V. A. Khakhlov,

instructor at the Siberian Technological Institute and docent of Tomsk State University.

Plant Remains from the Chernovskie Mines of Transbaikalia.

(With 11 figures).

The Chernovskoe coal deposit is located 20 km west of the city of Chita, in the immediate vicinity of the Chernovskaya station of the Chita Railway. It occupies an insignificant area, about 12–15 sq. km, on the left bank of the Ingoda River, between the valleys of the Chernovka and Kadala streams. The Chernovskie mines now in operation are situated 4–5 km from the railway station and are connected with it by a broad-gauge branch line.

It would seem that such a favorable geographical position of the mines, which have the greatest importance in the coal-industry life of Transbaikalia, might have guaranteed a far greater degree of study of the deposit than we in fact possess. In the literature one can note only two items that consider the Chernovskoe deposit on the basis of personal observations. These are an article by V. N. Zverev, published in the News of the Geological Committee for 1918, and a manuscript (1926) by the head of the Bureau for the Registration of Mineral Resources of the Siberian Branch of the Geological Committee, mining engineer I. A. Molchanov. As for other mentions of the deposit in the literature, they were for the most part made on the basis of materials obtained second-hand and not always verified or corresponding to reality.

According to data from the mines, the coal-bearing sequence lies almost horizontally and contains 5 seams of coal, among which only the First, or main, seam, reaching a thickness of 7.5 meters, is of industrial significance. The rocks overlying the seam differ in their character; throughout and everywhere they exhibit diagonal bedding, and they have been best studied in the enormous open section of Torm, the former Zamyatinsky mine. The roof of the seam is formed by a layer of weak argillite of light gray color with a slight dirty-greenish tint, 1–1.5 meters thick. Upon it lies a thick mass of unstratified white sandstone, consisting of slightly rounded quartz grains of varying size. Plant remains occur chiefly in the argillite horizon and more rarely at the base of the white sandstone bed. The fineness of the material composing the argillite layer conditioned, one may say, the ideal preservation of the plant material.

The paleobotanical material entrusted to me for detailed treatment was collected by mining engineer I. A. Molchanov during his brief stay at the mines and by mining technician I. P. Benyakh, who kindly agreed to send the material he had additionally collected to Tomsk.

DESCRIPTION OF THE PLANT REMAINS

Equisetales.

Equisetites sp.

(Fig. 1).

In the collection there is only a single specimen of gray argillite with numerous impressions of fragments of leaf sheaths, in rather poor preservation. It is shown in Fig. 1. The presence of leaf sheaths of the Equisetites Sternb. type leaves no doubt that the impressions belong to the genus Equisetites Sternb., but the insufficient degree of preservation does not make it possible to approach more closely the determination of the specimen.

On the leaf sheath only three or four leaf blades have been preserved, 1.5 mm wide and 8 mm long. The outline of the individual leaf segments is visible in the drawing and is an isosceles triangle 4 mm high and with a base of 1.5 mm.

The insufficiency of the material compels us to limit ourselves to an approximate determination of the fragments as Equisetites sp., and to note that the impressions differ sharply from the species Equisetites ferganensis Sew., common in the Jurassic deposits of Turkestan and Irkutsk Province.

Locality: Chernovskie mines.

Filicales.

Coniopteris burejensis Zall. sp.

(Fig. 2).

1. Dicksonia burejensis Zall. M. Zalessky (1). P. 181.
2. Coniopteris burejensis Sew. A. Seward (12). P. 6. Pl. 1, figs. 1—5.
3. Coniopteris burejensis Zall. sp. A. Turutanova (14). P. 12, figs. 18—21.
4. Coniopteris burejensis Zall sp. Novopokrovsky (23). P. 5.

On slabs of coarse-grained white sandstone there are impressions of leaves of the fern Coniopteris burejensis Zall. sp., common in the Jurassic deposits of Eastern Siberia and the Amur Region. The intense staining of the leaf by carbonaceous matter completely obscures the pattern of venation, and therefore the determination was made exclusively from the external outline of the pinnules and the general structure of the frond.

