KARAKAN DEPOSIT IN KUZBASS—A NEW BASE FOR OPEN-PIT COAL MINING

A. A. KURBATOVA, K. D. ZHDANOVA, V. E. EVTUSHENKO,
A. G. NOSKOVA

(Presented by Professor A. G. Sivov)

On the left bank of the Inya River, in the area of the village of Karakan, in 1964–1965 the Kuzbass Geological Expedition of the trust “Kuzbassuglegeologiya” established the development of a previously unknown brachysynclinal fold composed of highly productive deposits of the Yerunakovskaya suite ($P_2$). This brachyfold ($7 \times 20$ km) and the deposit of steam coals associated with it were named Karakan.

In the central part of the deposit, Jurassic deposits have been exposed; at their base, along the II Karakan exploration line, in the NE limb of the syncline, a member of variegated rocks and ancient burnt rocks was established, formed during the pre-Jurassic burning of seam Karakansky 2.

The maximum exposed thickness of the Jurassic deposits is 180 m: poorly sorted sandstones, siltstones, argillites, and intricately structured seams and lenses of brown coal. In contrast to the underlying Paleozoic rocks, the color of the Jurassic deposits, as a rule, has a greenish tint, and the rocks are distinguished by weaker cementation of the terrigenous material.

The polymictic sandstones of the Jurassic sequence are characterized by a considerable content of quartz–siliceous fragments (up to 26%), fragments of effusive rocks (12–14%), many of which are chloritized, as well as fragments of micaceous and quartz–micaceous composition (up to 20%); their cement is chlorite–clayey.

The variegated rocks, representing a pre-Jurassic kaolin-type weathering crust, have been preserved as a small lens at the foot of the burnt rocks. Macroscopically, the weathering crust is manifested in the bleaching of the rocks and the appearance of variegated shades due to the strong enrichment of individual areas with ferrous and ferric iron.

The weathering crust has a zonal distribution, which is manifested in a decrease from bottom to top in the role of hydromica and in an increase in the content of montmorillonite in the middle part, and of kaolinite in the upper part. Such zonality, enrichment with iron oxides, and also the presence of nontronite (a mineral formed during the weathering of rocks rich in iron and magnesium) indicate its formation in situ.

The productive deposits of the Yerunakovskaya suite at the Karakan deposit (thickness 1583 m) are briefly characterized below in Table 1.

The petrographic composition of the deposit was studied from sandstone samples, which is shown graphically in Fig. 1.

Table 1

In the section of productive deposits, polymictic sandstones predominate substantially; they are chiefly fine-grained, more rarely medium- and coarse-grained, gray and light-gray in color. Study of the petrographic composition of these sandstones makes it possible to distinguish clearly several horizons, differing from one another in the characteristic composition of their components; the latter may serve as correlation horizons. From bottom to top in the section three horizons are distinguished: the sandstones of the first (from seam 9 to seam 7) are strongly enriched in fragments of organogenic limestone (up to 22%). By this feature they are correlated rather confidently with sandstones occurring in the interval between the Tonkii and Neslozhnyi seams of the southern closure of the Leninskaya syncline of the deposit of the same name.

The sandstones of the second horizon (from seam 4 to seam 2) are characterized by a very high (up to 45%) content of water-clear grains of plagioclase—oligoclase-andesine with a distinct zonal structure and without products of alteration, a very low content of quartz (8–10%), and fragments of sedimentary rocks (up to 20%).

The sandstones of the third horizon (from seam 1 to the Karakansky 2 seam) are distinguished by a very high content of quartz (30–38%) and fragments of siliceous rocks (30–50%).

Stratigraphically, the Erunakovskaya Formation is subdivided into three subformations (from bottom to top): Leninskaya, Gramoteinskaya, and Tailuganskaya. The boundaries between the subformations, according to the character of coal-bearingness at the deposit, are drawn along the floor of coal seams: along seam 27, the boundary of the Leninskaya subformation with the underlying Ilyinskaya Formation; along seam 17, between the Leninskaya and Gramoteinskaya subformations; and along seams 8–8³, between the Gramoteinskaya and Tailuganskaya subformations.

