Vol. 236

1976

ON THE STRATIGRAPHY OF DEVONIAN VOLCANOGENIC FORMATIONS OF THE NORTHEASTERN MARGIN OF THE MINUSINSK BASIN

Yu. A. Fomin, V. G. Kryukov

(Presented by Professor, Doctor A. G. Sivov)

Within the Minusinsk Basin, and especially within its mountainous frame, Devonian volcanogenic formations are known to be fairly widespread; they continue to be of definite scientific and practical interest to researchers. Among the most complex, and at the same time important, questions in this connection remain those of subdividing the effusive sequences and correlating them, since the information available in the literature on the stratigraphy of these rocks is, to a considerable extent, fragmentary and contradictory. Some authors [2, 3, 8, 5, 6, 12, 18] confine themselves to a simple statement of the existence, within the Minusinsk Basin, of a Devonian volcanogenic-sedimentary complex of rocks, indicating its position in the section of this system and its approximate composition. The volcanogenic formations of the Minusinsk Basin are subdivided in sufficient detail by G. A. Ivankin [4], A. A. Mossakovsky [11], G. I. Teodorovich and B. Ya. Polonskaya [14], E. A. Shneider and B. P. Zubkus [17], and especially by I. V. Luchitsky [7, 8, 13]. However, among the large number of sections cited by these authors, only some [13, 11, 17] partially characterize the eastern and northeastern margins of the North Minusinsk depression, where effusive formations are especially widespread and are represented with the greatest diversity.

The present article provides data on the stratigraphy of the volcanogenic-sedimentary deposits of the Byskar Series on the northeastern margin of the North Minusinsk depression (the vicinity of Mount Stog). The structure of the Byskar Series in the indicated area can best be clarified by studying sections along Kukuyevsky Creek, the Sobolyem River, and the Skotsky Urman River, directly near Mount Stog and somewhat south of it (the Maltat River).

The most complete section is that along Kukuyevsky Creek, characterizing the upper part of the series and represented by the following rocks (from bottom to top):

1. Dark-gray to black olivine basalt porphyrites with a greenish tint, alternating with thin horizons of coarse-clastic tuffs. Thickness 180–200 m.

2. Several flows of dark-gray plagioclase-pyroxene and plagioclase porphyrites. The flows are separated from one another by slag formations. Thickness 70–80 m.

3. Coarse-clastic (psephitic) lithic-crystaloclastic tuffs of andesite-basalt porphyrites. Thickness 100–110 m.

4. Ash-gray, cherry-colored, recrystallized vitroclastic-

tic tuffs, agglutinates, pisolitic tuffs, characterized by fine bedding. Thin flows of cherry-gray oligophyric felsophyres are observed. The total thickness of these formations reaches 300–350 m.

1. Interbedding of gray and greenish-gray sandstones, tuffaceous sandstones, siltstones, and marls. At the base of the member, which rests unconformably on vitrophyric tuffs, conglomerates are observed with pebbles of the effusive formations described above. The thickness of the entire terrigenous-sedimentary member is 30–50 m.

2. Flows of dark-gray oligophyric basalt porphyrites with coarse spheroidal jointing. Thickness 50–70 m.

3. Gray, with a greenish tint, porous andesite porphyrites. Thickness 70–80 m.

4. Cherry-gray eutaxitic coarse-fragmental tuffs and tuff breccias, alternating with lava breccias of rhyolite porphyries. Thickness 120–130 m.

5. Lilac-gray and cherry-red rhyolite porphyries, apparently forming dome-shaped bodies. Thickness 200–220 m.

6. Heterogeneous coarse-fragmental lithoclastic tuffs. Thickness 50–70 m.

7. Cherry-gray and dark-cherry quartz and quartz-bearing porphyries, felsophyres, and banded felsites. Thickness 250–280 m.

8. Lilac-gray psephitic-psammitic litho-crystalloclastic tuffs of trachyte porphyries. Thickness 150–200 m.

9. Brownish-red fluidal trachyte porphyries forming a series of domes. Thickness 170–200 m.

On the eroded surface of felsites and trachyte porphyries, light-gray and pinkish-gray gravelites and sandstones, assigned to the Ilemor Formation \((D_2^{2}il)\), lie transgressively with a conglomerate horizon at the base.