Fig. 2 shows a fragment of a frond, the rachis of which is 0.5 mm thick and bears pinnules arranged at an acute angle. The pinnules have a linearly acuminate outline and, in the basal part of the frond, reach 25 mm in length and 6—7 mm in width. Each pinnule is dissected into separate segments, as if of the 2nd order, which, nearer the basal part of the frond, become quite independent, while toward the distal part they begin to merge with one another. The segments, in turn, undergo further dissection into separate lobes, and the degree of lobing of the margin varies noticeably. Sometimes the margin is dentate; sometimes it bears deep, pointed lobes; sometimes there are only barely indicated traces of dentation. The number of lobes varies. The greatest number of them falls to those pinnules of the 2nd order that sit nearer the base of the leaf. Usually no more than 6 can be counted, and nearer the distal part of the frond their number decreases noticeably and the segments become entire-margined. Pinnules of the 2nd order pri-

are attached to the petiole by a narrowed wedge-shaped base at very different angles: nearer the base—at a more obtuse angle, nearer the apex—at a more acute one. The lower margin of a pinnule of the second order descends toward the petiole. The greatest length of a pinnule is 5 mm, width 3 mm.

Other specimens confirm to a considerable degree the characterization given above, for which reason I do not consider it necessary to present them in the appended plates.

Locality: Gray-white sandstones of the roof of the main seam of the Chernovskie mines.

Coniopteris hymenophylloides (Brgn.).

(Figs. 3–5).

1. Coniopteris hymenophylloides (Brgn.). A. Seward (10). P. 10. Pl. 1, fig. 13. Pl. VI, figs. 67, 68.
2. Coniopteris hymenophylloides (Brgn.). A. Seward (11). P. 7. Pl. 1, fig. 10.
3. Coniopteris hymenophylloides (Brgn.). A. Turutanova (14) P. 14, fig. 22.

In working through the small collection of plant remains from the Chernovskie mines, I involuntarily noticed the extreme similarity of many pinnules of Coniopteris burejensis Zall. sp. and Coniopteris hymenophylloides (Brng.). Considering the broadest leaves of Coniopteris burejensis Zall. sp. and not having among the impressions any fertile segments, I came to the conclusion that many impressions, in the external outline of their pinnules close to those shown in fig. 3, may with equal probability be assigned to both species; consequently, I cannot insist on the correctness of the determination of the specimen shown in fig. 3. As for the leaves represented in figs. 4 and 5, they are typical of the species Coniopteris hymenophylloides (Brgn.) and agree well with the specimens of Prof. A. Seward from the Caucasus and Turkestan. In places the characteristic venation has also been preserved.

The most fundamental character for distinguishing the sterile leaves of Coniopteris burejensis Zall. sp. and Coniopteris hymenophylloides (Brng.) is the relatively greater width of the pinnules in Coniopteris hymenophylloides (Brgn.). The degree of dissection of the frond and, consequently, the number of lobes cannot be considered a guiding distinguishing character because of their tendency to strong variation.

The species Coniopteris hymenophylloides (Brgn.) has a wide geographic distribution. It occurs rather frequently in the Jurassic floras of Eastern Siberia and the Far East, the Caucasus and Turkestan. It has also been cited from the Antarctic region, Australia, Japan, and Korea. It is characteristic of Middle Jurassic and, in part, perhaps, Lower Jurassic floras.

Locality: gray-white sandstones of the roof of the main seam of the Chernovskie mines.

Ginkgoales.

Ginkgo digitata Brgn.

Fig. 6–7.

1. Ginkgo digitata Brgn. A. Seward (11) P. 17, Pl. III, fig. 40.
2. » » » A. Seward (10) P. 32, Pl. VII, figs. 53–55.
3. » » » F. Krasser (20) P. 16, Pl. II, fig. 3.
4. » » » V. Khakhlov (15) P. 4, figs. 3–4.

On the gray argillites of the Chernovskie mines there are impressions of certain ginkgo trees, one may say, of ideal preservation. The greatest number of impressions belongs to the typical Jurassic species Ginkgo digitata Brgn., the best specimens of which are shown on Plate II.

In Fig. 6 we have an almost complete leaf blade, with a broad base and with excellently preserved venation. It is evident that the leaf blade is divided by a deep sinus into two parts, each of which, in turn, is again divided by a corresponding sinus into two parts; moreover, the incision is most pronounced in those lobes that are situated closer to the principal sinus. As a result of the dissection we obtain a leaf consisting as it were of eight lobes, of which only one has to some extent preserved its oval outline. It reaches 7 mm in width.

