Ichthyofaunal Correlation of the Triassic Deposits from the Northern Cis-Caspian and Southern Cis-Urals Regions

Ichthyofaunal correlation of the Triassic deposits from the northern Cis-Caspian and southern Cis-Urals regions

Maxim G. MINIKH & Alia V. MINIKH Saratov State University, Moskovskaya street, 161, 410750 Saratov (Russia)

Minikh M. G. & Minikh A. V. 1997. — Ichthyofaunal correlation of the Triassic deposits from the northern Cis-Caspian and southern Cis-Urals regions, in Crasquin-Soleau S. & De Wever P. (eds), Peri-Tethys: stratigraphic correlations, Geodiversitas 19 (2) : 279-292.

ABSTRACT All the known data on the Triassic ichthyofauna from south-east European Russia are summarized. The material studied comes from thirty-nine locali ties from the Lower and Middle Triassic reference and stratotype sections of the South Cis-Urals and northern Cis-Caspian regions. Data on terrestrial vertebrates, ostracodes, and charae are used as well as paleomagnetic sam pling results. A certain stratigraphic importance of the Triassic gnathorhiza and ceratods is demonstrated relative to lungfish, the one of hybodontids relative to squaliforms and the one of saurichthiids among actinopterygians. Two super-ichthyocomplexes were revealed within the Triassic sections according to dipnoan distributions: those of gnathorhiza and ceratods. Their change in the region occurs in the middle of the Olenekian age and is asso ciated with the rather short Akhtuba time in the Cis-Caspian and with the synchronous Fyodorovka time in the South Cis-Urals. Considering the data on other fish groups, three independent ichthyocomplexes are recognized in the Triassic ichthyofauna: the Vetlugian and Yarenian ones in the Early Triassic and another one in the Middle Triassic. The Yarenian ichthyocomplex comprises two clearly manifested groups of different ages (the Akhtuba and Bogdo ones in the Cis-Caspian and the Fyodorovka and Gamskaya ones in the South Cis-Urals). The Middle Triassic ichthyocomplex comprises the Donguz and Bukobaj fish groups. The regularities revealed in fish-taxa changes with time, are traced within the sections across the adjacent territo ries from the Cis-Urals to the Cis-Caspian. The Lower Triassic Akhtuba suite from the Cis-Caspian Bogdo section was correlated by fish with the lowermost part of the Petropavlovka suite, and the overlying Bogdo suite KEYWORDS Ichthyofauna, with the rest of the Petropavlovka section from the Orenburg region. The Triassic, Middle Triassic Donguz and Bukobaj suites from the Cis-Urals are stratigra- northern Cis-Caspian, phically analogous to the Elton and Inder suites from the Middle Triassic southern Cis-Urals.

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section in the northern Cis-Caspian. The succession revealed in the Triassic ichthyofauna development is maintained all over the territory of European Russia. It is ttaced in the adjacent tegions and may serve as the basis fot stra tigraphie divisions and interregional correlations of differenr-facies marine and non-marine sections of the Triassic.

RÉSUMÉ Toutes les données connues sur l'ichthyofaune triasique du SE de la Russie européenne sont compilées. Le matériel étudié provient de ttente-neuf locali tés des coupes de téférences et stratotypiques du Trias inférieur et moyen du sud du Cis-Oural et du nord de la Cis-Caspienne. Les données sur les verté- brés terrestres, les ostracodes, les characées sont utilisées aussi bien que les résultats paléomagnétiques. Deux super-ichthyocomplexes sont mis en évi dence dans les coupes du Ttias. Leut changement dans la tégion se produit au milieu de l'Olenekien, il est tattaché à l'intervalle court de Akhtuba dans la région de la Cis-Caspienne er à l'intervalle synchrone de Fyodorovska dans la région du Sud du Cis-Oural. Considérant les données des autres groupes de poissons, ttois ichthyocomplexes indépendants sont reconnus dans le Trias. Le Vetlugian et le Yarenien dans le Trias inférieur et un autre dans le Trias moyen. L'ichthyocomplexe Yarenien comprend deux groupes d'âge dif férents (FAkhtuba et le Bogdo dans la Cis-Caspienne et le Fyodorovka et le Gamskaya dans le sud du Cis-Oural). L'ichthyocomplexe du Trias moyen comprend les groupes de poissons de Donguz et de Bukobaj. Les change ments dans le temps de la faune de poissons sont teportés sur les coupes à travers les tetritoires depuis le Cis-Oural jusqu'à la Cis-Caspienne. La suite d'Akhtuba, du Trias inférieur, de la coupe de Bogdo (Cis-Caspienne) est cor- rélée par les poissons avec la partie básale de la suite de Petrovpavlovka, et la suite de Bogdo sus-jacente avec le reste de la suite de Petrovpavlovka dans la région d'Orenbourg. Les suites du Trias moyen de Donguz et Bukobaj (Cis-Oural) sont stratigtaphiquement analogues aux suites de Elton et Indet de la coupe du Trias moyen du nord de la Cis-Caspienne. La succession dans le développement des ichthyofaunes du Trias est une constante sur tout le MOTS CLES Ichthyofaune, territoire de la Russie eutopéenne, elle est tracée pour les territoires adjacents Trias, et peut servir de base pour des divisions sttatigraphiques et des cottélations nord Cis Caspienne, interrégionales des différenrs faciès marins et continentaux du Trias. sud Cis Oural.

