The Jurassic Ammonite Zones of the Soviet Union Editedby G. Va. Krymholts Geological Faculty Leningrad University University emb. 7/9, 199034 Leningrad, U.S.S.R. M. S. Mesezhnikov VNIGRI Liteiny 39, 191104 Leningrad, U.S.S.R. G.E.G. Westermann Department of Geology McMaster University 1280 Main Street West Hamilton, Ontario L8S 4Ml, Canada
ContentsPreface vForeword viiIntroduction . G. Va. Krymholts and M. S. MesezhnikovHettangian 3 Ju. S. RepinSinemurian 6 Ju. S. RepinPliensbachian 10 Ju. S. RepinToarchian 14 E. D. KalachevaAalenian . . . . .. 19 K D. KalachevaBajocian 23 G. Va. KrymholtsBathonian 29 S. V. MeledinaCallovian 33 S. V. MeledinaOxfordian 39 M. S. MesezhnikovKimmeridgian 45 M. S. Mesezhnikov III
IV Contents Tithonian (Volgian) 50 M. S. Mesezhnikov Subdivision of the continental Jurassic basedon plants 63 V. A. Vakhrameev, V. I. Iljina, and N. I. Fokina Conclusion .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 73 G. Ya. Krymholts and M. S. Mesezhnikov Illustrations of index and guide Ammonites of the Soviet Union 75 References 110
Preface In August 1984,at the Moscow meeting of the International Geological Congress, I metwith Drs. Krymholts and Mesezhnikov and suggested that theirimportant work, TheJurassicZonesof the USSR (in Russian), shouldbe translated into English. Translation would makethe largeamount of data compiled in that book available to the world community of Jurassicworkers. As members of the International Commission on Jurassic Stratigraphy and ofProject 171, Circum-Pacific Jurassic, of the International Geological Correlation Program,all threeof us wereparticularly aware of the need to publish an English synthesis of the large,pertinent Russian literature from the several past decades, which unfortunately, has beenavailable to only a few in the non-Russian-speaking world. Agreement in principle with Drs. Krymholts and Mesezhnikov on a revised edition inEnglish was the result of my negotiations with the Books Editor of the Geological Society ofAmerica, Dr. C. Craddock, and of application to the copyright commission in the SovietUnion. I received the English version of the revised typescript, translated by Mr. Vassiljeva, inDecember 1986. Considerable technical and scientific editing as well as redrafting of tableswas required before the final typescript could be submitted to the GSA Books Editor.Internalconsistency had suffered underthe varying degrees of revision of the Russian originalcarried out by the different authors, such as the difficulty in tracing the Bajocian/Bathonianboundary in the Boreal Realm. Another basicproblemis the definition of the Middle/UpperJurassic boundary, which Sovietauthors consistently place at the base of the Callovian; therest of the world, as far as I know, follows the ruling of the International Subcommission onJurassicStratigraphy (IVGS Commission on Stratigraphy) drawing the boundaryabove theCallovian. Since the Sovietdecision cannot be altered by us, I have attempted to bypass thisproblem by omitting the use of the formal Series, writing instead "lower/middle/upper partof the Jurassic." I have also introduced the different spelling of standard and biozones bycapitalizing the species epithet for the former, following contemporary English and NorthAmerican practice. Gerd E. G. Westermann McMaster University, Hamilton, Canada January 1988 v
Foreword In the past few decades, due to intensive geological investigations, much attention wasgiven to stratigraphic studies of certain regions, constructing defined stratigraphic schemes,and restructuring the theoryof stratigraphy. Geological surveys and othergeological investiga-tionshavebecomemore detailed, and hence, require a moreprecise stratigraphic basis. At thesame time, problems of correlation, both within certain regions and over the entire country,have become more complicated. There is an increasing need to create a standardthat allowscorrelations for entirecontinents and the entireEarthssurface. Thishas required the construc-tion of a general, well-grounded stratigraphic standard, i.e., the Standard (International)Stratigraphic Scale, compiled in maximum detail. The present zonal scheme serves as such astandardfor the Phanerozoic. The Commission on the Jurassic System of the USSR analyzed and summarized thedata available and recommended a standard scale for subdivision of this system as the basisfor studying Jurassic deposits in the USSR. Documents of specialized international meetings(e.g., Luxemburg, 1962, 1967; Moscow, 1967; Budapest, 1969; Lyon-Neuchatel, 1973; Stutt-gart, 1977; Novosibirsk, 1977; and others) resulted from studies of type sections and theirfossils, as well as other investigations, in the USSR. The latter were synthesized at inter-departmental regional stratigraphic meetings (Russian Platform, 1958; Caucasus, 1977; Balticarea, 1976; Urals, 1977; western Siberia, 1976; central Siberia, 1978; North-east, 1975; FarEast, 1978; central Asia, 1971; Kazakhstan, 1967). The results of theseconferences are summarized herein. They werepreparedby a groupof authors and discussed and accepted by the plenary session of the commission. Alsoconsidered are the results of discussions on certain problems of Jurassic stratigraphy, whichwere carried out by the commission and published in Resolutions of the InterdepartmentalStratigraphic Committee and Its Commissions. We present the results obtained at differenttimes. A brief history is presented of the origin and subdivisions of each stage, its stratotype,and the composition and faunaof someof itsunits; problems are discussed, and data are givenon structural patterns of deposits in the mainJurassic regions in the USSR. Data on the sevenseparate Jurassic regions are presented separately from the structural-historical discussions.Each region has its own development of the Jurassic. Within each region, wherepossible, anarea is chosen with the most complete, best studied, and most reliably subdivided section. Insome cases, however, more or less remote parts of a region have to be usedto characterize acertain stage. The following regions were chosen as being the most characteristic (Fig. 1):1, Russian Platform; 2, Northern Caucasus, with the mostcomplete and beststudied section ofthe Mediterranean Geosynclinal Belt within the USSR; 3, Turan Plate, with the Kugitangtauarea at its southeastern margin; 4, Western Siberian Plate; 5, Siberian Platform; and 6, the Vll
