Quarterly Journal of the Geological Society of London/Volume 33/Remarks on the Coal-bearing Deposits near Erekli
Towards the end of March 1854, after the combined fleets of England and France had entered the Black Sea, as coal was known to be procured by the Turkish Government from the south coast, near Erekli (the ancient Heraclea), I was ordered to proceed there, and examine and report upon its quality and fitness for the use of war-steamers; for although two or three cargoes of the coal were seen at Constantinople by some naval engineers, the quality appeared to be so inferior as coal (from being so mixed with slate and rubbish), that a general opinion prevailed that it was only a better quality of lignite than that procured from the Tertiary deposits of the Sea of Marmora and the Archipelago.
It was therefore of first importance to ascertain the age of the Erekli coal-beds, as well as the quantity that could be procured from them with sufficient economy and of sufficiently good quality for the use of our war-ships for steaming at high speeds.
I could obtain no fragment of a fossil from the coal at Constantinople that I examined, nor any information regarding the deposits associated with them; for, although M. Tchihatcheff had shown that rocks of the Devonian age existed, no mention was made of these coal-deposits or of any Carboniferous strata in the neighbourhood, in his valuable work on Asia Minor, published in 1853. I now find, however, that M. Schlehan had, in the 'Zeitschrift der deutschen geologischen Gesellschaft' for 1852, given a full description of some patches of Carboniferous deposits that had recently been examined by him near Amasny, and from which he gives a list of seven genera of Carboniferous plants.
I also find that M. Tchihatcheff, in his description of Asia Mino published in 1867, has noticed M. Schlehan's account of these Carboniferous strata at Amasny, and has also given a list of fossils sent him by Mr. Barkley from the coal-beds at Kosloo, as he had not been able to visit the district.
Leaving Constantinople in H.M. ship 'Spitfire,' then under my command, on the evening of March 27th, I passed Erekli the following morning, and proceeded at once, as the weather was favourable, to the bay and valley of Kosloo, about thirty miles further to the eastward, where the coal was being worked for the Turkish Government under the direction of an English engineer, Mr. John Barkley.
Steaming thus along this open coast between Erekli and Kosloo, I saw that a succession of narrow valleys, confined between narrow and steep ridges from 500 to 1500 feet high, ran north and south at right angles to the coast, up to a curving ridge of limestone that seemed to be 3000 feet or more in height, and distant from four or five to ten or twelve miles.
Extensive forests and underwood covered the larger portion of these ridges and valleys, especially towards the interior; whilst near the coast the valleys were less wooded, and were in parts cultivated; but the cultivation was very sparse.
The position of Kosloo was recognized by the few houses forming the settlement that stood near the shore of the little bay, as well as by the heap of coal, about 9000 tons, accumulated near it ready for shipment when the anchorage in the bay was considered safe for the coast-craft that removed the coal to Erekli (as the local dépôt) before transhipment for Constantinople,—the favourable season for this not commencing, in general, before the middle or end of May.
I anchored in the little bay of Kosloo about noon, at about a quarter of a mile from the shore, and was immediately joined by Mr. Barkley, who I found had been in charge of the district, as its Manager, for the last three years. With him there were four Englishmen as foremen of the miners, who were chiefly natives, Sclavonians and Hungarians. But during this time Mr. Barkley's English colony of artificers, first introduced by him, had suffered greatly from the malignant fever that prevailed in the autumn months all through the district, as usual throughout Asia Minor—several having died, and others having been obliged to return home.
Having completed arrangements for the immediate shipment of about 100 tons of the screened coal, so as to fairly test its steam-generating properties on my return voyage to Constantinople, I landed with Mr. Barkley and proceeded up the valley with him to examine some of the mines or seams that were being worked by him; for, as the seams were seen cropping out on the sides of the valley between the associated shales and schists, they were worked by simple horizontal drifts or slightly inclined tunnellings into the hill, as far as the seams were thus traceable.
From the beach I found a tramway leading up the valley for a distance of nearly two miles, with branches to the different drifts or mines then being worked.