Spore-pollen analysis of the productive sequence somewhat refines the boundaries between the subformations.

The Tailuganskaya aspect of spores and pollen in the Kuznetsk Basin is typically Upper Permian [1]; it is dominated by fern-like plants of the group Triletes Reinsch, among which a complete absence of rimmed forms (Zonotriletes) and a predominance of non-rimmed forms (Azonotriletes) are noted. Among gymnosperms, pollen of cordaites (Zonaletes) is very widely represented in it; there are fewer ginkgo-like forms (Azonaletes) and still fewer bisaccate conifer pollen (Platysaccus), among which ribbed forms occur rather rarely.

For the Karakan deposit (II exploration line), a spore-pollen complex of this aspect is characteristic from the Verkhnii and Novyi seams to seam 9 inclusive (Fig. 1).

Finely tuberculate fern-like forms—Azonotriletes acutus f. microdentata Andr., A. adspersus Andr., A. globulus Andr., and others—make up as much as 45% of the total number of counted forms in the complex. Coarsely spiny forms are obligatorily present (about 10%): these are Azonotriletes papillarius Andr., A. exacutus, A. armipotens, A. abruptus Andr., and others. Among pollen, ginkgo-like forms (20%) of the type Azonaletes involutus Andr., A. caperatus var. Labrosus Andr.; cordaites (14.8%)—Zonaletes rotatus Lub., Zonaletes rugulifer Lub., Z. papiriformis Andr.; and a small amount of conifers (5%) of the type Platysaccus pumilus Dr. are obligatory.

The above-described spore-pollen complex is very close to that of the upper part of the section (from seam 1 to 8) of the Uropsky deposit [1].

The middle part of the section of the Karakan deposit includes coal-bearing seams from 10 to 17; in this part of the section, spiny-tuberculate forms of ferns sharply predominate—40%, including many coarsely spiny forms: Azonotriletes singulus Dr., A. horridus Dr., A. monstruosus Dr., A. armipotens, A. acinaciformis, and others; tuberculate forms: A. acutus Andr., etc. There is much cordaite pollen here—48%; ginkgo-

Petrographic composition of the terrigenous part of the sandstones of the Karakan deposit

Age

Seam names

Lithological column
M 1:5000

Sample number

Clastic grains

• Quartz — 10%, 30%
• Feldspars — 10%, 30%

Rock fragments

• Quartz and cherty rocks — 10%, 30%, 50%
• Clayey rocks — 10%, 30%
• Effusive rocks — 10%
• Siliceous rocks — 10%
• Carbonates — 10%, 20%

Spores and pollen

• Mesozoic spores — 20%, 40%
• Herbaceous spores — 20%, 40%
• Cordaites — 20%
• Angaropteridium
• Glossopteris
• Monosaccate zonate-bisaccate spores

Spore-pollen diagram

Jurassic

P₂

Permian

Verkhnyaya Podsevita
Tayluganskaya Podsevita
Gramoteinskaya Podsevita
Leninskaya Podsevita

Seams shown in the column:

• Karakansky 2
• Karakansky 1
• Upper
• 2
• 3
• 4
• 5
• 6
• 7
• 7a
• 7b
• 8–8a
• 8b
• 9
• 9a
• 10
• 11
• 12
• 13
• 14
• 15
• 15a
• 16
• 17
• 18
• 19
• 20
• 21
• 22
• 23
• 24
• 25
• 26
• 27

Visible sample numbers:

53, 54, 56, 1165, 1176, 1181, 1290, 1295, 1304, 1307, 1311, 1314, 1041, 1042, 1046, 1050, 1057, 1061, 1070, 1075, 1077, 79, 82, 86, 92, 94, 95, 96, 327, 339, 343, 560.