viii Foreword eastern parts of the USSR belonging to the Pacific Geosynclinal Belt. The northeastern and southern parts of the Far East of the Soviet Union are discussed separately. The section dealing with the Upper Jurassic is somewhat different from the other parts. Due to marked provincialism, no common stratigraphic scheme can be used. In order to establish the correlation between the zonations of the Tethyan and Boreal realms and north- western Europe, I have considered abundant evidence, including fossils; this has resulted in certain changes from the previous zonal correlations and a different interpretation of the Jurassic/Cretaceous boundary in the Boreal Realm. In the characterization of sections, ample use is made of data from the volume on Stratigraphy of the USSR Jurassic System (Krymholts, 1972b) and other summaries and original papers. We show that, in some cases, it is possible to distinguish both local and the standard zones in the Jurassic of the USSR. The zonal subdivision was discussed at the Plenary Meeting of the Commission on the Jurassic System of the USSR and was published in its preliminary form by Krymholts (1978). During the years that followed, some changes and additions were introduced. The subdivisions are based on ammonoid ranges, an archistratigraphic fossil group of great signifi- cance for the Mesozoic. In stratigraphic studies and their application, other groups of organisms are, of course, also used: above all, these include the foraminifers. These small fossils are of major signifi- cance for subdivision and correlation of subsurface deposits, since in boreholes, core fossils are rare and usually fragmented. The Upper Jurassic foraminifers have been studied most tho- roughly, and the subdivisions based on evolution of their assemblages are comparable to the biostratigraphic units in the Upper Jurassic based on ammonites. Some bivalves are used successfully in marine Jurassic stratigraphy. Among them are Buchia (Aucella auct.), which are among the most common fossils in the Upper Jurassic, particularly in the northern USSR. Mytiloceramus is common in the Middle Jurassic of the eastern USSR, where ammonites are rare, and is equally important. Bivalves are mostly benthic and reflect the conditions in paleobasins to a greater degree than cephalopods. Thus, they are useful not only in stratigraphy but also for facies and biogeographic analysis. It should be emphasized that during the Jurassic, biogeographical isolation of certain areas within the USSR underwent a significant evolution. At the beginning of the period, isolation in the seas was practically absent. At the end of the Early Jurassic, the differences had become evident, particularly in the composition of molluscs from the southern seas connected with Tethys and northern Boreal seas. Provincialism became more pronounced in the Middle Jurassic. The extreme provincialism that occurred in the Late Jurassic seas, particularly at the end of the period, is the main reason for distinguishing different strati- graphic schemes for certain basins, even when abundant fossils are present. Extensive areas of the USSR were covered by land in Jurassic time. The recognition of standard zones for continental deposits is, of course, impossible, and it is often difficult to establish the stage to which certain parts of the section belong. In many cases, however, correlation with pairs (or triplets) of stages can be made on the basis of plant remains, mainly leaves, spores, and pollen. Eight specialists have prepared this volume, each being responsible for a section, accord- ing to his or her specialization. Despite a common outline and editing, each section has retained its individuality, but during preparation the authors exchanged ideas and suggestions concerning the improvement of the presentation. Many new data have become available to Soviet geologists since publication of the Russian version of this volume in 1982. Supplementary investigation of the Middle Jurassic of Siberia and the Far East suggests, for example, that the boundaries of the Bajocian and Bathonian in these regions are very close to the boundaries used in such regions as East Greenland and Canada. We are grateful to A. I. Zhamoida, I. V. Polubotko, E. L. Prozorovskaja, K. O. Rostovt- sev, and I. I. Sey for reading the manuscript, and for their useful advice and remarks. G. Va. Krymholts, M. S. Mesezhnikov, 1986
Geological Society of America Special Paper 223 1988 The Jurassic Ammonite Zones of the Soviet Union INTRODUCTION G. Ya. Krymholts and M. S. Mesezhnikov The JurassicPeriodand its deposits in the SovietUnion are bigny, 1850, p. LIX); it is made up of lists of the characteristicwell known to specialists. The system has been the subject of a species for each Jurassicstage. A more detaileddescription of thenumber of general works, suchas the compilation and reconstruc- stages was later published (dOrbigny, 1852). Some stage namestion of the first paleogeographic and paleobiogeographic maps, used by dOrbigny, however, go back to earlier authors, e.g.,past climates, the notion of facies, the foundation of detailed Bathonian refers back to dOmalius dHalloy, 1843; Oxfordien,stratigraphy, and the distinction of stages and of smaller strati- to Brogniart, 1829; and Kimmeridgian, to Thurman, 1833.graphic units such as zones. The Jurassic is widespread with Arkell(1933) enumerated 120 Jurassicstagenames usedatdiverse deposits, and above all, it contains the remains of ammo- different times. In order to avoid disagreement in assigning prior-nites. Ammonoids belong to the few groups of fossil organisms ity, he proposed(Arkell, 1946)accepting the year 1850as mark-that wereboth widely distributed in old seasand evolved rapidly. ing the beginning of the stage concept (this is similar to zoology,Theirshells varygreatly in shape, ornamentation, and other char- where 1758,the yearof publication of the IOth editionof Linnesacteristics, permitting relatively easyrecognition of taxa. Systema Naturae, is designated as a beginning of binominal no- Concerning the history and problems of Jurassic stratigra- menclature). In the Stratigraphic Code of the USSR, the yearphy, we emphasize the role of the outstanding French 1881 was chosen for the application of priority right for generalpaleontologist-stratigrapher Alcide dOrbigny (1802-1875). Not stratigraphic units (Stratigraphic Code, 1977,Article IX.6).only washe the first to formulate the concept that "stageunitsare In England at the time of dOrbignys work, a number ofmanifestations of boundaries drawn by nature, but have nothing local units/strata weredistinguished by theircomposition, whicharbitrary" (dOrbigny, 1842-1851, p. 603), but he was also the corresponded to partsof the Jurassic System, e.g., Portland Rock,first to subdivide the Jurassic System into 10 stages (dOrbigny, Coral Rag, Cornbrash. These lithostratigraphic units are used by1842-1851), seven of which are usedtoday. geologists working in the British Isles up to the present day. DOrbigny (1852) listed a locality or area for each of the In Germany, F. A. Quenstedt (1809-1889), publishing instages wherethe type sectionis located(i.e., stratotype) and after the years of dOrbignys work, greatly advanced the triplesubdi-which it is named. He also listed other characteristic sections vision of the Jurassic System proposed by L. von Buch (1837),as(parastratotypes) in France, England, Switzerland, and West a result of studies in the Swabian Alb. In each of the Lower (orGermany, and he indicated the types of deposits (e.g., coastal, Black), Middle (Brown), and Upper (White) Jurassic, Quenstedtshallow, or deeper water). He published a list of fauna for each distinguished six lithostratigraphic units, which he characterizedstage, with numerous representatives of different fossil groups, by ammonites and other taxa and denoted by lettersof