ISSN 0869-5938, Stratigraphy and Geological Correlation, 2007, Vol. 15, No. 5, pp. 485Ð515. © Pleiades Publishing, Ltd., 2007. Original Russian Text © D.N. Kiselev, M.A. Rogov, 2007, published in Stratigrafiya. Geologicheskaya Korrelyatsiya, 2007, Vol. 15, No. 5, pp. 42Ð73.

Stratigraphy of the BathonianÐCallovian Boundary Deposits in the Prosek Section (Middle Volga Region). Article 1. Ammonites and Infrazonal Biostratigraphy D. N. Kiseleva and M. A. Rogovb a Ushinsky State Pedagogical University, Yaroslavl, Russia b Geological Institute, Russian Academy of Sciences, Moscow, Russia Received January 21, 2007; in final form, March 28, 2007

Abstract—In European Russia, the most complete succession of Boreal sediments of the terminal Bathonian and lower Callovian is exposed near the Prosek Settlement. After its revision, the infrazonal division of the upper Bathonian and lower Callovian and position of the BathonianÐCallovian boundary are difined more care- fully. The Calyx Zone and bodylevskyi Biohorizon are established in the upper Bathonian. The base of the lower Callovian is defined at the first occurrence level of Macrocephalites jacquoti. Based on four successive ammo- nite assemblages occurring in lower part of the Elatmae Zone, the breve, frearsi, quenstedti, and elatmae bio- horizons are identified. The joint occurrence of Boreal, Subboreal, and Tethyan ammonites in the section facil- itate its correlation with the other sections of the Panboreal paleobiogeogaphic superrealm. DOI: 10.1134/S0869593807050036

Key words: BathonianÐCallovian boundary, European Russia, East Greenland, ammonites.

INTRODUCTION national Stratigraphic Commission (Remane et al., The study of the BathonianÐCallovian boundary in 1996), the candidate type section should be (1) of European Russia is important now for several reasons. appropriate thickness and sedimentation rates, (2) con- When Boreal marine sediments of the upper Bathonian, tinuous, (3) lacking synsedimentary and tectonic dis- which contain ammonite assemblage of the East Green- tortions, (4) free of metamorphic and significant diage- land affinity in general, have been discovered in the netic alterations, (5) containing abundant and diverse Middle Volga region, first in the Novgorod oblast fossils throughout the entire succession, (6) without (Mitta and Starodubtseva,1998; Gulyaev and Kiselev, facies changes near the boundary, (7) composed of 1999a, 1999b) and then in Mordovia (Mitta, 2004a, marine sediments, (8) appropriate for magnetostrati- 2004b), it was a good opportunity to solve several graphic, chemostratigraphic, and isotopic studies and stratigraphic problems. Objectives of prime signifi- (9) accessible. cance were to get a deeper insight into the BathonianÐ Callomon and Dietl (2000) stated in addition that Callovian boundary stratigraphy in European Russia, to the GSSP candidate should correspond above and correlate directly the ammonite successions of East below the boundary to succession of standard biostrati- Greenland and Subboreal regions, to substantiate better graphic units (in rank of chronosubzone) possessing the BorealÐTethyan correlation, and to detail the stan- global or nearly global correlation potential and meet dard scale accepted for the Panboreal Superrealm requirements of the priority principle and existing con- (Zakharov et al., 1997) or the Boreal secondary stan- ventions. dard (Callomon, 1993, 2003). Researchers who studied The AlbstadtÐPfeffingen section in Germany is at the upper Bathonian sediments in the Middle Volga present the only candidate for the GSSP of the Callov- region suggested different ammonite zonations and ian Stage lower boundary (Callomon and Dietl, 1990; correlation schemes for the upper BathonianÐlower 2000). Having the historical priority, this section in the Callovian boundary sediments. The schemes were con- Swabian Alb, the type site of the Kepplerites keppleri troversial, requiring additional examination of most Subzone, is included into the standard scale as a basal complete, relatively continuous sections containing the zone of the Callovian Stage (Callomom et al, 1988; diverse paleontological remains. Callomon and Dietl, 1990). The high correlation poten- The BathonianÐCallovian boundary in Boreal sedi- tial of the section is determined by a wide geographic ments attracts attention in connection with intend to distribution of the Keppleri Subzone index species, and select the GSSP for the lower boundary of the Callov- the ammonite assemblage of the Keppleri faunal hori- ian Stage. According to recommendations of the Inter- zon consists of species belonging to different bio-

485

486 KISELEV, ROGOV chores, the representatives of four Tethyan to Sub- History of its investigation lasted 120 years since its Tethyan and two Boreal families (Callomon and Dietl, discovery by A.R. Ferkhmin in 1886. The first period of 1990). investigation was dedicated to description of its Callov- The section in question includes four faunal hori- ian part largely (Sibirtsev, 1886; Gerasimov and Kaza- zons, the lower one (hochstetteri) of the Bathonian and kov, 1939; Kulinich and Fridman, 1990; Gulyaev, three others of the lower Callovian Keppleri Subzone. 1997). The lower, sandy portion of the Middle Jurassic It is lacking internal breaks in sedimentation significant was attributed to the Bathonian conditionally, because in terms of biostratigraphy, being bracketed although macrofauna has not been found there. by hiatuses below the base of the hochstetteri faunal The diverse assemblage of Boreal marine fossils horizon and at the top of the suevicum faunal horizon discovered in the sandy member motivated its correla- (Dietl, 1994; Callomon and Dietl, 1990, 2000). tion with the upper Bathonian (Gulyaev and Kiselev, 1999a, 1999b). Found ammonites similar or identical to Besides the advantages mentioned above, the Albs- species from the Cadoceras calyx Zone of East Green- tadtÐPfeffingen section has serious disadvantages (R. land substantiated the late Bathonian age of sand beds. Jordan in Callomon and Dietl, 2000; Mitta, 2004b) The ammonite assemblage is dominated by Kepplerites diminishing its status of candidate for the GSSP. First, svalbardensis Sokolov et Bodylevski. Rare Cadocerati- these are signs of sediment condensation observable nae specimens have been determined as new species throughout the section, which mean potential gaps in Cadoceras infimum Gulyaev et Kiselev and Costaca- the biostratigraphic record. Callomon and Dietl are doceras pisciculus Gulyaev. The peculiar composition however of opinion that there is no unconformity of of the ammonite assemblage was inappropriate for con- biostratigraphic significance in the boundary interval fident identification of biostratigraphic units estab- proper, since …“where, ‘elsewhere,’ have additional lished in East Greenland, and Bed 1 of the section was distinguishable faunal horizons been found that are attributed to the new Infimum Zone and synonymous identifiably of ages intermediate between those of the 1 hochstetteri and keppleri horizons? The answer is, that biohorizon. after 140 years of intensive work, nowhere. And the Ammonites were found in concretions (well pre- close similarity of the faunas of these horizons suggests served) and matrix of the bed (deformed). The ammo- that the future chances are small” (Callomon and Dietl, nite assemblage consists mainly of forms from large 2000, p. 49). sandstone concretions, which have not been found first The existing doubts in appropriateness of the Albs- in situ. Their occurrence was thought to be in the inter- tadtÐPfeffingen section for the GSSP forced members val of 0.5Ð2.5 m below the top of the sand bed. It was of the International Working Group on the Callovian assumed that concretions occur at several levels. When Stratigraphy to propose alternative variants of the concretions were discovered in situ, it became clear that BathonianÐCallovian boundary stratotype section. they occur substantially lower, in a single horizon During the 7th International Congress on the Jurassic within the interval of 2.5Ð3.5 m (Gulyaev, 2001). System (Krakow, 2006), a group pf specialists paid In matrix of the sand bed upper part, Gulyaev (2001) attention to advantages of the section in the ProsekÐ found Cadoceratinae specimens close to C. infimum Isady area (Nizhni Novgorod oblast). Owing to abun- from concretions, although differing from the latter in dant and diverse fossils, obvious continuity, and other morphology. Because of a poor preservation, this form features, this section can certainly be a GSSP candidate was first described in open nomenclature as C. cf/aff. for the BathonianÐCallovian boundary. In October of infimum and attributed subsequently to new subspecies 2006, a multidisciplinary study of the section was car- C. infimum subsp. nov. (Gulyaev, 2005). According to ried out by a team of researchers from different regions its peculiar morphology and occurrence in the section and organizations of Russia. The team consisted of separately from C. infimum infimum. Gulyaev defined D.N. Kiselev (Yaroslavl State Pedagogical University), two biohorizons in the Infimum Zone (Table 1). M.A. Rogov, S.Yu. Malenkina (Geological Institute of Mitta (2000) attributed the sand member (Bed 1) to the RAS, Moscow), L.A. Glinskikh (Institute of Geol- the Callovian but not the Bathonian. He failed to find ogy and Geophysics, Siberian Division of the RAS, concretions with fossils under consideration. Mitta Novosibirsk), M.V. Pimenov, and A.V. Manikin (Sara- revised determinations by Gulyav and Kiselev and tov State University, Saratov). In this work, a detailed attributed Kepplerites svalbardensis Sokolov et infrazonal scale based on distribution of ammonites is Bodylevski to K. aff. keppleri (Oppel). After revision of suggested. Cadocertinae forms, he regarded specimens of Cadoceras infimum Gulyaev et Kiselev as different spe- cies: the holotype and all other species from concre- INVESTIGATION HISTORY tions as Cadoceras frearsi (d’Orbigny), and specimen The ProsekÐIsady section of MiddleÐUpper Jurassic from Bed 1 (Gulyaev and Kiselev, 1999a, Plate 2, deposits (Lyskovo area, Nizhni Novgorod oblast) is 1 The term “biohorizon” is used in this paper as a synonym of the exposed on the Volga River right bank between epony- term “faunal horizon” (see discussion in works by Page, 1995, mous settlements southwest of the former (Fig. 1a). and Gulyaev, 2002).

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007

STRATIGRAPHY OF THE BATHONIANÐCALLOVIAN BOUNDARY DEPOSITS 487

AB Unzha R.

Volga R. Makar’evo Prosek

Nizhni Volga R. Novgrod Volga R. Isady Moscow Oka R. Prosek

Lyskovo 1 km 100 km Sura R.

Fig. 1. Schematic location of sections near the Prosek and Isady settlements. (A) Large-scale scheme; (B) locaion of the main sec- tion and erosion outlier of Jurassic sediments in the Lyskovo area. Outlier boundaries are given along the isohyps of 160 m.

fig. 6) as C. bodylevskyi Frebold. As number of hori- lower Callovian. Gulyaev and Mitta suggested substan- zons with concretions was unknown at that time, Mitta tially different internal subdivision of the last zone assumed that they occur at two levels with different (Table 1). The controversial interpretation concerns pri- ammonite assemblages: at the lower one with marily the zone lower part approximately 5 m thick. C. bodylevskyi (the index of synonymous faunal hori- According to Mitta, this part of the section presumably zon in his opinion,) and at the upper level with corresponds to the keppleriÐfalsum horizons that is Cadoceras frearsi (a species from the keppleri faunal argued for only by its position in the section, since no horizon, as Mitta assumed). As is shown below, the data on ammonites from the respective sediments have specimen determined by Mitta as C. bodylevskyi is been presented. from a bed located above but not below concretions with ammonite identified as C. frearsi. In the same interval, Gulyaev (2001) discovered an ammonite assemblage consisting of both the Boreal All the researchers attribute the overlying clay (cadoceratins and Kepplerites) and Tethyan (Macro- member (Bed 2) to the Cadoceras elatmae Zone of the cephalites) species. He established that this assemblage

Table 1. Stratigraphy of the ProsekÐIsady section, according to different authors

Gulyaev and Gulyaev, 2001 Gulyaev, 2005 Mitta, 2000 This work Kiselev, 1999a Member subpatruus subpatruus Subpat- subpatruus Subpat- Surense surensis surensis surensisruus surensis ruus elatmae elatmae elatmae elatmae elatmae elatmae quens- anabarense tedti Clayey Elatmae elatmae Elatmae kepple- primae- ? Elatmae Elatmae

Lower Callovian Lower Callovian ri falsum frearsi vum -

jacquoti jacquoti Elatmae

jacquoti ?poultoni breve Lower Callovian infimum bodylev- cf./aff. keppleri infimum subsp. nov. bodylev- skyi infimum skyi Upper Upper Sandy infimum bodylev-

Infimum Infimum infimum Infimum infimum Calyx

Bathonian Bathonian infimum skyi Note: Double lines indicate boundaries of biohorizons, simple lines designate boundaries of zones and substages.

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007

488 KISELEV, ROGOV

elatmae Bed Thickness, m AB Lithology N = 55 Zone Biohorizon Substage quenstedti N = 77 13 11 frearsi N = 42

breve 12 terebratus N = 29 10 cf. elatmae bodylevskyi

Cadoceras similans N = 18 Macrocephalires verus 11 infimum Macrocephalires prosekensis sp. Macrocephalires zickendrathi

Macrocephalires N = 158

0 20 40 60 80 100 % 10 Toricellites Cadoceras elatmae

Lower Callovian 9 12 3

9 quenstedti cf.

8 Cadoceras Cadoceras elatmae Macrocephalites jacquoti

8 mundum keppleri aff.

