ISSN 08695938, Stratigraphy and Geological Correlation, 2016, Vol. 24, No. 4, pp. 364–380. © Pleiades Publishing, Ltd., 2016. Original Russian Text © V.R. Lozovsky, Yu.P. Balabanov, E.V. Karasev, I.V. Novikov, A.G. Ponomarenko, O.P. Yaroshenko, 2016, published in Stratigrafiya, Geologicheskaya Korrelyatsiya, 2016, Vol. 24, No. 4, pp. 38–54. The Terminal Permian in European Russia: Vyaznikovian Horizon, Nedubrovo Member, and Permian–Triassic Boundary V. R. Lozovskya, Yu. P. Balabanovb, E. V. Karasevc, I. V. Novikovc, d, A. G. Ponomarenkoc, and O. P. Yaroshenkoe a Russian State Geological Prospecting University, ul. MiklukhoMaklaya 23, Moscow, 117997 Russia b Kazan Federal University, Kazan, Russia c Paleontological Institute, Russian Academy of Sciences, Profsoyuznaya ul. 123, Moscow, 117997 Russia d University of Dodoma, Tanzania e Geological Institute, Russian Academy of Sciences, Staromonetny per. 35, Moscow, 119017 Russia email: [email protected], [email protected], [email protected] Received December 22, 2014; in final form, September 14, 2015 Abstract—The comprehensive analysis of the data obtained on terrestrial vertebrata, ostracods, entomologic fauna, megaflora, and microflora in deposits of the Vyaznikovian Horizon and Nedubrovo Member, as well as the paleomagnetic data measured in enclosing rocks, confirms heterogeneity of these deposits. Accordingly, it is necessary to distinguish these two stratons in the terminal Permian of the East European Platform. The com bined sequence of Triassic–Permian boundary deposits in the Moscow Syneclise, which is considered to be the most complete sequence in the East European Platform, is as follows (from bottom upward): Vyatkian deposits; Vyaznikovian Horizon, including Sokovka and Zhukovo members; Nedubrovo Member (Upper Permian); Astashikha and Ryabi members of the Vokhmian Horizon (Lower Triassic). None of the sequences of Permian– Triassic boundary deposits known in the area of study characterizes this sequence in full volume. In the north, the Triassic deposits are underlain by the Nedubrovo Member; in the south (the Klyazma River basin), the sec tions are underlain by the Vyaznikovian Horizon. The Permian–Triassic boundary adopted in the General Stratigraphic Scale of Russia for continental deposits of the East European platform (the lower boundary of the Astashikha Member) is more ancient than the one adopted in the International Stratigraphic Chart. The same geological situation is observed in the German Basin and other localities where Triassic continental deposits are developed. The ways of solving this problem are discussed in this article. Keywords: Permian, Triassic, entomofauna, terrestrial vertebrata, ostracods, macroflora, miospore com plexes, petromagnetism DOI: 10.1134/S0869593816040043 INTRODUCTION which occurred in the boundary region between the East European Platform and the Uralian orogen. At The sequences of Permian–Triassic transitional the end of the Permian, this territory was uplifted, continental deposits exposed in the Moscow Syneclise which resulted in its drying (Ignatiev, 1962). In Lozo are highly saturated with different organic remnants vsky’s opinion, there were specific conditions of sedi (terrestrial vertebrata, ostracods, conchostracans, mentation of the Nedubrovo Member caused by an mega and microflora, insects, etc.). Because of this, impact event. The preservation of this member in the these sections differ from similar sequences world Kichmenga River basin can be easily explained by wide. This is a reason why they are of importance for block movements on the wing of the Sukhonsky shaft. comprehensive study to reveal the Permian–Triassic Rejuvenated sedimentation in the Vyaznikovian time boundary in continental deposits. Using a complex of was locally confined only to the basins of rivers flowing methods, a similar composite section was described in from the Urals. Throughout the rest of the platform, (Lozovsky, 2013; Lozovsky and Korchagin, 2013). The sedimentation was absent or it was locally manifested. chronostratigraphic sequence proposed by Lozovsky In the Early Triassic, sedimentation occurred through for the PermianTriassic boundary includes Vyatkian out the entire East European Platform. deposits, the Vyazniki Horizon, and the Nedubrovo, The sequence of geological events at the Permian– Astashikha, and Ryabi members of the Vokhmian Triassic boundary proposed by Lozovsky (2013) was Horizon. The Vyaznikian Horizon and Nedubrovo accepted by Arefiev et al. (2015). These authors used Member occupy the central position in this sequence. this sequence as a basis for construction of a δ13С iso They formed at the turn of the geological evolution tope curve for the Permian–Triassic boundary in depos 364 THE TERMINAL PERMIAN