the Greekprimarily cephalopods and, of these, mainly ammonites. alphabet (alpha to zeta). The rank of these subdivisions was not,DOrbigny (1842-1851) described the ammonites in a classic however, indicated by Quenstedt or his followers; they corre-monograph and determined the total number of characteristic spond more or less in their magnitude to the stages as presentlyspecies for the Jurassicas 3,731 (dOrbigny, 1850),thus defining used. These notations are used even today by Germangeologistsa stage by stratotypes and parastratotypes as well as by fossils. in local descriptions. DOrbigny prepared the three mentioned works simultane- Quenstedts pupil, A. Oppel (1831-1865), was the first toously (1842-1851, 1850, 1852),so that discrepancies havearisen successfully correlate units of the Jurassic System adopted inamonghistorians concerning the date whenthe stages wereestab- England, France, and southwestern Germany (Oppel, 1856-lished. The preferred date is 1850, when the stratigraphic section 1858). He used dOrbignys stages as the framework for new unitsof the monograph on Jurassic cephalopods was published (dOr- distinguished in England and adoptedin West Germany, a major
The Jurassic Ammonite Zones of the Soviet Union 3this is not the place to introduce changes into a historically greatly. For example, according to Harland and others (1981),evolved system. In these cases, we make reference to both the the Jurassic was determined to have begun at 213 Ma and endedindex species and the author who named the zone. at 144 Ma, a duration of 69 m.y. According to Odin (1982), Radiometric data available for the Jurassic Period differ however, the dates are 204 and 130 Ma, a duration of 74 m.y. HETTANGIAN Ju. S. RepinHISTORY AND STANDARD ZONES yet clear whether this siliceous limestone member belongs to the Rhaetian or to the basal Jurassic (Zhamoida, 1975; Tollmann, The stage name Hettangian was proposed by Renevier 1976).(1864)* for the Ammonites [Psiloceras] planorbis and Am Commonly, in sections of marine Hettangian, the first am-[Schlotheimia] angulatus Zones as interpreted by Oppel, i.e., the monites are representatives of Psiloceras with smooth shells, viz.lower part of the Sinemurian stage of dOrbigny. The stage was P. planorbis (Sow.), P. erugatum (Phill.), P. psilonotum (Qu.).named after a quarry near Hettang-Grande Village in Lorraine, However, in the Omolon Basin (North-East USSR), ribbed psilo-22 km south of Luxembourg. This stratotype, however, is "unfa- ceratids now assigned to Primapsiloceras occur below (Polu-vourable for establishing the succession of ammonite assem- botko Repin, 1981). Initially named Psiloceras (Franziceras ?)blages. The whole stage is represented by sandstone, more or less primulum Repin (Field Atlas, 1968; Polubotko and Repin,calcareous, in places resting on Rhaetian beds, and in places on 1972), it defines a level at the base of the Psiloceras planorbisKeuper marls. The lower part, except for occasional oysters, con- Zone in the North-East USSR. Recently, remains of small "Schlo-tains no fossils; found above are accumulations of Cardinia and theimia" were found in Luxembourg, below the level with P.Lima together with a rich and well-preserved gastropod fauna" planorbis (Guerin-Franiatte and Muller, 1978). Judging by their(Arkel, 1956, p. 68). For all practical purposes, the succession of description and illustrations, these "Schlotheimia" resemble smallammonoid assemblages was established in sections of other areas representatives of the Asian Primapsiloceras and probably belongof France, England, and West Germany. For instance, Oppel, to this genus.when describing the Am planorbis Zone (Oppel, 1856-1858), The above facts allowed workers to regard beds containingpointed to characteristic sections on the Dorset coast near Lyme Primapsiloceras (Polubotko and Repin, 1981; Repin, 1983) as anRegis, quarries near Uplume, and-Watcher sections in Somerset. independent and lowermost Hettangian zone. The range corre-The last area was proposed as the stratotype for a lower zone of sponds to Pre-Planorbis Beds in England, equivalents of thesethe Hettangian by an English scientist (Morton, 1974). beds with small "Schlotheimia" in Belgium and beds with Primap- Regarding the lower boundary of the Hettangian, and of the siloceras primulum in northeast Asia.Jurassic System, the following should be noted. In the sections of In 1962, Hoffmann proposed to distinguish the NeophyllitesEngland, the Jurassic begins within the "Blue Lias"t shale mem- antecedens Subzone at the base of the Psiloceras psilonotumbers, where the first Psiloceras appears only in the middle part of (=planorbis) zone in northern Germany. The systematic status ofthe section. The lower part ofthe Blue Lias section ("paper" shale Neophyllites is vague. Some workers have acknowledged it as amember) is characterized by Ostrea liassica and Pleuromya tatei; genus (Lange, 1941), whereas others regard it as a junior syn-lacking ammonites, it was distinguished by Richardson (1911) as onym of Psilophyllites (Arkell, in Moore, 1957) or PsilocerasPre-Planorbis Beds. Donovan (1956) included these beds in the (Cope and others, 1980a). Its stratigraphic position is also notPsiloceras planorbis Subzone at the base of the Jurassic. quite clear. Distinguishing N. antecedens. Lange noted only that it The Rhaetian section in the Austrian Alps, 15 km west of was found below the Schlotheimia angulata Zone. HoffmannBad-Ischl in the upper Kendlbach stream, consists of massive found both N. antecedens and P. psilonotum in the same 0.65-m-siliceous limestone between a clay member (12 m) with Choris- thick layer, which he assumed to be condensed,toceras marshi Hauer (Choristoceras marshi Zone) and Hettan- Bloos, in a guide to the excursion in Franconia, gave agian limestone with Psiloceras ex. gr. planorbis (Sow.). It is not scheme of the stratigraphic range of Hettangian ammonites in northwest and southern West Germany. He distinguished two subzones within the planorbis Zone: a lower antecedens and an upper planorbis subzone. Neophyllites antecedens, found only in*A.Leymerie (1838) proposed the term Infra-Lias for the deposits almostequiva- the upper half of the subzone bearing that name, ranges throughlent to the present Hettangian; later, this name was also used for the underlyingRhaetian formations. It is now rejected. the planorbis Subzone. Due to an inadequate systematic and stratigraphic definition[Oppel alsoincluded "White Lias," underlying Blue Liaslimestone, in the Juras- of Neophyllites, an independent zonal unit on its basis is poorlysic. Now the White Liasis known to belongto the Rhaetian (Morton, 1974). grounded. On the other hand, this attempt to distinguish beds
