On Epiphytons from the Anastasyino and Ungut Formations of the Late Precambrian (?)–Lower Cambrian in the Northwestern Part of the Eastern Sayan

S. S. Gudymovich

(Presented by Prof. Dr. K. V. Radugin)

A group of staff members of the Department of General Geology of the Tomsk Polytechnic Institute, under the direction of Prof. K. V. Radugin, has in recent years collected and studied abundant material on the paleontology of ancient strata in the Mana district of the northwestern part of the Eastern Sayan; this makes it possible to refine the stratigraphy of the Upper Precambrian and Cambrian deposits of this area and to expand the paleontological characterization of the stratigraphic subdivisions distinguished.

The author has studied calcareous algae, chiefly epiphytons, from the Anastasyino and Ungut formations.

The upper part of the Anastasyino Formation and the entire Ungut Formation constitute, as a whole, a complexly built, essentially carbonate sequence up to 2000 m thick, characterized by frequent alternation, both in section and along strike, of packages of dolomites and limestones—predominantly bedded, dark-colored in the Anastasyino Formation and massive, light-colored in the Ungut Formation.

In the limestones, chiefly massive ones, of both formations, there occur remains of calcareous algae of the genera Epiphyton, often filling the rock, Proaulopora, Renalcis, Chabacovia, Botominella, Girvanella, previously known not lower than the Cambrian*); on this basis the age of the part of the formation section below the limestone package at the very top of the Ungut Formation (the Akhor geological formation, the lower pulsational formation according to K. V. Radugin), where T. V. Yankauskas has recently discovered archaeocyaths, should be considered Cambrian.

At the same time, K. V. Radugin believes that the wide development of the above-listed algal genera does not exclude a Precambrian age for the rocks [4]. I. I. Koptev [2] assigns the Anastasyino and Ungut formations to the Sinian. Recently V. V. Khomentovsky has assigned the Anastasyino Formation to the Vendian [5], although earlier he assigned it to the Aldan stage of the Lower Cambrian [6]. Thus, a Precambrian age of the indicated formations is not excluded.

The algal genera noted occur throughout the entire studied part of the section, but the species composition, especially of the epiphytons, is sufficiently clearly—

) If one does not count Ep. baicalicum Vologd., described from the Unguntui Formation of the Sinian [1], and K. V. Radugin’s indication of epiphyton finds at a level stratigraphically close to beds with Newlandia* in the Sredinnyi district [4].

which differs in different parts of the section, making it possible preliminarily to outline three complexes: the Anastasyino complex, characterizing the upper parts of the Anastasyino Formation; the lower Ungut complex, occurring throughout the entire thickness of the Ungut Formation except for its very top; and the upper Ungut (Akhor) complex, characterizing the limestone sequence of the very uppermost parts of the Ungut Formation.

For the Anastasyino complex, from which Ep. improcerum is described, the characteristic features are small thalli of epiphytons, often rounded in shape because of the centrifugal growth of the branches, no more than 3–5 mm in size, randomly oriented in thin sections. All this is apparently connected with insufficiently favorable conditions for the life and growth of epiphytons (agitation of the environment, currents, the influx of considerable quantities of terrigenous material and organogenic silt, consisting chiefly of fragments of the same epiphytons).

In the transition to the cleaner and lighter limestones of the Ungut Formation, a rather rapid, though gradual, increase in the size of the forms is observed, especially in height—to 10–15 mm; a uniform orientation of the long axes of the little bushes in space appears, in general perpendicular to the bedding. The species composition becomes more diverse, but for most species their predecessors can be found among the small forms of the Anastasyino complex. Thus, both complexes are closely connected, despite the presence of a tectono-denudational break between the formations, established by us in some areas; and the replacement of one by the other is due, above all, to a change in facies conditions, more favorable for the existence of epiphytons during the formation of the limestones of the Ungut Formation.

The forms characteristic of the Ungut complex, from which Ep. manaense and Ep. decumanum are described, pass through its entire thickness. Some of them also pass into its upper (Akhor) member, but here new forms of epiphytons are also encountered, of which Epiphyton achoricum, Ep. procerum, and Ep. fasciatum are described, as well as other algae, differing rather sharply from the Ungut forms; on this basis we distinguish the upper Ungut (Akhor) complex.

