Narva Stage

by A. Kleesment & E. Mark-Kurik

Original text from: Raukas, A., Teedumäe, A. (eds). 1997. Geology and Mineral Resources of Estonia. Estonian Academy Publishers, Tallinn. 436 pp. ISBN 9985-50-185-3. Available online at: sarv.gi.ee/geology.

As an independent stratigraphic unit the Narva Stage was distinguished and termed by Obruchev (1933). The left bank of the Narva River near Gorodenka, and the banks of the Gorodenka Brook and the Poruni River near the place where these watercourses flow into the Narva River in northeastern Estonia, make up the stratotype area of the stage. The outcrops are concentrated in northeastern Estonia, with the Narva and Sirgala quarry sections (Fig. 82) being most noteworthy.

The Narva Stage is spread in southern and eastern Estonia. The outcrop area extends as a 10–30-km-wide belt from Ruhnu to Halliku. Besides, there is a separate area in northeastern Estonia and a few isolated spots near the outcrop line. The total thickness ranges from 30 to 109 m, increasing from north to south (Fig. 82).

The lower boundary of the stage coincides with the base of a carbonate breccia or dolomitic marl, 0.2 to 10 m in thickness, which overlie sandy dolomite or sandstone of the Pärnu Stage (Figs. 75,76).

On the basis of palaeontological (acanthodians, inarticulates, brachiopodes, spores), lithological and mineralogical characteristics, the Narva Stage has been divided into three substages (Table 10) traceable from the stratotype area up to eastern Belarus (Valiukevičius et al. 1986, Kleesment et al. 1987).

The Narva oil shale quarry section, 10 km southeast of the Sirgala Settlement, has been selected for the stratotype of the lower, Vadja Substage. Its parastratotype is the outcrop on the left bank of the Narva River, 300 m downstream from the mouth of the Gorodenka Brook. The thickness of the substage in the stratotype area is about 16 m, in Estonia it varies from 10 to 31.9 m (Figs. 75, 76, 83).

The Luutsniku-451 drill core in the interval of 317–377.7 m has been selected as a stratotype for the Leivu (middle) Substage. In the stratotype area it is exposed at the Poruni and Narva rivers. The thickness of the substage in northeastern Estonia is about 5 m and it increases considerably in a southern direction reaching 60.7 m in the Luutsniku drill core (Figs. 75, 76, 83).

For the stratotype of the upper, Kernavė Substage the interval of the Ledai borehole in central Lithuania was proposed.

The Narva Stage is rich in fossil fishes, particularly its upper part - the Kernavė Substage [k] where the majority of the macroremains come from. In the Vadja Substage [v] and especially in the Leivu Substage [l] the fishes are more scarce. The fish fauna of the stage consists of Schizosteus striatus (Gross) [k], Pycnolepis splendens (Eichw.) [l?,k], Cephalaspidida, Actinolepis tuberculata Ag. [k], Holonema sp. A Mark-Kurik [v], Holonema sp. B Mark-Kurik [k], Homostius latus Asm. [k], Coccosteus cuspidatus Miller ex Ag. [k], Protitanichthys? sp.n. Mark-Kurik [v], Byssacanthus dilatatus (Eichw.), Asterolepis estonica Gross [k], Cheiracanthoides estonicus Valiuk. [v], Acanthodes? sp.C [v], Cheiracanthus crassus Valiuk. [v], Rhadinacanthus balticus Gross, Acanthodes? sp.B, Acanthodes? sp.D, Cheiracanthus brevicostatus Gross, C. longicostatus Gross, Ptychodictyon distinctum Valiuk. [l,k], P. rimosum Gross [l, k], Cheiracanthus sp. [l,k], Diplacanthus sp. [l,k], Acanthodes ? sp.A. [l,k], Cheiracanthus intricatus Valiuk. [k], Nostolepis kernavensis Valiuk. [k], Cheiracanthoides proprius Valiuk. [k], Markacanthus costulatus Valiuk. [k], Minioracanthus laevis Valiuk. [k], Ptychodictyon sulcatum Gross [k], Diplacanthus carinatus Gross [k], Acanthodii gen.n. Valiuk. [k], Archaeacanthus quadrisulcatus Kade, Haplacanthus marginalis Ag., Homocanthus gracilis (Eichw.), Thursius fischeri (Eichw.) [k], Osteolepididae, Glyptolepis quadrata Eichw. [k], Glyptolepis sp., Onychodus sp.[v,k], Dipterus serratus (Eichw.)[k], Dipnoi [v, l], Cheirolepis sp.sp., Orvikuina sp. [v, l], O. vardiaensis Gross [k].