INTRODUCTION cations. The Triassic accumulation, as well as the aquatic paleobiota development in these regions, In the territory of European Russia, the Triassic were directly or indirectly controlled by the deposits are developed in two disconnected Tethys paleo-ocean regime. The first paleontolo- extensive fields: the southern and northern ones. gically characterized Triassic deposits in Russia The present paper considers the ichthyofauna were established within the southern Triassic only from the southern Triassic field, embracing field, in the Bolshoye Bogdo Mountain, near the the territories of the northern Cis-Caspian (the lake of Baskunchak in the northern Cis-Caspian. Peri-Caspian Depression), the south of the Cis- In the middle of the eighteenth century, Pallas Ural Marginal Deflection, the southern slope of (1788) discovered ammonites in the Bogdo the Volga-Ural Anticlise (Obshchy Syrt) and, limestones; later on, those were described by partially, the zone of the Don-Medveditsa dislo Bukh (1885) as Ammonites bogdoanus Buch.

280 GEODIVERSITAS • 1997 • 19(2) Triassic Ichthyofauna of southern Urals

While making a layer-by-layer description of the Mojsisovich (1882) found ceratites in the ammo same section, Auerbakh (1871) found some nite fauna of Bolshoye Bogdo, late in the nine remains of labyrinthodont, Mastodonsaurus (?) teenth century, that the section could be sp., and fish, Hybodus plicatilis Agassiz, Acrodus compared to the Campilian layers of the Alpine dunkeri Auerbach, Sphaerodus minimus Agassiz, Lower Triassic. Later on, Khabakov (1932) des Saurichthys sp. Those fauna-bearing layers are cribed two lungfish tooth plates from the Bogdo comparable with the Middle Triassic limestones: Ceratodus ex gr. kaupi Agassiz, and Muschelkalk from Germany. It was only when C. facetidens Chabakov. It is worth mentioning

FIG. 1. — Principal ichthyofauna localities in the northern Cis-Caspian and southern Cis-Ural regions, main sections: 1, The Don Bend; 2, Gmelinka, well 5041-c (1521-1526 m int.); 3, Yuzhno-Yershovskaya, well 1 (931-934 m int.); 4, Bolshoj Bogdo Mountain; 5, Novokazanka, well k-6 (424.5-427 m int.); 6, Zhundykuduk, well 46 (depth 440 m); 7, Zhundykuduk, well 22 (487-491 m int.); 8, Barkhanny, well k-4 (358-365.5 m Int.); 9, Azi-Molla-1 ,-2; 10, Kok-Tau; 11, Kara-Bala-Kantemir; 12, Mechet; 13, Markovka; 14, Mirolyubovka; 15, Rossypnoye; 16, Nizhneozyornoye; 17, Chyornaya-1; 18, Donguz-1, -2, -12; 19, Berdyanka-2, -3; 20, Bukobaj-5; 21, Karagachka; 22, Kzyl-Saj-2; 23, Krasnogory-2; 24, Bekhteyev Gully; 25, Petropavlovka-1, -2; 26, Kaltayevo-2, -3; 27, Yaslav; 28, Muraptalovo; 29, Yamangulovo; 30, Sankubaj, well G-1 (890.1-893.6 m int.); 31, Rozhykha; 32, Yelshanka-I; 33, Dolgy Yar.

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that the first of the two forms was first described occur, which is clearly demonstrated by our from the German Muschelkalk. Subsequently, materials. At the boundary of the Vetlugian and lungfish remains were found within the Tfiassic Yatenian, in the Olenekian age, everywhere over beds from the Middle Don (the Don Bend loca the Russian Plate, ceratods appear in the dipnoan lity), the South Cis-Urals (Donguz-1 and fauna, with gnathorhiza still existing. They Kaltayevo-2 localities), and over vast areas of the co-exist during the rather short Fyodorovka time, northern Triassic field (Efremov & V'yushkov after which the gnathothiza vanish. This pheno 1955). menon is clearly evident in the Cis-Caspian, The authors began to study fossil fish from the within the Bolshoye Bogdo section, as well as in Triassic of Russia in the mid-sixties. An ample a number of localities from the Moscow and material from over 150 localities was collected, Mezen syneclises. The revealed changes in fossil- representing Early and Middle Triassic squali- fish compositions with time in this region were forms, lungfish and actinoptetygii from Eastern used for distinguishing the ichthyocomplexes Europe. The Late Triassic fishes from the region there: two in the Lower (the Vetlugian and are still unknown. There are over forty localities Yarenian) and one in the Middle Triassic. of the Triassic ichthyofauna in the south of the East European Platform and in the South Cis- 1. The Vetlugian ichthyocomplex is represented Urals (Fig. 1). It was largely this material that by gnathorhiza - Gnathorhiza triassica triassica provided the basis for revealing the stratigtaphic Minich, Gn. lozovskii Minich, and hyboduses - impottance of lungfish (Vorobyova & Minikh Hybodus spasskiensis A. Minich. The dominant 1968; Minikh M. G. 1969, 1977), squaliforms form here is Gn. triassica triassica Minich, which and actinoptetygii remains (Minikh A. V. 1975, does not occur in any younger deposits. This 1985, 1992). Frequent joint finds of fish and ichthyocomplex is more complete in the nor tetrapod remains proved to be of much use. The thern Triassic field; a number of stratigraphic study of both (Ochev et al. 1979), combined groups are recognized within it. with informations on other fossils and the data from lithologic (Tverdokhlebov 1966, 1970; 2. The Yarenian ichthyocomplex is subdivided Lipatova et al. 1965; Lipatova 1967, etc.) and into two groups: the early, the Akhtuba one paleomagnetic research (Molostovsky 1983), (with dipnoans: Gnathorhiza bogdensis Minich, made it possible to develop unified stratigraphic Gn. otschevi Minich, Gn. triassica baskunchakensis division schemes for the Triassic of European Minich, Ceratodus multicristatus Votobyova, Russia (Anonymous 1982). C. jechartiensis Minich, C. gracilis Vorobyova; and squaliforms: Hybodus spasskiensis A. Minich, Hybodus maximi A. Minich) and the later, the STRATIGRAPHIC ICHTHYOCOMPLEXES Bogdo one (with ceratods: Ceratodus recticristatus Vorobyva, C. donensis Vorobyva et Minich, Notwithstanding considerable taxonomic diversi C. multicristatus Vorobyva, C. multicristatus lipo- ty of certain Triassic fish groups, a number of vensis Minich, C. jechartiensis Minich, C. kaupi regularities are observed in theif evolution, which Agassiz, C. facetidens Chabakov; squaliforms: may be used for stratigraphic purposes. Hybodus maximi A. Minich, H. plicatilis Agassiz, Dipnoans served as the basis for recognition of Acrodus dunkeri Auerbach, Lissodus angulatus two major stages, or superichthyocomplexes, Stensio; and actinopterygii: Sphaerodus minimus changes in the Triassic from the East European Agassiz, Colobodus varius Giebel). Platform and the Cis-Ural deflection: the gna- thothizian and ceratodian ones. The first one has 3. The Middle Triassic ichthyocomplex is also a worlwide distribution from the Late subdivided into two groups of various ages. In Catboniferous to the Early Triassic. The second the earlier group, the Donguz one, fishes ate one appears in the Early Triassic and exists up to represented by Ceratodus gracilis Vorobyva, now. It is in the Lower Triassic that their change C. bucobaensis Minich, C. orenburgensis Minich,

