Stratigraphy and Geological Correlation, Vol. 12, No. 7, 2004, pp. 35—57. Translated from Stratigrafiya. Geologicheskaya Korrelyalsiya, Vol. 12, No. 1, 2004. pp. 41-66. Original Russian Text Copyright © 2004 by Rogov. Translation Copyright © 2004 by MAIK "Nauka/lnterperiodica" (Russia). Ammonite-Based Correlation of the Lower and Middle (Panderi Zone) Volgian Substages with the Tithonian Stage M. A. Rogov Geological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017 Russia Received May 15, 2002; in final form, November, 13, 2002 Abstract — Based on stratigraphic distribution of ammonite genera in common for the Volgian and Tithonian stages, a new correlation scheme of the lower-middle Volgian with the Tithonian is proposed. The lower Vol- gian Substage corresponds to the lower Tithonian Substage coupled with the middle Tithonian semiforme Zone at least. The panderi Zone is correlative with the interval from the middle Tithonian fallauxi Zone to the upper part of the upper Tithonian microcanthum Zone. The absence of ammonite genera in common hinders the direct correlation between higher levels of the Volgian and Tithonian stages. Peculiarities in Boreal-Tethyan migra- tions of ammonites during the early-middle Volgian are discussed. Lingulaticeras blaschkei, a species very important for correlation of the panderi Zone with the Mediterranean zonation is described and figures of some other ammonite species, such as Sutneria asema and S. cf. eugyra, are given for the first time. Key words: ammonites, Boreal-Tethyan correlation, Volgian, Tithonian. Since the 1960s, some specialists in stratigraphy of Kimmeridgian sediments of the Russian plate the Jurassic-Cretaceous boundary beds (e.g., R. Casey, because of a high provincialism of their ammonite A. Zeiss) called in question the equality of ranges of the faunas and impossibility of tracing in Russia the Volgian and Tithonian stages. During last decades, new zonal units previously proposed for the Tithonian and schemes based on mixed ammonite assemblages with Portlandian stages. Slightly later on, some ammonite Boreal and Mediterranean elements were proposed for species known from the Tithonian were found, how- correlation of these stratigraphic units. According to the ever, in sediments, which are now referred to the Interdepartmental Stratigraphic Committee resolution, lower Volgian Substage. For instance, Semenov [4] the Tithonian Stage is now considered as representing a described Aspidoceras sp. from the Orenburg oblast. stratigraphic equivalent of the lower-middle Volgian The examination of the Semenov's collection stored substages with the lower Volgian Substage correspond- at the Chair of Historical Geology of the St. Peters- ing to the lower-middle Tithonian [1]. Stratigraphic burg University (no. 95) revealed that this form distribution of perisphinctids occurring both in the belongs to the lower Volgian species Anaspidoceras Boreal and Submediterranean realms is consistent with neoburgense (Oppel). The representative of the same such a correlation. species was likely described by Sokolov ([5], p. 23) 1 Nevertheless, new data obtained during the last as Aspidoceras sp. a few years later. Soon after, three decades on distribution of Submediterranean Rozanov, ([6], p. 29) mentioned a fragment of ammo- aspidoceratids, oppeliids, and haploceratids in the nite “characterized by the Tithonian habitus and close lower and middle Volgian substages of the Russian probably to Hoplites callisto” in sediments referred plate, which were virtually not taken into account until recently to the virgatus Zone and Subzone of the mid- recently, allowed a new variant of the Volgian-Titho- dle Volgian Substage. Unfortunately, this ammonite nian correlation to be proposed [2]. The availability of was not figured and no similar forms were ever several different correlation schemes based on recorded in the virgatus Zone. ammonoid succession implies the necessity to analyze Approximately at that time, first data on the occur- all the data on co-occurrence of Subboreal and Sub- rence of Boreal and Subboreal ammonites in areas adja- mediterranean ammonite genera. cent to the Russian plate appeared. Par example, Abel [7] mentioned Ammonites virgatus from Lower Austria and Vetters ([8], Plate 22, fig. 5) figured Perisphinctes AMMONITE GENERA IN COMMON cf. nikitini. The last form was subsequently revised and FOR THE VOLGIAN AND TITHONIAN STAGES: described as a new species Isterites austriacus [9]. Dor- A REVIEW 1 In 1881, S.N. Nikitin [3] proposed the name Vol- In his description, Sokolov paid attention to the absence of any tubercles in this form, which feature characterizes A. neobur- gian Formation (Stage subsequently) for the post- gense. 