner of the map, two outcrops of black shales may be observed, one on the south slope of Benan Hill [NX 64553 68495], south of Loch Stroan, and the other in Cleuch Burn. A third exposure is seen in the Oastramont Burn about two miles from the granite margin. In these instances, the Moffat Shales come to the surface along isoclinal folds, inclined to the south-east, but the beds are too much altered to yield graptolites.

Barlay Burn. — [NX 61587 58209] About two miles to the north-east of Gatehouse, at a marked bend in the Barlay Burn, representatives of the Lower Birkhill group appear, much contorted and traversed by faults. At the first exposure, in the ascent of the burn, the black shales are cleaved and corrugated, dipping to the southeast at low angles. Here they have yielded specimens of Climacograptus normalis. A few feet above this outcrop, thin bands of black shales with seams of white clay occur, from which have been obtained Monograptus triangulatus, M. tenuis, M. lobiferus, and Climacograptus normalis. These are overlain by grey shales. A fault running in a north-west and south-east direction bounds these beds on the west side, bringing them into conjunction with grey greywackes. Further up stream the band is traversed by two faults, but the shales are traceable as far as the bridge across the burn. A thin band at this north-east exposure yielded Diplograptus acuminatus, D. tamariscus, Monograptus tenuis, &c. Near the bridge, Monograptus gregarius and some of its associates were found.

Coal Heugh. — [NX 67788 59053] In this small tributary of the Tarff Water, and also in the Tarff section, the Birkhill Shales are visible on another fold. Indeed, the Coal Heugh receives its name from this outcrop of black shales, which led to excavations in search of coal. Ascending the Tarff from Ringford, we find brown-crusted flags, blue shales, and fine-grained greywackes, inclined to the north-west. On the west bank of the Tart, opposite Liggatcheek, and near the mouth of Coal Heugh, shattery green shales, flags, and jointed greywackes veined with calcite appear. These are succeeded by grey shaly clays and thin bands of black shale. They are prolonged up the Coal Heugh, the best exposure being at the site of an old mine. The beds are much slickensided, and fossils are difficult to obtain, but specimens of Diplograptus acuminatus and Climacograptus normalis were here collected.

From the evidence adduced in the foregoing pages, it appears that the highest zone of the Moffat series in the district between the Nith and the Fleet is that of Monograptus gregarius. The Moffat type of the Upper Birkhill division has not as yet been detected in this area. It is probably represented by some of the coarser sediments. The occurrence of Monograptus Sedgwicki (Portl.) in a dark seam interleaved in greywackes and shales in the Tarff Water west of Upper Lairdmannoch [NX 67141 61827] seems to support this conclusion.

Black Shale Bands near the South-west Margin of the Cairnsmore of Fleet Granite Mass. — Along the southern margin of the granite mass of Cairnsmore of Fleet between Little Water of Fleet [NX 58164 61204] and Creetown Station [NX 47547 58784], and again along the western edge of the granite, there are various outcrops of the Moffat Shales appearing along sharp anticlinal folds. In this district the black shales., after passing from black to blue and dull grey, have been so much hardened and altered as to have become schistose and to have lost all traces of the original bedding. When in this altered schistose condition, they become remarkably tough, generally split up into large square blocks, and usually contain various contact minerals. No traces of graptolites have been observed in the more highly altered bands; near Palnure Station, however, graptolites are recognisable, but too imperfect for identification.

River Cree, One Mile North of Newton-Stewart. — [NX 40410 66948] About a mile to the north of the Bridge of One at Newton-Stewart the Glenkiln–Hartfell black shales and Barren Mudstones come to the surface in the midst of greywackes and shales. From evidence obtained near Glenluce it is probable that the latter sediments are of Llandovery age, though no Birkhill Shales are visible in this section. The members of the Moffat series appear about half a mile above the junction of the Cree with the Penkill Burn, at a point where the Cree flows for 200 yards in an E.N.E. direction. On the north bank of the stream at this bend the Glenkiln–Hartfell black shales are visible, and have there yielded Diplograptus foliaceus, Climacograptus, &c. This outcrop crosses the Cree to the west bank, and is followed on the south limb of the fold by a fine development of the Barren Mudstones, of the type so characteristic of the central Moffat region, and these in turn are succeeded by thick grits. Northwards the Hartfell Shales are succeeded by Barren Mudstones, rolling about at low angles and forming flat arches. The Hartfell Shales reappear, however, on a second anticline about fifty yards north of the main exposure, and yield certain forms characteristic of the Pleurograptus linearis zone, viz.: Diplograptus quadrimucronatus, Dicellograptus Morrisi, Climacograptus. Again, the Barren Mudstones reappear to the north of this latter exposure and occupy the stream for a distance of 120 yards, where they are followed by massive grits and shales which dip southwards, and are thus inverted, at high angles. A careful search for graptolites was made in the shaly bands at the base of the grits, but without success.

Following the Cree southwards from the main outcrop of Hartfell Shales at the prominent bend in the river, the observer finds two arches of the Barren Mudstones ere he reaches the point of junction between the Cree and Penkill Burn, the more northerly of the two having a thin core of black shales. The black shales and Barren Mudstones appear in the Penkill Burn to the north-east of these arches. About a mile and a half up this tributary of the Cree, near the footbridge leading to Cumlodden School, much contorted and crushed black shales yielded Climacograptus, Diplograptus, and Dicellograptus, thus indicating a Glenkiln–Hartfell horizon. This band of shale stretches for some distance to the E.N.E., but owing to the contact metamorphism induced by the Cairnsmore of Fleet granite, its horizon cannot be fixed by fossil evidence. At the band of the Well Burn, Talnotry, and about 300 yards N.N.W. from Talnotry [NX 48627 71835], the altered black shales were mined for plumbago on the outcrop of the Drumlawhinnie and Loch of the Lowes band.