4 The Jurassic AmmoniteZonesof the Soviet Unionwith Psiloceras planorbis below the level of other older ammo- lum (Qu.). (b) Caloceras johnstoni Subzone. Trueman, 1922.nites is highly instructive. Index species-C. johnstoni (Sow.). Base defined by appearance Initially, Oppel distinguished two zones, viz., Ammonites of genus Caloceras and the index species. Caloceras belcheri[Psi/oceras] planorbis (below)and Ammonites[Schlotheimia] an- (Simps.) and C. bloomfieldense Donovanpass into the baseofthegulatus (above) in deposits of the Hettangian. Collenot (1896) overlying zone.proposed a triplesubdivision of the Hettangian and distinguishedthe Alsatites liasicus Zone in its central part. Subdivision of the Upper HettangianHettangian into three zones was supported by Lange (1941) andis now universally accepted. An attemptat a more detailed subdi- 3. Alsatites liasicus Zone. Collenot, 1896. Index species-vision of the Hettangian was made by the Frenchgeologists Elmi A. liasicus (Orb.). Defined by appearance and flourish of Waeh-and Mouterde (1965). Proceeding from the studies of sections in neroceras; upperhalfdominated by Alsatites. (a) Waehnerocerassoutheastern France (Ardeche), they proposed subdividing the portlocki Subzone. Lange, 1941. Index species- HI: portlockiHettangian into five zones; however, the same scientists (Mou- (Wright). Characteristic are species of Waehneroceras; in certainterde and others, 197I; Elmi and others, 1974)later decided that sections also rare Alsatites. (b) Alsatites laqueus Subzone.it wouldbe morelogical to acceptonlythreezones, reducing their Reynes, 1879. Indexspecies-A. laqueus (Qu.). Base defined byCaloceras johnstoni and Waehneroceras portlocki Zones to the appearance of index and species of Saxoceras. Some Waehneroc-rank of subzones. eras pass into subzone. Generally, two successive Alsatites levels As for grouping the Hettangian zones into substages, thereis are present, a lower level with Alsatites laqueus (Qu.), and anno universally accepted viewpoint. German workers (Lange, upper level with Alsatites liasicus (Orb.). Upper Hettangian.1941, 1951; Holder, 1964; Urlichs, 1977a), proceeding from the 4. Schlotheimia angulata Zone. Oppel, 1856-1858. Indexscheme for the Lower Jurassic of southwestern West Germany species-So angulata (Schloth.). Range zone of Schlotheimia. (a)workedout by Quenstedt(1843),subdivided the Hettangian into Schlotheimia extranodosa Subzone. Donovan, 1956. Indextwo substages. The lower substage corresponds to the Black Ju- species-So extranodosa (Waehner.). Rangesubzone. (b) Schlot-rassic ad (Psiloceras planorbis and Alsatites liasicus Zones); and heimia complanta Subzone. Spath, 1942. Index species-Sothe upper one, to the Black Jurassic a2 (Schlotheimia angulata complanata Koenen; Schlotheimia similis Spath.Zone), i.e., it corresponds to local lithologic units. Arkell, subdi-viding the Hettangian into substages, preferred paleontologic fea- SOVIET UNIONtures, i.e., grouping successive ammonite levels on the basis oftheir common characteristics or differences. According to this In the Soviet Union, marine Hettangian deposits are notauthor (Arkell, 1933), the Lower Hettangian corresponds to the widespread. Mainly they are found in the north and east of thePsiloceras planorbis Zone and the UpperHettangian to the restof country; rare deposits are recorded within the Mediterraneanthe stage. Geosynclinal Belt (Fig. 2). On the Russian Platform, the Hettan- Following Arkell and takinginto accountnew data, we take gian has not been recorded, although some authors so dated theLower Hettangian as comprising two successive levels: Primapsi- upper part of the Novorajskoe Formation at the northwesternloceras and Psi/oceras. The Upper Hettangian in this casecorre- margin of the Donetsfolded structure (Krymholts, 1972b).sponds to the development of representatives of Schlotheimiidae Mediterranean Geosynclinal Beltand Arietitidae, viz., Waehneroceras, Alsatites, and Schlotheimia. Zonal subdivision can be based on the division of the Het- Hettangian deposits occur in the Crimea. Part of the Uppertangian in Western Europe (Dean and others, 1961), with the Tauride Group, they are composed of dark gray clay shale withPrimapsiloceras primulum Zone distinguished at the base of the interbeds of siltstone and quartz sandstone (50-150 m), The dis-Jurassic. covery of Schlotheimia angulata (Schloth.) at the Bodrak River establishes this upper Hettangian zone (Krymholts, 1972b). InLower Hettangian the northern Caucasus, there are no paleontologically confirmed Hettangian deposits. 1. Primapsi/oceras primulum Zone. Polubotko & Repin, On the Turan Plate, Lower Jurassic continental and1981. Index species-P. primulum (Repin). Range zone of Pri- weathering-crust deposits are recorded. It is impossible to distin-mapsiloceras; in England coeval to Pre-Planorbis Beds and their guish stages in thesesections, which often are characterized onlystratigraphic equivalents. by plant remains. In Kugitangtau, deposition of the thin Sandzhar 2. Psi/oceras planorbis Zone. Oppel, 1856-1858. Index Formation possibly continued into the early Jurassic with brec-species-s-P planorbis (Sow.). Generally, range zoneof Psiloceras cias, red mudstone, and siltstone (Resolutions, 1977).s. str. and Caloceras. (a) Psiloceras planorbis Subzone. Trueman, West Siberian Plain1922. Two levels are distinguished: the lower one with smoothPsiloceras planorbis (Sow.), P. erugatum (Phill.), P. psilonotum On the West Siberian Plain, the lower part of the Jurassic(Qu.), and the upperone with distinctly plicate Psiloceras plicatu- consists mainlyof the limnicLowerTyumenMember, with only
The Jurassic Ammonite Zones of the Soviet Union 5 EUROPEAN STANDARD ZONES KUNI- RUSS. N. TANGTAU W. FAR Stage PLAT. CAUCA. RANGE SIBERIA SIBERIAN PLATFORM NORTH·EAST Zones Subzones EAST COMPLANATA E E E 0 Mudstone ANGULATA 0 " 0 ~ with " " S. angulala Zone 6 co EXTRANODOSA "Pseudomyl." smuosus ., U ;.:..5 cD ~ ~ LAQUEUS -CUi 0", Z ~ L1ASICUS " _ ~ Ul a.= ::=-e::: ~ 0 Kolymon. steesctiei, A. tiesicus Zone c: el c: E cD "- J:l Ul ~ Z PORTLOCKI ~ "E ~ o e::: E"g Meleagrin. subolifex " e::: 0 0 e ~: 0 -" <C I- l- 0 e::: -" " Ul J:l U-iii ~"C 1ii "C e::: 2- W JOHNSTONI e::: 2- .!!!. " -fi E" e::: " " e::: E.s " E :I: "C P. planorbis Zone PLANORBIS e::: ui ,.,"C " Ul I- e::: PLANORBIS " u U) " o :;; " Ul P. olenekense beds e ~ 0 L J:l ...J P. primulum Zone PRIMULUM 100·120 m Figure 2. The Hettangian of the major regions of the U.S.S.R.spore-pollen assemblages. The major part (60 to 100 m) of this Hettangian zones can be recognized as in the standard sequencemember, made up of sandstone, siltstone, and mudstone, is pre- and therefore have been given similar names. Their ammonitesumed to belong to the Hettangian and Sinemurian. assemblages are characterized by diverse generaand, usually, low species diversity.Siberian Platform The lower Jurassic outcrops are classified into two major types, subplatform and geosynclinal. On the Siberian Platform, marine Hettangian occurs on the The reference section of subplatform-type Hettangian in thenortheastern and eastern margins (Lena-Anabar and Cis- area is a section along the Kedon River in the Omolon MassifVerkhoyanye Troughs). The rare faunal remains permitdatingas (Polubotkoand Repin, 1972; Strat. Jurassic System, 1976). TheHettangian only. In the inner zone of the Cis-Verkhoyanye Hettangian is represented by fine alternated mudstone, siliceousTrough (Undyulyung, Begidzhan, Mengkere, Dzhardzhan Riv- mudstone, and tuffaceous mudstone, with a total thickness