The section of the volcanogenic series along the Sobolema River and the Skotskii Urman River (approximately 15 km east of the Kukuevsky settlement) characterizes its lower part, which rests with a sharp angular unconformity on formations of the ancient basement represented by Proterozoic crystalline schists and marbles intruded by granitoids of the Lower Paleozoic.

The section is represented by the following rocks (from bottom to top):

1. Conglomerates with pebbles of marbles, crystalline schists, and granitoids of the Olkhovka complex. Thickness 10–20 m.

2. A thick series of flows of dark greenish-gray diabase porphyrites and aphyrites, more rarely basalt porphyrites, separated by slaggy crusts. Thickness 500–600 m.

3. Varicolored tuffaceous sandstones interbedded with cherry-gray tuffs and tuffites. These formations rest on the eroded surface of diabase porphyrites, with isolated lenses of gravelites at the base. Thickness 20–100 m.

4. Gray, dark-gray, or almost black basaltic, plagiobasaltic, and andesitic porphyrites, representing a series of flows. At the base and top of individual flows, lavoclastic formations are observed. The total thickness of the rocks is 600–700 m.

5. Cherry-red recrystallized crystallo-vitroclastic tuffs alternating with flows of lilac-gray quartz-bearing porphyries, reddish-brown dacite porphyries, and orthophyres. Thickness 180–200 m.

6. Greenish-gray conglomerates, tuff-gravelites, and tuffaceous sandstones, lying unconformably on vitroclastic tuffs. Thickness 30–50 m.

7. Greenish-gray andesite porphyrites. Thickness 40–50 m.

Directly in the area of Mt. Stog, the section of the volcanogenic series is represented by the following formations (from bottom to top):

1. Dark-gray, almost black, with a greenish tint, oligo-phyric basalt porphyrites. Thickness up to 100 m.

2. Gray and dark-gray andesite-basalt and plagiobasalt porphyrites, forming several sheet-like bodies. Amygdaloidal varieties of the rocks are found in the upper parts of the bodies. Thickness 120–150 m.

3. Predominantly vitroclastic tuffs with a small admixture of crystal clasts, alternating with thin flows of finely fluidal feldspar, trachydacite, and quartz-bearing porphyries. The coloration of both the effusive and pyroclastic varieties of the rocks is characterized by the presence of cherry, reddish-brown, or lilac tones. Thickness 140–160 m.

4. Interbedding of gray and greenish-gray tuff-gravelites, tuff-sandstones, and siltstones, lying unconformably, with conglomerates at the base, on an eroded surface of vitroclastic tuffs. The pebbles of the conglomerates include practically all varieties of the underlying rocks. Approximately the middle part of the section of this member includes several flows, or perhaps sills, of andesite-basalt porphyrites with a total thickness of 50–70 m. The thickness of the described formations is 200 m.

5. Cherry-gray vitroclastic (ash) tuffs with an admixture of litho- and crystal clasts. Thickness 60–70 m.

6. Greenish-gray andesite porphyrites containing small bombs of rocks of basic composition. Thickness 50–80 m.

7. Dark-cherry psephitic lithoclastic heterogeneous tuffs. Thickness 40–50 m.

8. Dark-cherry clastolavas of rhyolite porphyries. From bottom to top, the amount of lithoclasts decreases. Thickness 30–40 m.

9. Gray, reddish-gray, and brownish-red rhyolite porphyries forming dome-shaped bodies. Thickness 150–170 m.

10. Finely fluidal lavas and lava breccias of felsites, often having a spherulitic structure. Thickness 80–100 m.

11. Coarse-block lava conglomerates of basalt porphyrites, lying unconformably on the uneven surface of rhyolite porphyries and other underlying effusives. Thickness 20–30 m.

12. Black olivine-bearing basalt porphyrites. They form flows that lie almost horizontally on elevated areas. At their base they contain lava conglomerates. Thickness 60–80 m.