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C. recticristatus Vorobyva, C. donensis Vorobyva part of the Vetlugian series, the Kzylsaj suite; it is et Minich, C. jechartiensis Minich, Saurichthys situated along the right bank of the Chyornaya dongusensis A. Minich, Hybodus otschevi River, 5 km to the south of Krasny Kholm villa A. Minich, Hybodus karagatshkaensis A. Minich. ge, Orenburg region. A typical Early Triassic Ceratodus recticristatus Vorobyva, Hybodus otsche gnathorhiza form, Gnathorhiza otschevi Minich, vi A. Minich and Saurichthys dongusensis was found there in red-brown sands (10 m). A. Minich are characteristic of the considered There is another known locality, the one of group. In the younger, the Bukobaj group, fishes Muraptalovo-I, on the right bank of the Bolshoy are represented by Ceratodus bucobaensis Minich, Ynshatyr River near Muraptalovo village, C. gracilis Vorobyva, C. orenburgensis Minich, Kyurgazy district in the south of Bashkiria. The Saurichthys ultimus A. Minich, Hyboduskara section is represented by a sequence of red brown gatshkaensis A. Minich, Ceratodus bucobaensis cross-bedded sandstones (over 25 m). In one of Minich and Saurichthys ultimus A. Minich. the lenticular interlayers was found a fin spine of General information on all the known ichthyo a squaliform, Hybodus spasskiensis A. Minich, fauna localities, within the southern Triassic typical of the Early Triassic deposits. Hybodus field, is presented below and its correlative possi spasskiensis A. Minich fin spines were also encountered higher in the section, near Yakutovo bilities are revealed. village, in similar sandstones containing remains of the Vetlugian tetrapod fauna (Wetlugasaurus sp., Benthosuchus bashkiricus Otchev). Two other REVIEW AND CORRELATION bone-bearing sites from the Kzylsaj suite of the OF ICHTHYOFAUNAL LOCALITIES Vetlugian series, containing a typical Vetlugian ichthyocomplex, are known from Buzuluk dis THE VETLUGIAN ICHTHYOCOMPLEX trict, Orenburg region. One of them is Dolgiy Within the Vetlugian series of the Lower Triassic Yar locality in the same-named gully falling into from the South Cis-Urals and the adjacent from the Pogromnaya River (the Samara left tributa the west regions of Obshchy Syrt, fish remains ry), from the left 2.3 km north-west of were encountered in several bone-bearing sites. Logachyovka village. Sevetal well-preserved lung- The most ancient of those is Yelshanka-I, a loca fish tooth plates were found in an interlayer of lity 9 km to the south of the town of Buzuluk in brown clayey aleurolites within a sequence of Orenburg region. Tooth plate temains belonging cross-bedded sandstones. They belonged to to Gnathorhiza lozovskii Minich, typical of the Gnathorhiza triassica bereznikiensis Minich, typi Vetlugian ichthyocomplex, were found there in cal of the uppermost layers of the Vetlugian series an interlayer of red brown aleurolites within a of the more northerly regions of the East sand sequence of the Kopanskaya suite. The European Platform. The second site, Rozhikha soundness of this gnathorhiza being assigned to locality, is situated in the mouth of Rozhikha the Kopan level is confirmed by the discoveries Gully, falling into the Grachyovka River (the of Tupilakosaurus sp. vertebra, typically represen Buzuluk left tributary) 1.4 km north of tative of the tupilakosaur group of the vetluga- Grachyovka village, Buzuluk district. In the simi saur terresttial vertebrate fauna (Ochev 1992). lar rocks of the Kzylsaj suite there, a large tooth Another locality, Nizhneozyornoye, is situated in plate of Gnathorhiza otschevi Minich was found, the left wall of a gully, falling into the Ural River typically representative of the Vetlugian ichthyo near Nizhneozyornoye village, Krasnokholmsk complex. The Vetlugian level of the Triassic sec district, Orenburg region. The Early Triassic tion from the Peri-Caspian Depression is hybodont shark remains, Hybodus spasskiensis penetrated by a substantial number of wells, but A. Minich, were found there in an abandoned- with incomplete core selection, lung fish remains channel suite, represented by a sequence of (Gnathorhiza triassica triassica Minich) were brown cross-bedded sands with clay and sandsto found only in well No. G-l (Sankubaj), within ne interlayers with apparent thickness up to 5 m. the 890.1-893.6 m depth interval. These dip- Chyornaya-I locality is associated with the upper