During the remainder of this and the following day I examined the different seams worked under Mr. Barkley, and entered three or four mines or drifts that were then being so worked, as also one or two that had already been worked out in consequence of faults (or "troubles" as they are technically termed) that cut off the continuance of the seam, and left no indication whether it was the result of a downcast or otherwise.
These drifts extended from about 100 to nearly 400 yards only into the hill; for the district was so disturbed by faults and displacements, which occurred at every 200 or 300 yards, that several had already been worked as far as practicable, and few extended a greater distance before a fault was met with; and as the seams corresponded on both sides of the valley the same difficulties also occurred in respect to the frequency of faults in both. One of them, on the west side, that had been so worked out, Mr. Barkley informed me, was found to be bent both downwards and upwards, as well as being partly horizontal in the central portion, somewhat in this form:—
On the west side of the valley the coal-seams were not so plainly seen cropping out at the surface, nor so numerous as in the eastern ridge, where there were no less than eleven or twelve seams thus existing, of varying thickness and quality.
The extent in which this number of beds or seams occur on the east side of the valley is about two miles; the seams being interstratified with shales, sandstones, and conglomerates of quartz-pebbles, with thin bands of clay occasionally, and also with thin bands of ironstone, the whole comprising a considerable thickness of these Coal-measures. See following sketch section:—
Sketch Section of the Coal-bearing deposits near Erekli.
(Length about 2 miles.)
The following are the details of one of the seams now being worked in the upper part of the valley:—
| Overlying shale. Dip 26° S.E. | |
| Thin band with fossil plants. | |
| 22 inches. | Coal, of good quality. |
| 7 inches. | Shale. |
| 14 inches. | Coal-seam, very good. |
| 5 inches. | Shale. |
| 36 inches. | Coal-seam, very good. |
| 2 inches. | Clay. |
| Uncertain. | Shales and sandstones. |
From this seam I was so fortunate as to procure a few fragments of fossil plants that seemed to be unmistakably of the true Coal-measures; and thus the important difference between them and the lignites of the Levant was at once evident to me. In the roof of this mine I observed an impression of what appeared to be an almost circular leaf, that measured nearly 4 feet in diameter.
Mr. Barkley informed me that in one of the mines trunks of trees had also been found in situ, the diameter of which never exceeded about one foot,—the outer part of these trunks being converted into pure coal, whilst the interior or core was composed of pure shale, thus indicating their hollow or soft pithy heart, like large tree ferns &c.
The remains of plants were, however, rare. I was fortunate in finding some fragments amongst the heaps of refuse near the mouth of some of the drifts; and I was indebted for some others to Mr. Barkley, who kindly gave them to me so as to lead to the true identification of the age of this singularly isolated patch of the true Coal-measures, as they have proved to be. The fossils I then procured are now for the first time exhibited; for, although they were sent to England to my lamented friend Edward Forbes, for identification, at the same time as my report was sent to the Admiralty, by some mischance the box containing them was detained in some Custom House until the end of 1854 or beginning of 1855, and only reached him shortly before his removal from the Museum in Jermyn Street to Edinburgh, and consequently just previous to his death; so that only an extract from a hasty letter to him, sent at the same time, has ever been published in reference to my examination of these Black-Sea coal-beds. This appeared soon after his arrival in Edinburgh, in the 'Edinb. New Phil. Journ.,' 1855, pp. 172, 173.
The fossils themselves have, fortunately, remained at the Jermyn-Street Museum since that time; and, on recently inquiring about them through the General Curator, Mr. Reeks, they were readily found. A list of them has been kindly made by Mr. Etheridge to accompany these long delayed remarks upon this important coal-district; and as there are ten genera of fossil plants amongst them, they will more fully establish the age of these beds than has hitherto been done. For, although a brief visit was made to Erekli and to the Kosloo Valley (by sea) by Mr. Poole, soon after the extract from my letter appeared in the Edinburgh Journal, that gentleman has only briefly referred to the existence of the Coal-deposits, without giving any details.
