Notes on the geology of Southerness, Kirkcudbrightshire

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Parallel to the Silurian and Old Red Sandstone belts of Scotland, and running from north-east to south-west, stretches a narrow stripe of Carboniferous strata from the head waters of the Liddel, at the junction of the Cheviots and the Lowthers, to Locher Moss, in the south of Dumfriesshire. This line of the Coal Measures disappears under the Solway at the mouth of the Nith, forming there the extended Blackshaw Bank, but reappears at two points in Galloway, in the same line of strike. One of these is at Southerness, and forms a rough triangle, of which the Ness is the apex, a narrow patch of but a few miles in extent, but rich in fossils and geological points of interest. The other is at Abbey Head, east of Kirkcudbright Bay. These two little patches of the Coal-Measures seem at first sight strange and isolated, as lying apart in the wide Silurian district of Galloway; but their strangeness and isolation at once disappear when they are seen to form part of a Carboniferous belt that stretches from the Northumberland coal-field to Abbey Head in Kirkcudbright; a belt, the counter part and parallel of a smaller patched belt stretching from Girvan to Dunbar on the north; and interesting, moreover, as remnants of the great Carboniferous sheet that probably once covered the wide Silurian uplands of the south of Scotland. The Carboniferous belt just spoken of is, according to the new geological map of Murchison and Geikie, the Carboniferous Limestone series, which lies above the Lower Carboniferous or Calciferous Sandstones, and below the millstone grit and True Coal-Measures. Along this shore the Carboniferous Limestone series is represented by different limestones, shell, coral, and encrinital sandstones, shales, and seams of coal and ironstone, variously intermingled, and laid beautifully open for inspection by the restless action of the Solway waves. Of the whole shore we made a careful survey. The shore is skirted by a high cliffy bank at various distances from tide-mark, clothed with shrubbery and grass, that once formed the old coast line. Underneath this cliff stretches the rocky shore, washed by the daily tides, exhibiting a belt of Carboniferous strata. The rocks are of different heights, and variously sloped and contorted, always jagged and dark, sometimes rising high and striking, and then sinking under the fine sand of the Firth. The most interesting portion of these rocks lies between Borron Point and the Thirlstone, stretching to equal distances on both sides of the gardener’s house of Arbigland, which forms the centre of observation. The limestone is found chiefly between the gardener’s house and Borron Point; the coal and iron south of the Thirlstone; the sandstone all along the shore, but best at and near the Thirlstone; the shales everywhere, but more between the Thirlstone and the Great Boulder, a little south of the gardener’s house. South of his house the old coast line becomes the present sea cliff, and has been worn into caves, and hollowed into various picturesque masses by the fierce waves that roll in from the Irish Sea. South of the Thirlstone the rocks leave the beach and run across Gillfoot Bay, which is sandy, but again strike the coast at Southerness, where they form the shore, but soon again disappear in the wide waste of the Mersehead Sands. It is this carboniferous shore that exhibits the notable phenomena to which we would now shortly direct your attention, and from which the specimens we exhibit have been brought. The Variety of the Strata. —One of the first features that strikes a visitor is the varied character of the rocks exposed, their sudden transitions, and strange interminglings. Here in a walk of a mile or two we pass over a varied succession of granite, Silurian slate, carboniferous sandstone, shale, limestone, ironstone, coal, and trap; while the shore is strewed with boulders (and rocks) of various size, representatives of the inland rocks, brought thither by the glaciers of the past. All these are beautifully exposed and laid open for inspection in successive lines, like as in a great seaside museum, in which a tyro in the science might learn to distinguish the different kinds of rocks. Variations in Dip and Strike, Slip. —Another feature of this shore is the remarkable and sudden variations in the dip and strike of the various rocks that skirt it. It is almost impossible to give any one direction as the general one; but they incline more to run from north-east to south-west than in any other direction that is in the line of the general strike of the Carboniferous belt. But they look towards every point of the compass. North of Borron Point the strike goes variously north-west; immediately south of it they sweep round to north-east; towards the gardener’s house they turn round