Northwest of Mt. Stog, the volcanogenic deposits of the Byskar series are unconformably overlain by gray limestones of the Bey suite \((D^2_2bs)\).

The section considered is similar to the section of effusives traced in the area of the Maltat River (10 km south of Mt. Stog), where the following rock varieties are recorded (from bottom to top):

1. Dark greenish-gray basalt porphyrites, forming numerous flows with a total thickness of more than 200 m.

2. Psephitic lithoclastic tuffs of andesite porphyrites. Thickness 100–110 m.

3. Psammitic crystal-lithoclastic tuffs of andesite porphyrites. Thickness 200–250 m.

4. Gray to dark-gray andesite porphyrites (several flows). Thickness 130 m.

5. Gray, with a cherry tint, vitroclastic (ash) tuffs with lapilli. Thickness 90 m.

6. Gray and dark-gray gravelites, sandstones, tuff-sandstones, silt-

rhyolites, alternating with one another and containing separate horizons of vitroclastic (ash) tuffs. These deposits lie unconformably on ash tuffs and other rocks described earlier. Thickness 200–210 m.

1. Lilac or dark-cherry psephitic lithoclastic tuffs of rhyolite porphyries. Thickness 80 m.

2. Reddish-gray rhyolite porphyries. Thickness on the order of 300 m.

3. Black basalt porphyrites with olivine, forming sheet-like bodies lying very gently on the eroded surface of rhyolite porphyries and other formations of the Byskar Series. At the base, lava and tuff conglomerates are observed. Thickness of the basalt porphyrites 30–40 m.

Comparison of this group of sections (Fig. 1) makes it possible to establish certain features of the structure of the volcanogenic series in the area studied.

Fig. 1. Correlation diagram of sections of volcanogenic formations of the Byskar Series of the northeastern margin of the Minusinsk Basin:
1 — limestones; 2 — marls; 3 — siltstones; 4 — sandstones, tuffaceous sandstones; 5 — gravelites, tuff-gravelites; 6 — conglomerates; 7 — tuffites; 8 — basalt porphyrites, plagiobasalts, andesite-basalts; 9 — lava conglomerates of basalt porphyrites; 10 — orthophyres, trachyte porphyries; 11 — litho-crystalloclastic tuffs of trachyte porphyries; 12 — quartz porphyries, felsophyres, felsites, cryptofelsophyres; 13 — lithoclastic tuffs of quartz and quartz-bearing porphyries; 14 — rhyolite porphyries; 15 — clastolavas of rhyolite porphyries; 16 — predominantly vitroclastic (ash) tuffs; 17 — andesite porphyrites; 18 — psammitic crystalloclastic tuffs of andesite porphyrites; 19 — psephitic lithoclastic tuffs of andesite porphyrites; 20 — trachyandesite porphyries; 21 — tuff breccias, conglomerate-like tuffs of basic composition; 22 — diabase porphyrites; 23 — granitoids; 24 — crystalline schists and marbles.

in the region and, above all, to subdivide it into three independent formations (from bottom to top): trachyandesite, trachyliparite, and basalt, characteristic of orogenic, mainly geoanticlinal mobile zones [6]. Such a subdivision was carried out not only by petrographic study of sections, but also, first and foremost, on the basis of a whole series of general geological observations that make it possible to draw conclusions about the conditions of occurrence of the effusive formations of each formation, as well as about the character of volcanism inherent in it. The most important criterion for distinguishing formations is the manifestation in this territory of two rather major interruptions in Devonian volcanic activity. Although the composition of the formations is reflected in their names, it is nevertheless distinguished, as a rule, by an abundance of petrographic varieties of rocks entering into them, which served as the basis for distinguishing effusive members within the formations. Individual members are characterized by the presence of proper effusive and pyroclastic rocks of a definite composition and are often separated from one another by weakly expressed breaks of local significance.

The trachyandesite formation, having basal conglomerates at its base, rests with a sharp angular unconformity on the dislocated formations of the basement and includes the following effusive members (from bottom to top):

1. A member of diabase porphyrites and aphyrites with subordinate development of basalt porphyrites. Thickness 500–600 m.