A few words on comparing the forms described by us with already known species, the overwhelming majority of which were described by K. B. Korde and A. G. Vologdin. The study of ancient algae, in comparison with other groups of organisms, is still very weak. Naturally, the methods of study and the principles of the taxonomy of epiphytons, based on the description and measurement of the external form and the structure of the thallus, are still far from perfect and differ greatly among different authors. Apparently, for this reason it is practically impossible to compare with one another the species described by A. G. Vologdin and K. B. Korde.

The absence of clear criteria for distinguishing lower taxonomic units among epiphytons greatly complicates the work. The author was constantly confronted with the question: are the observed differences of a given form from others the result of intraspecific variability (which, in the author’s opinion, is very highly developed in epiphytons) of a previously described species, or is this a new species?

On the basis of the available differences, and also taking into account the fact that the epiphyton forms under consideration are situated stratigraphically considerably below almost all previously published species (from this level descriptions of two species have been published [4]), they are described as new species.

In view of all that has been said above, it is still too early to correlate, on the basis of epiphytons, the Anastasyino and Ungut formations with deposits of other regions.

It can only be noted that forms of epiphytons entirely analogous to Ep. procerum of the Upper Ungut (Akhor) complex were encountered by the author in the collection of B. D. Vasil’ev, gathered in the Ust’-Kundat Formation (northwestern part of the Kuznetsk Alatau, Kiya River) below beds characterized by archaeocyathids of the impoverished Bazaikha complex.

In conclusion, descriptions are given of several of the most characteristic and widely distributed species of epiphytons from all three complexes.

In describing them, the author, following the method of K. B. Korde, added to the set of elements of morphological structure used by her as the basis for the taxonomy of epiphytons one more element—the character of the structure of the branching node, distinguishing several of its types (Fig. 1). It should also be noted that, with a U-shaped branching node, the value of the angle of division becomes indeterminate.

Fig. 1. Types of structure of branching nodes in epiphytons:
I—U-shaped. II—Y-shaped. III—V-shaped. Subtype “a,” as a rule, in forms with a constant diameter of branches; subtype “b,” as a rule, in forms with branches whose diameter increases toward the branching point.

Type Rhodophyta

Family Epiphytaceae Korde, 1959

Genus Epiphyton Bornemann, 1886

Type species—Epiphyton flabellatum Bornemann, 1886, island of Sardinia, Lower Cambrian.

Diagnosis (after K. B. Korde [3], abridged). The thallus is bushy, multicellular, branching dichotomously, rarely sympodially. Branching is often periodic, serial. The distal ends of the branches often terminate at a certain common level. The distances between the branches of the bush and their lengths vary.

Species composition and geological distribution. More than 80 species are known, with a range from the Sinian to the Devonian. Siberia, the Urals, the Russian Platform, France, Italy, Antarctica.

Epiphyton improcerum sp. nov.

Table 1, fig. 1.

Holotype. Thin section No. G-205/1. Collections of the Department of General Geology, TPI. Northwestern part of the Eastern Sayan, Mana River, near the settlement of Malyi Ungut; upper part of the Anastas’yino Formation; Late Precambrian (?)–Lower Cambrian.

Description. The thallus is low, uniform, no more than 0.5 mm high, semicircular in form with a diameter of up to 2 mm. The individual bushes making up the thallus are formed as a result of two- or threefold dichotomous division at intervals of 0.05–0.1 mm, first at an angle of 45–60°, and then 25–30°. In the central bushes of the thallus, which grow more strongly, the distance between branching points during the formation of higher-order branches increases to 0.15–0.2 mm. Some of the newly formed branches, especially in the peripheral bushes of the thallus, do not divide further, growing to 0.08–0.1 mm. Distal ends 0.1–0.2 mm long are flattened. The diameter of the branches and distal ends increases toward the branching point from 0.025–0.033 mm to 0.04–0.05 mm. The branching node is V-shaped; the U-shaped type also occurs, especially during the formation of higher-order branches in the central bushes of the thallus at a small branching angle.