of 53ers), part of the formations (Tarynnakh, Setegei) at the baseof the to 55 m. All four standardzones are present.Jurassic section belong to the Hettangian, which is characterized 1. Primapsiloceras primulum Zone, with the index speciesby Pseudomytiloides sinuosus Polub., Kolymonectes ex gr. stae- (9 m).schei Polub. Its thickness is estimated at 100 to 120 m. The only 2. Psiloceras planorbis Zone, with the index species andindication of the Psiloceras planorbis Zone is the find in the P. viligense Chud. et Polub., P. suberugatum Chud. et Polub.,Ust-Olenek area of an ammonite described as Psiloceras jacuti- P. plicatulum (Qu.) (8 m).cum A. Dagis(Dagis and Vozin, 1972; Discovery ..., 1978). The 3. Alsatites liasicus Zone, with Waehneroceras portlockiauthor of this species later (Discovery ..., 1978) placed it as (Wright) at the base, and Alsatites cf. corogonensis (Sow.), Dis-junior synonym in Psiloceras olenekense (Kipar.), which was camphiceras sp. indet., Psilophyllites sp. indet. in upper partinitially regarded as a Triassic Japonites (Kiparisova, 1937). Be- (35 m).sides theseammonites, Pseudomytiloides sinuosus Polub.and Di- 4. Schlotheimia angulata Zone, established by S. exgr.angu-myodon sp. were also collected. lata (Schloth.) (3 m). In the Viluj Syneclise, the Hettangian is presumably conti- In additionto ammonites, the Hettangian of thissection alsonental (lower Ukugut and Irelyakh Formations). yields the bivalves Oxytoma ex gr. sinemuriense Orb., Otapiria originalis (Kipar.), Meleagrinella subolifex Polub., KolymonectesNortheast staeschei Polub., Pseudomytiloides ex gr. rassochaensis Polub., and the brachiopod Ochotorhynchia omolonensis Dagys, The Marine Lower Jurassic is widespread and rather well The most representative Hettangian section of geosynclinal-characterized by bivalves, brachiopods, and ammonites. Four type in this region is in the Viliga Basin (northern Okhotsk area)
6 The Jurassic Ammonite Zones ofthe Soviet Union(Strat.Jurassic System, 1976),whereit consists of mudstone 270 grounded. Inmarinefacies, the Hettangian occursin geosynclinalto 300 m thick. Established on ammonites are (1) Primapsiloce- structures of the Pacific Belt and adjacent areas of the Siberianrasprimulum Zone, with index species; (2) Psiloceras planorbis Platform. It is presumably present in some areas of the Mediter-Zone, with P. cr. planorbis (Sow.), P. viligense Chud. et Polub., ranean Belt. In spiteof single finds of ammonites in these regions,P. suberugatum Chud. et Polub., P. plicatulum (Qu.); and a zonal division of the stage is impossible. Zonation has been(3) Alsatites liasicus Zone, with A. cf. coregonensis (Sow.) and accomplished only in the northeast USSR, where typical Hettan-Schlotheimia ? sp. A bivalve assemblage in this section is repres- gian ammonite assemblages are represented by a depauperatedented by Otapiria originalis (Kipar.), 0. pseudooriginalis Zakh., set of European genera. These assemblages comprise index spe-Pseudomytiloides sinuosus Polub., and P. latus Polub. ciesor their vicariants, eitherfacilitating correlation with Hettan- In the Far East, there is no evidence for the Hettangian. gian standard zones of Western Europe or allowing a similar zonal division. Within most of the northeastern USSR zones,SUMMARY "beds" or biohorizons can be distinguished which correspond to subzones of the Europeanstandardzones. This indicates a similar From the above data, it follows that Hettangian deposits are succession in the evolution of Hettangian ammonites. Generally,relatively restricted on USSRterritory. On the Russian Platform, species differentiation of Hettangian ammonoids in the NorthernWest Siberian Plate,and centraland southern Siberian Platform, Hemisphere wasonlyslight, pointing to gradualclimatic zonationthey are in continental facies, with identification of the Hettan- and free connections among water areas of Europe, northeastgian in the Jurassic sections conventional and not always well Asia, and the Pacific. SINEMURIAN Ju. S. RepinHISTORY AND STANDARD ZONES Jurassic System held in Luxembourg in 1962 (Resolution au Luxembourg, 1964), the range of the Sinemurian was restricted DOrbignydistinguished the Sinemurian stage at the baseof from the Arietites bucklandi Zone,below,to the Echioceras rari-the Jurassic. Subsequently, when its lower part was separated as costatum Zone,above. It was recommended to draw the Lower/an independent Hettangian stage, the Sinemurian acquired its Upper Sinemurian boundary between the Arnioceras semicosta-presentrange. The stage was namedafter the town of Simur Oat. tum and Caenisites turneri Zones.Sinemurium) in the Cote dOr department (France). There, ac- Thus, the principle of priority, i.e., the initial grouping ofcording to dOrbigny, "the best type of deposits is found which I zones by Oppel, was not taken into account at the colloquium.regard as a standard for comparison purposes" (dOrbigny, The use of the term Lorraines in the general scale should be re-1842-1858). jected,and it shouldbe leftas a localunit.The subdivision should The subdivision was made by Oppel (1956-1858), who remain as the Upper and Lower Sinemurian, as understood bydistinguished five zones. Subsequently, slight corrections included Oppel, as wasjustly done in the summaryon the LowerJurassicthe replacement of the Pentacrinus tuberculatus Zone of Oppel- zones in northwestern Europe (Dean and others, 1961).namedafteran echinoderm-by the Caenisites turneri ammonite In the type area (the vicinity of Sinemurium), the LowerZone (Wright, 1869),and the distinction of the upper part of the Sinemurian hasseveral breaksand consists ofgray semicrystallineArietites bucklandi Zone,OppelsBeds with Ammonites geometri- limestone, interbedded with clay with ripple marks on the bed-cus, as an independent Arnioceras semicostatum Zone (Judd, ding surface and filled with Gryphaea arcuata shells. The total1875). Oppel also grouped zones into substages. According to thickness of the Lower Sinemurian is 6.2 m. The following bio-him, Upper Sinemurian comprises three zones, i.e., Ammonites stratigraphic levels are distinguished (in ascending order) (Mou-(=Asteroceras) obtusum; Am. (=Oxynoticeras) oxynotum, and terde and Tintant, 1964):Am (=Echioceras) raricostatum. 1. Coroniceras rotiforme Zone. (a) below (0.70 m), ho- Haug (1910) distinguished the Lorraine, including the rizon with Vermiceras cordieri Canav., Coroniceras haueriUpperSinemurian of Oppel,plusthe Asteroceras turneri Zoneof Waehner, O. westfalicum Lange var. elegantula Lange; (b) abovethe Lower Sinemurian. Erroneously, Spath (1942) showed the (1.10 m), horizon with Coroniceras rotiforme (Sow.)Lorraine as coeval to the Upper Sinemurian only. Later, some 2. Arietites bucklandi Zone (2.0 m). (a) below, horizonFrench and German geologists, following Haug, used the Lor- with Megarietites meridionalis (Reynes), Arnioceras densicos-raine as an independent stage after reducing the Sinemurian by tata(?) Qu., A. kridioides Hyatt; (b) above, horizonwith Arietitestwo lower zones, Arietites bucklandi and Arnioceras semicosta- bucklandi (Sow.), A. aff. sinemuriensis (Orb.), Arnioceras cerati-tum Other workers used the term Lotaringian (Gignoux, 1950) toides Qu.as an upper substage of Sinemurian. At the colloquium on the 3. Arnioceras semicostatum Zone. (a) below (1.0 m),