GEODIVERSITAS • 1997 • 19(2) 283 Minikh M. G. & Minikh A. V.

noan forms are extremely common in Vetlugian Burtya River basin (a left tributary of the Ural) deposits, included the area of the northern near Andreyevka village (Burtinskij district, Triassic field, and may serve as good correlatives Orenburg region), in the sand-conglomerate of the host beds. sequence of the Petropavlov-skaya suite, tepresentatives Gnathorhiza and Ceratodus occur, cha THE YARENIAN ICHTHYOCOMPLEX racteristic of the early Yarenian group Formations of the Yarenian age are widely distri (Gnathorhisa triassica baskunchakensis Minich buted over the considered regions of the South and Ceratodus multicristatus multicristatus Cis-Urals and northern Cis-Caspian. Bone Vorobyova). In the suite section they are associa remains of terrestrial vertebrates and fishes occur ted with hybodont shatks remains, Hybodus there rather frequently. Taken togethet, they spasskiensis A. Minich. Thus, the presence of constitute the basis for determination of the rela Gnathorizds and Ceratodids in the Lower tive geologic ages of the deposits. Within the Triassic sections makes it possible to correlate the Peri-Caspian Deptession, the Yarenian ichthyo Akhtuba suite of the Peri-Caspian Depression complex was studied in the Triassic section from with the lowermost part of the Pettopavlovka the Bolshoye Bogdo Mountain, on the south suite of the South Cis-Urals in the reference sec western bank of Baskunchak brine lake (Minikh tion along the Kyzyl-Say Gully. Two explanations 1972, 1977). Diverse fish remains from both may be offered for the lack of representativeness groups of the Yarenian ichthyocomplex were of this fish-group in the suite stratotype section found there at various levels, in the Akhtuba and near Petropavlovka village. The first one seems to Bogdo suites (Fig. 2). Numerous gnathorhiza be optimistic: the discoveries are waiting ahead. and ceratod remains were found in the red-bed The second one runs as follows: either this part clayey aleurolites of the Akhtuba suite (bone-bea of the section is absent from the stratotype or the ring site A): Gnathorhiza triassica baskunchakensis conditions for fish burial were unfavourable near Minich, Gn. bogdensis Minich, Gn. otschevi Pettopavlovka at that time. Minich, Gn. sp., Ceratodus multicristatus multi- The late Yarenian (Gamskaya) group of the Early cristatus Vorobyova. Combinations of gnathorhi Triassic ichthyofauna is reasonably completely za and cerarod remains within the Lower Triassic represented in the South Cis-Urals and in the sections are characteristic of the Akhtuba group adjacent western region of the East European from the Yarenian ichthyocomplex of the Platform. First of all, let us mention the availabi Cis-Caspian. Saurichthian remains {Saurichthys lity of a purely ceratod dipnoan association in sp.) occur within the Akhtuba suite from the Petropavlovka suite stratotype (Tverdo- Bolshoye Bogdo alongside with dipnoans. A khlebov 1967a). This is situated on the bank of typical form of the Akhtuba group, Gnathorhiza the Sakmara (Fig. 1), in the vicinity of triassica baskunchakensis Minich, was also Petropavlovka village, Sakmara district, encountered at the depth of 553 m in a core Orenburg region. It is mainly built (Fig. 2) of from K-6 well (Barkhannaya), drilled between greyish brown sandstones with aleurolite and the Ural and the Volga. This part of the Triassic clay intetlayers of a total thickness up to 250 m. section was assigned to the upper half of the Dipnoan remains {Ceratodus multicristatus lipo- Olenekian stage, accotding to the ostracode vensis Minich and C. jechartiensis Minich) were [Gerdalia triassiana (Belousova), G. wetlugensis found there at various levels (Petropavlovka-1 Belousova) and charofite (Porochara triassica and -2 localities). These fish widely occur in the (Saidakovsky), Auerbachichara achtubensis late Yarenian deposits of the East European Kisilevsky) complexes. The lungfish from this Platfotm. Ceratodus multicristatus lipovensis section indicates an Akhtubian age of deposition. Minich tooth plates were also encountered In the South Cis-Urals, the early Yarenian (Fig. 3) in the Petropavlovka suite-developed (Fyodorovka) group of the Lower Triassic ich- along the Donguz River (Donguz-9 locality) near thyofauna is only represented in Kyzyl-Say-2 Mescheryakovka village, Sol-Iletsk district, locality (Garyainov & Ochev 1962). In the Otenburg region, in Bekhteyev Gully within the

284 GEODIVERSITAS • 1997 • 19(2) Triassic Ichthyofauna of southern Urals

S ° ™ I- H w CORRELATION OF PRINCIPAL SECTIONS BY ICHTHYOFAUNA CO U *- >- IU (0

Barkhanny well K5 leo-LJjgj 5 BukobaiV

Ix / 1 Marl I—lAleurolile Argillite Fish

I^H Clay [ , | Sand ^H;v| Sandstone Conglomerate

FIG. 2. — Correlation of the Triassic sections from the northern Cis-Caspian and southern Cis-Urals regions according to ichthyofauna.