7 frearsi quenstedti ex gr. cf. Cadoceras Kepplerites 6 breve Pseudocadoceras nordenskjoeldi cf. bodylevskyi jacquoti

frearsi 7 cf. cf. Pseudocadoceras pisciculus/mundum Cadoceras Cadoceras 5 Toricellites pauper breve 6 Cadoceras

bodylevskyi 5 Unnamed

4 Pseudocadoceras pisciculus Kepplerites svalbardensis calyx Cadoceras infimum 4 cf. Pseudocadoceras mundum

3 Cadoceras

3

infimum 2 Upper Bathonian Cadocerax calyx

2 1 Kepplerites rosenkrantzi

1 1234567

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007

STRATIGRAPHY OF THE BATHONIANÐCALLOVIAN BOUNDARY DEPOSITS 489 includes Macrocephalites jacquoti H. Douvillé, an Additional sections are exposed in two ravines crossing index species of the basal Callovian biohorizon that is the riverbank at a distance of 1.5 km to the north of the analogue of the Keppleri biohorizon. Being first found main section. Their visible parts are composed of the in Russia, this very important species indicated pres- Bathonian sediments overlying the Upper Permian ence of the jacquoti Biohorizon defined originally in deposits. Between these sections and the Isady site, West Europe (Westermann and Callomon, 1988; Thi- Jurassic sediments are unexposed and their last outcrop erry et al., 1997), and accordingly the base of the Call- within the erosion remnant is observable right near this ovian Stage can be established in the section. Since site. Since only the lower Callovian and Upper Jurassic M. jacquoti is also known from two upper faunal hori- strata are exposed in this section, it is not considered zons (hollandi and hochstetteri, see in Callomon et al., here. 1989; Dietl, 1994) of the Bathonian Stage, Gulyaev The lower part of the Middle Jurassic succession in (2002, p. 82) supposed possibility to correlate the lower the main section is concealed under talus, and part of the Elatmae Zone containing M. jacquoti with described below (from the base upward) is only the the upper part of the Bathonian Stage. upper part of the observable composite section. The Gulyaev mentioned also the Kepplerites species upper Bathonian interval studied above the talus spans close to K. keppleri in the assemblage from this bioho- approximately a half of the stage total thickness. rizon. Because of their poor preservation, these species were identified only in open nomenclature, but despite this their occurrence was an additional argument for Upper Bathonian defining the Callovian lower boundary at the base of 1. Sand, fine-grained, silty, yellowish gray, obscurely Bed 2. bedded, compact, bioturbated; at the top there is a 2- to Later on, Gulyaev (2005) attempted to establish 5-mm-thick lamina of ferruginate sand. The apparent thick- more detailed subdivision of the Elatmae Zone lower ness is 0.6Ð0.8 m. half based on distribution of cardioceratids. He defined 2. Sand, fine-gained, clayey to silty, brownish gray, here three the poultoni, primaevum, and elatmae ana- obscurely bedded, compact, with rounded inclusions of inco- barense biohorizons like in the Pizhma River basin and herent light gray sand. The bed encloses a horizon of large (up to 0.7 m) concretions of carbonate sandstone (compact in proposed the same subdivision of the Elatmae Zone in their central part and loose around) and small potato-shaped the ProsekÐIsady section. nodules of phosphatic sandstone. Sandstone concretions fre- The ProsekÐIsady section is of key importance by quently contain abundant shells of ammonites Kepplerites constructing and detailing the upper Bathonian and (Kepplerites) svalbardensis Sokolov et Bodylevsky (Plate I, lower Callovian biostratigraphic scales of European figs. 1–3), K. (K.) rosenkrantzi Spath (Plate I, fig. 4; Plate II, fig. 1), Toricellites pauper (Spath), Cadoceras (Cataca- Russia. As is shown above however, there is no uniform doceras) infimum Gulyaev et Kiselev (Plate III, figs. 3–7), C. viewpoint on the section structure and age of its beds. (Bryocadoceras) calyx Spath (Plate III, fig. 1), and All the units of the stratigraphic hierarchy (stages, Pseudocadoceras (Costacadoceras) pisciculus (Gulyaev) zones, infrazones) are controversially interpreted, and (Plate III, figs. 8–9). The bed upper surface is uneven, undu- this stimulated reconsideration of previous concepts lating. The apparent thickness is 0.8Ð0.9 m. based on a more comprehensive study. 3. Sand, fine-gained, clayey to silty, slightly micaceous, ocherous, grayish brown, compact. Closer to the top, the bed contains pocket-shaped inclusions of incoherent sand. DESCRIPTION OF STUDIED SECTION Among fossils occurring as slightly ferruginous sand casts, ammonites are rare, represented by taxa of the previous Jurassic sediments of the Lyskovo area are exposed assemblage. Upper boundary of the bed is slightly undulat- along the right bended bank of the Volga River between ing, marked by a thin lamina of ferruginate sand. The thick- the Prosek and Isady settlements in the erosion remnant ness is 1.9 m. approximately 7 km long and up to 1.5 km wide (Fig. 1b). 4. Bed similar to the previous one. Its top is marked by a The base of the Jurassic section is at the altitude of thin lamina of ferruginous sand. The thickness is 0.5 m. approximately 160 m, being underlain by the Upper 5. Bed similar to the previous one. The ammonite assem- Permian strata. Outcrops of the Jurassic rocks are blage includes K. (K.) ex gr. keppleri (Oppel) (cf. plenus observable in several ravines crossing the bank slope McLearn) (Plate I, fig. 5), T. pauper (Spath), C. (Paraca- and in the quarry near the Prosek site. The main section doceras) cf. bodylevskyi Frebold (Plate IV, figs. 1, 2), with visible contact between the Bathonian and Callov- Ps. (Cos.) cf. pisciculus (Gulyaev) (Plate IV, fig. 7). The ian sediments is located immediately below the quarry. thickness is 0.75Ð0.8 m.

Fig. 2. (A) Upper BathonianÐlower Callovian section near the Prosek Settlement. (1) ClayeyÐsilty sand; (2) sandyÐsilty clay; (3) sandstone; (4) marlstone; (5) ichnofosil casts; (6) phosphorite concretions; (7) nest- like sandy “concretions.” (B) Changes in the taxonomic composition of ammonites in the upper Bathonian (Elatmae Zone)Ðlower Callovian Prosek section (sampling of 2006). (1) Cadoceratinae; (2) Kosmoceratidae; (3) Macrocephalitinae. (N) number of specimens in the selection.

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 490 KISELEV, ROGOV

Plate I

3

6

5 1

4b

4‡ 2

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 STRATIGRAPHY OF THE BATHONIANÐCALLOVIAN BOUNDARY DEPOSITS 491

Lower Callovian admixture of clayey particles, while clayey beds are 6. Clay, sandy to silty, slightly micaceous, dark gray, enriched in sand grains. The more clayey member massive, intensely bioturbated. Ammonites are represented (beds 6Ð11) is composed of alternating clayey and by strongly deformed casts. Their assemblage consists of C. sandy beds, the former becoming thicker upward. (P.) cf. breve Blake (Plate IV, fig. 6), C. (Cat.) cf. norden- There is only a general trend of growing abundance of skjoeldi Callomon et Birkelund (Plate IV, fig. 5), Ps. (Cos.) clay material upward in the section. The examined sed- cf. pisciculus (Gulyaev), K. (K.) ex gr. keppleri (Oppel), imentary succession corresponds to a transgressive Macrocephalites jacquoti (Douvillé) (Plate II, figs. 4–6) . series of sediments deposited most likely during a con- The thickness is 0.3Ð0.4 m. tinuous sedimentation. 7. Sand, fine-grained, clayey to silty, slightly micaceous, compact, brownish gray to yellowish gray with ocherous Ammonites found throughout the succession (Fig. 2A) limonite patches. The bed with abundant depressed clayey facilitate a detailed biostratigraphic subdivision. They casts of ichnofossils contains rare potato-shaped inclusions represent six successive assemblages of species from of incoherent fine-grained sand. In the upper half, it encloses the subfamilies Cadoceratinae, Keppleritinae, and lenses of sandy clay with abundant sandy casts of ichnofos- Macrocephalitinae. Proportions of these subfamilies in sils. Deformed casts of ammonites belong to K. (K.) ex gr. assemblages vary notably in different intervals of the keppleri (Oppel) (Plate I, 6), C. (P.) cf. frearsi (Orbigny), Ps. section (Fig. 2B). Only the family Cadoceratinae is dis- (Cos.) mundum (Sasonov), Ps. (Cos.) aff. mundum (Sasonov) tributed throughout the section being represented by (Plate IV, fig. 4), M. jacquoti (Douvillé) (Plate II, fig. 3). The thickness is 1.2Ð1.3 m. successive species of the common phylogenetic lineage Cadoceras (Catacadoceras)ÐC. (Paracadoceras). The 8. Clay sandy to silty, slightly micaceous, dark gray, intensely bioturbated, with abundant creamy-gray spots and infrazonal biostratigrahic units are defined Based on limonite patches. The ammonite assemblage includes C. (P.) this lineage. The Keppleritinae and Macrocephalitinae cf. quenstedti Spath (Plate IV, figs. 8–10), Ps. (Cos.) mundum species occur only at separate levels, being indicators (Sasonov), M. jacquoti (Douvillé) (Plate II, fig. 7). The thick- of zonal and stage units. ness is 1.9 m. 9. Clay, sandy to silty, creamy-gray, with dark gray spots and limonite patches, massive, containing abundant sand Upper Bathonian casts of depressed ichnofossils. Ammonites are represented Beds 1Ð5 that previously united into a uniform by deformed casts of Ps. (Cos.) mundum (Sasonov) and rare sandy bed (Bed 1) are attributed to the upper Batho- C. (P.) elatmae (Nikitin) (Plate IV, fig. 11). The thickness is nian. Their Bathonian age is confirmed by finds of 3.1 m. Cadoceras calyx in beds 1Ð4. The Calyx Zone defined 10. Sand as in Bed 7, although lacking inclusions. The in East Greenland (Callomon and Birkelund, 1973, in ammonite assemblage is similar to that from Bed 9. The thickness is 0.9 m. Surlyk et al., 1973) is established in the section owing to occurrence of the index species Cadoceras (Bryoca- 11. Clay, dark gray, calcareous, homogeneous, massive. The basal part (0.3Ð0.5 m) encloses a horizon of large oval doceras) calyx Spath and associated Kepplerites (Kep- septate marl concretions (gray in central parts and dark plerites) svalbardensis Sokolov et Bodylevski, K. (K.) around). Ammonites occurring as deformed casts in clays rosenkrantzi Spath, and Toricellites pauper (Spath). All (Plate IV, fig. 1) are better preserved in concretions. Concre- of these species are characteristic of the Calyx Zone in tions yielded the most diverse ammonites of the Elatmae East Greenland (Callomon, 1993). Zone: C. (P.) elatmae (Nikitin) (Plate VI, fig. 2), C. (Bryoca- The main ammonite assemblage includes species doceras) simulans Spath, Ps. (Cos.) mundum (Sasonov), M. verus Buckman (Plate V, fig. 3), M. prosekensis Gulyaev from sandstone concretions found in situ. We defined (Plate V, fig. 2), M. cf. terebratus (Phillips) (Plate V, fig. 1), the real position of concretions in the section interval of M. zickendrathi Mitta. The apparent thickness is 1.1 m. 3.7Ð3.9 m below the first occurrence of clay (Bed 6), i.e., is slightly lower than it was assumed in previous works (Gulyaev and Kiselev, 1999a, 1999b) and is SUBSTANTIATION close to the interval determined later (Gulyaev, OF BIOSTRATIGRAPHIC SUBDIVISION 2001). Concretions are confined to a single level and A thorough study showed that the section is of a have yielded the whole assemblage of the infimum more complex structure than was previously thought Biohorizon. (Gulyaev and Kiselev, 1999a, 1999b; Gulyaev, 2001). It The Calyx Zone correspond only to the infimum is indivisible clearly into sandy and clayey sequences. Biohorizon defined earlier (Gulyaev and Kiselev, All the beds consisting largely of sandy fraction contain 1999a, 1999b). The biohorizon corresponds to a largest

Plate I. Bathonian Kepplerites from the Prosek section (1-3) Kepplerites (Kepplerites) svalbardensis Sokolov et Bodylevsky: (1) R-form, 33 primary ribs, YarGPU Pr2-7, concretion 2/2, (2) S-form, 43 primary ribs, YarGPU Pr2-5, concretion 2/2, (3) YarGPU Pr2-65, concretion 2/1; (4) Kepplerites (Kepplerites) rosen- krantzi Spath. YarGPU 6/1, concretion 2/1: (a) side view, (b) ventral view. All the specimens from upper Bathonian, Calyx Zone, infimum Biohorizon; (5, 6) Kepplerites (Kepplerites) ex gr. keppleri (Oppel): (5) YarGPU Pr5-3. Bed 5, 0.6 m above the base. Upper Bathonian, bodylevskyi Biohorizon, (6) YarGPU Pr7-3. Bed 7, 0.8 m above the base. Elatmae Zone, frearsi Biohorizon