This fact, and the special interest that has recently sprung up in reference to the East, has induced me to think that a fuller description of these coal-bearing deposits and of the district in general, such as my notes and private journal enabled me to give, were now desirable, in a general as well as in a geological point of view.
I was informed by Mr. Barkley that the coal-bearing deposits extended to the eastward of Kosloo to within a mile of Amasny, and were found in almost every intermediate valley. On the west side of Kosloo they extend to within three or four miles of Erekli, thus embracing an area of nearly fifty miles east and west, and from three to ten or twelve miles north and south. Their northern margin terminates on the coast, and therefore must pass under this part of the Black Sea for an unknown and probably considerable extent. But the entire area is characterized by great disturbances and numerous faults.
The existence of these coal beds was first brought into notice about the year 1838 or 1840; but they were not systematically worked by the Turkish Government until five or six years before my visit, although Croat squatters worked at some of the best-developed and most easily worked seams near the coast, for some years previous to this time.
The following are the names of localities near to Kosloo where coal was known by Mr. Barkley to exist, with a description of its quality:—
Okoosnu, five miles from Kosloo. Several seams exist near the summit of the mountains, at two and a half miles from the coast, quality both good and bad, and are being worked by Croats.
Yani Arman. Coal obtained from the hills by Croats, but the quality indifferent.
Doomooz Dereh. Contains a seam of coal 8 feet thick and of good quality, but deteriorating rapidly by exposure. Was being worked by Mr. Barkley.
Zungledek, Has seven or eight workable seams of varying quality, and all lying at various inclinations. Once worked by Croat squatters, but now abandoned by them, from the difficulties encountered in consequence of being so disturbed, and of their want of capital to meet these difficulties.
Baluk and Uzulmas. The coal in this valley is similar to that in the Zungledek. One seam exists at two miles from the sea, which is 12 feet thick and of good quality. The coal at Uzulmas is nine miles from the coast.
Feeling it necessary, or rather desirable, to see something of the coal-bearing deposits in the neighbourhood, I started on the morning of March 30th with Mr. Barkley to ride across the intervening district between Kosloo and Erekli, where I ordered my ship to meet me, the distance being nearly thirty miles.
A short delay occurred in the time of starting, in consequence of an explosion of gas in one of the mines, on the miners first entering it soon after daylight, by which three native miners were rather severely burnt, one poor fellow especially so, in the face and neck. This was only the second instance of the kind that had occurred since Mr. Barkley had been in charge of the mine.
In reference to the geology of the district crossed in our ride to Erekli, I feel that, from the distance of time since it occurred, I can simply give a few extracts from my private journal, without attempting to enlarge or enter into details. Deep drifts of snow lay on some parts of the route, where the road ascended over the higher parts of the ridges crossed, and thus hid some of the beds and associated shales &c. from view and examination.
After ascending for half an hour the western ridge bounding the Kosloo valley, where a mass of limestone decidedly overlies the coal-bearing deposits, we reached and followed the backbone of a ridge nearly 2000 feet above the sea, where the shales and schists composing it appeared to be but little inclined from the horizontal position, but whether conformable or not with the former or latter could not be determined; and after crossing two valleys, with a small hamlet in each, we descended into the valley of Karditch at three and a half hours from Kosloo.
In our descent on the east side of it we came upon the coal- bearing beds, dipping to the S.W. at angles of 40° and 50°, and at about three miles from the coast. We had also seen coal-seams in the other valleys we had crossed, but situated nearer the sea.
To the southward of Karditch masses of limestone appeared on both sides of the valley, with the coal-bearing deposits, apparently dipping under them. But as these latter deposits were inclined at all angles, sometimes the relative superposition of these beds was not identifiable without a more perfect examination. Considerable local disturbances seemed to exist here, as the result of proximate volcanic action; a dyke of igneous rock, although somewhat resembling an altered shale, seemed to form the crest of the ridge near the village of Karditch, and dipped at an angle of 60° and upwards S.W. and S.S.W.