Comparison. Some forms, in the presence of a V-shaped branching node, are similar to Ep. furcatum Korde [3]. In general, our species is confidently distinguished by the character of its growth, the larger branching angle, and the predominance of the V-shaped type of branching node.

Geological and geographic distribution. Northwestern part of the Eastern Sayan, middle course of the Mana River; upper parts of the Anastasyino Formation, Late Precambrian (?)—Lower Cambrian.

Material. A large number of specimens in several thin sections taken from different points.

Epiphyton decumanum sp. nov.

Table 1, fig. 2.

Holotype. Thin section No. G-184/7, collection of the Department of General Geology, CPI; northwestern part of the Eastern Sayan, Kolba River, right bank, 2 km below the village of Anastasyino; lower parts of the Ungut Formation, Late Precambrian (?)—Lower Cambrian.

Description. The thallus is a sparse, separate bush growing sideways and upward from a single point, up to several millimeters high, formed as a result of five- to sixfold dichotomous division, first at intervals of 0.15–0.2 mm, and higher up to 0.4 mm. Some of the newly formed branches, especially those deviating to the side from the vertical axis of the bush, divide only two or three times, more rarely once, or do not divide at all, but grow to the point of division of the branch paired with them and cease growth. Distal ends 0.2–0.4 mm long are flattened or rounded-flattened. The diameter of the branches, as a rule, increases toward the branching point from 0.06–0.08 to 0.08–0.11 mm. In some branches, the most strongly growing ones, the increase toward the branching point is almost imperceptible. The branching node is U-shaped, subtype “b.” The branching angle cannot be determined precisely; approximately it changes from 45–60° in the lower part of the bush to 25–30° in the upper. Sometimes rare transverse bands are visible on the branches, more often immediately before branching (traces of cellular structure).

Comparison. From the very similar Ep. anigaicum Korde [3] in external appearance and dimensions (in fact, comparison of the descriptions, if one does not take into account the differences arising from different methods of description, does not make it possible to distinguish them), our species differs by the presence of traces of cellular structure in the form of rare transverse banding, a more irregular character of growth, and lower density.

Geological and geographic distribution. Northwestern part of the Eastern Sayan, middle course of the Mana River, lower course and headwaters

r. Kolby, r. Murtuk; Ungut Formation (without the upper (Akhor) member), Late Precambrian (?)—Lower Cambrian.

Material. A large number of specimens in almost all thin sections from the Ungut Formation.

Epiphyton Manaense sp. nov.

Table 1, fig. 3.

Holotype. Slide G-16/6 of the collection of the Department of General Geology, TPI. Northwestern part of the Eastern Sayan, Mana River, right bank 1 km below the settlement of Bol. Ungut; lower part of the Ungut Formation, Late Precambrian (?)—Lower Cambrian.

Description. The thallus is a graceful little bush growing strictly upward, up to 5 mm high, formed as the result of eight- to ninefold dichotomous division in the central branches and three-, four-, fivefold division in the lateral ones. A smooth curvature of the branches and a clearly expressed U-shaped branching node are characteristic, subtype “a.” The distal branches end in a flattened manner. The diameter of the branches does not increase toward the point of division, but gradually increases as the bush grows, from 0.04–0.05 mm in the lower part to 0.06–0.08 mm in the upper part. Correspondingly, the distance between points of division also increases from 0.1–0.2 to 0.3–0.7 mm (an example of individual variability in epiphytons connected with growth). At the very top of the bush the branches again divide two or three times at intervals of 0.1–0.15 mm; their diameter decreases to 0.03–0.04 mm. As a result, a dense series of short distal ends is formed. It is possible that this is the beginning of the next cycle of development of the thallus.

Comparison. From the similar Ep. zonatum Korde [3], our species is confidently distinguished by the character of growth, by the branching node (according to comparison of the figures), by the absence of branching more complex than dichotomous, and, in general, by the larger diameter of the branches.