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 492 KISELEV, ROGOV

Plate II

4

6 7

5 2c

3

2b

1Ò

2‡ 1‡ 1b

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 STRATIGRAPHY OF THE BATHONIANÐCALLOVIAN BOUNDARY DEPOSITS 493 part of the zone, beds 2 and 3 included. Most of C. infi- Blake (= C. poultoni Gulyaev), the index species of the mum specimens are found in concretions of Bed 2. The defined biohorizon, which belongs to the C. (Cataca- matrix of Bed 3 yielded several deformed specimens of doceras) Ð C. (Paracadoceras) phyletic lineage. In ammonites similar to their counterparts from Bed 2. beds 7 and 8, this species is replaced by C. (P.) quenst- Bed 3 yielded also the deformed cast of specimen with edti Spath, the next member of this lineage and simul- the terminal body chamber (Plate II, fig. 2) figured ear- taneously the other index species of the biohorizon. lier (Gulyaev and Kiselev, 1999a, 1999b, Plate 2, fig. 6) Consequently, the jacquoti Biohorizon corresponds to and erroneously determined by Mitta as Cadoceras two Cadoceras biohorizons. bodylevskyi Frebold (this specimen retains primary and Bed 6 yielded also an ammonite specimen similar to secondary ribs up to the terminal aperture edge that is C. (Catacadoceras) nordenskjoeldi Callomon et Birke- typical of the Catacadoceras forms). lund, an index species in ammonite zonation of the East Bed 5 contains a peculiar ammonite assemblage Greenland. Its occurrence in the jacquoti Biohorizon represented predominantly by deformed casts of suggests different correlation of the Apertum and Nor- Cadoceratinae macroconchs. We class the Cadoceras denskjoeldi zones with the West European zonal stan- specimens with Cadoceras cf. bodylevskyi Frebold. dard (see below). The latter corresponds to morphotype transitional The Kepplerites forms are rare in beds 6 and 7. between C. (Catacadoceras)ÐC. (Paracadoceras) being poorly preserved, they are identified with K. ex being similar to species C. breve Blake and C. apertum gr. keppleri. Therefore, it would be untimely to define Callomon et Birkelund from the BathonianÐCallovian the keppleri Biohorizon in the section under consider- boundary strata of the Panboreal Superrealm. These ation. species characterize probably the isochronous strati- graphic intervals. C. apertum is reliably recorded above Beds 9Ð11 are attributed to the elatmae Biohorizon, the Calyx Zone in East Greenland (Callomon, 1985, the most representative ammonites of which are known 1993) and serves as an index form of the Apertum Zone from concretions of Bed 11. This unit is easily recog- with the BathonianÐCallovian boundary inside accord- nizable in the section and corresponds to bioturbated ing to opinion of Callomon. Based on occurrence of sandy clays with concretions occurring at a single level. C. cf. bodylevskyi in Bed 5, we define the bodylevskyi Ammonites of the elatmae Biohorizon are represented Biohorizon of the Bathonian age that is substantiated by the classical assemblage of Cadoceratinae and Mac- by its position below the first occurrence level of Mac- rocephaloitinae described in publications (Gulyaev, rocephalites jacquoti and Kepplerites ex gr. keppleri 1999, 2001; Mitta, 2000). that marks the base of the Callovian Stage (jacquoti bodylevskyi Biohorizon). The belonging of the Bioho- DIAGNOSIS OF AMMONITES rizon to the previously defined zone remains unclear, although its index species similar to C. apertum sug- The ambiguity of most biostratigraphic scales pro- gests its correlation with one of the biohorizons of the posed recently for the BathonianÐCallovian boundary Apertum Zone. strata of European Russia is a consequence of many reasons. In our opinion, the main problem is taxonomic diagnosis of indicative ammonite species. The compet- Lower Callovian itive schemes of biohorizons proposed by Gulyaev The lower Callovian begins in the section with (1999, 2001, 2005) and Mitta (Mitta, 2000, 2005, 2006; Bed 6 being largely represented by clayey sediments of Mitta and Starodubtseva, 1998) are based on recon- the Elatmae Zone. Its lower boundary corresponds to structed phyletic lineages of three ammonite subfami- the first occurrence level of Macrocephalites jacquoti lies Keppleritinae, Cadoceratinae, and Macrocephaliti- (Douvillé), the index species of the basal Callovian bio- nae. Evolution of these taxa progressed with insignifi- horizon in West Europe (Westermann and Callomon, cant quantitative changes in morphological parameters 1988; Thierry et al., 1997). The jacquoti Biohorizon of their shells, which can be determined using statisti- spans in the section three beds, including Bed 6 with cal approach only. Therefore, identification of close most abundant index species. Subordinate ammonites species of a common phyletic lineage based on single from this bed are Cadoceratinae forms whose macro- specimens is fraught with serious errors. The objective conchs are similar or identical to Cadoceras breve reasons are (a) really negligible morphological distinc-

Plate II. BathonianÐCallovian ammonites from the Prosek section (1) Kepplerites (Kepplerites) rosenkrantzi Spath. YarGPU Pr2-21, concretion 2/2: (a, c) side view, (b) ventral view; (2) Cadoceras (Catacadoceras) infimum Gulyaev et Kiselev. YarGPU 6/3, Bed 3. Upper Bathonian, Calyx Zone, infimum Biohorizon. Reproduced from (Gulyaev and Kiselev, 1999a, Plate 2, fig. 6): (a) side view, the shape is corrected to reduce deformation, (b) view from the left, with the terminal aperture, (c) ventral view; (3Ð7) Macrocephalites (Macrocephalites) jacquoti (Douvillé), all the specimens from lower Callovian, Elatmae Zone: (3) YarGPU Pr7-8. Bed 7, 0.55 m above the base. frearsi Biohorizon, (4) YarGPU Pr6-2. Bed 6, 0.25 m above the base. breve Biohorizon, (5, 6) YarGPU Pr6-6. Bed 6, 0.23 m above the base. breve Biohorizon, (7) YarGPU Pr8- 4. Bed 8, 0.75 m above the base. quenstedti Biohorizon.

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 494 KISELEV, ROGOV

Plate III

7 6b 9b 9‡ 8 6‡

4b 4‡

3b 3‡ 5‡

5b

1e 2b 1d 2c 2‡

1b 1c 1‡

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 STRATIGRAPHY OF THE BATHONIANÐCALLOVIAN BOUNDARY DEPOSITS 495

Plate III. Cardioceratidae from the Bathonian Calyx Zone (imfimum Biohorizon) of the Prosek section (1, 2) Cadoceras (Bryocadoceras) calyx Spath: (1) YarGPU Pr2-49: (a) side view, (b) apertural view, (c) ventral view, (d) side view with visible internal whorls, (e) ventral view with visible internal whorls; (2) YarGPU Pr2-58: (a) side view, (b) apertural view, (c) ventral view; (3Ð7) Cadoceras (Catacadoceras) infimum Gulyaev et Kiselev: (3) YarGPU Pr2-50: (a) side view, (b) apertural view, (4) YarGPU Pr2-52: (a) side view, (b) ventral view, (5) YarGPU Pr2-54: (a) side view, (b) apertural view, (6) YarGPU Pr2-56: (a) side view, (b) ventral view, (7) YarGPU Pr2-57; (8, 9) Pseudocadoceras (Costacadoceras) pisciculus (Gulyaev): (8) YarGPU Pr2-63, (9) YarGPU Pr2-64: (a) side view, (b) ventral view. All the specimens originate from concretion 2/2. tions of close species, (b) parallelism, and (c) recurrent known species using such sculptural features as density development of diagnostic features with time periods of primary ribs (pr) in the terminal whorl and rib ratio observable, for example, in genera Kepplerites (Cal- (RR) or ratio between secondary and primary ribs.2 lomon, 2004) and Cadoceras. A objective reason con- sists in ignoring the phylogenetic trend, when species Correlating data on sculptural features, it is possible are identified based on highly variable features. to determine the morphological space of the subgenus Kepplerites s. str., where each species is characterized A confusion in current nomenclature led to an by its own field. The field size reflects the variability impass, as researchers proposed sometimes two or extent of ornamentation and, to some degree, the more taxonomic names defining the same biostrati- amount of measured specimens. The most reliable data- graphic unit. The validity of nomenclature can be esti- base is obtained for K. keppleri (18 specimens, ten of mated only after the morphometric analysis of phyloge- which are topotypes) and K. svalbardensis (19 speci- netic diagnostic features in a whole phyletic lineage. mens, 14 specimens from the Prosek section and 5 topotypes inclusive). Other specimens represent largely Kepplerites nomenclature types of different species. When determining position of the BathonianÐCall- The analysis of the Kepplerites s. str. morphological ovian boundary based on the Kepplerites genus, it is space leads to the following inferences: important to establish whether the specimen under con- (1) Sculptural features are correlative in a certain sideration belongs to Kepplerites keppleri or not. In this manner: the rib density is reversely proportional to the case, inaccuracy in taxonomic determination automati- rib ratio. Correlation of this type is generally character- cally results in stratigraphic error of a substage rank. As istic of ammonites with fine ornamentation, being for the Prosek section, debatable here is diagnosis of observable in different families, Cardioceratidae Kepplerites from Bed 2. According to the first determi- included (Kiselev, 1999a, 1999b). nation (Gulyaev and Kiselev, 1999a, 1999b), which are (2) Morphological distinctions in sculptural features accepted in this work, this genus is represented largely of species represent a phylogenetic trend, as is noted by by K. svalbardensis Sok. et Bodyl. (approximately Callomon (2004). The BathonianÐinitial Callovian, 150 specimens) and rare K. rosenkrantzi Spath (3 spec- evolution of Kepplerites species from the K. tychonisÐ imens). In opinion of Mitta (2000), all the figured spec- fasciculatus group to the K. keppleriÐplenus group is imens are close to K. keppleri (Opp.). Mitta determined accompanied by the rib density decrease (Fig. 3). K. keppleri (= K. svalbardensis in our opinion) in col- Beginning from the keppleri chron, the reversed tend lection by V.A. Shchirovskii (Mitta and Starodubtseva, (only in the Arctic basin) resulted in appearance of spe- 2000, Plate 5, fig. 1). He considers presence of well- cies K. ingrahami sensu Imlay and K. tenuifasciculatus developed tubercles at furcation points ribs in adult with denser arranged ribs (Fig. 4). whorls as a diagnostic feature of this species. In opinion of Callomon (2004), the main morpho- (3) The fields of K. keppleri and K. svalbardensis logical trend in phylogeny of Kepplerites s. str. corre- are located in different areas of the morphological sponds to changes in density of primary ribs on the ter- space (Fig. 5) with overlap not exceeding 25%. Greater minal whorl. Even taking this trend into consideration, parts of the K. keppleri and K. svalbardensis fields are it is difficult to individualize close Kepplerites species occupied respectively by topotypes from Germany and because of recurrent development of that morphologi- by specimens from the Prosek section. This means that cal character. For example, according to Callomon, the identification of the latter with K. keppleri would be early Callovian K. tenuifasciculatus Callomon is mor- erroneous. The average rib density is 25Ð27 and 35Ð40 phologically close to the upper Bathonian Kepplerites in K. keppleri and K. svalbardensis, respectively. Vari- forms from the K. tychonis Ravn group. Therefore, dis- ability of the rib density in both species is relatively tinctions of species even having remote phylogenetic high, and K. svalbardensis with rare ribs resembles positions are “perceptible only by the trained eye” (Cal- therefore K. keppleri or K. traillensis with the dense lomon, 2004, p. 45). arrangement of ribs. In addition, variability of rib den- sity in K. svalbardensis is accompanied by develop- In order to solve the problems in question, we car- ried out the morphometric comparison of Kepplerites 2 Tables with measured data are accessible via Internet at: specimens from Bed 2 of the Prosek section with well- http://jurassic.ru/msm.htm.

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 496 KISELEV, ROGOV

PO 5.5

5.0 keppleri-traillensis, k1-1

4.5

4.0 tychonis-fasciculatus, bt3-1 3.5

3.0 rosekrantzi-landuskiensis, bt3-2 2.5 svalbardensis-peramplus, bt3-3 2.0 20 25 30 35 40 45 50 55 60 65 70 pR

Fig. 3. The distribution of Kepplerites species in the morphological space of the terminal body chamber features from the late Batho- nian to the initial Keppleri chron. The group of coeval species is contoured by line.

RR 5.5

5.0

4.5 keppleri-traillensis, k1-1

4.0

3.5 tenuifasciculatus, k1-2 3.0

2.5 ingrahami sensu Imlay, k1-2

2.0 20 25 30 35 40 45 50 55 60 pR

Fig. 4. The distribution of Kepplerites species in the morphological space of the terminal body chamber features from the initial to the terminal Keppleri chron. The group of coeval species is contoured by line. ment of tubercles at the rib furcation points, and variet- curtilobus (Buckman) and K. (G.) crucifer (Buckman). ies with rare ribs have coarser ornamentation (Plate I, In the case of K. svalbardensis, smoothed forms retain fig. 1). primary ribs on the casts being deprived of ornamenta- An error in identification can also be connected with tion on the ventral side. the development degree of ornamentation on the inter- According to combinations of different sculptural nal surface of a shell. Kepplerites species are com- features, 16 morphotypes of K. svalbardensis are deter- monly divisible in two relatively discrete varieties: mined (Table 2). S-forms with smoothed internal surface of shells well (4) Arctic Kepplerites forms close to K. keppleri ribbed outside (their casts look smoothed, Plate I, fig. 2) (K. plenus McLearn 1927, K. gitinsi McLearn 1927, and R-form with the ornamented internal surface (their K. mcevoyi McLearn 1928, K. traillensis Donovan casts are always ribbed, Plate I, fig. 1). These varieties 1953) fall into morphological field of K. keppleri but have been repeatedly determined as species of different correspond there to extreme varieties of this species Keppleritinae groups, for example as K. (Gowericeras) with high-density ribs (Fig. 5). These forms should be

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 STRATIGRAPHY OF THE BATHONIANÐCALLOVIAN BOUNDARY DEPOSITS 497

RR 5.5 1 2 5.0 3 m kepplery 4 @ 5 4.5 traillensis 6 t 7 t p p 8 4.0 9 g g 10 3.5 p 11 m 12

3.0 svalbardensis “peramplus” – dietli 2.5

2.0 20 25 30 35 40 45 50 55 60 pR

Fig. 5. Morphological areas of the Kepplerites species from the upper BathonianÐlower Callovian interval in the morphological space of the terminal body chamber features. The group of coeval species is contoured by a line. Nomenclature types are shown by larger symbols. (1) Kepplerites keppleri; (2) K. svalbardensis (topotypes); (3) K. svalbardensis (Prosek); (4) K. svalbardensis (Middle Volga region); (5) K. dietli (topotypes); (6) K. peramplus (topotypes); (7) K. aff. paramplus (Middle Volga region); (8) K. traillensis (holo- type); (9) K. ex gr. traillensis (Middle Volga region); (10) K. ginitsi (holotype); (11) K. plenus (holotype and topotype); (12) K. mce- voyi (topotype). considered as subspecies of K. keppleri not identified and the same type specimens, which are differently completely with this taxon as it has been done by Cal- named in each scale (Tables, 1, 3). lomon (2001). Among them, K. plenus is of senior pri- ority and the given form (species or subspecies) should Gulyaev and Mitta differently understand not only be identified under this name. species, but also higher taxonomic groups of the genus and subgenus ranks. This concerns primarily genera Paracadoceras Crickmay and Catacadoceras Bodylevsky. Cadoceras Such a difference in understanding of the Cadoceras There is no uniform viewpoint on taxonomic affinity taxonomy is explainable by objective reasons, not only of macroconchiate Cadoceratinae forms occurring in by subjectivism that is unavoidable by identification. the BathonianÐCallovian boundary strata below the Difficulties in diagnosis of the Bathonian–Callovian elatmae Biohorizon. In competitive scales proposed by Cadoceratinae are connected, in our opinion, with Gulyaev and Mitta for the BathonianÐlower Callovian uncertain morphology of their shells by transition from of European Russia, this interval is subdivided based on Catacadoceras to Paracadoceras. Transitional species practically identical succession of Cadoceras species have features of both the ancestral (plesiomorphic) and