The Jurassic Ammonite Zones of the Soviet Union 7horizon with Agassiceras scipionianum (Orb.), Arnioceras sp.; zone. Tutcher, 1923. Index species-Eo sauzeanum (Orb.). With(b) (0.40 m), horizon with Euagassiceras sauzeanum (Orb.) [=E. Euagassiceras spp. and Paramioceras alcinoe (Qu.).resupinatum (Simps)], Metarnioceras sp.; (c) above (1.0 m), ho- 3. Caenisites turneri Zone. Wright, 1860. Index species-rizon with Arnioceras semicostatum (Y. et B.), A. miserabile C turneri (Sow.). Lower part characterized by Caenisites, certain(Qu.), Pararnioceras sp., Angulaticeras d. lacunata(J. Buckm.), speciesof which range higher; upper half dominated by Microder-Sulciferites sulcifera S. Buckm., S. miscellus (Opp.). oceras and Promicroceras. (a) Caenisites brooki Subzone. Lange, The Upper Sinemurian zones of Asteroceras obtusum, Oxy- 1914. Index species-C brooki (Sow.). Also with C preplottinoticeras oxynotum, and Echioceras raricostatum are represented Spath and C costariformis Spath. (b) Microderoceras birchi Sub-in the stratotype by a condensed horizon of phosphorite nodules zone. Collenot, 1869. Index species-M birchi (Sow.). Rangeabout 25 em thick; the stratotype does not show the succession of zone of Microderoceras; Caenisites has disappeared and Promi-ammonite assemblages. These shortcomings of the stratotype are croceras capricomoides (Qu.) is common.made up by more complete and ammonite-rich sections in theSwabian Alb (e.g., Quenstedt, 1882-1885; Oppel, 1856-1858; Upper SinemurianHoffman, 1964) and England (Arkell, 1933; Dean and others,1961). On the basis of the succession of ammonite levels in these 4. Asteroceras obtusum Zone. Oppel, 1856-1858. Indexregions, Spath (1942) compiled a scheme of zonation for the species-A. obtusum (Sow.). Characterized by the Asterocerati-Sinemurian, later amplified by Donovan (Dean and others, nae Asteroceras, Aegasteroceras, Epophioceras, and, in the upper1961). This scheme is presently used for worldwide correlation of part, Eparietites: also with the Eoderoceratidae Promicroceras,the Lower Jurassic; the Sinemurian has 16 zones and 17 sub- Xipheroceras, and the last Amioceras. Subzones reflect the trendzones; the zones are grouped in substages as understood by in Asteroceratinae evolution toward increased whorl compres-Oppel. sion and decreased umbilical walls. (a) Asteroceras obtusum Sub- zone. Characteristic also is Asteroceras stellare (Sow.); common, but also found above are Promicroceras planicosta (Sow.) andLower Sinemurian Xipheroceras dudressieri (Orb.). (b) Asteroceras stellare Sub- zone. Buckman, 1910. Index species-A. stellare (Sow.). Range 1. Arietites bucklandi Zone. Oppel, 1856-1858. Index zone. (c) Eparietites denotatus Subzone. Buckman, 1919. Indexspecies-A. bucklandi(Sow.). Characterized by Coroniceras, Ar- species-Eo denotatus (Simps.). Characteristic are Eparietitesietites, Arnioceras, Pararnioceras, Vermiceras, and Charmassei- species.ceras. (a) Coroniceras conybeari Subzone. Tutcher, 1918. Index 5. Oxynoticeras oxynotum Zone. Oppel, 1856-1858. Indexspecies-C (Metophioceras) conybeari (Sow.). The appearance species-O. oxynotum (Qu.). Most characteristic of this zone areof the subgenus Metophioceras marks the base of the Sinemurian Oxynoticeras, Gagatyceras, angulaticeras, Palaeoechioceras, Bi-throughout the entire Northwest European Province. In addition fericeras, Slatterites, and Che/tonia. On the basis of succession ofto the index species, C (Metophioceras) longidomum (Qu.) and Oxynoticeras species, two subzones are distinguished. (a) Oxyno-C (M) brevidorsale (Qu.), and Vermiceras scylla (Reynes) are ticeras simpsoni Subzone. Spath, 1942. Index species-a. simp-also common. (b) Coroniceras rotiforme Subzone. Collenot, soni (Simps.). Also with Gagatyceras gagateum (Y. et B.) and1879. Index species-C rotiforme (Sow.). Lower boundary Cheltonia spp. but also range higher. (b) Oxynoticeras oxynotummarked by appearance of subgenus Coroniceras. The ammonite Subzone. Range zone. Also found are Bifericeras bifer (Qu.),assemblage comprises also Coroniceras schloenbachi (Reynes), Angulaticeras, and Palaeoechioceras spp.C (C) caprotinum (Orb.), and C (C) rotiforme (Sow.). In 6. Echioceras raricostatum Zone. Oppel, 1856. Indexsouthwestern Germany, C (C) hyatti (Donovan) passes into the species-Eo raricostatum (Zieten). Paltechioceras and Eoderoce-overlying subzone and is found together with Arietites bucklandi ras range zone. Common in lower part are Bifericeras,(see Urlichs, 1977a). (c) ArietitesbucklandiSubzone. Besides the Crucilobiceras, Echioceras, and Gleviceras. (a) Crucilobicerasindex species occur Epammonites, and, probably, the first densinodulum Subzone. Lange, 1926. Index species-C densinod-A mioceras. ulum Buckm. Base at appearance of Crucilobiceras and 2. Amioceras semicostatum Zone. Judd, 1875. Index Paltechioceras; also common are Eoderoceras bispinigerumspecies-A. semicostatum (Y. et B.). The assemblage comprises (Buckm.) and E. armatum (Sow.); Gleviceras appears.Arnioceras, Coroniceras, Paracoroniceras, Metarnioceras, and (b) Echioceras raricostatum Subzone. Base at first appearance ofEuagassiceras. (a) Coroniceras reynesi Subzone. Dononvan, Echioceras, i.e., E. raricostatum (Zieten), E. aeneum Truem. et1961. Index species-C reynesi (Spath). Also found are Paraco- Will; also Bifericeras, Crucilobiceras, and Epideroceras.roniceras gmuendense (Opp.) and Pararnioceras meridionale (c) Leptechioceras macdonnelli Subzone. Lange, 1926. Index(Reynes). (b) Agassiceras scipionianum Subzone. Tutcher, 1918. species-L. macdonnelli (Portlock). Leptechioceras range zone,Index species-A. scipionianum (Orb.). Also common are Ami- with different Echioceratidae, and, to a lesser degree, Eoderocerat-oceras acuticarinatus (Simps.), Agassiceras nodosaries (Qu.), idae. (d) Paltechioceras aplanatum Subzone. Lange, 1926. Indexand subgenus Metophioceras. (c) Euagassiceras sauzeanum Sub- species-P. aplanatum (Hyatt). Range zone.
00 EUROPEAN STANDARD KUGI- RUSSIAN TANGTAU WEST SIBERIAN Subzones PLATFORM N.CAUCAUSUS SIBERIA PLATFORM NORTH-EAST FAR EAST Stage Zones RANGE E E E APLANATUM 0 0 0 N 0 .... 0 6 <0 MACDONNELL! RARICOSTA TUM RARICOSTA TUM Angulat/c. Bugunzha Form.: mudst., sandst. kolymicum Zone DENSINODULUM Echioceras declivus, Oxynotic. oxynotum, iii "C Microderoc. birch; :::> OXYNOTUM E U gJ OXYNOTUM SIMPSONI iii ~ iii iii Silts!. Silts!. "C :::> iii "C Otapiria Angulatic. ocnoticum, DENOTATUS E l: Iimaeformis, Oxynoticeras sp.,Z ., Vi " II> "Pseudomytil. Otapiria timeetormis,<l: OBTUSUM STELLARE r: u ~ rassochaensis "Pseudomytil. rassochaensis ~i2 0 " ~ ~~:;; e .c 0 =- .,W OBTUSUM "" c 2- 1: ~ c 0 .c u;Zen BlRCHI ~" ., E "C :::> Coroniceras E :lii :lii TURNERI (; LL ., l: siverti Zone BROOKI E - - - - 130-170- -- m ~ ... J: "C :::> >- .... SAUZEANUM c ~ ~ " en 0 ..J L SEMICOSTA TUM SCIPIONIANUM REYNESI BUCKLANDI BUCKLANDI ROT/FORME BUCKLANDI ZONE CONYBEARI 200 m 300 m Figure 3. The Sinemurian of the major regions of the U.S.S.R.