Legend:

Fig. 1. Petrographic composition of the terrigenous part of the sandstones of the Karakan deposit.

Legend:

• Coal seams
• Sandstones
• Argillites
• Siltstones
• Coarse sandstones
• Weathering crust

various—10%, conifers—2%. The complex presented characterizes the Gramoteino aspect of spores and pollen; consequently, the interval of the section from seam 9 through seam 17 should be assigned to the Gramoteino subformation.

The lower part of the section (from seam 17 and below) is represented by a fairly large number of spiny-tuberculate forms (30.1%), among which there are many finely tuberculate forms (up to 20%) of the type Azonotriletes acutus f. microtuberculata Andr.; many sharp-spined forms; a rather large amount of cordaite pollen (40%); and a considerable quantitative decrease in ginkgo-like pollen (4.5%) and conifer pollen (1.2%). This aspect of spores and pollen characterizes the Lenino subformation.

The faunal characterization of the section is based on the uneven distribution of the fauna of pelecypods and phyllopods, the study of which also makes it possible to outline the boundaries between subformations. In the very uppermost part of the section little fauna is noted; it has a Taylugan aspect: anthraconauts are almost entirely absent (if present, they are of small size), conchostracans predominate, and abiels are rare. These pelecypods, in combination with phyllopods (borehole 2098, seam Karakanskii 5 through seam 8?), correspond to the abiel-phyllopod horizon of Yu. S. Papin and to seams 82–84 of the coastal section of the Erunakovskaya suite.

Two faunal horizons with somewhat different characteristics are typical of the Gramoteino subformation, separated by the interval of seams 8^б–10. Isolated imprints of tersiellas occur in the Lenino subformation together with typical microdontellas of the “subovata” group of normal size; upward in the section the number of tersiellas increases, the size of the microdontellas decreases, and already in the second half of the Gramoteino subformation (upper faunal horizon) the microdontellas are almost completely replaced by tersiellas. Above the Gramoteino subformation, tersiellas do not occur. On the basis of the pelecypod fauna, the boundary between the Lenino and Gramoteino subformations is drawn at seam 15–16. The fauna in the interval of seams 16–20 characterizes the Lenino subformation: a flourishing fauna of anthraconauts and microdontellas, with subordinate importance of pelecypods of other genera.

Thus, according to paleontological data, the productive sequence of the Karakan deposit in Kuzbass is clearly divided into three parts corresponding to the principal regional subdivisions: the upper Taylugan ($P_2^{tl}$), from the Karakan seams to seam 8–9; the middle Gramoteino ($P_2^{gr}$), from seams 8–9 to seams 16–17; and the lower Lenino ($P_2^{ln}$), from seam 16–17 to 27.

Conclusions

1. The upper part of the productive sequence at the Karakan deposit contains burned rocks and small lenses of Dogger weathering crust formed in situ.

2. Against the general background of the polymictic composition of the clastic rocks, horizons with a petrographic composition of sandstones characteristic of them stand out clearly; such horizons may serve for correlation.

3. According to paleontological data, the section of the Karakan deposit is divided into three parts corresponding to the principal regional subdivisions: the Taylugan subformation from Karakanskii 2 to seams 8–9, the Gramoteino subformation—to seams 16–17, and the Lenino subformation—from seams 16–17 and below.

REFERENCES

1. O. A. Betekhtina, K. D. Zhdanova, A. A. Kurbatova, A. F. Sedakova. Lithologic-paleontological characteristics of the section of the Urop deposit of Kuzbass. Academy of Sciences of the USSR, Siberian Branch, issue 2, 1962.

2. L. L. Dryagina. Permian spore-pollen complexes. Biostratigraphy of the Paleozoic of the Sayan-Altai Region, vol. III, issue 21, Proceedings of SNIIGGiMS, 1962.