Table 2. Affiliation of figured K. svalbardensis specimens with different variability forms

With rare ribs With relatively rare With frequent ribs With very frequent (32Ð34) ribs (35Ð42) (43Ð50) ribs (>50)

Tubercles S form Mitta and Starodubtseva, Pr2-5; A/30 are undeve- 2000, Plate 3, fig. 1 loped R form 6/4 2/675 Holotype; Pr2-13 Mitta, 2004b, Plate 1, fig. 1 Tubercles S form Pr2-3; Mitta, 2004b, are slightly Plate 2, fig. 1 developed R form Pr2-7; ?Mitta, 2004b, Pr-2-10; Kopik and Wierz- Plate 2, fig. 2 bowski, 1988, Plate 20, fig. 2; Plate 21, fig. 2

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 498 KISELEV, ROGOV

Table 3. Revision of Cadoceras from the BathonianÐCallovian interval figured by D.B. Gulyaev and V.V. Mitta

Nomenclature type Identification of Cadoceras species Gulyaev, 2001, 2005 Mitta, 2000, 2005a This work C. (Cat.) infimum Gulyaev et Kiselev: Par. infimum Gulyaev et C. bodylevskyi Frebold C. (Cat.) infimum Gulyaev Gulyaev and Kiselev, 1999a, Plate 1, Kiselev et Kiselev fig. 1, 2 (holotype) C. bodylevskyi Frebold: Frebold, 1964, C. bodylevskyi Frebold Plate 17, fig. 1 (holotype) C. bodylevskyi Frebold: Poulton 1987, Par. poultoni Gulyaev C. bodylevskyi Frebold C. breve Blake Plate 27, figs. 4Ð6 C. variabile Spath: Meledina, 1994, Par. poultoni Gulyaev ?Par. keuppi Mitta C. breve Blake Plate 8, fig. 1 C. frearsi (Orbigny): Sazonov, 1957, Par. primaevum C. frearsi (Orbigny) Plate 4, fig. 1 (neotype) (Sasonov) C. primaevum (Sasonov): Sazonov, Par. primaevum C. frearsi (Orbigny) 1957, Plate 6, fig. 1 (holotype) (Sasonov) C. (Par.) anabarense Bodylevsky: Par. elatmae anabarense C. (Par.) anabarense Bodylevsky, 1960, Plate 4, fig. 3 (Bodyl.) Bodyl. (holotype) descendant (apomorphic) taxa. Therefore, its is difficult gemicum and C. poultoni (= C. bodylevskyi sensu Poul- to attribute species of such morphotype to a certain ton, 1987; Mitta, 2000). taxon. Accordingly, when identifying fossils, each (2) The Cadoceras morphotype evolved from invo- author uses features most important from his stand- lute (bodylevskyi chron) to moderately evolute (elatmae point, chron) forms. The Early Callovian species C. apertum In order to solve the problem, one should determine and C. frearsi are of a close morphotype. They are principal morphological features that characterize the probably vicarious species in the Arctic basin and Cen- phylogenetic trend of a taxon. Like in most ammonites, tral Russian sea. these features in Cadoceras representatives are local- (3) During the late BathonianÐearly Callovian, evo- ized on the terminal body chamber (TBC). Main dis- lution of Cadoceras was of a recurrent character. The tinctive features of Cadoceras forms from the Batho- evolute morphotype with high rib density (UR) and nianÐCallovian transition are the relative size of umbi- involute morphotype with rare ribs (ur) originated licus (U%) and number of primary ribs. The latter are repeatedly (Fig. 7). The UR-morphotype characteristic preserved on the TBC as oblique tubercles (bullae) rep- of the earliest late Bathonian species C. barnstoni, resenting frequently the only sculptural elements. Cor- C. subcatostoma, C. keuppi, C. nageli, and C. infimum relation of both features that form the morphological was replaced by the ur-morphotype of C. bodylevskyi space can be used to evaluate morphological distinction and C. breve. The intermediate ur/UR morphotype is between Cadoceras species. Only specimens with the characteristic of C. apertum and C. frearsi. The TBS have been measured. UR-morphotype appears again in species C. quenstedti Analysis of the morphological space of BathonianÐ and C. elatmae during the elatmae chron. The subpar- early Callovian Cadoceras species shows the follow- tus chron is marked by next development of the ur-mor- ing: photype (Cadochamoussetia tschernyschewi, Cadoch. (1) There is a distinct morphological trend in surensis, and other species), which gave rise to appear- changes of the umbilicus width and rib density on the ance of Chamoussetia. In the terminal early (Koengi TBS of Cadoceras shells from the BathonianÐCallov- chron) and middle Callovian, phylogenesis was charac- ian transition. Both features are well correlative (R2 = terized by the other morphological changes. 0.7815), thus being of a high diagnostic potential. (4) It is logical to consider diagnosis of the Based on this inference, individualism of species Cadoceras from the standpoint of phylogenetic trend described in publications can be tested. For example, it assuming that its reversals define morphological limits is clearly seen (Fig. 6) that type specimens of C. poul- of subgenera (Fig. 7). The genus Cadochamoussetia toni (Gulyaev, 2005) correspond, in terms of morphol- Mitta 1996 was defined (Mitta, 1999) using such a prin- ogy, to specimens of C. tchegemicum Lominadze 2004. ciple, i.e., the appearance of ur-morphotypes in the Accordingly, the former species represents a junior Subpartus chron. Meanwhile, two preceding reversals synonym of the latter. Similarly, the results prove that of trend are not reflected in taxonomy. In recent works C. bodylevskyi Frebold 1964 differs from C. tche- by Gulyaev (2005) and Mitta (2005a, 2005b), late

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 STRATIGRAPHY OF THE BATHONIANÐCALLOVIAN BOUNDARY DEPOSITS 499

pR 24

23 22 C. elatmae 21 C. apertum 20

19 C. poultoni C. frearsi 18 C. tschegemicum 17

16 C. breve

15 C. bodylevskyi 14 19 21 23 25 27 29 31 33 35 37 39 41 43 45 U, %

Fig. 6. Correlation between the umbilicus width (U%) and number of primary ribs (pR) in the terminal body chamber of Cadoceras from the BathonianÐCallovian boundary interval. Larger symbols designate nomenclature types of species.

U, % pR 45 30 CATACADOCERAS PARACADOCERAS CADOCHAMOUSSETIA

40 U, % (R2 = 0.8341) UR 25 infimum 35 pR (R2 = 0.7555) UR/ur

stupachenkoi 20 30

ur frearsi elatmae apertum

25 surensis breve

keuppi-nageli 15 tschernyschewi 20 10

15 bodylevskyi

Bathonian Callovian 10 5 012 3 4 5 6 7 8 9 10 11 Time (phylogenetic succession)

Fig. 7. Evolution of terminal body chamber features in macroconchiate Cadoceratinae during the late BathonianÐearly Callovian. The thick line shows the trend in development of the umbilicus width (U%), thin line demondtrates that of the ornamentation density (pR). (UR) evolute morphotype with dense rib arrengement; (ur) involute morphotype with rare ribs; (UR/ur) transitional morphotype.

Bathonian species of the UR-morphotype, having ribs Meledina 1977 was already proposed for these forms. covering the TBC are referred to the genus Paraca- The genus Paracadoceras includes younger species, doceras Crickmay 1930 emend Imlay 1953. This development of which begins with the ur-morphotype seems unsubstantiated properly the more so that the (C. bodylevskyi) and terminates with the UR-morpho- name Catacadoceras Bodylevsky 1960 emend type (C. elatmae).

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 500 KISELEV, ROGOV

Bullae quantity at the terminal body chamber 2 40 R = 0.8837 2 glabrum (h) R = 0.7258

35 anabarense

multiforme 30

multiforme (h)

25 multiforme (p) chisikense (h) R2 = 0.7815 el el el pizhmae (h) el el el (n) poultoni el 20 poultoni (h) apertum (h) fr 2 el R = 0.8508 tschegemicum fr apertum fr tschegemicum 15 bodylevskyi

10 24 26 28 30 32 34 36 38 40 42 44 U, %

Fig. 8. Correlation trends showing changes in terminal body chamber features of Cadoceratinae from Central Russia (solid line) and the Arctic region (gray line). Dashed line demonstrates corresponding lines of the exponential dependence. (fr.) Cadoceras fiearsi; (el) C. elatmae; (h) holotype; (n) neotype.

(5) Younger C. (Paracadoceras) species from Arctic C. elatmae. In his opinion, the main feature of the regions and Central Russia characterize own (Paraca- former that differs it from the latter is later appearance doceras) morphotype (TBC of the UR-type with of smooth shell in ontogenesis. Accordingly, C. anaba- smooth ventral and lateral sides). Phylogeny of North rense is of a more archaic morphotype. Meanwhile, Siberian and South Alaskan species C. anabarense amount of tubercles in C. anabarense is 1.5 times Bodylevsky 1960, C. glabrum Imlay 1953, and C. mul- greater than in C. elatmae. Therefore, in terms of the tiforme Imlay 1953 evolve in line with the phylogenetic phylogenetic trend, the TBC of C. anabarense is of a trend of Central Russian forms, i.e., from the ur- to more advanced morphotype. UR-morphotypes. At the same time, they deviate near the C. apertum field toward the involute morphotype The number of bullae on the TBC of C. anabarense with higher quantity of bullae on the TBC, as compared corresponds to that of primary ribs on C. elatmae shells with the C. elatmae. This happened likely after the 20Ð45 mm across, and its umbilicus is 70Ð75 mm in apertum chron (Fig. 8). diameter. This likely means that the C. anabarense C. anabarense and C. elatmae are stratigraphic and morphotype (as well as C. glabrum and C. multiforme) morphological analogues of C. elatmae. Both of them could appear owing to bradygenesis (retardation in represent index species of equivalent zonal units in development) of C. (Paracadoceras) species, which North Siberia and European Russia. Gulayev (2005) were at the point of phylognetic trend close to that of suggests that C. anabarense is an older subspecies of C. elatmae. C. chisikense Imlay that was at the same

Plate IV. Cardioceratidae from the BathonianÐCallovian boundary sediments of the Prosek section (1, 2) Cadoceras (Paracadoceras) cf. bodylevskyi Frebold: (1) YarGPU Pr5-2. Bed 5, 0.4 m above the base, (2) YarGPU Pr5-5. Bed 5, 0.55 m above the base. Upper Bathonian, bobylevskyi Biohorizon; (3) Cadoceras (Catacadoceras) infimum Gulyaev et Kiselev: YarGPU Pr4-2. Bed 4, 0.15 m above the base. Upper Bathonian, Calix Zone, infimum Biohorizon; (4) Pseudocadoceras (Costaca- doceras) aff. mundum (Sasonov): YarGPU Pr7-6. Bed 7, 1.2 m above the base. Elatmae Zone, frearsi Biohorizon; (5) Cadoceras (Catacadoceras) cf. nordenskjoeldi Callomon et Birkelund: YarGPU Pr6-3. Specimen with the terminal aperture (half destroyed) and constriction shown by asterisk): (a) deformed cast with an impression fragment, (b) impression (tone of the image is inverted). Bed 6, 0.05 m above that base. Elatmae Zone, Breve Biohorizon; (6) Cadoceras (Paracadoceras) cf. breve Blake: YarGPU Pr6-1. Bed 6, 0.25 m above the base. Elatmae Zone, breve Biohorizon; (7) Pseudocadoceras (Costacadoceras) cf. pisciculus (Gulyaev): YarGPU Pr6-1. Bed 5, 0.3 m above the base. Elatmae Zone, bodylevskyi Biohorizon; (8Ð10) Cadoceras (Paracadoceras) cf. quen- stedti Spath: (8) YarGPU Pr8-10. Bed 8, 0.83 m above the base, (9) YarGPU Pr8-7. Bed 8, 0.02 m above the base, (10) YarGPU Pr8- 6. Bed 8, 0.32 m above the base. All the specimens from the Elatmae Zone, quenstedti Biohorizon; (11) Cadoceras (Paracadoceras) elatmae (Nikitin): YarGPU Pr9-1. Bed 9, 2.6 m above the base. Elatmae Zone, elatmae Biohorizon.

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 STRATIGRAPHY OF THE BATHONIANÐCALLOVIAN BOUNDARY DEPOSITS 501

Plate IV

2 1 * 4 3

7

6

9

5a 8

*

11

10

5b

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 502 KISELEV, ROGOV

Ratio between rib length and whorl height

1.1

0.9 1 2 3 0.7 R2 = 0.6117 4

0.5

R2 = 0.3729 0.3 R2 = 0.6308 R2 = 0.9407 0.1 0 –0.1 20 40 60 80 100 Whorl height Fig. 9. Changes in the ornamentation reduction degree in BathonianÐCallovian Macrocephalites species belonging to the M. trian- gularisÐM. pavlowi lineage. (1) M. triangularis; (2) M. jacquoti; (3) M. prosekense; (4) M. pavlowi.

60

50

40 M. jacquoti 30 M. prosekense

20 2 M. triangularis R = 0.618 M. pavlowi M. jacquoti 10 Bathonian Callovian

012 3 4 5 6 Time (phylogenetic succession)

Fig. 10. Gradual reduction of the stage with the ornamented periumbilical segment of the shell in Macrocephalites species belong- ing to the M.triangularisÐM. pavlowi lineage. Age is shown along the abscissa (numerals designate evolutionary stages from M. triangularis to M. pavlowi). point can be considered as a true ancestor of C. anaba- represent largely the autonomous Cadoceratinae group rense. distributed from West Europe (Germany) to the north- Thus, beginning from the C. frearsi chron, younger ern Caucasus. Its appearance was probably caused by C. (Paracadoceras) forms from the Central Russian sea expansion of the Central Russia sea during the early

Plate V. Macrocephalites from Bed 11 (concretions from the elatmae Biohorizon of the Elatmae Zone) of the lower Callovian Prosek section. Figures 1 and 2 are diminished (bar is 1 cm) (1) Macrocephalites (Pleurocephalites) cf. terebratus (Phillips): NGPU-1: (a) side view, (b) ventral view; (2) Macrocephalites (Macrocephalites) prosekensis Gulyaev: NGPU-2; (3) Macrocephalites (Macrocephalites) verus Buckman: NGPU-3: (a) side view, (b) ventral view.