The venation is typical for the species. From the base only a few veins enter the leaf, immediately undergoing dichotomous branching. They undergo a second dichotomous branching after passing a very short distance along the leaf blade, so that a considerable number of veins, subject to further dichotomy, already enter the leaf lobes. As a result of fourfold branching the venation becomes sufficiently dense and numerous. At the base of the leaf blade the parallel veins pass at a distance of 1 mm from one another, while closer to the distal part of the leaf, approximately at a distance of 7–9 mm, 10–12 veins pass. On all impressions, dark, short longitudinal stripes between the veins are plainly visible to the naked eye, parallel to the vascular bundles and corresponding to the elongated secretory canals, which may also be observed in the species Ginkgo Obrutschewi Sew., established by A. Seward in describing specimens from Chinese Dzungaria.

In Fig. 8 a leaf is shown which is characterized by a considerable dissection of the leaf blade and a denser venation. If we recall that the leaves described by A. Seward under this same specific name and presented by him in Plate 11, Figs. 10–12, are characterized by considerable dissection, then we are justified in leaving these leaves under the name Ginkgo digitata Brgn. Moreover, it is already considered definitively established that the degree of dissection of the leaves of ginkgo trees varies and cannot be regarded as a decisive character in dividing the genus into separate species.

As for the venation, the arrangement of the veins at a distance of 0.75 mm from one another might serve as some indication for establishing at least a new variety within this same species; but careful study of the venation has shown that at a distance of 10 mm we have 14 veins only in those places where they have not yet had time to diverge completely after their dichotomy. Weighing all these characters, this impression too must be included in this same species, Ginkgo digitata Brgn.

Many other impressions in the collection can be well compared with the figures of A. Seward, O. Heer, and other authors from various Jurassic deposits, so that there is no reason to doubt the correctness of assigning all our specimens to the species Ginkgo digitata Brgn.; although it should be noted once again that the intermediate short longitudinal stripes between the veins, corresponding to the secretory canals in Ginkgo Obrutschewi Sew., are encountered for the first time on typical leaves of Ginkgo digitata Brgn.

Locality: dark-gray argillites of the Cheremkhovskie mines.

Ginkgo sibirica Heer.

Figs. 9–10.

1. Ginkgo sibirica Heer. O. Heer. (17) p. 61. Pl. VII. Fig. 6; Pl. IX, fig. 5b; Pl. XI.

1. Ginkgo sibirica Heer. A. Seward (10) p. 33. Pl. VII, figs. 56—57.
2. » » » A. Seward (12). p. 5.
3. » » » A. Krishtofovich. (3). Vol. II. Issue IV. p. 116.
4. » » » V. Khakhlov. (15). p. 4, figs. 5—6.

In figs. 9 and 10 are shown impressions of several leaf blades of Ginkgo sibirica Heer.

The strong dissection of the leaf blade, characteristic of the species mentioned, makes the separate lobes to a certain degree independent. Each inner leaf lobe is 4—5 mm wide, and the outer one 7 mm. Parallel veins run through them, of which 7 can be counted in the outer lobes and 4 in the inner ones, so that the nerves pass at a distance of 1 mm from one another.

The species Ginkgo sibirica Heer, owing to its strongly dissected leaf blade, is a connecting link between forms included in the genus Ginkgo L. and the genus Baiera F. Br. It occurs in Jurassic deposits of many parts of the world, and is considered the most common member of the Jurassic floras of Siberia.

Locality: dark-gray argillites of the Chernovskie mines.

Ginkgoales incertae sedis.

Phoenicopsis angustifolia Heer.

1. Phoenicopsis angustifolia Heer. O. Heer (17). p. 54. Pl. I, fig. 1; Pl. 11, fig. 36.
2. » » F. Krasser. (21) p. 11, pl. II, fig. 5. Pl. III, fig. 4-a
3. » » F. Krasser. (20) p. 24. Pl. III, figs. 2—4.
4. » » V. Khakhlov. (16). p. 18, figs. 26—32.

On many pieces of whitish-gray sandstone and argillite we have impressions of various fragments of the genus Phoenicopsis Heer. Many of them may be assigned to the typical Jurassic species Phoenicopsis angustifolia Heer. The leaf fragments are 6—7 mm wide, and 6—9 longitudinal parallel veins run through them, between which no additional veins are observed. All the impressions in the collection agree fully with the specimens described by Prof. Heer from Eastern Siberia and the Amur region. They are also identical with the specimens cited by F. Krasser from Transbaikalia and Manchuria, and by A. Krishtofovich from the Ussuri region.

The species Phoenicopsis angustifolia Heer has a broad geographical distribution, being a typical member of the Jurassic flora of Siberia and the Far East.