To the westward of Karditch we crossed several valleys leading to the coast, in which coal existed. In one of these, near the village of Aliagazzi, there were two seams, now being worked by Croat squatters, the dip of one of which seams was as much as 70°.
At another valley and village called Arnout-keni, there was a seam of good coal, between 8 and 10 feet thick, that had not yet been worked.
In all these valleys and intervening ridges I found that the Coal- seams and associated shales, &c. represented a series of anticlinally and synclinally disposed undulations of the beds, indicative of great lateral as well as local pressure and disturbance, the anticlinal summits of these flexures having been considerably denuded of the continuing strata.
The view to the southward, over these parallel ridges, where attainable on our route, from being for the most part clothed with dense forests of oak, beech, and wild fruit-trees, and from being devoid of any conspicuous peak or mountain until nearer Erekli, resembled the broad waves of the ocean, and were in unexplored beauty—in apparently primeval condition.
In this part, and also near Erekli, we found the shales over which the road passed much decomposed and soft, as well as showing metamorphic action from volcanic influence, the focus of which seems to be at or near Erekli, as I shall show by a brief description of the locality, which I was enabled to examine during the two following days, before my return to Constantinople; for as Erekli was the depot to which the coal was sent from the localities at which it was procured along the coast, chiefly in small coasters, for transhipment to Constantinople in vessels of larger burden, it became important that my Report should be accompanied by a survey of the only secure anchorage near the Coal-bearing district.
On the Geology of Erekli.
The Acropolis and part of the town walls of Heraclea stood upon the crest and slopes of a bold and almost isolated hill rising from the east side of the bay, formed by the promontory of land to the north-west of it, now called Cape Baba, but anciently the Acherusian Peninsula by Xenophon; for this city was the place from which he embarked for Greece, with his army, after his celebrated retreat.
The summit of this hill (Acropolis) consists of a capping of reddish indurated shale, a few feet only in thickness, and overlying stratified beds of tuffs, greenstone, volcanic mud, and trachyte conglomerates, by the outburst of which the reddish shales were evidently uplifted and altered in their colour and character; but Mr. Poole calls it sandstone, no doubt from a too hasty examination.
A portion of the same altered shales, or rather marls, appears also at the base of the Acropolis, near the shore, on its west side—likewise to the north and eastward of it, with the lavas intermediate.
A valley to the south of the Acropolis, in which is a large part of the modern town of Erekli, separates it from another hill over the coast, which is composed of whitish and grey marls, belonging, no doubt, to the same group as the indurated stratum capping the Acropolis, and the altered marls existing at its base.
These white and grey marls dip to the south-west at an angle of 30°, except on the east side of the hill, near the large burying- ground at its base, where they are nearly vertical, and where they are much discoloured and decomposed through contact with the trachyte conglomerates and stratified lavas which have burst out beneath them.
The age of these marls I was not able to ascertain, as the only fossil obtained from them was an oyster, too friable, however, to be preserved, but sufficient to show that they were of marine origin. From the form of the oyster I was disposed to consider the deposit to be of Miocene, or perhaps an earlier age.
In the promontory to the north and north-west of Erekli the volcanic productions of tuffs, trachytes, and basaltic conglomerates prevailed, having in some parts both uplifted and also overflowed the marine marls.
It is perhaps worth noticing, in concluding these remarks upon the volcanic character of the locality, that the ancients must evidently have recognized the plutonic or igneous origin of these lava-beds, notwithstanding their general stratified condition; for Xenophon states that a cavern was shown in the Acherusian Peninsula that led to the gates of Hades, and from which Hercules drew forth Cerberus, the guardian of its portals.
Strabo says it lay to the north of the town, and was two stadia deep; but I could hear of no such cavern in the neighbourhood. Yet it is possible that some traces of an extinct crater or volcanic vent may exist here, where, as I have shown, lavas and beds of igneous production appeared to have covered some extent of the neighbouring district.
A cavern, however, penetrates into the Acropolis hill for 300 or 400 yards, but seems to have been wholly artificial, and was perhaps originally a quarry for building-stone.