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 STRATIGRAPHY OF THE BATHONIANÐCALLOVIAN BOUNDARY DEPOSITS 503

Plate V

1‡ 1b

3b

2

3‡

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 504 KISELEV, ROGOV

Plate VI

6‡ 6b

1

2b

2‡ 5

4 3‡ 3b

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 STRATIGRAPHY OF THE BATHONIANÐCALLOVIAN BOUNDARY DEPOSITS 505

Table 4. Infrazonal stratigraphy of the Bathonian--lower Callovian sediments in European Russia Gulyaev and Kiselev, 1999a, 1999b; Mitta, 2000, 2004a, 2004b, 2005a, 2005b, 2006 This work Gulyaev, 2001, 2005 Paracadoceras elatmae elatmae Cadoceras elatmae C. elatmae Elatmae Paracadoceras elatmae anabarense Cadoceras falsum C. quenstedti Paracadoceras L.C. Macrocephalites Kepplerites keppleri/Cadoceras C. frearsi

Elatmae primaevum jacquoti frearsi

Paracadoceras poultoni Elatmae Keppleri C. breve

Lower Callovian K. trail- C. bodylevskyi Paracadoceras “infimum subsp. nov.” C. bodylevskyi lensis C. nordenskjoeldi Hiatus? Unnamed Cadoceras apertum Paracadoceras infimum infimum C. infimum Kepplerites vardekloeftensis Infimum Kepplerites aff. peramplus

Upper Bathonian Keuppi Paracadoceras keuppi ?C. keuppi Upper Bathonian Paracadoceras nageli C. nageli Note: In Tables 4 and 5, boundary between the Bathonian and Callovian stages is shown by triple line; boundaries between biohorizons are shown by double line and between zones and subzones, by simple line; (L.C.) lower Callovian.

Callovian transgression maximum. Development of cal changes in many lineages (Callomon and Dietl, C. (Paracadoceras) lineages in Arctic regions and Cen- 1990), and, as a result, wide stratigraphic ranges of tral Russia presumably was concurrent and indepen- some species diminish their stratigraphic significance. dent. Phylogenetic transformation of the TBC in two It become clear recently that some Macrocephalites lineages was different: ammonites of Central Russia species considered previously as reliable stratigraphic evolved in line with the gerontogenesis (de Beer, 1958) markers are of wide stratigraphic ranges, for instance, or prolongation of ontogenesis, whereas development the IndianÐMadagascar forms such as M. triangularis, of Arctic taxa corresponded to bradygenesis (a variety M. madagascariensis, and M. formosus (see Wester- of paedogenesis after Ivanov, 1969) avoiding last onto- mann and Callomon, 1988; Datta et al., 1996; Jain, genetic stages. Evolution of the second type led to ori- 2007). Diagnosis of Macrocephalites forms meets gin of morphotypes combining plesiomorphic and apo- additional difficulties because of different specializa- morphic features. The last type of evolution character- tion ways of these ammonites. For example, the main istic of the Arctic Cadoceratinae up to the middle trend in evolution of this group toward more flattened Callovian. cross-section (Lominadze, 1967) was probably accom- panied by development of lineages terminating with morphotypes having low cross-sections. As Callomon Macrocephalites et al. (1992, p. 20) noted, “The easily apprehensible Representatives of this genus from the basal Callov- characters of whorl-inflation, size, strength of ribbing ian zone are the only ones of the Tethyan origin and and density of ribbing seemed to occur in all combina- offer opportunity for remote correlation up to Madagas- tions.” car and Indonesia. At the same time, frequent parallel- It seems that evolution of the genus Macrocepha- ism, wide variation spectrum, low rate of morphologi- lites progressed without significant morphological

Plate VI. Lower Callovian Cadoceras (1, 2) Cadoceras (Paracadoceras) elatmae (Nikitin): (1) YarGPU Pr1-12. Bed 11, 0.95 m above the base, (2) YarGPU Pr1-14. Bed 11, from concretions: (a) side view, (b) ventral view. All the specimens are from the Elatmae Zone, elatmae Biohorizon; (3Ð6) Ca- doceras (Paracadoceras) breve Blake: (3) Holotype BM C11763 (cast of the original; the image is kindly donated by K.Page). En- gland, Dorset, near Weymouth, East Fleet. Lower Callovian, Fleet Member: (a) side view, (b) apertural view; (4) Sample 1158, col- lection by T.A. Lominadze (=holotype of Cadoceras tschegemicum Lominadze). North Caucasus, Chegem River. Bed 3, lower Call- ovian (after Liminadze, 1982, p. 228); (5) Sample 12/1528, collection by D.B. Gulyaev. Chuvashia Republic, Khvadukasy Village. Lower Callovian, Elatmae Zone; (6) Sample 8/1353, collection by D.B. Gulyaev. Komi Republic, Pizhma River, Churkino Village. Churkinskaya Shchel’ya section, Bed 3 (after Gulyaev, 2005), lower Callovian, Elatmae Zone, breve Biohorizon: (a) side view, (b) apertural view.

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 506 KISELEV, ROGOV

Table 5. Corelation of BathonianÐCallovian infrazonal scales of Europaen Russia, Germany, and East Greenland. Correla- tion of the largest part of the Elatmae Zones with the Apertum Zone is based on phylogenetic analogues East Greenland1 European Russia West Europe (Germany)2 cf./aff. breve Elatmae suevicum α, β tenuifasciculatus quenstedti Elatmae apertum γ jacquoti frearsi jacquoti Lower Lower Lower Herveyi Keppleri

Callovian Apertum Callovian keppleri Callovian apertum β breve

By Discus apertum α Unnamed bodylevskyi Discus position Hollandi vardekloeftensis Calyx Calyx Infimum Hannoveranus peramplus Orbis rosenkrantzi keuppi By

Upper Bathonian Variabile Upper Bathonian Keuppi Blanasense Upper Bathonian inflatus nageli position 1 Callomon, 1993. 2 Dietl, 1994; Callomon and Dietl, 1990, 2000; Callomon et al., 1989. changes during the BathonianÐCallovian transitional M. verus known from the same stratigraphic level in period. At any rate, all the species known from the southern Germany (Callomon and Dietl, 1990). Mitta uppermost Bathonian (M. triangularis, M. madagas- defined the genus Eckhardites Mitta, 1999, with the cariens, M. lamellosus, M. formosus, and M. subcom- type species Macrocephalites pavlowi referred to the pressus in India, Indonesia, and Madagascar; M. jac- subfamily Arctocephalitinae. He also attributed to the quoti in West Europe) occur also at the base of the Call- new genus the close or identical species Chamoussetia ovian Stage. Despite this fact, even insignificant menzeli described from approximately the same strati- morphological changes should be taken into account in graphic level (Mönnig, 1995). Presenting extended order to substantiate boundaries of biostratigraphic description of the genus a year later, Mitta (2000, p. 34) units based on well-manifested morphological trend in noted some similarity between Eckhardites and Macro- numerous specimens (see below). cephalites jacquoti: “…morphogenesis of ornamenta- Macrocephalites species from the Russian platform tion in representatives of this genus is fairly typical of are interpreted in different works less controversially Cardioceratidae being unknown in Macrocephalitinae significant than in the genera considered above. Of (development of ‘ventral’ ribs along with general prime importance for our purpose is the phyletic lin- smoothing of ornamentation is repeatedly observable in eage M. jacquoti (Plate II, figs. 3–7)–M. prosekense the Cardioceratidae phylogeny).” Nagel and Pirkl (Plate V, fig. 2)–M. pavlowi and finds of M. verus and (2001, pp. 294Ð295) presented almost the same diagno- M. terebratus. Gulyaev (1999) was first to outline this sis is their article. However, the ornamentation smooth- phyletic lineage connecting M. ex gr. jacquoti ing around umbilical part of the shell is characteristic of (=M. prosekense) and M. pavlowi. Owing to subse- most Stephanocerataceae similar in morphotype to quent finds of abundant M. jacquoti at the base of the “Eckhardites.” The same feature is widespread in Mac- Elatmae Zone (Gulyaev, 2001), the lineage acquired rocephalites forms. Disappearance of ornamentation in accomplished form with distinct morphological trend lower part of the lateral surface is already typical of of progressively earlier disappearance of primary ribs many Bathonian species at different stages of their and gradual narrowing of the ventral side. Other sculp- ontogeny: near the TBC (M. madagascariensis, M. tri- tural features, a high rib ratio in internal whorls inclu- angularis, see Thierry, 1978, Plate 18, fig. 1; Krishna sive, remain unchanged in this group of species (Plate and Westermann, 1987, Plate 1; Westermann and Cal- II, figs. 3–7; Gulyaev, 1999, Plate 1, figs. 1, 4). Later on, lomon, 1988, Plate 15, fig. 3; Datta et al., 1996, Plate 1; Gulyaev (2005) added M. cf./aff. jacquoti characteris- and others) or in phragmocone (M. mantataranus, see tic of the “elatmae anabarense” (here =quenstedti) Thierry, 1978, Plate 24, fig. 5; Westermann and Cal- Biohorizon and placed it between M. jacquoti and lomon, 1988, Plate 10, figs. 1–5). Many Callovian spe- M. prosekense. In our collection, similar forms are cies with high oval whorl sections, the forms with rela- either missing or cannot be discriminated from M. jac- tively wide whorls such as M. verus included, are lack- quoti. We do not exclude that these ammonites are close ing ornamentation in the peri-umbilical area, and in to forms that combine features of M. jacquoti and their macroconchs there is a stage, when only ventral

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 STRATIGRAPHY OF THE BATHONIANÐCALLOVIAN BOUNDARY DEPOSITS 507 ribs are observable. Proximity between external seg- (3) M. pavlowi should be attributed to the family ments of septal suture in “Eckhardites” and Chamous- Macrocephalitidae. setia (Mönnig, 1995, fig. 19) cannot be an argument Macrocephalites verus (Plate VI, figs. 4, 5) appears favoring attribution of “Eckhardites” to a particular in West Europe in the quenstedti Biohorizon and is also family. The matter is that external segments of septal characteristic of the overlying suevicum Biohorizon suture in different Stephanocerataceae are very similar (Callomon et al., 1989; Dietl and Gygi, 1998). In the in form, frequently depending on shape of the whorl East European platform, this species is widespread in section rather than on taxonomic affinity (see for com- the elatmae Biohorizon (Mitta, 2000; Gulyaev, 2005). parison septal sutures in Kosmoceras (Catasigalo- This is consistent with correlation based on Cardiocer- ceras) and Macrocephalites tcherekensis in Lomi- atidae species. It is also noteworthy that some research- nadze, 1967, fig. 29). On the other hand, even neighbor- ers (Gulyaev, 2005) consider Cadoceras suevicum and ing septal sutures in representatives of the same C. elatmae as synonyms. Rare finds of M. cf. terebratus Macrocephalites species may differ significantly from (Plate V, fig. 1) at the same level concretions in the each other. In other words, “… the intraspecific vari- Prosek section, where M. verus occurs, are also impor- ability of the septal suture in representatives of Macro- tant for correlation. In England (Rage, 1989), these cephalitidae is so strong that it is difficult to find two Macrocephalites forms are accepted for index species specimens with identical septal sutuures” (Lominadze, of neighboring faunal horizons. The level with concre- 1967, p. 74). Substantial difficulties in attributing the tions inside the elatmae Zone in the Prosek section cor- pavlowi species to the Arctocephalitinae subfamily are responds likely to the boundary between these biohori- connected with the significant stratigraphic gap (almost zons. a half of stage) between these taxa. Unfortunately, almost all the M. jacquoti and M. prosekense specimens available in our collection are BIOSTRATIGRAPHIC UNITS deformed, and published data on changes in whorl sec- Principles of Definition tion of ammonites of this group during ontogenesis are Two biostratigraphic zonations have been suggested scarce. Hence, only the reduction degree of peri-umbil- recently for the upper BathonianÐbasal lower Callovian ical ribs can be used for discriminating between taxa. of European Russia (Table 4). They differ in ranges of Although the last feature is also variabile and depends, the Elatmae Zone and upper Bathonian, as far as it con- in addition, on preservation of ammonites, it seems to cerns infrazonal units, and in position of the Batho- be most useful. nianÐCallovian boundary. The morphological analysis of the BathonianÐCall- The stratigraphic scale considered below is based on ovian Macrocephalites species with narrow whorl sec- the synthesis of available scales and data of this study. tions in adult stages shows the following: The following modifications are introduced: (1) There is a distinct morphological trend of reduc- (1) The Calyx Zone is included into the upper ing degree of ornamentation observable from M. jac- Bathonian zonal scale to replace the previous Infimum quoti to M. pavlowi. It should be noted that despite sig- Zone taking into consideration the priority principle. nificant morphological similarity, which allowed Dietl (1994, p. 14) to note that “Die Macrocephalen ‘Popula- (2) Three previous biohorizons of the infazonal tion’ aus dem hochstetteri-Horizont unterscheidet sich scale are renamed based on revision of their index spe- nur geringfugig von der des keppleri-Horizonts…Auch cies: brevi (= poultoni Gulyaev 2002, 2005); frearsi hier ist also der Evolutionsschritt innerhalb einer (= primaevum Gulyaev 2002, 2005); quenstedti (= fal- Ammonitengruppe von einem zum anderen Faunenho- sum Mitta and Starodubtseva, 1998; Mitta, 2000; rizont sehr klein, wahrscheinlich kleiner als die Zeit- = elatmae anabarense Gulyaev 2002, 2005). dauer eines einzigen Faunenhorizonts,” and similar (3) The BathonianÐCallovian boundary is defined at trend in development of Bathonian and Callovian the top of the bodylevskyi Biohorizon in contrast to M. jacquoti specimens, the Callovian species loss orna- Mitta (2000) who correlated it with the biohorizon mentation earlier than the Bathonian ones (Fig. 9). This base. is clearly seen in the plot demonstrating changes in the These modifications are introduced because of the whorl height, at which ornamentation begins reducing following reasons: within the same lineage (Fig. 10). (A) The validity of infrazonal units is determined by (2) Despite its “older” morphotype, Indian–Mada- the triple priority and subordinate principles (Gulyaev, gascar M. triangularis is very close to M. jacquoti that 2002) of (1) resolution degree, (2) succession, and was noted previously (Westermann and Callomon, (3) seniority. According to the second principle, the 1988, p. 16; Dietl, 1994, p. 13). Nevertheless, owing to scale of biohorizons should be based, if possible, on less frequent and coarser ribs in internal whorls (Datta links of the phylogenetic succession. This determines et al., 1996, Plate 1, figs. 3, 4) and peculiar subrectan- the resolution degree of the scale (first principle) and its gular cross-section in adult whorls, M. triangularis is completeness. In accord with the second principle, the readily distinguishable from European species. succession of biohorizons in suggested scale is deter-