Locality: dark-gray argillites of the Chernovskie mines.

Phoenicopsis media Krasser.

Fig. 11.

1. Phoenicopsis media Krasser. F. Krasser. (21) p. 9. Pl. III, figs. 4 and 4.
2. Phoenicopsis angustifolia Heer, media Krasser A. Seward. (11). p. 21. Pl. III, figs. 32—36;
3. Phoenicopsis media Krasser. F. Krasser. (20). p. 24.

Among the numerous fragments of leaves of the genus Phoenicopsis Heer on the gray argillites of the Chernovskie mines, besides fragmentary remains of leaves of the species Phoenicopsis angustifolia Heer, one can establish entire bundles,

belonging to the species Phoenicopsis media Krasser. F. Krasser proposed this species name for those leaves from China whose bundle consists of 6 or 7 leaf blades, 6–8 mm wide, and having 11 parallel veins, between which there passes one additional intermediate vein. Prof. A. Seward does not consider it possible to separate such leaves, which in their character occupy an intermediate position between Phoenicopsis angustifolia Heer and Phoenicopsis latior Heer, although they are closer to the first species, as an independent species, on the grounds of our ignorance of the degree of variation in the leaves, and describes them under the name Phoenicopsis angustifolia Heer, media Krasser.

The bundle of leaves shown in Fig. 11 differs in its external appearance from bundles of Phoenicopsis angustifolia Heer. The individual leaves reach 6–8 mm in width, and through them pass up to 11 longitudinal parallel veins, between which here and there one additional intermediate vein is observed. The complete coincidence of the characters of our bundle with F. Krasser’s diagnosis makes it possible to distinguish these impressions under the species term Phoenicopsis media Krasser.

The species Phoenicopsis media Krasser occurs in the Jurassic deposits of China and Chinese Dzungaria. It is possible that some forms described from Franz Josef Land by A. Nathorst under the name Phoenicopsis angustifolia Heer belong to this same species.

Locality: gray argillites of the Chernovskie mines.

The plant remains of the Chernovskie mines of Transbaikalia are represented, in treated form, by the following forms: 1) Equisetites sp., 2) Coniopteris burejensis Zall sp., 3) Coniopteris hymenophylloides (Brgn., 4) Ginkgo digitata Brgn., 5) Ginkgo sibirica Heer, 6) Phoenicopsis angustifolia Heer, 7) Phoenicopsis media Krasser.

The number of species is too small to make it possible to determine precisely the horizon of the Jurassic system to which the strata of the Chernovskie mines belong, but the flora as a whole resembles a typical Middle Jurassic flora. A detailed comparison of the individual Middle Jurassic floras shown in the table of distribution of fossil plants indicates that the closest floras will be the fossil floras of the Fergana region and of the Irkutsk coal basin.

Plate I

Note: dots indicate the background of the plant remains.

Fig. 1.

Fig. 2.

Fig. 3.

Plate 2.

Fig. 4

Fig. 5

Fig. 6

Fig. 7

Fig. 8

Fig. 9.

Fig. 10

Fig. 11

The flora found in the Fergana region near Kizil-Kiya and Kosh-Bulak, with such a limited number of species, seems as though it were homotaxial with the Jurassic flora of the Irkutsk coal basin, whereas in reality they belong even to different divisions of the Jurassic system. It is therefore clear that the resolution of age relationships, with so small a number of species having a broad geological and geographical distribution, cannot take place here until such types have been established in the Jurassic floras by means of which the task of determining the age of the deposits will be considerably facilitated. Unfortunately, however, until the very latest time due attention has not been paid to the establishment of such types.

Explanation of the Figures

1. Equisetites sp.
2. Coniopteris burejensis Zal. sp.
   3–5. Coniopteris hymenophylloides (Brgn).
   6–8. Ginkgo digitata Brgn.
   9–10. Ginkgo sibirica Heer.
3. Phoenicopsis media Kr.

Bibliography

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3. Kristofovich, A. Materials toward the knowledge of the Jurassic flora of the Ussuri region. Proceedings of the Geological and Mineralogical Museum of the Academy of Sciences, Issue 4, Vol. II. 1916.

4. Kristofovich, A. Jurassic plants from the Tyrma River of the Amur region, collected by V. Dokturovsky. Transactions of the Geological and Mineralogical Museum of the Academy of Sciences, Vol. VIII. 1914.

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8. Lesnikova, A. Jurassic plants from the Caucasus. Proceedings of the Geological Committee for 1915.

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