The Jurassic Ammonite Zones of the Soviet Union 9SOVIET UNION Hettangian-Sinemurian yields Meleagrinella cf. subolifex Polub. and Otapiria sp. Marine Sinemurian occurs mainly in northern Siberia, theFar East, and Northeast, as well as within the Mediterranean NortheastGeosynclinal Belt. On the Russian Platform, marine sedimentsare absent (Fig. 3). Previous authors assumed that the upper Platform-type sediments (Kedon, Vizualnaya rivers) (Strat.Novorajskoe Formation at the northwestern margin of the Jurassic System, 1976; Polubotko and Repin, 1972, 1974) repre-Donets Folded Structure was Sinemurian. sent the Sinemurian, with 70 m of finely alternating mudstone, tuff mudstone, and tuffite. Three zones are distinguished on theMediterranean Geocynclinal Belt basis of ammonite assemblages: 1. The lower zone corresponds in its range to the Bucklandi Marine Sinemurian deposits, widespread in this belt, are Zone of the Standard Scale and retains this name; the two uppercharacterized by ammonites. In the Carpathians, Crimea, ones are local units.northern and southern slopes of the Great Caucasus, Minor 2. The assemblage of the Coroniceras siverti Zone yieldsCaucasus, and Southern Pamirs, index or guide species of certain also C. reynesi Spath, C. cf. bisulcatum (Brug.), and Paradasyc-standard zones are found. In the northern Caucasus, the marine eras(?) sp.Sinemurian is most complete in the Laba Basin (Bugunzha For- 3. The Angulaticeras (Gydanoceras) kolymicum Zone is themation), at the base of the Jurassic section, resting unconforma- range zone of the local subgenus Gydanoceras, with A. (G.)bly on Paleozoic and Triassic rocks. The formation is divisible kolymicum Repin and A. (G.) ochoticum Repin. Correlation ofinto two parts: below, massive sandstone with conglomerate and these zones (lonas) with the standard zones, and the position ofgritstone lenses (Veriyut horizon of V. N. Robinson, 1932), 10 to the boundary between them, are rather uncertain and based on20 m thick; above, a sequence of silty mudstone (120 to 150 m). convention; however, representatives of the ammonite assem-This formation contains Microderoceras birchi (Sow.), Arietites blages are rather widespread, from Verkoyanye to Beringia.pseudospiralis Vad., Oxynoticeras oxynotum (Qu.), and Echioc- Far Easteras declivis Truem. et Will., indicative of Turneri, Oxynotum,and Raricostatum Zones (Beznosov, 1973; Resolutions, 1984). The Sinemurian is reported from the south Bureya Trough, On the southern slope of the Great Caucasus, in the Mzymta Sikhote-Alin, and Southern Primorye. The siltstones are charac-and Shakhe Basins, the Sinemurian comprises the Eskisadok terized by Angulaticeras (Gydanoceras) cf. ochoticum Repin, Ox-Formation. This is a sequence of banded clay shale with ynoticeras sp., Otapiria limaeformis Zakh., and Pseudomytiloidessandstone and comglomerate interbeds, which yields Arietites cf. rassochaensis Polub. Possibly, the Sinemurian comprises thebucklandi (Sow.) and A. grossi (Wright) (Krymholts, 1972b). upper part of the Kiselevka Formation, in the Lower Amur River, from which Juraphyllites amurensis (Kipar.), variousCentral Asia Cardinia; Chlamys textoria (Schloth.), and other bivalves were described. In most areas, the Sinemurian is continental and cannot bedistinguished as an independent unit. In Kugitangtau, it includes SUMMARYthe upper Sandzhar Formation (Resolutions, 1977). The distributional pattern of the continental and marineWest Siberian Plate Sinemurian is similar to that of the Hettangian. With the begin- ning of the Sinemurian age, the transgression extended over The Sinemurian is present in the Lower Tyumen Member most of the Mediterranean Belt, as shown by ammonite finds in(see under Hettangian). the Carpathians, Crimea, northern Caucasus, Transcaucasus, and In northern Siberia and northeast USSR, Sinemurian depos- Pamirs. The ammonites belong to Western European genera andits are known from Anabar Bay in the west, to the Okhotsk and indicate the presence of most standard zones.Bering Sea coasts in the east. In this area, the marine Sinemurian In boreal areas of the USSR, the depauperated assemblageis almost ubiquitous and can locally be recognized if fauna is of Sinemurian ammonites is represented by Arietues, Coronic-present. In other places, it is presumably present but cannot be eras, Paracoroniceras, Eparietites, Paradasyceras, anddistinguished, as on the Anabar Bay coast, where undivided Angulaticeras.
10 The Jurassic Ammonite Zones ofthe Soviet Union PLIENSBACHIAN Ju. S. RepinHISTORY AND STANDARD ZONES and the overlying Amaltheus Clay into the Upper Pliensbachian and subdivided it into the threezones oflower Ammonites [Amal- The term Pliensbachian was proposed by Oppel (1856- theus] margaritatus, upper Am [Amaltheus] margaritatus, and 1858) to replace Lias (etage liasien), which had no geographic Am. [Pleuroceras] spinatus. Since the time of Oppel, no changesbase in the scheme of dOrbigny (1842-1851). The stage was have been introduced into the subdivision of Lower Pliensbach- named after the village of Pliensbach (Geppingen, Baden- ian. All workers who have recently studied the problems of zonal Wiirttemberg, West Germany). The stratotype is35 km southeast stratigraphy of the Pliensbachian regard this subdivision as quiteof the town of Stuttgart, in the Swabian Alb. Along the Pliens- satisfactory and rational. There are only certain differences atbach streamare a numberof smalloutcrops, which, together with subzonal level. They concern the number of subzones distin-excavations for a water pipe, made it possible to compile a com- guished by different authors, and sometimes the choice of theplete composite section of this stage (Schlatter, 1977; Urlichs, index species. The two A. margaritatus zones of Oppel are now 1977a). The fossil characterof the LowerPliensbachian is ampli- regarded as a single zone (Spath, 1942), with the three subzonesfied by ammonites from the Niirtingen section 15 km to the of A. stokesi, A. subnodosus, and A. gibbosus (Howarth, 1955,southeast. Fossils from the type area of Pliensbachian have long 1958-1959; Dean and others, 1961).attracted the attention of investigators. In the first description of In 1971,Frenchstratigraphers proposed elevating the lowerthe naturalhistory of Wiirttemberg, published in 1602,numerous subzone of the Margaritatus Zone, without the index, to a fullammonites were described and illustrated, and in Wiirttemberg, zonal rank (Mouterde and others, 1971), which seems reasona-Quenstedt and Oppel carriedout their studies. ble. Although the Stokesi Zone is stratigraphically small, it is Charmouthian, Carixian, and Domerian stages were at dif- widely recognized in the Northern Hemisphere. Besides theferent times distinguished within the Pliensbachian. The Char- North-West European Zoogeographic Province, the index speciesmouthian (Charmouthien) of Renevier (1864) is a later synonym is recorded from Bulgaria; the Caucasus; the north USSR-of Pliensbachian and was not used further. Carixian, derived from Anabar and Begidzhan (right tributary of the Lena) Rivers; theCarixia (=Charmouth), was distinguished by Lang (1913) and Sededema, Bolshoi Anyuj, Gizhiga, and Omolon Basins (north-corresponded to the LowerPliensbachian of Oppel. The Domer- east USSR); the Far East;the Transbaikal area; and Japan (Kyu-ian was proposed by Bonarelli (1894) and corresponded to the shu Island), Alaska, and Canada.Thus, the increase in rank of theUpper Pliensbachian. Stokesi Subzone to a zone isjustified. This is particularly impor- The Colloquium on Jurassic Stratigraphy, held in Luxem- tant for correlating Upper Pliensbachian in boreal areas of thebourg in 1962 (Resolution, 1964), used Carixian and Domerian USSR and North America, wherezonal subdivision of the entirein its recommendations as Pliensbachian substages. However, Upper Pliensbachian is basedon a succession of species of Amal-use of these names in the standard scale seems unwarranted, theus. It existed in this region throughout Late Pliensbachian,since they only duplicate the Lower and Upper Pliensbachian. whereas Pleuroceras was locally restricted.The use of the term Domerian in the general scale is also a The stratotype of Pliensbachian is best shown among thosecause for objection: in distinguishing the Upper Pliensbachian, of the LowerJurassicstages, and its abundant fossils madepossi-Oppel noted that it corresponded to the range of Amaltheidae ble Oppels zonation. Later, many European scientists worked(seealsoBonarelli, 1894). However, in the stratotype namedafter out a scheme of Pliensbachian subzones, based on the successionSan Domaro Mount in the Lombardian Alps (Brescia Province, of ammonite assemblages in Western Europe.Italy), Amaltheidae are practically absent. Thelowerboundaryofthe Domerianin the stratotype has not been traced,and its upper Lower Pliensbachianboundary is rather arbitrary. The stratotype of the Pliensbachian consists, below, of mas- 1. Uptoniajamesoni Zone. Oppel, 1856.Indexspecies-U.sive marl and flag-like limestone, the Numismalis Marl (Numis- jamesoni (Sow.). In the stratotype 5 m thick and comprising fivemalismergel) or Lias-gamma (Black Jurassic "), according to subzones, in contrastto the scheme of Donovan (Dean and oth-Quenstedt); above, it consists of clayand marlyclay(Amaltheen- ers, 1961), which combines the Masseanum Subzone and Ibexthone) of Lias-delta (Black Jurassic 0), crowned by a 2-m-thick Zone. (a) Phricodoceras taylori Subzone. Spath, 1923. Indexmarl bed. The thicknesses are approximately 12 and 24 m, re- species-i-P taylori (Sow.). Base in stratotype defined by appear-spectively (Urlichs, 1977a). ance of Apoderoceras nodogigas (Qu.); index species appears in Oppel subdivided Pliensbachian into zones and substages, the upper part of the subzone. (b) Polymorphites polymorphusand regarded the Numismalis Marl (except for the upper 3 m) as Subzone. Spath, 1923. Index species-s-P polymorphus (Qu.).Lower Pliensbachian, comprising the three zones of Ammonites Base defined by appearance of Radstockiceras (=Metoxynotice-[Uptonia]jamesoni, Am. [Tragophylloceras] ibex, and Am [Pro- ras) and index species. Other species of Polymorphites appear indactylioceras] davoei. He placedthe uppermost Numismalis Marl upper part of subzone and persist to middlepart of nextsubzone.