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 508 KISELEV, ROGOV mined on successive species of the phyletic lineage Russia, respectively (Callomon, 1993). As is men- C. (Catacadoceras)ÐC. (Paracadoceras). Species Cado- tioned, morphological similarity between these species ceras (Bryocadoceras) falsum Voronetz 1962 that was appears to be real according to characteristic features of selected (Mitta and Starodubtseva, 1998; Mitta, 2000) their TBCs (Fig. 7). for index species of one biohorizons of the Elatmae Correlation between the Apertum and Elatmae Zone, the equivalent of our quenstedti Biohorizon, does zones is based on species from the Kepplerites kep- not belong to this phyletic lineage and cannot be used pleriÐplenus group occurring in both of them and char- as an index species our scale. acteristic of the Keppleri Subzone. K. keppleri and K. (B) In the standard scale, the BathonianÐCallovian traillensis (= plenus) are usually considered as close boundary is defined at the base of the keppleri Biohori- and, consequently, almost isochronous species (Cal- zon (Callomon et al., 1988). This universally recog- lomon, 2001; Callomon and Dietl, 1990, 2000) that is nized position corresponds approximately to the base substantiated in this work by morphometric data of the jacquoti Biohorizon (Thierry et al., 1997), (Fig. 6). As is shown, they are not identical however in although in southern Germany these levels differ nota- detail: K. traillensis is a transitional morphotype bly. Accordingly, the biostratigraphic boundary unit between K. keppleri and true Bathonian Kepplerites defined or established below the base of the kepleri forms. (jacquoti) Biohorizon should be attributed to the Batho- (B) Correlation based on identical or close index nian and the higher unit to the Callovian. Taking this species. The Nordenskjoeldi Zone is correlated with the into consideration, we referred the bodylevskyi Bioho- basal part of the Elatmae Subzone and, correspond- rizon to the Bathonian, whereas Mitta (2000) consid- ingly, the Apertum Zone is attributed to the Bathonian ered it as the basal faunal horizon of the Callovian. Stage. This version was first proposed by Mitta (2004b, 2005a, 2005b) who took into consideration the joint Problems of Correlation occurrence of Cadoceras form morphologically similar to C. nordenskjoeldi and K. traillensis in the YazykovoÐ Recently, the suggested scale can be correlated at Lekarevka section (Sura River basin). We found in the the infrazonal level only with scales of Germany and Prosek section a form close to C. nordenskjoeldi East Greenland, which are of a high resolution and (Plate V, figs. 5, 12) along with first M. jacquoti, and based in some intervals on similar ammonites succes- this indicates as well that the Nordenskjoeldi Zone sions. should be at substantially lower level than it is usually Correlation with the German scale, primarily for the thought. lower Callovian, is the least controversial (Table 5). This version is favored also by close stratigraphic Infrazonal units are directly correlative based on iden- occurrence of C. nordenskjoeldi and C. breve. In Cal- tical index species (jacquoti and quenstedti biohori- lomon’s scale, they represent index species of neigh- zons), which can considered as isochronous geographic boring biohorizons. In the Prosek section, both species subspecies (elatmae Biohorizon in Russia and suevi- (determined in open nomenclature) are found in the cum α, β in Germany), and on associated species of the breve Biohorizon. The forms identified by Callomon as ammonite assemblage (Calyx Zone and Hannoveranus C. cf./aff. breve are probably similar to Cadoceras Subzone, see below). Other intervals of the scales under forms of the underlying bodylevskyi Biohorizon, but consideration are lacking species in common in ammo- this is only a suspicion, since the specimens have not nite assemblages, being correlated according to their been figured. stratigraphic position. It is reasonable to think also that the top of the Nor- Correlation between infrazonal scales of European denskjoeldi Zone in East Greenland is marked by hiatus Russia and East Greenland is more difficult. The direct corresponding to the largest part of the Elatmae Zone. correlation is admissible only for the upper Bathonian In section 43 Fossilbjerget, at the top of Bed 26 with Calyx and, to a lesser extent, for Variabile zones based Fauna 30 (nordenskjoeldi β) there is a sharp boundary on identical or close index and associated species. The and abundant concretions near it (Alsen and Surlyk, overlying interval equivalent to Apertum and Norden- 2004; Callomon, 2004). This may indicate a condensed skjoeldi is almost lacking species in common. interval of sediments. We accept the traditional correla- Two alternative versions can be proposed now for tion model, which seems best substantiated. correlation between infrazonal scales of European Rus- Given below is description of biostratigraphic units sia and East Greenland using different approaches and located immediately near the BathonianÐCallovian index species. boundary (Calyx Zone, bodylevskyi and breve biohori- (A) Correlation based on phylogenetic analogues zons). (Table 5). The Apertum Zone entirely or almost entirely We omit description of other biohorizons estab- corresponds to the Elatmae Zone. This version accords lished in the Prosek section (infimum, frearsi, quens- with available ideas on the phylogenetic affinity taedti (= falsum Mitta and Starodubtseva, 1998; between index species Cadoceras apertum and = Gulyaev, 2005); = elatmae anabarense Gulyaev, Cadoceras frearsi from East Greenland and Central 2005). They are described in other works: infimum in

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 STRATIGRAPHY OF THE BATHONIANÐCALLOVIAN BOUNDARY DEPOSITS 509

Table 6. Ammonite assemblages of the Calyx Zone

European Russia East Northern Ammonites 2 3 Prosek Alatyr II1 Greenland Siberia 1. Cadoceras (Bryocadoceras) calyx Spath ? h 2. C. (Catacadoceras) infimum Gulyaev et Kiselev h ? 3. C. victor Spath h 4. C. franciscus Spath h 5. C. ammon Spath h 6. C. cf. franciscus Spath 7. C. cf. victor Spath 8. C. aff. variabile Spath 9. C. perrarum Voronetz 10. Pseudocadoceras (Costacadoceras) pisciculus (Gulyaev) h 11. Kepplerites (Kepplerites) svalbardensis Sokolov et Bodylevsky 12. K. (K.) peramplus Spath h 13. K. (K.) antiquus Spath h* 14. K. (K.) nobilis Spath h* 15. K. (K.) vardekloeftensis Spath ? h 16. K. (K.) rosenkrantzi Spath 17. K. (K.) aff. peramplus Spath ?* 18. K. (K.) aff. dietli Schairer 19. Toricellites pauper (Spath) h Note: Asterisk designate forms identified here as Kpplerites (K.) svalbardensis Sokolov et Bodylevsky. Question mark in Tables 6Ð8 indi- cates species identified with uncertainty. 1 Mitta, 2004b, 2005a, 2005b, 2006. 2 Callomon, 1993. 3 Knyazev et al., 2006.

(Gulyaev and Kiselev, 1999; Gulyaev, 2001; and oth- Keuppi Zone (pars): Mitta, 2005a, 2005b ers); frearsi in (Gulyaev, 2005 (as primaevum); quenst- Index species: Cadoceras (Bryocadoceras) calyx edti in (Gulyaev, 2005 as elatmae anabarense); elatmae Spath. Holotype is figured in Spath, 1932, Plate 20, in (Mitta, 2000; Gulyaev, 2001, 2005; and others). The fig. 1; East Greenland, near the Constable Point, Vard- frearsi (= primaevum Gulyaev, 2005) Biohorizon is ekloft Formation, K. tychonis Horizon. renamed for new index species (C. frearsi (Orb.) and C. primaevum Sasonov are considered as synonyms); Stratotype: East Greenland, Jamson Land, western their nomenclature is discussed in Callomon, 1993; coast of Hurry Inlet, Mount Zackenbjerg, Section 12 Mitta, 2000). The quenstedti Biohorizon (Callomon (after Callomon, 1993). et al., 1989) is introduced instead of the former one Range: in East Greenland biohorizons Kepplerites (elatmae anabarense) because of the other reason: peramplus (Fauna 22; Callomon, 1993) and Keppler- C. anabarense Bodylevsky is widespread in Arctic ites vardekloeftensis (Fauna 23; Callomon, 1993); regions only (see above) and cannot be considered as Cadoceras infimum Biohorizon (Gulyaev and Kiselev, ancestor of C. elatmae (C. quenstedti Spath is accepted 1999) in European Russia. for index species in this work). Ammonites: see Table 6 Upper Bathonian Correlation. In European Russia, the zone is estab- lished based on species in common in the ammonite CALYX Zone Callomon and Birkelund 1973 (in Sur- assemblage of the Calyx Zone of East Greenland. In the lyk et al., 1973) emend Callomon 1993 Alatyr River basin, the zone is recognizable in the Infimum Zone (pars): Gylyaev and Kiselev, 1999a, upper part of the Keuppi Zone, primarily in the Alatyr 1999b; Gulyaev, 2001, 2005 II section, where Mitta (2005) defined preliminarily the

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 510 KISELEV, ROGOV

K. vardekloeftensis faunal horizon and defined the internal whorls as well. Unfortunately, ammonites K. aff. peramplus unit. Mitta (2004, Plate I, fig. 2; 2005, found in situ in the Calyx Zone stratotype were figured p. 641, Plate 8, fig. 1) described and figured Cadoceras after Spath only occasionally. Hence, the taxonomic calyx from the same stratigraphic level. status of species under consideration remains ambig- In West Europe (Germany, Swabian Alb), the Calyx uous. Zone can be correlated with the upper part of the Orbis Zone (Hannoveranus Subzone) containing Kepplerites bodylevskyi Biohorizon Callomon 1984 forms close to the index species of the peramplus Bio- horizon (Dietl and Callomon, 1988). It is conceivable = fauna C11. Cadoceras bodylevskyi (pars): Cal- that the lower part of the Calyx Zone corresponds also lomon, 1984 to the upper part of the Blanasense Subzone, which = Kepplerites ex gr. svalbardensisÐCadoceras ex gr. yields Kepplerites species close to forms from the per- frearsi Beds (pars): Mitta and Starodubtseva, 1998 amplusÐK. dietli Schairer 1990 Biohorizon. = Cadoceras bodylevskyi faunal horizon (pars): Remarks. The peramplus and vardekloeftensis bio- Mitta, 2000 horizons of East Greenland are unrecognizable in the Prosek section for several reasons. Index species: Cadoceras (Paracadoceras) bodylevskyi Frebold. The holotype is figured by Fre- First, identification of K. peramplus and K. vardek- bold (1964, Plate 17, fig. 1); Canadian Arctic Archipel- loeftensis is quite difficult. Figures of K. peramplus ago, Axel Heiberg Island, Strand Fiord; Savik Forma- topotypes are reproduced in two works only. The holo- tion, lower Cadoceras Beds. type (Spath, 1932, Plate 24, fig. 1) corresponds to S-morphotype, and the TBC cast is therefore lacking Stratotype is undefined. The type locality of index secondary ornamentation that is the most important species can be considered as representing the latter. feature. After first description of the holotype by Spath, two topotypes have been figured under the same name (Dietl and Callomon, 1988). They differ from the holo- Ammonites: see Table 7 type in quantity of primary ribs on the terminal whorl: Correlation. When defining the bodylevskyi Bioho- 32Ð33 instead of 45 in the holotype. Since we accept rizon, Callomon (and, subsequently Mitta, 2000) sug- this feature for parameter of the phylogenetic trend in gested its occurrence in the northern Yukon region (the the genus Kepplerites, such a difference is significant. Bodylevskyi Zone, Poulton, 1987) in addition to the When defining K. vardekloeftensis, Callomon Canadian Arctic Archipelago. As is shown, specimens (1993, p. 102) distinguished holotype (Spath, 1932, figured by Poulton and Frebold and named Plate 25, fig. 2) and paratype (Spath, 1932, Plate 25, C. bodylevskyi belong to different, although close spe- fig. 1). Description of the species is missing from pub- cies of the Paracadoceras phyletic lineages: lications, and species diagnosis cannot be established C. bodylevskyi Frebold and C. breve Blake. The first of based on Spath’s specimens because of their poor pres- them marks the top of the Bathonian Stage, while the ervation (ornamentation is eroded); the holotype is second one is confined to the Callovian basal strata. The unsuitable therefore for counting ribs on the TBC. bodylevskyi Biohorizon belongs to the Bathonian Second, according to Callomon, Kepplerites sval- Stage, as it is below the Kepplerites keppleriÐMacro- bardensis and Cadoceras calyx occur in East Green- cephalites jacquoti Beds, which determine the base of land at different levels: the first species in the peram- the Callovian Stage. The overlying breve Biohorizon plus Biohorizon and second one in the vardekloeftensis bears M. jacquoti found in several sections of European Biohorizon. In the Prosek section, they are found in one Russia (see below) and should be attributed to the Call- concretion. ovian Stage. The biohorizon correlation with the standard Discus Third, the aforementioned species are found in asso- α ciation with K. rosenkrantzi Spath, the index species of Zone and apertum Biohorizon in East Greenland is biohorizon in the Variabile Zone that is below the Calyx conditional since ammonite assemblages from these Zone. This species is probably of a wider stratigraphic units are lacking species in common. range than that suggested by Callomon. Ammonites, Remarks. The Kepplerites specimens from the which we determined as K. rosenkrantzi, bear coarse YazykovoÐLekarevka section (Sura River basin) are ribs with distinct tubercles at their furcation points on figured and identified by Mitta (2000, 2004b) as Kep- middle whorls. This morphotype corresponds to speci- plerites traillensis. Morphometric comparison shows men of Spath, which is the species paratype (Spath, that one of the specimens falls into the morphological 1932, Plate 19, fig. 3). Callomon (1993, Plate 1) identi- field of the K. plenus (= traillensis); the other one into fied this specimen with K. cf. vardekloeftensis referring the field of K. svalbardensis. In any case, both speci- to the same species also the holotype K. nobilis Spath mens from the same stratigraphic interval are morpho- (Spath, 1932, Plate 23, fig. 4). The latter form is consid- logically closer to the Bathonian Keplerites forms. ered as an “anomalously involute variety of K. vardek- Hence, the bodylevskyi Biohorizon is certainly subdivi- loeftensis.” The holotype K. nobilis has coarse ribs in sion of the Bathonian Stage.