again towards the north-west, but some run nearly north and south; south of the house they strike east and west; opposite the garden gate a new series suddenly interrupts the others, and runs south and east, and this continues unchanged for a considerable distance till south of the Thirlstone the strata abruptly take a north-east direction, only to be again and again interrupted by some new and abrupt strike. The rocks have a tendency to sweep in great circles, as seen at Borron Point, and in both sides of the gardener’s house. But at two points the strata take the form of very complete concentric circles. One of these lies a little north of the gardener’s house. Unless seen, it could not be thought that such a beautiful circular section of rocks could be shown in so small a space. The other concentric series is near the Arbigland Boulder, south of the gardener’s house; but though evident enough, it is not so remarkable as the other to the north, and cannot be looked down on from above in the same way. The change of dip of the rocks is as varied and sudden as that of the strike. They lie at every angle from horizontal to perpendicular; they have even been thrown to a wide angle over the perpendicular. This variation in dip, even in the same seam, is well seen at Borron Point, where one sandstone bed runs very nearly north and south, quite erect and high, like a long black artificial wall. ‶Troubles″ are plentiful, other rocks suddenly appearing in the midst of any one formation, and it is often impossible to say which is the original rock, so numerous and mixed are the seams. Of this a very fine example may be seen near the Great Boulder, where the rock has been thrown in every direction, and is composed of every material in the most incredible manner. ‶Slips″ are common, and some very fine examples are shown. One in particular occurs, just at Borron Point, and runs in a right line, as if drawn by a ruler from south-east by south to that cape. Here the amount of displacement may be measured, the various seams on each side of the slip being distinctly seen standing up and bared by the action of the waves. ‶Dykes″ are abundant of trap and greenstone, and rise literally like dykes striking, like the great Chinese wall, right across all obstacles, but unlike it not surmounting them, but cutting right through them. The sandstone near the Thirlstone is remarkable also as exhibiting folds and plications similar in a great degree to those of the Silurian rocks. They have been crushed up into those wavelike bends, so well known in slate rock, but rarer in sandstone. Carboniferous Limestones. —The fossil remains most beautifully exhibited along this shore are those of corals. The most exquisite specimens may be gathered of Lithostrotion Portlockii, L. cylindricum, L. fasciculatum, and other varieties. Whole beds of these corals may be seen, with the dome-shaped masses in natural form and position as they lived, rising like the bosses of shields above the general surface of the rocks on which they rest. Some of the masses of L. Portlockii have been beautifully cleaned out by their alternate wetting and drying by the sea, and by the action of the weather, except where they have, from long exposure, been rubbed with the stones of the beach. They exhibit in perfection the most beautiful honey-comb surface, with the interior radiation perfectly preserved in some of the specimens shown. Corals are the chief fossil productions of the shore. Some of them are of immense size, and I know no other spot where they may be seen in such fine condition. Ripple-marks, Worm-castings. —Various other interesting phenomena are seen along this shore. Fine examples of ripple-marks on the sandstone, covered also with worm-tracks over a large surface, occur near the Thirlstone, and some fine ones near Borron Point. Some seams of sandstone show annelide borings, similar to those on the Bathgate Hills. On various sandstone surfaces along the shore certain remarkable hollows and indentations are frequent, that seem to have been the base or nest of the worm borings, and some of them run horizontally for a considerable distance. South of Borron Point the indentations are as large as the palm of the hand, and palmated in shape, and occur so regularly in lines over a large surface, that they look like the prints of some gigantic reptile impressed in tenacious mud. They have likely some connection with borings, but their great size makes this doubtful. On other surfaces decided worm-castings of varied thickness, length, and character are abundant; some near the Great Boulder being close, thick, and large; others, near Borron Point, being small and interlacing, the whole surface showing a pretty appearance. These things are seen elsewhere, but here the surfaces on which they are shown are so finely bared and so extensive that they become very striking. They look almost as if