35 36 ROGOV soplanites panden from the North Caucasus was also used as index species of the basal Volgian zone2. The described and figured ([10], Figs. 1,2). Simultaneously, species is common in sediments of the Russian plate, Renz [11] reported on the occurrence of Dorsoplanites where it occurs beginning from the base of the Volgian dorsoplanus and Lomonossovella lomonossovi in the Stage. Simultaneously, the transition from Sarma- North Caucasus, although he did not reproduce their tisphinctes fallax (How.) to llowaiskya klimovi (Ilov.) is figures. very gradual and, if ammonites are poorly preserved, In the 1930s, ammonites characteristic of the West the boundary between Kimmeridgian and Volgian European Jurassic were mentioned from Volgian sec- stages can be established more confidently based on the tions in several works dedicated to geology of the Volga last occurrence of Aulacostephanus. region. N.T. Zonov was the first to pay attention (with- In their work dedicated to stratigraphy of the upper out mentioning of particular sections) to the occurrence Upper Jurassic succession and relevant ammonites of of a peculiar horizon with oppeliids within the Kim- southern Germany, Berckhemer and Hölder ([20], meridgian-Volgian boundary beds of the Volga region. p. 58, Plate 14, fig. 68) described a species among He emphasized ([12], p. 39) that "...of significant inter- ammonites from the upper Kimmeridgian-lower Titho- est is the presence of poorly preserved forms similar to nian referred it to the Boreal genus Pavlovia (?Acuti- both some lower Tithonian Ochetoceras and upper costites). This form differing from typical Acuticostites Kimmeridgian Haploceras, for instance, to H. in ornamentation patterns at early ontogenetic stages (Glochiceras) ex gr.fialar, in the uppermost layers with and in stratigraphie position should be attributed to the Aulacostephanus. Higher, these beds with lower Tithonian genus Berkhemeria Schweigert et Glochiceras(?)-Ochetoceras are defined as an autono- Zeiss, 1998. mous marly unit lacking any signs of Aulacostepha- Soon after, Mikhailov [21] demonstrated the occur- nus... The belonging of these beds to the Oppelia rence of Glochiceras and Neochetoceras in the klimovi (Ochetoceras) zio Subzone, i.e., to the basal part of the Zone of the Ul'yanovsk Volga region. In addition, he O. steraspis Zone is highly probable". In the Gor'kii described a form from the sokolovi Zone and referred it, oblast and Chuvash Republic, Gerasimov and Kazakov in the open nomenclature, to the species Franconites [13] noted the occurrence of a peculiar horizon enclos- vimineus known from southern Germany ([22], p. 56, ing large bun-shaped concretions with Oppelia sp. and Plate 11, fig. 1). Perisphinctes sp. above the last finds of Aulacostepha- nus. Similar concretions are known in the Nizhnii I should mention also ammonites found mainly in Novgorod oblast from the uppermost Kimmeridgian the upper Volgian Substage of North Siberia (and later (Isady locality) and Volgian (Murzitsy locality). At the on in eastern Greenland, Spitzbergen, and sub-Polar same time, in the Chuvash Republic they are of the Urals) and attributed to the Mediterranean genera Ber- early Volgian age and contain either Paralingulaticeras riasella, Virgatosphinctes, and Lemencia [23]. Prevail- efimovi (Rogov) and llowaiskya cf. klimovi (Ilov.) ing among Virgatosphinctes forms, there were species (Poretskoe Village, Sura River), or an older assemblage similar to Indian and Argentinean taxa [24]. In neigh- with Neochetoceras steraspis and Lingulaticeras sole- boring areas, similar forms were unknown, and their noides (Polevye Bikshiki Village). A similar horizon occurrence among Boreal ammonites called in question with "rare slightly deformed ammonites referred to the the correctness of species identification. I tend to accept Ochetoceras-Haploceras (Glochiceras) group" above the standpoint of some researchers [25] who consider the last finds of Aulacostephanus was also registered in these forms as descendants of some Boreal ammonites, the Tatar Republic [14]. which have nothing to do with true Virgatosphinctes. Slightly later on, first figures of lower Volgian Approximately at the time, when first data on Anaspidoceras neoburgense (Oppel), which previously Neochetoceras and Glochiceras from Volgian sedi- were only described or mentioned in the faunal lists, ments of the Volga region appeared, first Haplocerata- were reproduced by Ilovaiskii and Florenskii ([15], ceae or "indeterminable oppeliids" were found in the Plate XXIII, figs. 42, 42a). Soon after, this species was Volgian Stage of Poland. Their range was assumed to extend up to the middle Volgian Beds with Zaraiskites found in the Moscow outskirts and in the Ul'yanovsk 3 4 oblast of the Volga region [16]. In