The Jurassic Ammonite Zones ofthe Soviet Union 11 Characterized by abundant Tragophylloceras numismale (Qu.), Upper Pliensbachian which account for about two-thirds of all ammonites; also single Epideroceras, Microderoceras, Hyperderoceras, and Coelodero- 4. Amaltheus stokesi Zone. Lange, 1936. Index species-A. cas(?), ranging from the base of Pliensbachian; first Liparocerati- stokesi (Sow.). In stratotype (- 1.4 m) characterized also by dae also appear, e.g., Liparoceras (Parinodiceras) reineckii (Qu.). Protogrammoceras monestieri Fischer. In Western Europe, this (c) Platypleuroceras brevispina Subzone. Spath, 1922. Index zone also yields Amaltheus bifurcus How., A. wertheri (Lange), species-s-P brevispina (Sow.). In the stratotype (-0.8 m) Platy- A. evolutus Buckm., and Amauroceras ferrugineum (Simps.). pleuroceras is rare; base defined(Niirtingen section) by the index 5. Amaltheus margaritatus Zone. Oppel, 1856* emend. species Crucilobiceras submuticum (Opp.) and C. rotundum Mouterde et al., 1971. Index species-A. margaritatus (Mont- (Qu.). In the middle of the subzone, a 3- to 7-cm-thick bed is fort). (a) Amaltheus subnodosus Subzone. Howarth, 1955 filled with Polymorphites lineatus (Qu.), P. mixtus (Qu.), etc. (=nodifer Subzone, Spath, 1942). Index species-A. subnodosus (d) Uptonia jamesoni Subzone. Base defined by appearance of (Y. et B.). In stratotype (8.6 m), the base is at appearance of index Uptonia with index species passing throughentiresubzone; 20 em species. The lower half also yields Amaltheus gloriosus Hyatt, below top in the Pliensbach section, a layer (15 em) yields numer- Lytoceras fimbriatum (Sow.), Derolytoceras tortum (Qu.). Amal- ous Coeloceras pettos (Qu.), C. pettos grenouillouxi (Orb.), C. theus striatus How., A. margaritatus Montf., Amauroceras fer-pettos planula (Qu.), and rare C. pettos pinguecostatum Bremer; rugineum (Simps.), and Sowerbyceras tortisulcoides (Qu.) pass Polymorphites is found more rarely than below. (e) Tropidoceras through the entire subzone and into the next subzones. (b) Amal- masseanum Subzone. Spath, 1923. Indexspecies-T. masseanum theus gibbosus Subzone. Kuhn, 1935. Index species-A. gibbosus (Orb.). Appearance of Tropidoceras masseanum and similarspe- (Schloth.). Base of subzone (14 m) at appearance of index spe- cies marks lower boundary in stratotype; Uptonia is also found. cies. Besides index species and ammonites, ranging upward from At Pliensbach and Niirtingen, Tropidoceras passes into beds with (a), also common Amaltheus laevigatus How., Cymbites centri-Acanthopleuroceras valdani (Orb.). The jamesoni/masseanum globus centriglobus (Opp.), C. centriglobus nanus Schindewolf, subzonal transition is marked by appearance of Tragophylloceras Fuciniceras compressum (Monestier), Protogrammoceras depres- undulatum (Smith). sum (Qu.). 2. Tragophylloceras ibexZone.Oppel, 1856.Indexspecies- 6. Pleuroceras spinatum Zone.Oppel, 1856. Indexspecies- T. ibex (Qu.). (a) Acanthopleuroceras valdani Subzone. Spath, P. spinatum (Bruguiere). (a) Pleuroceras apyrenum Subzone. 1942. Index species-A. valdani (Orb.). Base in stratotype Spath, 1942. Index species-i-P apyrenum Buck. In stratotype marked by appearanceof Acanthopleuroceras maugenesti (Orb.), (2.8 m), base marked by appearance of Pleuroceras transiensA. arietiforme (Oppel), and similar species. The index species (Frentzen);also Amaltheus gibbosus (Schloth.) and Amaurocerasappears higher, but Tragophylloceras ibex (Qu.) is common here ferrugineum (Simps.), ranging upward from the Margaritatusand occurs with single specimens also below. The upper part of Zone. (b) Pleuroceras hawskerense Subzone. Spath, 1942. Index the subzonealso yields Beaniceras centaurus (Orb.), Liparoceras species-s-P hawskerense (Y. et B.). In stratotype (1 m), P. cf.zieteni (Qu.), and L. bronni Spath. (b) Beaniceras luridum Sub- hawskerense occurs, which defines lower boundary; also zone. Dean and others, 1961. Index species-B. luridum Pleuroceras cf. spinatum (Brug.) characteristic of the upper half. (Simps.). Stratotype with poorly preserved Beaniceras luridum(Simps.), B. costatus Buckm., and B. rotundum Buckm. SOVIET UNION 3. Prodactylioceras davoei Zone. Oppel, 1856. Indexspecies-i-P davoei (Sow.). Varying numbers of subzones, with The marine Pliensbachian, especially Upper Pliensbachian,differentnames, have been proposed. Based on the stratotype,we is more widespreadthan Hettangianand Sinemurian (Fig. 4); butaccepted two subzones: (a) Androgynoceras maculatum-capri- Pliensbachian is unknown from the Russian Platform. cornus Subzone. Schlatter, 1977. Index species-A. maculatum(Y. et B.) and A. capricornus (Schloth.). Alsocharacteristic are A. Mediterranean Geosynclinal Belt henleyi (Sow.), A. heterogenes (Y. et B.), A. infracapricornus(Qu.), A. sparsicosta (Truem.), A. lataecosta (Sow.), and Liparoc- In the northern Caucasus, the Pliensbachian makes up theeras divaricosta (Truem.), etc. In England, where the index spe- upper part of the Khumara Formation, and the base of theciesoccur at successive levels, Donovan (Dean and others, 1961) Sebelda Series comprises several formations (Beznosov, 1973;separates two subzones, Maculatum and Capricornus. However, Resolutions, 1984).on the continent, in West Germany (stratotype), and in France, Lower Pliensbachian deposits are characterizedby brachio-these and associated species originated from the same beds. (b) pods, bivalves, and foraminifers; ammonites are rare. At theOistoceras figulinum Subzone. Lange, 1936. Index species-O.figulinum (Simps.). Base marked by appearence of Oistoceras,together with Prodactylioceras davoei (Sow.). Also characteristic *Retention of the name of the zone by the French workers, while changing itsare Oistoceras angulatum (Qu.), O. curvicorne (Schloenb.), O. rangeappreciably, is unfortunate. However, we haveno opportunity to proposea wrighti Spath, and O. omissum (Simps.). different solution (eds.).