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 STRATIGRAPHY OF THE BATHONIANÐCALLOVIAN BOUNDARY DEPOSITS 511

Table 7. Ammonite assemblages of the bodylevsky Biohorizon European Russia Ammonites Arctic Canada Prosek Sura River basin1 1. Cadoceras (Paracadoceras) bodylevskyi Frebold ? h 2. C. (P.) cf. bodylevskyi Frebold 3. C. (Catacadoceras) nordenskjoeldi Callomon et Birkelund 4. Pseudocadoceras (Costacadoceras) cf. pisciculus Gulyaev 5. Kepplerites (Kepplerites) cf. keppleri (Oppel) ? 6. Toricellites pauper (Spath) Note: 1 Mitta, 2000, 2004. (h) holotype

LOWER CALLOVIAN holotype C. tschegemicum (Lominadze, 2004, Plate 1, fig. 5). ELATMAE Zone The terminal body chamber of C. breve is similar to Breve Biohorizon (Callomon 1984) emend that of C. bodylevskyi Frebold, being different from it (Gulyaev 2002) in several phylogenetic features of the C. (Paraca- = Paracadoceras breve + Kepplerites keppleri doceras) trend, i.e., in greater number of ribs and wider (fauna): Callomon, 1984 umbilicus (see above). Gulyaev who was first to note = fauna C11. Cadoceras bodylevskyi (pars): Cal- these differences regarded specimens figured by Poul- lomon, 1984 ton as species different from C. bodylevskyi. The TBC of the C. tschegemicum paratype (Lominadze, 2004, ?= Fauna 28. Cadoceras (Paracadoceras) cf. or aff. Plate 2, fig. 1) fits parameters of the C. breve mor- breve: Callomon, 1993 phologal field like C. poultoni (Poulton, 1987, Plate 27, = Cadoceras variabile Beds: Meledina and figs. 4–6), and both forms can be considered as identi- Zakharov, 1996 cal species and, consequently, as junior synonyms of = Cadoceras bodylevskyi Horizon (pars): Mitta, C. breve. 2000 = Cadoceras poultoni Biohorizon: Gulyaev, 2002 Ammonites: see Table 8 (in Gulyaev et al, 2002), 2005 Index species: Cadoceras (Paracadoceras) breve Stratotype is defined by Gulyaev (2005) in the Chur- Blake 1905. Holotype is figured by Blake (1905, Plate 5, kinskaya Shchel’ya site (Pizhma River, Komi, Repub- fig. 1) and reproduced in unpublished dissertation lic); lower Callovian, Elatmae Zone, Bed 3 (silt with (Page, 1988, Plate 17, fig. 3) and in this paper (Plate VI, large siltstone concretions). The type locality of the fig. 3). England, Dorset, near Weymouth, East Fleet. index species holotype (one specimen found in Lower Callovian. England) is unsuitable for stratotype, since exact posi- tion of the found specimen inside the Fleet Member of Synonymy of C. breve includes ammonites the Upper Cornbrash is unknown. described under names C. bodylevskyi Frebold 1964 (Poulton, 1987, Plates 27, 28), C. tschegemicum Lomi- Stratigraphic position and correlation. As is known, nadze 2004 (Lominadze, 2004, Plate 1, figs. 4, 5; Plate 2, the holotype is confined to the Fleet Member of the fig. 1; this paper, Plate VI, fig. 4), C. variabile Spath Upper Cornbrash spanning the Keppleri, Terebratus, (Meledina, 1994, Plate 8, figs. 1, 2); C. poultoni and basal Kamptus zones in the Weymouth area (Page, Gulyaev 2005 (= C. bodylevskyi Frebold sensu Poulton; 1989). Callomon (1984) suggested joint occurrence of holotype in Poulton, 1987, Plate 27, figs. 4–6).The this species with K. keppleri found below the holotype C. breve is represented by adult whorls lack- Cadoceras elatmae Beds. Later on, he assumed that the ing the terminal body chamber. The morphotype of this holotype originates from the upper part of the Keppleri Zone (Callomon, 1993), or more precisely from the ter- specimen is characterized by peculiar features: primary α ribs half-transformed into tubercles cover not only ebratus Biohorizon (Callomon et al., 1988) of the umbilical but also lateral sides of whorls, being Terebratus Subzone (Page, 1989). These are hypotheti- obliquely oriented. Slightly above the umbilical shoul- cal speculations, however, and the real position of holo- der, the bullae-shaped primary ribs bifurcate into three type inside the Fleet Member remains unclear. secondary ribs. The morphotype is characteristic of When studying Bathonian and Callovian sections in adult whorls (although not of the TBS) in all the speci- the Pizhma River basin, Gulyaev (2005) established mens figured by Poulton (1987, Plate 28) and of the that this species (identified as Paracadoceras poultoni,

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 512 KISELEV, ROGOV

Table 8. Ammonite assemblages of the breve Biohorizon European Russia North East Arctic Ammonites Pizhma Cauca- England Green- Canada4 Prosek River sus2 land3 basin1 1. Cadoceras (Paracadoceras) breve Blake h 2. C. (P.) cf. breve Blake ? 3. C. (Catacadoceras) cf. nordenskjoeldi Callomon et Birkelund ? 4. Pseudocadoceras (Costacadoceras) cf. pisciculus Gulyaev 5. Kepplerites (Kepplerites) ex gr. keppleri (Oppel) ? 6. Macrocephalites jacquoti Douville ? 7. M. tumidus (Rein.) ? 8. M. pila (Nikitin) ? Note: (h) holotype. 1 Gulyaev, 2005; Meledina, 1994; 2 Lominadze, 1982; 3 Callomon, 1993; 4 Poulton, 1987.

Plate VI, fig. 6) occurs in association with first Macro- (defined here as C. breve) was found in situ: in the Che- cephalites forms of the Macrocephalites jacquoti group gem River basin (Bed 3, 1.8Ð2.2 m above the base) and between the P. infimum subsp. nov. and P. primae- in Cherek BalkarskiiÐPsygansu watershed (approxi- vum (= frearsi in this paper) biohorizons. The latter mately, in the lower 9 m above the base of Bed 1) (Lom- units contains Macrocephalites forms of the given type inadze, private communication, 2006). The index spe- as well. Thus, the species characterizes the basal lower cies is accompanied in these sections by different Mac- Callovian, namely the lower part of the jacquoti Bioho- rocephalitidae forms, which are more diverse in the rizon, an equivalent of the keppleri Biohorizon. As is Chegem section (M. tumidus, M. pila, according to noted above however, M. jacquoti occurs in southern Lominadze). First Macrocephalitidae representatives Germany in two upper Bathonian biohorizons (hollandi are found in Bed 2 of the Chegem section; these are and hochstetteri) (Callomon et al., 1989; Dietl, 1994). Indocephalites sphaericus tchegemensis Lominadze According to reduction degree of ornamentation, (Lominadze, 1967, Plate XVIII, fig. 2; = ?Bullatomor- M. jacquoti differs from Bathonian species and falls phites sp.) and Kamptokephalites grantanus (Opp.) into the morphological field of Callovian forms. Kep- (Lominadze, 1967, Plate IV, fig. 4 = Macrocephalites plerites ex gr. keppleri found in association with this sp. (m). Consequently, this bed also belongs to the taxon proves the assumption that M. jacquoti marks the breve Biohorizon, although it can be of the Bathonian base of the Callovian Stage in the Prosek section. In age as well. addition, the ammonite assemblage of the Keppleri Subzone in England is “dominated by compressed and fine-ribbed macrocephalitid macroconchs belonging to CONCLUSIONS the species M. jacquoti (Douville) and M. verus Buck- The complete succession of ammonite zones and man” (Page, 1989, p. 369). Thus, it can be assumed that biohorizons of the terminal upper Bathonian and basal appearance of M. jacquoti in different areas of the Sub- lower Callovian, which are characteristic of European boreal Realm (England and European Russia) was syn- Russia, is established in the Prosek section. The infi- chronous most likely. mum Biohorizon corresponding to the Calyx Zone of It is relatively difficult to correlate the breve Bioho- East Greenland is distinguished in the upper Bathonian. rizon with the fauna cf./aff. breve from East Greenland. The BathonianÐCallovian boundary is defined at the First, specimens of this species from East Greenland base of the breve (jacquoti) Biohorizon. Infrazonal bio- have not been figured and originate, according to Cal- stratigraphic units of the BathonianÐCallovian bound- lomon (1993), from different localities of different ary interval established in the section are of the wide ages. Some of them may originate from the Apertum geographic distribution and high correlation potential Zone. We correlate conditionally this biohorizon with in the Panboreal Superrealm, i.e., in European Russia, the Apertum Zone based on morphological affiliation of northern Caucasus, West Europe, East Greenland, Arc- both species with the indicated phylogenetic trend. tic Canada (breve and, to a lesser extent, bodylevskyi In the northern Caucasus, the biohorizon in question biohorizons) and in the Tethyan Superrealm, the adja- is recognizable only in the lower part of “Macrocepha- cent European areas inclusive (jacquoti Biohorizon). lites macrocephalus Beds” (nomenclature of Lomi- The section studied meets most requirements con- nadze, 1982) in two sections, where C. tschegemicum cerning the GSSP selection (Remane et al., 1996) and

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 STRATIGRAPHY OF THE BATHONIANÐCALLOVIAN BOUNDARY DEPOSITS 513 can be considered as a candidate for the GSSP of the 8. J. H. Callomon, “Fossils as Geological Clocks,” in The Callovian Stage. The BathonianÐCallovian boundary Age of the Earth: from 4004 BC to AD 2002, Ed. by strata are represented here by marine facies containing C. L. E. Lewis and S. J. Knell (Geological Society, Lon- abundant and diverse ammonoids throughout the inter- don, 2001), pp. 237Ð252. val under consideration. The section is lacking signifi- 9. J. H. Callomon, “The Middle Jurassic of Western and cant biostratigraphic hiatuses and reveals the ammonite Northern Europe: Its Subdivisions, Geochronology and succession similar in many aspects with those known in Correlations,” Bull. Geol. Surv. Denmark and Green- West Europe (largely for the lower Callovian) and East land, No. 1, 61Ð73 (2003). Greenland (for the upper Bathonian). 10. J. H. Callomon, “Description of a New Species of Ammonites precisely sampled from the section are Ammonite, Kepplerites tenuifasciculatus n.sp., from the Middle Jurassic, Lower Callovian of East Greenland,” used to substantiate the modified succession of biohori- Appendix in: “Maximum Middle Jurassic Transgression zons in the BathonianÐCallovian boundary sediments in East Greenland: Evidence from New Ammonite Finds, of the East European platform. The Boreal and Tethyan Bjarnedal, Traill,” Ed. by P. Alsen and F. Surlyk, Bull. ammonoids found in association near the BathonianÐ Geol. Surv. Denmark and Greenland. No. 5, (2004), Callovian boundary ensure possibility to reliably corre- pp. 42Ð49. late the defined succession of biohorizons with bios- 11. J. H. Callomon and G. Dietl, “Proposed definition of the tratigraphic scales of West Europe and East Greenland. Callovian Stage. Field Symposium in Swabia, Stut- tgart/Albstadt (16Ð21 September, 1990) ISJS, Callovian Working Group (1990) (unpublished). ACKNOWLEDGMENTS 12. J. H. Callomon and G. Dietl, “On the Proposed Basal This work was supported by the Russian Foundation Boundary Stratotype (GSSP) of the Middle Jurassic for Basic Research (project no. 06-05-64284) and by Callovian Stage,” in Advances in Jurassic research. the Russian Science Support Foundation. We express GeoResearch Forum, Ed. by R. I. Hall and P. L. Smith our gratitude to the participants of the field observa- (Trans. Tech. Publ., UetikonÐZurich, 2000), Vol. 6, tions in October of 2006 (A.A. Sudovykh, L.A. Glin- pp. 41Ð54. skikh, S.Yu. Malenkina, M.V. Pimenov, A.V. Manikin). 13. J. H. Callomon, G. Dietl, and H.-J. Niederhöfer, “On the We thank also our colleagues, who provided published True Stratigraphic Position of Macrocephalites macro- data and materials on structure of the BathonianÐCall- cephalus (Schlotheim, 1813) and the Nomenclature of ovian boundary sediments in the northern Caucasus the Standard Middle Jurassic “Macrocephalus Zone,” (T.A. Lominadze, Georgia), India (S. Jain, the United Stuttg. Beitr. Naturk. Ser. B, No. 185 (1992). States), and Germany (G. Dietl). We are grateful also to 14. J. H. Callomon, G. Dietl, and H.-J. Niederhofer, “Die V.A. Zakharov (Geological Institute of the RAS) and Ammonitenfaunen-Horizonte im Grenzbereich Batho- V.V. Mitta (Paleontological Institute of the RAS), who nium/Callovium des Schwabischen Juras und deren Kor- reviewed carefully the manuscript. relation mit W-Frankreich und England,” Stuttgarter Beitr., Naturk. Ser. B, No. 148, 1Ð13 (1989) 15. J. H. Callomon, G. Dietl, and H.-J. Niederhofer, “On the Reviewers V.A. Zakharov and V.V. Mitta Ammonite Faunal Horizons Standard Zonations of the Lower Callovian Stage in Europe,” in 2nd International Symposium on Jurassic Stratigraphy (Lisboa, 1988), REFERENCES pp. 359Ð376. 1. P. Alsen and F. Surlyk, “Maximum Middle Jurassic 16. K. Datta, D. Bhaumik, S. K. Jana, and S. Bardan, “Age, Transgression in East Greenland: Evidence from New Ontogeny and Dimorphism of Macrocephalites triangu- Ammonite Finds, Bjarnedal, Traill ,” Bull. Geol. Surv. laris Spath—the Oldest Macrocephalitid Ammonite Denmark and Greenland, No. 5, 31Ð41 (2004). from Kutch, India,” J. Geol. Soc. India 47, 447Ð458 2. G. G. de Beer, Embryos and Ancestors (Oxford Univ. (1996). Press, London, 1958). 17. G. Dietl, “Der hochstetteri-Horizont—ein Ammoniten- 3. J. F. Blake, A Monograph of the Fauna of the Cornbrash faunen-Horizont (Discus-Zone, Ober-Bathonium, Dog- (Monogr. Paleontogr. Soc., London, 1905Ð1907). ger) aus dem Schwäbischen Jura,” Stuttg. Beitr. Naturk., 4. V. I. Bodylevsky, “Callovian Ammonites of Northern No. 202, 1Ð39 (1994). Siberia,” Zap. Leningrad. Gorn. In-ta 37, 49Ð82 (1960) 18. G. Dietl and J.H. Callomon, “Der Orbis- Oolith (ober- 5. J. H. Callomon, “A Review of the Biostratigraphy of the Bathonium, Mittl. Jura) von Sengenthal/Opf., Frank. Post-Lower Bajocian Jurassic Ammonites of Western Albh, und seine Bedeutung für die Korrelation und and Northern North America,” Spec. Pap. Geol. Ass. Gliederung der Orbis-Zone,” Stuttg. Beitr. Naturk. Canada, No. 27, 143Ð174 (1984). Ser. B, No. 142 (1988). 6. J. H. Callomon, “The Evolution of the Jurassic Ammo- 19. G. Dietl and R. Gygi, “Die Basis des Callovian (Mit- nite Family Cardioceratidae,” Spec. Pap. in Palaeontol- tlerer Jura) bei Liesberg BL, Nordschweiz,” Ecl. Geol. ogy, No. 33, 49Ð90 (1985). Helv. 91, 247Ð260 (1998). 7. J. H. Callomon, “The Ammonite Succession in the Mid- 20. H. Frebold, “The Jurassic faunas of the Canadian Arctic. dle Jurassic of East Greenland,” Bull. Geol. Soc. Den- Cadoceratinae,” Bull. Geol. Surv. Canada, No. 119 mark 40, 83Ð113 (1993). (1964).

