Main Regional Stratigraphic Units of the Devonian in the Kolyvan-Tomsk Zone
Abstract Generated abstract
The paper reviews and revises the regional stratigraphic subdivision of Devonian deposits in the Kolyvan-Tomsk folded zone, comparing earlier schemes based on lithology, fossil evidence, and local sections. It argues that several previously correlated units differ in age and distribution, and proposes a working scheme that distinguishes regionally distributed suites, more restricted subsuites, and local members across the Lower, Middle, and Upper Devonian. The contribution emphasizes that lithological boundaries in this Middle Paleozoic region do not necessarily coincide with international biostratigraphic stage boundaries, reflecting uneven block development, and notes that hydrogeochemical characteristics may aid mapping in covered areas.
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PROCEEDINGS
OF THE TOMSK ORDER OF THE OCTOBER REVOLUTION
AND ORDER OF THE RED BANNER OF LABOR
POLYTECHNIC INSTITUTE named after S. M. KIROV
Vol. 288
1976
MAJOR REGIONAL-STRATIGRAPHIC UNITS OF THE DEVONIAN OF THE KOLYVAN–TOMSK FOLDED ZONE
P. N. PARSHIN
(Presented by the scientific seminar of the Department of Hydrogeology
and Engineering Geology and the Problem Geological Laboratory)
The first, most substantiated regional-stratigraphic scheme of the Devonian of the Kolyvan–Tomsk folded zone should be considered the scheme of B. F. Speranskii (1924) for the central (Prigorlovo) part of this region. He distinguished the Tufogenovaya (Lower–Middle Devonian in age) and Inskaya (Middle–Upper Devonian in age) formations. Later (1934), A. I. Gusev, on the basis of lithological composition, subdivided the Inskaya Formation into three parts under the names (from bottom to top): the iniocendroid, spiritos, and slate beds. But subsequent studies by T. F. Vasyutinskaya and V. A. Kutolin showed that the slate beds contain fauna permitting their correlation with the Frasnian stage, while in the iniocendroid and spiritos beds fauna and flora were found that allow the enclosing rocks to be assigned to the Famennian and Etrœungtian (Kutolin, 1959).
For the Pachinsko–Yurginskoe Pritom’e, the first most substantiated stratigraphic scheme was developed by A. V. Tyzhnov (1931). He distinguished the following units: the Mitrofanovskaya unit (Givetian–Frasnian in age), the Pachinskaya (Frasnian) and Yurginskaya (Famennian). This scheme is extended by many geologists to the entire Kolyvan–Tomsk folded zone. However, even for the Pritom’e part of the region, other views appeared on the regional-stratigraphic scheme of the Devonian (Fomichev, 1940; Lupov, 1958). The latter were based on the study not of the bank sections of the Tom’ River, on which the scheme of A. V. Tyzhnov was created, but of other areas, where formations similar in composition but of different ages are exposed (Parshin, 1969).