GEODIVERSITAS -1997-19(2) 28 5 I Minikh M. G. & Minikh A. V.

Ural-Sakmara watershed, and in the vicinity of Within the Peri-Caspian Depression, the Late Yazlav Farm, Kyurgazy disttict, Bashkiria. There Yarenian (Bogdo) group of the Early Triassic ich- is a major Triassic vertebrates locality, thyofauna is most clearly seen in the Bogdo suite Rossypnoye, to the west of the Cis-Ural deflec section (Fig. 2), from the Bolshoye Bogdo tion, in the territory of Obshchiy Syrt (Efremov Mountain (bone-bearing site B). Fish remains are & V'yushkov 1955). It is located in the right represented there by dipnoans (Ceratodus multi- slope of Mayachnaya Gully, opened from the cristatus lipovensis Minich, Ceratodus facetidens right into the Ural valley 1.0 km to the north Chabakov and Ceratodus ex. gr. kaupi Agassiz) east of Rossypnoye village, Ilekskij district, and squaliforms (Hybodus plicatilis Agassiz and Orenburg tegion. Cetatod tooth plates Cemtodus Acrodus dunkeri Auerbach). Actinopterygii are recticristatus Minich (Fig. 3) occur here alongside represented by perleidids (Colobodus varius Giebel with parotosuchian fauna tetrapod remains, in and Sphaerodus minimus Agassiz) and saurichtiids red clays. (Saurichthys apicalis Agassiz and Saurichthys sp.). An even richer locality of Early Triassic verte Evolutionary levels identities, and similarities in brates, the Don Bend (Rykov & Ochev 1966), is a numbet of lungfish, squaliforms and actinopte- known from the south-eastern slope of the rygians from the single late Yarenian group of the Voronezh antecline dislocations. It is situated Early Triassic ichthyofauna within the (Fig. 1) in a large bend of the Don, north of Cis-Caspian Bogdo section and those from the Sirotininskaya village, in Lipovskij Gully (a Don Triassic section of the Don Bend (Ceratodus right tributary). Diverse fish remains occur there multicristatus lipovensis Minich, Lissodus sp. and in the upper, sand-conglomerate portion of the Saurichthys sp.), make it possible to correlate Lipovskaya suite, together with the parotosu with certainty the Bogdo suite with the chian tetrapod fauna remains. Among fish, dip- Lipovskaya suite of the Middle Don, the noans are found there: Ceratodus mulicristatus Petropavlovka suite of the south-eastern slope of lipovensis Minich, C. jechartiensis Minich and the Volga-Ural antecline and the south of the C. donensis Vorobyova et Minich; sharks Hybodus Cis-Ural deflection. The presence in the Bogdo maximi A. Minich, Lissodus angulatus Stensio, group of ceratods, Ceratodus kaupi Agassiz, very actinopterygii Saurichthys sp., and other, forms of common in the Middle Triassic Muschelkalk of squaliform and actinopterygian fish that are not the German basin implies, in its turn, probable decribed yet. On the whole, according to the paleogeographic and ichthyofaunal connections composition of fossils encountered there, the between the Bogdo and German marine sedi Don Bend locality belongs to the Late Yarenian mentation basins towards the end of the Early (Lipovskaya) group of the Early Triassic ichthyo- Triassic. Such a connection between the fauna, and may be correlated by fish with most Peri-Caspian and North German Depressions of the Petropavlovka suite from Obshchiy Syrt might be accomplished through the Cis- and from the Cis-Ural Deflection; through these, Caucasian marginal deflection, the system of the it may also be correlated with the Gamskaya Dnieper-Donets depressions, Pripyat Deflection suite from Safonovsky Deflection of Mezen syne- and Polish-Lithuanian syncline. At the end of the clise. It is interesting to compare Ceratodus Early Triassic, a lot of interconnected freshened donensis Vorobyova et Minich, very common in semi-marine basins existed all over that region, the Lipovskaya suite and described by the Don which might provide the exchange of btackish Bend material, with the Triassic ceratodes known faunas. from all over the world. Among the European forms, C. priscus Fraas from the Lower Triassic of THE MIDDLE TRIASSIC ICHTHYOCOMPLEX Schwarzwald (medium mottled sandstones) In the territory of European Russia, the Middle seems to be the most similar one. This allows us Triassic ichthyofauna was first discovered and to correlate, in a first approximation, the Lower described from the South Cis-Urals (Vorobyova Triassic dipnoan bearing beds from the East European and West European Platforms. & Minikh 1968). It comes from the Donguz and Bukobaj suites (Tverdokhlebov 1967b) and is