Geological and geographical distribution. Northwestern part of the Eastern Sayan, middle course of the Mana River, headwaters of the Kolby River; Ungut Formation, Late Precambrian (?)—Lower Cambrian.

Material. A large number of specimens in many thin sections.

Epiphyton achoricum sp. nov.

Table 1, fig. 4.

Holotype. Slide 280 of the collection of the Department of General Geology, TPI. Northwestern part of the Eastern Sayan, middle course of the Mana River, 8 km NE of the settlement of Bol. Ungut; upper part of the Ungut Formation (Akhor member), Lower Cambrian.

Description. The thallus is a low bush, not more than 2–5 mm, consisting of three to four separate fan-shaped groups of branches arranged one above another. Each group is formed as the result of three- or fourfold dichotomous division, first at an interval of 0.05, then 0.1–0.2 mm, of one of the branches of the preceding group. The length of the sharply flattened, as if truncated, distal ends is 0.2 mm, and that of the branch giving rise to a new group is 0.25–0.4 mm. The diameter of the branches in the lower groups increases toward the branching point from 0.06 to 0.08 mm. The branching node in them is Y-shaped, subtype “b”; the angle of division is at first 45–60°, and then 25–30°. In the upper groups the diameter of the branches increases from 0.04 to 0.07 mm; along with a V-shaped branching node, a U-shaped one is also present. The branching angle in this case decreases to 15–25°.

Comparison. The lower fan-shaped groups of thallus branches, if they had been encountered separately, would have been practically impossible to distinguish from Ep. mirabile Korde [3]; the upper ones are very similar to Ep. benignum Korde [3]. As a whole, in the character of its growth the entire thallus very much resembles Ep. furcatum Korde [3], differing from it in being twice as large.

Geological and geographic distribution. See holotype.
Material. A large number of specimens in many thin sections.

Epiphyton procerum sp. nov.

Table 1, fig. 5.

Holotype. Thin section 3423, collection of the Department of General Geology, TPI. Northwestern part of the Eastern Sayan, r. Murtuk; upper Ungut Formation (Akhor member), Lower Cambrian.

Description. The thallus is a small bush up to 10 mm high, growing strictly upward, with an incipient serial structure, expressed in the fact that, as the bush develops and attains considerable density, part of the branchlets, 0.2 to 0.6 mm long, no longer divides further but ceases growth at approximately the same level, ending in a flattened manner. Another part continues to grow, and as a result of two- or threefold division of these branchlets the next dense series is formed. The distance between branching points is 0.4–0.6 mm and up to 1 mm when a branchlet, without branching, grows into the next cycle. The diameter of the branchlets almost does not increase during growth and is 0.6–0.7 mm, increasing only immediately before the branching point to 0.1–0.12 mm. The branching node is V-shaped and transitional from V-shaped to subtype “b” of U-shaped. The branching angle is 10–15°.

Comparison. From the similar in growth character Ep. simplex Korde [3], our species differs in its larger size (diameter) and in the absence of traces of cellular structure.

Remarks. The lower part of the bush differs sharply in structure. From the lower main branchlet, as a result of repeated irregular branching at intervals first of 0.05 mm and higher up to 0.15 mm, a dense tuft of branchlets 0.15–0.2 mm long is formed, with a diameter increasing toward the branching point from 0.04–0.05 to 0.06–0.07 mm, and serving as the base for the entire bush. Thus, this form represents a good example of age-related individual variability in epiphytons.

Geological and geographic distribution. Northwestern part of the Eastern Sayan, r. Murtuk, headwaters of the r. Bazaiha; upper Ungut Formation (Akhor beds). Kuznetsk Alatau, r. Kiya; Ust-Kundat Formation, Lower Cambrian.

Epiphyton fasciatum sp. nov.

Table 1, fig. 6.

Holotype. Thin section G-96/8, collection of the Department of General Geology, TPI, Northwestern part of the Eastern Sayan, headwaters of the r. Bazaiha; upper Ungut Formation, Lower Cambrian.