Invertebrates are represented by lingulate brachiopods (Bicarinatina sakalana Rõõmusoks et Gravitis a.o.) which are especially numerous in the upper portion of the Leivu Substage. Ostracods (Lepertitia tartuensis Öpik var. geographica Hecker, Ostracoda inc. gen.) are less common and so are unidentified lamellibranchs in the Kernavė Substage. Conchostracans Pseudestheria pogrebovi Lutk., Trigonestheria triangularis Mir., Glyptoasmussia quadrata Mir., G. aff. willweratica Nov., Concherisma eifelense Raym., Ulugkemia sinuata Lutk., U. mesodevonica Mir., Asmussia membranacea Pacht, Praeleaia quadricarinata Lutk. are characteristic for the Vadja Substage and the lowermost part of the Leivu Substage. The lists of animal fossils are given after Sorokin (1981), Valiukevičius et al. (1986) and Valiukevičius (1994).

Microspore assemblage from the Narva Stage is restricted to the Vadja Substage. It includes Retusotriletes raisae Tchib., R. devonicus Naumova, R. concinnus Kedo, R. incomptus Kedo, R. planituberculatus Kedo, R. cf. brandtii Streel, R. fragosus Arkh., R. microsetosus Kedo, R. lanceolatus Kedo, R. luxispinus Kedo, R. engurensis Kedo, R. clivosiformis Kedo, Hymenozonotrietes cf. marginodentatus Kedo, H. altus Kedo, H. cf. echiniformis Kedo, H. ludzus Kedo, Camarozonotriletes apertus Kedo, Grandispora protea (Naumova) Moreau-Benoit, Phylotecotriletes triangulatus Tiw. et Schaarschmidt. The Vadja Substage has also revealed acritarchs, not yet identified (data from Valiukevičius et al. 1986, modified). Gyrognites (?) of charophyte algae (Sycidium) have been found from all members of the Narva Stage. The Kernavė Substage comprises poorly preserved plant macroremains.

In Estonia and adjacent regions, the Narva Stage is represented by the Narva Formation with a highly variable lithology. Its lower part consists mostly of dolomitic marl with interlayers of dolomite and dolomitic clay. Siltstone, very fine-grained and silty sandstone intercalating with interlayers of dolomitic marl and clay, forms the upper part of the Narva sequence. The sequence of the formation is divided into three members corresponding in volume to substages (Table 10, Fig. 83).

In the basal part of the lower, Vadja Member the breccia of dolomitic marl with unsorted irregular pebbles of dolomite, dolomitic marl and siltstone are common. In general this member is characterized by a thin-bedded complex of dolomitic marl, dark-grey to black silty clay and pale yellowish-grey dolomite which often includes crystalline dolomite, chalcedony, pyrite or sphalerite filled vugs. The detrital component of the rocks in the lower part of the unit is mineralogically relatively mature with the quartz content reaching 50–80%. In the upper part, the rocks are often micaceous containing quartz 20–50, feldspars 15–30 and micas 20–60%. The heavy mineral suite is prevailed by Fe hydroxides or pyrite, in some interlayers baryte is dominating. Nonopaque heavy minerals are dominated by garnet, followed by zircon (Fig. 78).

The middle, Leivu Member is prevailed by dolomitic marl. The section varies both lithologically and in thickness. Within the section four beds have been distinguished (Valiukevičius et al. 1986, Kleesment 1995). Two lower beds are thinning towards the north-east (Fig. 83). The lowermost bed of grey dolomitic marl contains a remarkable amount of silty-sandy particles with a diameter up to 1–2 mm. The next bed is a grey thin-bedded complex formed of intercalating dolomitic marl, dolomite and dolomitic clay. The third bed from the bottom comprises interlayers of grey silt- and sandstone. The topmost bed consists of reddish-brown, purplish-grey and grey mottled massive argillaceous dolomitic marl which serves as a good correlative level. Mineralogically, the detrital part of the rocks in the lowest bed belongs to the feldspatic arenites, in other beds – to the arcosic and micaceous arenites. The heavy fraction is dominated by Fe hydroxides, more rarely by pyrite or micas. The beds differ from one another by the nonopaque heavy mineral suite. In the two lower beds garnet is clearly dominating, while in the overlying beds it is accompanied by apatite, zircon and tourmaline. Significant is the presence of sphen (titanite) and corund in the two lower beds (Fig. 78).

The upper, Kernavė Member consists of brownish-red and grey loose and dolomite-cemented silty sandstone with intercalations of siltstone, dolomitic marl and clay. The complex is horisontal-, lenticular-, more rarely cross-bedded. Mineralogically, the rocks of the Kernavė Member belong to the arcosic arenites with the quartz content of 50–80%. In heavy fraction micas (30–60%), more rarely Fe hydroxides (up to 92%) are prevailing. The heavy nonopaque mineral suite is mostly dominated by apatite, followed by tourmaline, zircon and garnet (Fig. 78).