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 514 KISELEV, ROGOV

21. P. A. Gerasimov and M. P. Kazakov, “Geology of the cephalites in Karachi, Western India,” Can. J. Earth Sci. Southeastern Part of the Gor’kii Region, MASSR, and 24, 1570Ð1582 (1987). ChASSR,” Tr. Mosk. Geol. Uprav., Issue 29 (1939). 36. S. G. Kulinich and B. I. Fridman, Geological Journeys 22. D. B. Gulyaev, “New Ammonites of the Family Cardio- across the Gor’kii Region (Volga–Vyatka, Gor’kii, ceratidae from the Lower Callovian of the Russian Plat- 1990) [in Russian]. form,” Paleontol. Zh., No. 1, 37Ð41 (1997). 37. T. A. Lominadze, Callovian Macrocephalitidae of Geor- 23. D. B. Gulyaev, “Macrocephalitinae and Govericeratinae gia and North Caucasus (Metsniereba, Tbilisi, 1967) (Ammonoides) fro the Elatmae Zone and Stratigraphy of [in Russian]. the Lower Callovian in Central Areas of the Russian 38. T. A. Lominadze, Callovian Ammonites of the Caucasus Platform,” in Problems of Mesozoic Stratigraphy and (Metsniereba, Tbilisi, 1982) [in Russian]. Paleontology (VNIGRI, St. Petersburg, 1999), pp. 63Ð 86 [in Russian]. 39. T. A. Lominadze, “Callovian Cadoceratinae of the Cau- 24. D. B. Gulyaev, “Infrazonal Ammonite Scale for the casus,” Tr. Geol. Inst. AN Gruzii, Nov. Ser., No. 119, Upper Bathonian-Lower Callovian of Central Russia,” 347Ð360 (2004). Stratigr. Geol. Korrelyatsiya 9 (1), 68Ð96 (2001) 40. S. V. Meledina, “Boreal Middle Jurassic of Russia,” Tr. [Stratigr. Geol. Correlation 9, 65Ð92 (2001). Inst. Geol. Geofiz. SO RAN, Issue 819 (1994). 25. D. B. Gulyaev, “Ammonite-based Infrazonal Strati- 41. S. V. Meledina and V. A. Zakharov, “Succession of graphic Units in Jurassic Stratigraphy (Definition and Bathonian and Callovian Ammonite Zones in the Nomenclature),” in Recent Geological Problems Pechora River Basin - Key for Zonal Correlation of the (Nauchnyi Mir, Moscow, 2002), pp. 271Ð274 [in Rus- Siberian Middle Jurassic with the Standard,” Geol. sian]. Geofiz. 37 (2), 25Ð36 (1996). 26. D. B. Gulyaev, “Infrazonal Subdivision of the Upper 42. V. V. Mitta, “The Genus Cadochamoussetia in the phy- Bathonian and Lower Callovian in the East European logeny of the Jurassic Cadoceratinae (Ammonoidea),” in Platform Based on Ammonites,” in Materials of the First Advancing Research on Living and Fossil Cephalopods All-Russian Meeting “The Jurassic System of Russia: (Plenum Publishers, New York, 1999), pp. 125Ð135. Problems of Stratigraphy and Paleogeography” (GIN, 43. V. V. Mitta, “Lower Callovian Ammonites and Bios- Moscow, 2005), pp. 64Ð70 [in Russian]. tratigraphy of the Russian Platform,” Byull. Coll. Fond. 27. D. B. Gulyaev and D. N. Kiselev, “Boreal Upper Batho- VNIGNI, No. 3, 1Ð144 (2000). nian in the Volga River Middle Courses (Ammonites and 44. V. V. Mitta, “On Problems of Middle Jurassic Biostratig- Stratigraphy),” Geol. Korrelyatsiya 7 (3), 79Ð94 (1999a) raphy in European Russia,” Nedra Povolzh’ya [Stratigr. Geol. Correlation 7, 279Ð293 (1999a). Prikaspiya, No. 39, 28Ð33 (2004a). 28. D. B. Gulyaev and D. N. Kiselev, “The Boreal Marine 45. V. V. Mitta, “To Evolution of Ammonites and Stratigra- Upper Bathonian in the Central Part of the Russian phy of BathonianÐCallovian Boundary Sediments in the Steppe,” Dokl. Akad. Nauk 367 (1), 95Ð98 (1999b) Volga River Basin,” in Ecosystem Reorganizations and [Doklady Earth Sciences 367, 641Ð644 (1999b)]. Evolution of the Biosphere (PIN RAN, Moscow, 2004b), 29. D. B. Gulyaev, D. N. Kiselev, and M. A. Rogov, “Bios- issue 6, pp. 125Ð136 [in Russian]. tratigraphy of the Upper Boreal Bathonian and Callovian of European Russia,” in 6th International Symposium on 46. V. V. Mitta, “Paracadoceras keuppi ZoneÐa New Upper the Jurassic System, September 12Ð22, 2002, Palermo. Bathonian Zone of the Russian Platform,” in Materials Abstracts and Program, Ed. by L. Martire (Palermo, of the First All-Russian Meeting “The Jurassic System of 2002), pp. 81Ð82. Russia: Problems of Stratigraphy and Paleogeography” (GIN, Moscow, 2005a), pp. 158Ð160 [in Russian]. 30. A. N. Ivanov, “Significance of Neoteny an Other Types of Deceleration in Development of Mesozoic Ammo- 47. V. V. Mitta, “Late Bathonian Cardioceratidae (Ammo- nites,” in Trends and Regularities in Historical Develop- noidea) from the Middle Reaches of the Volga River,” ment of Animal and Plant Organisms. Abstracts (PIN, Paleontol. Zh. 39, 629Ð644 (2005b). Moscow, 1969), pp. 31Ð33 [in Russian]. 48. V. V. Mitta, “On the Bathonian–Callovian Boundary in 31. S. Jain, “The Bathonian-Callovian Boundary in the Mid- the Boreal Scale,” in Paleontology, Biostrtaigaphy, and dle Jurassic Sediments of Jaisalmer Basin, Western Raj- Paleogeography of the Boreal Mesozoic: Materials of asthan (India),” J. Geol. Soc. India (2007) [in press] the Sci. Session, Novosibirsk, April 26Ð28, 2006 (GEO, Novosibirsk, 2006), pp. 115Ð117 [in Russian]. 32. D. N. Kiselev, “Ontogenesis and Taxonomic Position of Callovian Ammonites from the Genus Pseudoca- 49. V. V. Mitta and I. A. Starodubtseva, “Field Works of 1998 doceras,” Byul. Mosk. O-va Ispyt. Prir., Otd. Geol. 71, and Lower Callovian Biostratigraphy of the Russian Issue 3, 82Ð98 (1996). Platform,” VM-Novitates, No. 2 (1998). 33. D. N. Kiselev, “Morphogenesis and Taxonomy of the 50. V. V. Mitta and I. A. Starodubtseva, “V.A. Shchirovskii Genus Pseudocadoceras (Ammonoidea),” Paleontol. and the Study of the Mesozoic in the AlatyrÐKurmysh Zh., No. 3. 15Ð27 (1996). Area (Middle Volga Region),” VM-Novitates, No. 5 34. J. Kopik and A. Wierzbowski, “Ammonites and Stratig- (2000). raphy of the Bathonian and Callovian at Janusfjellet and 51. E. Möning, “Die Macrocephalen-Oolith von Hildesheim,” Wimanfjelet, Sassenfjorden, Spitzbergen,” Acta Paleont. Mitt. Roemer-Museum. N. F., No. 5, 1Ð76 (1995). Pol. 33, 145Ð168 (1988). 52. O. Nagel and V. Pirkl, “Eckhardites Ein seltener Ver- 35. J. Krishna and G. E. G. Westermann, “Faunal Associa- treter der Familie Cardioceratidae,” Fossilien, No. 5, tions of the Middle Jurassic Ammonite Genus Macro- 293Ð297 (2001).

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007 STRATIGRAPHY OF THE BATHONIANÐCALLOVIAN BOUNDARY DEPOSITS 515

53. K. N. Page, The Stratigraphy and Ammonites of the Brit- 60. L. Spath, “The Invertebrate Faunas of the Batonian-Call- ish Lower Callovian, Thesis unpublished (1988). ovian Deposits of Jameson Land (East Greenland).” Medd. Grönland 87 (7), 1Ð47 (1932). 54. K. N. Page, “A Stratigraphical Revision for the English Lower Callovian,” Proc. Geol. Ass. 100, 363Ð382 61. F. Surlyk, J. H. Callomon, R. G. Bromley, and T. Birke- (1989). lund, “Stratigraphy of the Jurassic-Lower Cretaceous Sediments of Jameson Land and Scoresby Land, East 55. K. N. Page, “Biohorizons and Zonules: Intra-Subzonal Greenland,” Bull. Grönl. Geol. Unters., No. 105, 1–76 Units in Jurassic Ammonite Stratigraphy,” Paleontology (1973). 38, 801Ð814 (1995). 62. J. Thierry, Le genre Macrocephalites au Callovien 56. T. P. Poulton, “Zonation and Correlation of Middle inférieur (Ammonites, Jurassique moyen). Systématique Boreal Bathonian to Lower Callovian (Jurassic) Ammo- et evolution. Biostratigraphie. Biogéographie: Europe nites, Salmon Cache Canyon, Porcupine River, Northern et domaine indo-malgache. Thèse Doctoral Etat Dijon Yukon,” Bull. Geol. Surv. Canada, No. 358, 1Ð155 (Mém. géol. Univ., Dijon, 1978), no. 4, pp. 1Ð490. (1987). 63. J. Thierry, E. Cariou, S. Elmi, et al., “Callovien,” in Bio- 57. J. Remane, M. G. Bassett, J. W. Cowie, et al., “Revised stratigraphie du Jurassique Ouest-Européen et Méditer- Guidelines for the Establishment of Global Chronos- raneen, Ed. by E. Cariou and P. Hantzpergue (Bull. Cen- tratigraphical Standards by the International Commis- tre Rech. Elf Explor. Prod., 1997), Mém, 17, pp. 63–78. sion on Stratigraphy (ICS),” Episodes 19, 77Ð81 (1996). 64. G. E. G. Westermann, and J. H. Callomon, “The Macro- cephalitinae and Associated Bathonian and Early Call- 58. N. T. Sazonov, Jurassic Deposits in Central Regions of ovian (Jurassic) Ammonoids of the Sula Islands and the Russian Platform (Gostoptekhizdat, Leningrad, Papua New Guinea,” Palaeontographica, Abt. A 203, 1Ð 1957) [in Russian]. 90 (1988). 59. N. M. Sibirtsev, “Notes on Jurassic Sediments of the 65. V. A. Zakharov, Yu. I. Bogomolova, V. I. Il’ina, et al., Northern Nizhni Novgorod Region (Makar’ev, Semenov, “Boreal Zonal Standard Biostratigraphy of the Siberian and Balakhna Areas),” Zap. St. Petersburg. Mineral. Mesozoic,” Russian Geol. Geophysics 38, 965Ð993 O-va, Ser. 2, Pt. 23, 72Ð81 (1886). (1997).

STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 15 No. 5 2007