Description. The thallus consists of several simply constructed, sparse bushes, growing only upward to 3 mm. The bushes are formed as a result of three- or fourfold dichotomous and sympodial branching at intervals of 0.2 mm in the lower part, up to 0.4 mm in the middle, and 0.1–0.2 mm in the upper part of the bushes. In the case of sympodial branching, one of the branchlets formed alternately now from one—

1

2

3

4

5

6

Fig. 1. Epiphyton improcerum sp. nov., holotype, thin section G-205/1, TPI collection; oblique section of the thallus (×20); northwestern part of the Eastern Sayan, Mana River near the settlement of Mal. Ungut; upper part of the Anastasyino Formation, Late Precambrian (?)—Lower Cambrian.

Fig. 2. Epiphyton decurranum sp. nov., holotype, thin section G-184/7, TPI collection; longitudinal-oblique section of the thallus (×20); northwestern part of the Eastern Sayan, Kolba River below the settlement of Anastas’yino; lower part of the Ungut Formation, Late Precambrian (?)—Lower Cambrian.

Fig. 3. Epiphyton manaense sp. nov., holotype, thin section G-16/6; TPI collection, longitudinal section of the thallus (×20); northwestern part of the Eastern Sayan, Mana River below the settlement of Bol. Ungut; lower part of the Ungut Formation, Late Precambrian (?)—Lower Cambrian.

Fig. 4. Epiphyton achoricum sp. nov., holotype, thin section 280, TPI collection, longitudinal section of the thallus (×20); northwestern part of the Eastern Sayan, Mana River northwest of the settlement of Bol. Ungut; upper part of the Ungut Formation, Lower Cambrian.

Fig. 5. Epiphyton procerum sp. nov., holotype, thin section 3423, TPI collection; longitudinal section of the thallus (×20), northwestern part of the Eastern Sayan, Murtuk River, upper part of the Ungut Formation, Lower Cambrian.

Fig. 6. Epiphyton fasciatum sp. nov., holotype, thin section G—96/8, TPI collection; longitudinal-oblique section of the thallus (×20); northwestern part of the Eastern Sayan, headwaters of the Bazaikha River; upper part of the Ungut Formation, Lower Cambrian.

on the other side of the axis of the little bush, grows to 0.1–0.3 mm and ceases growth, ending in a sharply flattened form. The diameter of the branches increases toward the point of branching from 0.07 to 0.11–0.13 mm, and at the flattened distal ends from 0.06 to 0.09 mm. The branching node is V-shaped. The angle of branching is 10–12° and up to 45° in the upper part of the little bushes when the distal ends are formed. The transverse banding of the branches is clearly visible, caused by the alternation of dark and light bands (rows of cells, according to K. B. Korde), 0.005 to 0.012 mm high, predominantly 0.008 mm.

Comparison. From the very similar Ep. Suvorovae Korde [3], our species differs in the flattening of the distal ends and in the smaller height of the rows of cells (transverse bands).

Geological and geographic distribution. See holotype.

Material. Holotype.

LITERATURE

1. A. G. Vologdin. The Most Ancient Algae of the USSR. Publishing House of the Academy of Sciences of the USSR, 1962.

2. I. I. Koptev. On the stratigraphy of the Lower Cambrian of Krasnoyarsk Krai. Izvestiya TPI, vol. 120, 1962.

3. K. B. Korde. Algae of the Cambrian of the southeastern Siberian Platform. Transactions of PIN, vol. XXXIX, 1961.

4. M. V. Stepanova, K. V. Radugin. “On filamentous algae of the Precambrian of the NW part of the Eastern Sayan.” Materials on the Geology and Mineral Resources of Western Siberia. Publishing House of Tomsk State University, 1964.

5. V. V. Khomentovskii, L. N. Repina et al. Biostratigraphy of the Lower Cambrian of the Sayano-Altai Folded Region. Publishing House “Nauka,” 1964.

6. V. V. Khomentovskii et al. Stratigraphy of the Precambrian and Lower Paleozoic deposits of the western part of the Eastern Sayan. Regional Geology of the USSR. Publishing House of the Academy of Sciences of the USSR, vol. IV, 1961.