2. A member of basalt, plagiobasalt, andesitobasalt, and andesite porphyrites, alternating with horizons—sometimes of considerable thickness—of conglomerate-like tuffs, tuff breccias, and psephite-psammite tuffs of analogous composition. The variegated tuffaceous-sedimentary formations observed at the base testify to a temporary interruption of volcanic activity, apparently of local character. The total thickness of the deposits described reaches 700–800 m.

3. A member of essentially ash accumulations, represented by vitroclastic tuffs with an insignificant admixture of litho- and crystalloclasts, alternating with thin proper effusive bodies of felsophyres, quartz-bearing porphyries, trachydacite porphyries, more rarely orthophyres. The thickness of these formations varies from 90 to 300–350 m.

On the whole, the two lower members, which represent eruptions of basic composition, are characterized by great thicknesses of bodies and their persistence over considerable areas, as well as by a subordinate amount of pyroclastic material in the products of volcanism. Subvolcanic facies are represented exclusively by dikes, which, like the flows, have a northwestern strike. In some cases it is possible to observe a direct transition of dikes into sheet-like bodies.

The essentially acid effusive-pyroclastic formations of the third member are characterized by a more local manifestation, with a sharp increase in thickness near established or inferred ancient eruption centers.

The deposits of the trachyandesite formation are to a considerable degree dislocated, with the formation of fairly tense folded structures of complex type, with steep angles of dip of the limbs.

The trachyliparite formation. Its deposits everywhere rest with angular unconformity on the eroded rocks of the trachyandesite formation, having at the base a terrigenous-sedimentary member with an admixture of tuffaceous material, with a thickness from 30–50 to 260–270 m. It is not without interest to note the presence within the member of individual horizons of vitroclastic (ash) tuffs. In addition to essentially terrigenous-sediment-

deposits, the trachyliparite formation includes the following effusive members (from bottom to top):

1. A member of rhyolite porphyries. The latter are interbedded in their lower part with tuff lavas and clastolavas of analogous composition. Everywhere at the base of the member there is a persistent horizon of psephitic lithoclastic tuffs. In places these tuffs are underlain by andesite and basalt porphyrites. The thickness of the member is variable—from the first hundred meters to 220–260 m.

2. A member of acidic effusives, represented by quartz and quartz-bearing porphyries, felsophyres, and banded felsites. In the area of Mt. Kuzhuyevsky, where they are most widely developed, at the base of the member of effusive bodies proper there lies a thin horizon of heterogeneous conglomerate-like tuffs. The thickness of the acidic effusives varies widely, increasing locally to 300–350 m or decreasing to 80–100 m, and even pinching out completely.

3. A member of subalkaline effusives. At the base there are litho-crystalloclastic tuffs of trachyte porphyries, replaced upward in the section by their effusive analogues proper. The thickness of these formations reaches 300–400 m.

As a whole, the trachyliparite formation is characterized by a relatively local occurrence, dome-like forms of rapidly pinching-out bodies of effusives proper, an abundance of pyroclastic material in the eruption products, and comparatively small thicknesses. However, near eruption centers the thicknesses of the formation’s deposits increase sharply. Such areas are striking in the abundance and variety of subvolcanic facies, represented by necks, sills, laccoliths, and dikes of acidic and subalkaline rocks.

In terms of their mode of occurrence, the deposits of the trachyliparite formation differ sharply from the formations below. They are characterized by weak dislocation, with the formation of indistinctly expressed brachyform structures with gentle dip angles of the limbs.

The basalt formation in this area is only slightly widespread, cropping out on elevated sites characterized by a weak erosional cut. It lies almost horizontally on the eroded surface of rocks of both lower formations, usually having at its base horizons of lava conglomerates and tuffs 20–30 m thick. It is represented by sheet bodies of basalt porphyrites with a total thickness of up to 100 m. The subvolcanic facies are represented mainly by dikes and sills. In areas subjected to significant erosion, only subvolcanic facies of this formation are manifested, sometimes very abundantly. This gives grounds for assuming a wider distribution of the sheets of the basalt formation directly in the depressions of the Minusinsk Basin.