IN EUROPEAN RUSSIA 365 its of the Moscow Syneclise. Interpretation of this zon includes underlying clayeysiltstone members con sequence by Sennikov and Golubev (2014) was in con taining plant complexes, ostracods, insects, etc. This tradiction with the Lozovsky’s idea. On one hand, this horizon was considered as the “Vyaznikovian Stage” in interpretation was “in good agreement with the inter (Lozovsky and Kukhtinov, 2007), the “Zhukovian pretation of the reference section of the Zhukov ravine” Horizon” in (Sennikov and Golubev, 2010), and the (Sennikov and Golubev, 2014, p. 61); on the other “Vladimirian Stage” in (Naugolnykh, 2005). hand, these authors consider that the upper (Zhukovo) The stratotype of the Vyaznikovian Horizon is sandy unit of the Vyaznikovian sequence is a facies ana located in the marginal zone of the Moscow Syneclise log of the Nedubrovo Member (Golubev and Sennikov, (the Klyazma River basin), where a few sequences are 2015). This problem is discussed below. cropped out along the right bank of the river between In this connection, we should note that the well towns of Vyazniki and Gorokhovets (Zhukov ravine). exposed Sukhona–Northern Dvina sequence (Arefiev These outcrops contain a rich complex of organic et al., 2015), which was demonstrated to participants of remnants characterizing the Vyaznikovian faunistic the XVIII International Permian–Carbonaceous Geo complex of the likenamed stratotypical region. logical Congress, is incomplete in its upper part, where The Vyaznikovian deposits occupy the specific the Vyaznikovian Horizon is missing. In the strati stratigraphic position in the sequence between faunis graphic scheme of the terminal Permian (Arefiev et al, tically characterized Late Permian Vyatkian and Early 2015, fig. 6, p. 11), the Komaritsa Member is conform Triassic Vokhmian deposits. Their deposition was pre ably overlain by the Nedubrovo Member. There is a gap, ceded a longterm stratigraphic gap, which resulted in corresponding to the Vyaznikovian Horizon, at the the formation of the erosional surface. This is con boundary between these units. This gap is observable in firmed by unconformable overlap of the Vyaznikovian the section located between the villages of Glebovo and deposits on differentdepth levels of the Vyatkian Vaganovo, where Nedubrovian gray deposits with flora Stage up to the uppermost level of the Severodvinian remnants are overlain by basal sands with conglomer Horizon (Lozovsky, 2011; Golubev et al., 2012).2 ates at the lower boundary. The latter sharply uncon 1 The lower parts of paleoincisions, which we called formably overlies Komaritsa marls. the Sokovka Member, are represented by gray thinly Because of existing differences in the paleontolog laminated clays and siltstones with plant detritus accu ical characteristics, we do not consider the Nedubrovo mulated in oxbow and oxbow swamp relief depressions. Member as a facies analog of Vyaznikovian sands con The upper part of the Vyaznikovian deposits (Zhukovo taining the Archosaurus rossicus Zone (Golubev and Member) is largely made of crossstratified polymictic Sennikov, 2015). In contrast to the Vyaznikovian sands of channel alluvium containing intercalations of Horizon, the Nedubrovo Member contains no rem gravellites and conglomerates with clayey pebbles and nants of terrestrial vertebrata. Moreover, these stratons boulders of local rock varieties (midstream facies). significantly differ in paleofloristic, entomological, According to the dip and azimuth of the oblique and ostracods complexes, as well as in paleomagnetic bedding in alluvial sands, they were deposited in river characteristics. Accordingly, we can consider them as channels of southwestern orientation (Golubev et al., separate chronostratigraphic subdivisions. This work 2005). is aimed at demonstrating that these stratons must be The above alluvial flow from the Klyazma River included in the General Stratigraphic Scale of Russia basin is traced further to the northeast. Sandy alluvial as independent subdivisions in order to determine the deposits, similar to the Zhukovo Member, are cropped exact position of the Permian–Triassic boundary. out in the area of the settlement of Voskresenskoe (Vetluga River basin). These deposits contain the VYAZNIKOVIAN HORIZON Vyaznikovian assemblage of terrestrial vertebrata AND NEDUBROVO MEMBER (Lozovsky and Blom, 1998, p. 11). Lithologically sim ilar sandy formations were described in the core of well The analysis of the late Tatarian fauna of terrestrial 14 Pereprava (depth interval of 20–48 m) (Ignatiev, vertebrata shows the possibility to distinguish an inde 1962). At a distance of 150 km to the southeast (near pendent Vyaznikovian Horizon in the upper part of the the village of Purly, Nizhny Novgorod