286 GEODIVERSITAS • 1997 • 19(2) o o

to FIG. 3. — Ichthyofauna distribution within the sections of the Triassic from the southern Cis-Urals regions. oc a \1 Minikh M. G. & Minikh A. V.

known from the faunas of a number of localities, karagatshkaensis A. Minich, H. otchevi where it is often encountered together with the A. Minich) and actinopferygians (Saurichtbys remains of eriosuchian and mastodonsaurian ter dongusensis A. Minich). All these forms may be restrial vertebrate faunas (Ochev 1992). The regarded as typical of the Middle Triassic ich principal localities of the Middle Triassic ichthyocomplex on the whole. The combination of thyofauna are associated with type and reference these forms with those known from the Early sections of both suites. The Donguz suite strato- Triassic deposits (Ceratodus recticristatus type is located along the Donguz River (left tri Vorobyova and C. jechartiensis Minich) makes it butary of the Ural) near Perovka village, possible to separate the Donguz group both from Sol-Iletsk district, Orenburg region. The section the earlier and from the younger groups of the is generally composed of variegated aleuro-clayey Triassic ichthyofauna. and arenaceous rocks up to 150 m thick. In the Along with fish remains in the Donguz suite of middle part of the suite, in the conglomerate-like the South Cis-Urals, the remains of eriosuchian interlayers among variegated aleurolites and clays fauna tetrestrial vertebrates occut, which correla of the Donguz-I locality (Figs 1-3), lung fish te with the Ladinian tetrapod association from tooth plates were discovered (Ceratodus gracilis the uppermost Muschelkalk and lower Keuper of Vorobyova, C. recticristatus Vorobyova, C. oren- Germany, according to common plagiosaur burgensis Minich and C. jechartiensis Minich). genera (Plagiosternum and Plagioscutum). The latter forms, although quite common in the The Donguz suite correlates with the Elton suite upper layers of the Lower Triassic, are rathet rare established in the northern Cis-Caspian, accor in the Middle Triassic. About 75 m higher in the ding to the ichthyofauna. The section of the section of the Donguz suite, in the Donguz-12 Middle Triassic and its ichthyofauna were stu locality in a lens of unsorted sandy-aleurite rocks died thete (Fig. 4) from the cores of several refe together with bones of tetrapod eriosuchian rence and parametric wells and from the natural fauna and tooth plates of ceratods {Ceratodus outcrops on the north-eastern shore of Inder gracilis Vorobyova, C. recticristatus Vorobyova, Lake. The lake is situated in the left-bank region C. orenburgensis Minich and C. bucu-baensis of the Ural, south-east of Inderborsky settlement, Minich), some other fossils were found: hybo- Gurjev region, Kazakhstan. A rather complete dontid fin and head spines (Hybodus otschevi section of the Triassic, typical of the central parts A. Minich), teeth of Lissodus angulatus Stensio, of the Peri-Caspian Depression, is known there teeth of new squaliform genera and species (their on the slopes of the Kok-Tau Range and along descriptions are being prepared for publication) the lake shores. The Early Triassic Cis-Caspian and actinopterygian jaws {Saurichtbys dongusensis series are represented in the Inder section by the A. Minich). Almost the same set of taxa occurs basal red-bed clayey sequence (over 200 m). The among the lungfish and squaliform remains, Middle Triassic is represented by the Elton (a from a number of other vertebrate localities, at red-bed arenaceous-conglomerate sequence, up various levels of the Donguz suite of the South to 110 m and an arenaceous-clayey one up to Cis-Urals. These are Berdyanka-2, Berdyanka-3, 60 m) and Inder suites (grey-coloured limestone- Karagachka, Kaltayevo-2 localities (Figs 1-3). Fin clayey sequences about 250 m). The Late Triassic pines of yet another Hybodus species were found variegated sandstone sequence lies above them in the latter two ones: Hybodus karagatshkaensis (up to 100 m), the Masteksaj horizon A. Minich, typical of the whole of the Middle (Anonymous 1982). Triassic ichthyocomplex. The Lower/Middle Triassic boundary was Thus, the Donguz group of the Middle Triassic previously drawn (Ochev & Smagin 1974) ichthyofauna clearly stands apart from the above within the Elton suite, between the basal sandy- considered Early Triassic ones, because of the conglomerate and the red-bed sandy-clayey new dipnoan species appearing within the sec sequences. Our point of view regarding this pro tions (Ceratodus gracilis Vorobyova, C. bucobaen- blem was determined after the discovery of typi sis Minich), new squaliforms (Hybodus cal Middle Triassic ichthyofauna remains in the

288 GEODIVERSITAS • 1997 • 19(2) o o < FAUNA CONTAINING BEDS GENERAL-SCALE REGIONAL Principal fish UNITS UNITS < O localities from

ILI S « i the Northern < £ § Q_ m e e » LU m m .N .Ns .sN W I- Cis-Caspian O) (f) ra 2 -2 -2 ì 1 S > •*-< dj co g JC CO Co cj aoaucjoouoro

Inder (Kara-Bala)j fi Inder (Kok-Tau) Azy - Molla 2 Well 5041 Gmelln. o Well K4 Barchan. Azy - Molla-1 co Well 1 Yershov co Don Bend < é-é Bogdo mount-B

Bogdo mount-A

er (Well K6 Barkhan.

Well-GI Sankub.