The age of the volcanic formations of this area can be determined on the basis of comparison of the sections given above with previously known, paleontologically characterized sections of effusive-sedimentary deposits of the Minusinsk Basin and, chiefly, of the North Minusinsk Depression (Fig. 2).

It should be noted at once that among researchers there is still no consensus regarding the time of the beginning and end of Devonian volcanic activity in the Minusinsk Basin. Concerning the lower age boundary of the Byskar Series, actually determined by its transgressive overlap onto the Lower Paleozoic basement formations, there are several opinions. Ya. S. Edelshtein [19] assigned the first manifestations of volcanism in the Minusinsk Basin tentatively to the Upper Silurian. Most researchers [12, 15, 5, 8, 17, 11, 3] consider them Lower Devonian. N. G. Chochia et al. [16] specifically date the lower

the upper boundary of the series as the Koblenzian. V. S. Meleshchenko [9] assigns the beginning of volcanism in the North Minusinsk Depression to Eifelian time. As for the upper age boundary of the volcanogenic series, determined by the replacement of volcanogenic–sedimentary formations by terrigenous–sedimentary ones, some authors [12, 3, 5] assign it to the Eifelian stage, whereas others [9, 16] believe that volcanism continued into Givetian time as well.

Comparison of the various sections of the volcanogenic series of the Minusinsk basin is possible because, in this region, among the effusive rocks there are substantially terrigenous–sedimentary deposits containing psilophyte flora of the Lower Devonian [1] and indicating an interruption in volcanic activity at that time. Such an interruption is reflected in the constructions of all authors. In particular, in the scheme of A. G. Sivov [12], this interruption is expressed by the Imek and Tolochkov formations of the Tashtyp Formation. In the vicinity of the town of Stog, the Tashtyp Formation corresponds to a tuffogenic–sedimentary member lying at the base of the trachyliparite formation. Corresponding to A. G. Sivov’s [12] Kharadzhul Formation \((D_2^1)\) are the deposits of the trachyandesite formation, and to the Pechinov Formation \((D_2^1)\)—the effusive members of the trachyliparite and basalt formations. With respect to the latter, we note that its analogues apparently include the olivine–augite porphyries described by G. A. Ivankina [4], lying on the Shunet Formation in the vicinity of Lake Itkul, as well as basalts in the region of Lakes Shunet and Matarak and near Shira Station in the upper parts of the sections of I. V. Luchitskii [8].

On the effusive formations, unconformably after a break which, as shown by the works of Ya. S. Edelshtein [18], A. G. Sivov [12], and A. A. Mossakovskii [10], has regional significance for the entire Minusinsk basin, lie faunistically characterized terrigenous–sedimentary deposits of the Chemorov and Bey formations of the Bey Formation of the Givetian stage [12]. N. G. Chochia et al. [16] also note, for the marginal parts of the Minusinsk basin, the overlap of the Byskar Series by the Askiz Formation, belonging to the very lowermost Givetian. On the basis of all the foregoing, the age of the effusive formations of this region should be regarded as pre-Givetian, but apparently not older than Gedinnian.

Conclusions

1. The sections of effusive–sedimentary deposits of the Byskar Series presented in the article, located at considerable distances from one another, are highly specific, are marked by a diversity of rock composition, and testify to their facies variability. Nevertheless, these sections are comparable with one another, which is the basis for compiling a composite section of the series in this region.

2. The volcanogenic formations of the series in the vicinity of the town of Bolshoi Stog are confidently subdivided into three independent formations—the trachyandesite, trachyliparite, and basalt formations—which differ from one another in petrographic composition, character of occurrence, and conditions of formation.

3. The age of the distinguished formations is determined on the basis of correlation of their sections with previously known, paleontologically characterized sections of effusive–sedimentary deposits of the Minusinsk basin within the Gedinnian–Eifelian stages.