By many researchers the Mitrofanovskaya unit, distinguished by A. V. Tyzhnov, is correlated with Givetian formations developed farther south, within the Bugotak horst-anticline, and assigned by A. L. Matveevskaya to the Bugotak suite (Matveevskaya, Ivanova, 1960, and others). At the same time, all Devonian formations below the Frasnian stage, and sometimes also volcanogenic-sedimentary packages of sediments of younger Devonian age, are usually included in the Bugotak suite (or its analogues) (geological surveys of A. A. Gorshkov, 1965, N. V. Grigor’ev 1964, 1968, and others). Only for certain such packages has a more precise stratigraphic position now been proven. These are the andesite porphyrites and their tuffs of the Gorlovo trough, the Upper Devonian age of which is shown in the work of T. F. Vasyutinskaya (1968), the Mitrofanovskaya (Pachinskaya suite of the Middle–Upper Devonian) and Baranovskaya (Yur-
Stratigraphic scheme of the Devonian of the Kolyvan–Tomsk folded zone
(compiled by P. N. Naryin on the basis of materials by the geological-survey parties of the Academy of Sciences of the USSR, SNIGGIMS, NTGU, ZSGU, and TPI)
Table 1
| Division | Stage | Suite | Subsuite | Thickness, m | Members and characteristic features of rocks | Thickness, m | Composition |
|---|---|---|---|---|---|---|---|
| Upper | Famennian | Southern | upper | up to 100 m | Kulakovskaya | up to 400 m | Gray sandstones, phyllitized shales with phosphate concretions. |
| Upper | Famennian | Southern | lower | up to 400 m | Baranovskaya | up to 100 m | Arkose–gravelly, greenish-gray sandstones with interbeds of clayey shales. Diabase porphyrites, tuffs, tuffaceous rocks, shales. |
| Upper | Frasnian | Pamir | upper | 600 m | — | — | Interbedding of gray and greenish-gray psammitic and arkosic sandstones and siltstones, and bluish-gray clayey shales. |
| Upper | Frasnian | Pamir | middle | 500 m | Mitrofanovskaya | — | Dark-gray, light-gray, greenish-gray clayey shales with interbeds of sandstones and limestones. |
| Upper | Frasnian | Pamir | middle | 500 m | Yashkinskaya and Iskitimskaya | 400–500 m | Conglomerates, tuff-sandstones, limestones, calcareous shales, diabase porphyrites. |
| Upper | Frasnian | Pamir | lower | up to 400 m | — | — | Gray, greenish-gray clayey shales with calcareous and phosphatic concretions. |
| Middle | Givetian | Bugotak | upper | 800 | Toguchinskaya | 70 | Felsite porphyries, albitophyres, and their tuffs; sandstones. |
| Middle | Givetian | Bugotak | middle | 800 | — | — | Albitophyres, tuff-siltstones, and tuff-sandstones. |
| Middle | Givetian | Bugotak | lower | 800 | — | — | Tuff-sandstones. |
| Middle | Eifelian | Bugotak | middle | 800 | Talmenka | — | Diabase and amygdaloidal porphyrites and their tuffs. |
| Lower | Emsian | — | lower | 800 | — | — | Conglomerates, sandstones, psammitic shales, albitophyres and their tuffs, metamorphic shales. |
Fig. 1. Geological section at the southwestern outskirts of the village of Mitrofanovo (right bank of the Tom River).
1 — shales; 2 — sandstones, siltstones; 3 — conglomerates; 4 — tuffs; 5 — albitophyres; 6 — diabases; 7 — quartzites; 8 — fossil locality; 9 — faults; 10 — erosion surface.
of the Pachin suite of Famennian–Etrenovian (?) age, and of the Mitrofanovo horst-anticline (Parshin, Kraevskaya, 1969; Parshin, 1969). The fact that the Mitrofanovo member near the village of Mitrofanovo lies at the base of the Pachin suite (Fig. 1) should be regarded merely as a special case. It seems to us that, at the present stage of investigation of the semi-covered structures of the Kolyvan–Tomsk folded zone, the regional stratigraphic scheme presented in Table 1 may be adopted as a basis.
Under the conditions of the region, for the Middle Paleozoic, which is characterized by the instability of individual lithological units both vertically and laterally, we consider it most expedient to distinguish suites having regional distribution; subsuites, as a rule developed in one or several adjacent structural-facies zones; and members, developed more locally, within one or several adjacent sections of a single structural-facies zone. At the initial stages of investigation it is advisable to distinguish, within suites, members with their own names, characterized by specific lithological and geochemical properties and (or) organic remains, which in many cases may serve as markers for further stratigraphic subdivision and correlation. The boundaries of the regional stratigraphic units of the Middle Paleozoic of the Kolyvan–Tomsk folded zone do not strictly coincide with the biostratigraphic boundaries of the International Stratigraphic Scale, and in different structural-formational zones these boundaries correspond to different levels of biostratigraphic subdivisions. This is apparently a natural reflection of the uneven block-type development of the region in the Middle Paleozoic.
Within the closed areas of the region, in mapping individual lithostratigraphic units, considerable assistance may be provided by the features of the dynamics and chemical composition of groundwaters, identified in exposed and well-studied areas (Parshin, 1971; Udodov, Parshin, Levashov et al., 1971).
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