Fig. 4. — Ichthyofauna distribution within the sections of the Triassic from the northern CIs-Casplan region. ho oo Minikh M. G. & Minikh A. V.

sand-conglomerate sequence of the Elton suite. bank of the Bolshoj Yushatyr river near Lungfish tooth plates {Ceratodus gracilis Starokaltayevo village (Efremov & V'yushkov Vorobyova) and undefinable tetrapod bone frag 1955). In the Kaltayevo-3 location there, within ments wete found there in the Kok-Tau and the grey sandstones, besides tetrapods Azi-Molla-1 locations. This ceratod species is Mastodonsaurus torvus Konzhukova and others, known as a component of the Middle Triassic squaliforms were found, Hybodus karagatshkaen- (Donguz) ichthyocomplex from the South sis A. Minich, which occurs as early as at the Cis-Urals. In the northern Cis-Caspian, this spe Donguz level, and the latest of the saurichthiids cies is also found in some cores from the wells known from the region, Saurichthys ultimus penetrating the Middle Triassic sections (the age A. Minich, similar in their morphologic features was determined from ostracodes and charo- to saurichthys from the Ladinian stage of Turkey phytes). These are the sections of the Yuzhno- (Minikh A. V. 1992). Yershovskaya-1 well (931.0-934.0 m interval), In the northern Cis-Caspian, the Inder suite is Barkhanny K-5 well (379.0-385.9 m and cotrelated to the Bukobaj suite from the South 385.9-392.9 m intervals) and Zhundykuduk-46 Cis-Urals by tetrapod and fish faunas. A verte well (490 m depth). Besides ceratods, some sec brate locality, Kara-Bala-Kantemir, was discove tions contain the remains of hybodont sharks red in the suite stratotype in the vicinity of Inder typical of the Donguz fish-group [Hybodus Lake (Ochev & Smagin 1974). This is situated otschevi A. Minich; Gmelinka 5041-C well, on the north-eastern shore of Inder Lake on the 1521-1526 m interval) and new species of the hill top, 200 m to the south of Kara-Bala- shark genus Lissodus (Barkhanny K-4 well; Kantemir graves (masars). There, in the greyish- 361.5-365.5 m interval). green clays of the Inder suite, along with the The presented data on ichthyofauna distribu bones of mastodonsaur fauna tetrapods, ostra tions within the Middle Triassic deposits, codes and charae (Lipatova et al. 1969), the confirm that Ceratodus gracilis Vorobyova remains were found that are typically representa belongs to the Middle Triassic ichthyofauna of tives of the Middle Triassic Bukobaj ichthyofau- the Donguz group; its taxonomic composition is nal group: ceratodontid tooth plates [Ceratodus rather stable within the whole of the southern orenburgensis Minich) and a cartilaginous ganoid field of the Triassic development in European (Saurichthys ultimus A. Minich). Russia. On the basis of these lungfish discoveries, the age of the basal sandy-conglomerate sequence of the Elton suite, from the Inder Triassic sec tion, may be defined as the Middle Triassic. CONCLUSION The younger, Bukobaj group of the Middle Triassic ichthyofauna, from the South Cis-Urals, The wide distribution of ichthyofaunas, similar is known from the stratotype section of the in composition, in the south-east of the Russian Bukobaj suite in Bukobaj-5 locality. It is situated Plate and in the northern Cis-Caspian, as well as in Bukobaj Gully falling in the Berdyanka river the general succession in its change with time, (left tributary of the Ural) from the right, up indicate the unity of depositional basins in the stream Belyayevka village, Sol-Iletsk district, Triassic, all over the considered territory. Such Orenburg region. Within the light-grey sands fishes as hyboduses, ceratods and saurichthii and sandstones of this area, lungfish tooth plates prove to be very cosmopolitan. They are wides were discovered (Ceratodus gracilis Vorobyova pread and common in the Triassic deposits from and C. bucobaensis Minich), as well as the practically all the continents of the globe remains of saurichthiid Saurichthys ultimus (Minikh 1977; Minikh A. V. 1982). This may be A. Minich, typical of the Bukobaj fish group. used for solving the important problems of dis Some mastodonsaur tetrapod fauna remains were tant inter-regional and intercontinental correla also found there. The Bukobaj suite comprised tions of marine, semi-marine and continental also the deposits, outcropping along the fight Ttiassic deposits.