they had been left by the morning tide. Fossils Found. —The following is a list of some of the fossils found in the Carboniferous strata along this shore, made out from the fossils gathered by my friend Mr Linn of Whitburn, a member of the Society, and myself. This list sufficiently established that the carboniferous rocks here exhibited are rightly coloured by Sir R. Murchison and Mr Geikie, as members of the Carboniferous Limestone series; for all those found belong to the limestones of this series, as developed in other parts of the country. The list is very partial, but it is sufficient to prove the horizon of the strata, and the rich fossil field there laid open to view by the waves of the Solway tides. List of Fossils from Carboniferous Strata on Arbigland Shore:— Corals. Lithostrotion Portlockii. ... irregulare. ... cylindricum. ... fasciculatum. ... junceum. Zaphrentis cylindrica. Clisiophyllum turbinatum. Aulophyllum fungites. Fenestella plebeia. Stenopora fumida. Archæocidaris Urii. Actinocrinus stems. Poteriocrinus do. Shells, etc. Porcellia Armata. Productus longispinus. ... Martinii. ... punctatus. ... scabriculus. ... semireticulatus. Athyris ambigua. Streptorhynchus crenistria. Spirifera trigonalis, and others. Sanguinolites. Conularia quadriculata. Bellerophon Urii. Loxonema. Euomphalus catillus. Natica. Macrocheilus. Nerita. Orthoceras. Goniatites diadema. Dentalium priscum. ... ingens. Edmondia sulcata (?) Annelide burrows. Palatal tooth—large—of—(?) Cauda-Galli. Few land plants—large Stigmaria exposed in rock at Thirlstone, also at Borron Point. Sea Action is well seen all along the shore, especially near the Thirlstone, where it has formed ‶stacks″ and natural arches, and hollowed out large caves. One thing deserving of notice near the same cape is the great number of ‶pots″ formed in the sandstone by stones rotating and revolving under the action of the sea-water, as is seen so often in river beds, especially near waterfalls, as at Rumbling Brig and Caldron Linn, on the Devon, beyond Dollar. In the matter of grand and picturesque cliff scenery, few coasts could surpass the ‶Craigs of Colvend,″ of hard Silurian, which are equal to, if they do not surpass, the cliffs of the Forfarshire and Caithness coasts, and which have been rendered classical, as exhibiting the scenery of ‶Guy Mannering.″ No one should visit that district without walking along the high cliff road between Southwick and Colvend. Glacial Remains. —The whole of the low lands below the Criffel range are covered with a very thick deposit of boulder clay, consisting of gravel, clay, and sand. The sand, gravel, and boulders are always granitic, showing that the deposit has been carried down from the granite heights to the sea. It lies in great thickness, in wide flats, and dome-shaped mounds, especially towards the base of the hills, and forms a striking element in the scenery. Kirkbean lies in a basin-shaped hollow, amidst glacier deposits 60 or 70 feet high, which have been cut through by the Kirkbean and Preston Mill burns. Between Kirkbean and Dalbeattie the very best illustrations of the local character of the deposit may everywhere be seen. Between New Abbey and Kirkbean remarkably fine examples of such deposits occur, consisting of hillocks so rounded that they look like artificial mounds. The very soft character of their contents is proved by the deep excavations made by the smallest streamlets. Near Hillhead, in the Drum Burn, a very fine example of a deep valley excavated in these superficial deposits occurs, and is all the more striking that it is now entirely without water. Travelled blocks are very abundant, a remarkable one, called the ‶Arbigland Boulder,″ being known to local fame. Splendid granite blocks are scattered on the side of Criffel above Loch Kinder, and cause astonishment at their number and immense size. They are all more or less angular, being of granite, carried but a short distance, having, in fact, come from the Criffel range, on the side of which they lie. Loch Kinder is remarkable also as being an example of a lake barred back by glacial debris, the waters being kept in at two ends by gravelly accumulations, but resting on the granite at other points. On the north side very little would send its whole mass of water into the Abbey Pow Burn. Recent Deposits. —Good examples of these occur in this interesting corner. We have sandhills along the shore near Southerness. West of Southerness we have an example of the true merse land or salt marsh, with its peculiar herbage, grazed on by many cattle, and which is the home of the gull, and the oyster-catcher, the kittywake and the curlew, the heron and the plover. A recent deposit of thick moss of a strange composition occurs below Carsethorn, and has been dyked back from the inroads of the sea by a strong stone bulwark.

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