LITERATURE

1. A. R. Anan’ev. The Most Important Localities of Devonian Floras in the Sayano-Altai Mountain Region. Publishing House of TSU, Tomsk, 1959.

2. A. I. Anatol’eva. Stratigraphy and certain questions of the paleogeography of the De...

zone of the Minusinsk intermontane trough. Transactions of the Institute of Geology and Geophysics, Siberian Branch, Academy of Sciences of the USSR, issue 2, 1960.

1. A. I. Anatol’eva. On the stratigraphic position of Devonian volcanogenic rocks of the Sayan–Altai folded region. In: Problems of Paleovolcanology, Transactions of the Laboratory of Paleovolcanology, issue 1, Alma-Ata, 1963.

2. G. A. Ivankin. Stratigraphy of the Devonian of the western margin of the Minusinsk basin. Transactions of Tomsk State University, vol. 146, Geological Series, Tomsk, 1960.

3. Ya. G. Kats, B. N. Krasil’nikov et al. Stratigraphy of the Paleozoic deposits of the Minusinsk basin and its mountainous framing. Transactions of VAGT, issue 4, 1958.

4. Yu. A. Kuznetsov. Principal Types of Magmatic Formations. Nedra, 1964.

5. I. V. Luchitskii. On the Devonian volcanogenic red-bed series of the Minusinsk intermontane trough. Reports of the Academy of Sciences of the USSR, 116, no. 2, 1957.

6. I. V. Luchitskii. Volcanism and Tectonics of the Devonian Depressions of the Minusinsk Intermontane Trough. Publishing House of the Academy of Sciences of the USSR, 1960.

7. V. S. Meleshko. On some questions of the stratigraphy of the Devonian deposits of the Minusinsk basin. Collection “Paleontology and Stratigraphy.” Gosgeoltekhizdat, 1953.

8. A. A. Mossakovskii. On the pre-Givetian break and angular unconformity in the Devonian of the Minusinsk depressions. Reports of the Academy of Sciences of the USSR, vol. 132, no. 6, 1960.

9. A. A. Mossakovskii. Tectonic Development of the Minusinsk Depressions and Their Mountainous Framing in the Precambrian and Paleozoic. Gosgeoltekhizdat, 1963.

10. A. G. Sivov. Elements of the stratigraphy and tectonics of the Devonian deposits of the Minusinsk basin. Transactions of Tomsk State University, vol. 132, Geological Series, Tomsk, 1954.

11. Comparative Paleovolcanology of the Middle and Upper Paleozoic of Southern Siberia and Eastern Kazakhstan. Siberian Branch, Academy of Sciences of the USSR, Nauka, 1966.

12. G. I. Teodorovich, B. Ya. Plotnikova. Stratigraphy, petrography, and facies of the Devonian of the Minusinsk and Nazarovo depressions. Academy of Sciences of the USSR, 1958.

13. G. I. Teodorovich. Stratigraphy and correlation of Devonian sections of the Minusinsk and Nazarovo depressions. Transactions of the Institute of Petroleum, Academy of Sciences of the USSR, vol. 9, 1958.

14. N. G. Chochia, E. E. Belyakova et al. Geological structure of the Minusinsk intermontane depressions and prospects for their oil and gas potential. Transactions of the All-Union Scientific Research Petroleum Geological Exploration Institute, issue 120, 1958.

15. E. A. Shneider, B. P. Zubkus. Stratigraphy of the Lower and Middle Devonian deposits of the North Minusinsk and Sydo-Erbinsk depressions. Materials on the Geology of Krasnoyarsk Krai, issue 3, 1962.

16. Ya. S. Edelshtein. Geological sketch of the Minusinsk basin and the adjacent parts of the Kuznetsk Alatau and Eastern Sayan. Essays on the Geology of Siberia, Publishing House of the Academy of Sciences of the USSR, 1932.

17. Ya. S. Edelshtein. A Brief Geological Description of the Part of the Khakass Autonomous Oblast Situated on the Left Side of the Yenisei to the West and Northwest of the Village of Bateny. ONTI, NKTP, 1936.