290 GEODIVERSITAS • 1997 • 19(2) Triassic Ichthyofauna of southern Urals

Acknowledgments Triassic of the east of the European USSR and their We would like to express our gratitude to Prof. stratigraphic importance. An abstract of the Candidate of Geology Thesis. Satatov Univetsity V. G. Ochev, Prof. D. A. Kukhtinov and Dr. publication, 22 p. [in Russian]. V. P. Tverdokhlebov for granting the stone mate — 1985. — New tepresentatives of Hybodus genus rials on the Triassic ichthyofauna and for their squaliforms from the Ttiassic of the USSR helpful consultations on some sections from the European east. Paleontological journal, No. 3: 66-70 South Cis-Urals and northern Cis-Caspian. [in Russian]. — 1992. — Sautichthyid (Sautichthyiformes order) from the Middle Triassic of the South Cis-Urals: 146-151 [in Russian], in Paleontology problems, REFERENCES Saint-Petersburg University Publication, volume 10. Minikh M. G. 1969. — The Importance of Dipnoan Anonymous 1982. — Decisions of the intetdepart- Remains for Stratigraphy of the Triassic beds from ment stratigraphic Conference on the Ttiassic of the bast of the USSR European Part, in Geology the East European Platform (Saratov, 1979). With Problems of the South Urals and Volga Region, tegional sttatigtaphic schemes. VSEGEI, Leningtad, Saratov University Publication 6: 137-145 [in 66 p. [in Russian]. Russian]. Auerbakh I. B. 1871. — Bogdo Mountain. — 1972. — Fish, Stratotype section of the Lower Transactions of Russian Geographic Society, volu Triassic Baskunchak series from Bolshoye Bogdo me 4, 82 p. [in Russian]. Mountain. Saratov. Saratov University Publication: Buch L. von 1885- — Explication de trois planches 48-50 [in Russian]. d'Ammonites. Gesammelte Schriften, volume IV, — 1977. — Triassic lungfish from the east of European parr. 1, 94 p. USSR. Saratov University Publicarion, 96 p. [in Efremov I. A. & V'Yushkov B. P. 1955. — Catalogue Russian]. localities of the Permian and Triassic terrestrial ver- Mojsisovich E. 1882. — Die Cephalopoden der tebtates in the USSR territory. USSR AS Meditettanen Triasprovinz. Abchandlungen d.k.-K. Paleontological Institute Transactions, volume 46, Geol. R.-A., vol. X. 185 p. [in Russian]. Molostovsky E. A. 1983. — Paleomagnetic stratigra Garyainov V. A. & Ochev V. G. 1962. — Catalogue phy of the Upper Permian and Triassic from the east of vertebrate localities within the Permian and of the European USSR. Satatov University Triassic deposits from the Orenburg Cis-Urals and the Publication, 168 p. [in Russian]. south of Obshchy Syrt. Saratov University Ochev V. G. 1992. — To the history of the Ttiassic Publication, 63 p. [in Russian]. vetterbrates from the Cis-Urals. MOIP Bulletin, Khabakov A. V. 1932. — On lungfish (Ceratodon- geological department, volume 67, No. 4: 30-43 [in tida fam.) remains from the Lower Triassic of Russian]. Bogdo mountain. USSR AS Paleozoological Institute Ochev V. G. & Smagin B. N. 1974. — On the Transactions, volume 1: 45-55 [in Russian]. Triassic vertebrates localities neat Inder Lake. Lipatova V. V. 1967. — On the German type of the MOIP Bulletin, geological department, volume 49, Triassic from the Peri-Caspian Depression. USSR No. 3: 74-81 [in Russian]. AS Transactions, geological serie, No. 1: 58-67 [in Ochev V. G., Tverdokhlebova G. I., Minikh M. G. & Russian]. Minikh A. V. 1979.— Stratigraphic andpaleogeo- Lipatova V. V., Rykov S. P., Starozhilova N. N., graphic importance of the Upper Permian and Lopato A. Yu. & Makarova I. S. 1965. — New Triassic vertebrates from the East European Platform data on the Ttiassic deposits from the Peri-Caspian and Cis-Urals. Saratov University Publication, Depression: 282-287 [in Russian], in Regionalgeo- 160 p. [in Russian]. logic-geophysic research in the border zone of the Peri- Pallas L. von 1788. — Travel over various Provinces of Caspian Depression. Saratov. Russia, Pan 3. Saint-Petersburg [in Russian]. Lipatova V. V., Sajdakovsky L. Ya. & Starozhilova Rykov S. P. & Ochev V. G. 1966. — On the Triassic N. N. 1969. — Paleontologic grounding fot teco- vertebtar.es localities in the Don Bend, in Geology gnition of the Middle Triassic within the problems of the South Urals and Volga region, Saratov Peri-Caspian Depression. USSR AS Transactions, University Publication, issue 3: 58-62 [in Russian]. geological serie, No. 3: 77-87 [in Russian]. Tverdokhlebov V. P. 1966. — New data on stratigta- Minikh A. V. 1975. — Ichthyodotulites and their phy of the Lowet and Middle Triassic deposits importance for stratigraphy of the Tatarian and from the Cis-Ural Deflection within the Orenburg Kasanian deposits from the east of European USSR, and Bashkiria Cis-Urals, in Geology problems of the in Stratigraphy and paleontology problems, Saratov South Urals and Volga region, The Mesozoic, Saratov University Publication 1: 29-32 [in Russian]. Univetsity Publication, issue 3, part 2: 3-24 [in — 1982. — Saurichthiids and hybodontids from the Russian].

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— 1967a. — New data on the stratigraphy of the — 1970. — The Baskunchak deposits from the left- Lower Triassic deposits from the Orenburg and bank region of the Samara River and Obshchy Syrt Bashkiria Cis-Urals, in Geology problems of the (Orenburg and Bashkiria Cis-Urals), in Geology South Urals and Volga region, Saratov University problems of the South Urals and Volga region, The Publication, issue 4, part 1: 45-77 ([in Russian]. Paleozoic and Mesozoic, Saratov University — 1967b. — Stratigraphy of the Middle and Upper Publication, issue 7, part 1: 96-101 [in Russian]. Triassic from the South Cis-Urals, in Geology pro Vorobyova E. I. & Minikh M. G. 1968. — An expe blems of the South Urals and Volga region, Saratov rience of biometry application to ceratodontid University Publication, issue 4, part 1: 78-91 [in tooth-plates study. Paleontological journal, No. 2: Russian]. 77-87 [in Russian].

Submitted for publication on 15 January 1996; accepted on 1 October 1996.

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