Faunal trends and sea-level changes: biogeographic patterns of Kimmeridgian ammonites on the Western European Shelf

The Kimmeridgian series of the northern Aquitaine margin is representative of the marine sedimentation on the Western European Shelf. It has been used to demonstrate a fundamental relationship between relative sea-level changes and the biogeographic dynamics of the Kimmeridgian ammonites.This synthesis, based on comparative sedimentological and paleobiogeographical studies, shows that the shelf was settled by submediterranean and/or subboreal ammonites during transgressive phases and maximum sea-level rises. Endemic lineages differentiated during the sea-level highstands and the beginning of lowstands. Correlative with the long-term sea-level rise, endemic elements have progressively taken a prominent role within the Kimmeridgian ammonite faunas of the shelf.The patterns of faunal changes have been deduced from studies of ammonite lineages from distinctive biogeographic origins: Rasenioides, Lithacosphinctes, Orthaspidoceras and Gravesia. Compared with subboreal ammonites, it seems that the submediterranean species were more tolerant of changing environments and adapted to new environments more easily. Therefore most of the endemic lineages which settled the Western European area originated in submediterranean faunas.     

Biostratigraphy and ammonites of the Middle Oxfordian to lowermost Upper Kimmeridgian in northern Central Siberia

The Middle Oxfordian to lowermost Upper Kimmeridgian ammonite faunas from northern Central Siberia (Nordvik, Chernokhrebetnaya, and Levaya Boyarka sections) are discussed, giving the basis for distinguishing the ammonite zones based on cardioceratid ammonites of the genus Amoeboceras (Boreal zonation), and, within the Kimmeridgian Stage, faunas–for distinguishing zones based on the aulacostephanid ammonites (Subboreal zonation). The succession of Boreal ammonites is essentially the same as in other areas of the Arctic and NW Europe, but the Subboreal ammonites differ somewhat from those known from NW Europe and Greenland. The Siberian aulacostephanid zones—the Involuta Zone and the Evoluta Zone—are correlated with the Baylei Zone (without its lowermost portion), and the Cymodoce Zone/lowermost part of the Mutabilis Zone (the Askepta Subzone) from NW Europe. The uniform character of the Boreal ammonite faunas in the Arctic makes possible a discussion on their phylogeny during the Late Oxfordian and Kimmeridgian: the succession of particular groups of Amoeboceras species referred to successive subgenera is revealed by the occurrence of well differentiated assemblages of typical normal-sized macro and microconchs, intermittently marked by the occurrence of assemblages of paedomorphic “small-sized microconchs” appearing at some levels preceeding marked evolutionary modifications. Some comments on the paleontology of separate groups of ammonites are also given. These include a discussion on the occurrence of Middle Oxfordian ammonites of the genus Cardioceras in the Nordvik section in relation to the critical review of the paper of Rogov and Wierzbowski (2009) by Nikitenko et al. (2011). The discussion shows that the oldest deposits in the section belong to the Middle Oxfordian, which results in the necessity for some changes in the foraminiferal zonal scheme of Nikitenko et al. (2011). The ammonites of the Pictonia involuta group are distinguished as the new subgenus Mesezhnikovia Wierzbowski and Rogov.     

Ammonites from the Pawpaw Shale (Upper Albian) in northeast Texas

The lower part of the Pawpaw Shale in northeast Texas yields an abundance of diminutive limonitic ammonites, the assemblage being: Tetragonites sp. juv., Engonoceras serpentinum (Cragin, 1900), Conlinites wrighti gen. et sp. nov., Cantabrigites wenoensis (Adkins, 1920), Neophlycticeras (Neophlycticeras) sp., Neophlycticeras (Paradolphia) occidentalis sp. nov., Stoliczkaia (Stoliczkaia) clavigera Neumayr, 1875, Stoliczkaia (Lamnayella) worthense (Adkins, 1920), Stoliczkaia (Shumarinaia) asiatica Matsumoto and Inoma, 1975, Enigmaticeras riceae gen. et sp. nov., Flickia simplex Pervinquière, 1907, Ficheuria pernoni Dubourdieu, 1953, Ficheuria americana sp. nov., Anisoceras armatum (J. Sowerby, 1817), Hamites venetzianus Pictet, 1847, Mariella (Mariella) worthensis (Adkins and Winton, 1920), Mariella (Mariella) asper sp. nov., Lechites (Lechites) comanchensis (Adkins, 1920), Worthoceras worthense (Adkins, 1920), and Scaphites hilli Adkins and Winton, 1920.This assemblage is correlated with the Mortoniceras (Subschloenbachia) rostratum Subzone of the European sequence on the basis of the occurrence of that species in the underlying Weno Limestone, in the passage beds between the Pawpaw Shale and the succeeding Main Street Limestone, and the lower part of the Main Street.Some previous authors have interpreted the diminutive limonitic ammonites of the Pawpaw as being “dwarf” or “stunted”. The overwhelming majority of individuals are nuclei of much larger ammonites, with smaller numbers of adults of small species that occur in other facies and geographic locations, together with a smaller number still of paedomorphic dwarfs. The fauna is interpreted as a preservational one, where diagenetic pyrite formed in relatively small voids, either the early phragmocone chambers of larger ammonites, or the phragmocone and body chambers of genuinely diminutive species which oxidised to limonite during the weathering process.     

The ammonite fauna and genesis of a mid-Cretaceous siliceous oolite from the Alagoas Basin, Brazil

Acanthoceratid ammonites from near Maceió, in the State of Alagoas, provide evidence of a mid-Cretaceous marine incursion into the present onshore part of the Alagoas Basin. The ammonites Pseudocalycoceras sp. cf. P. harpax (Stoliczka, 1864) and Kamerunoceras sp. are assigned a late Cenomanian age. The rock is a siliceous oolite that occurs as derived nodules and fragments in late Cenozoic continental sediments. It is interpreted as an originally calcareous oolite formed in a near-shore, high-energy environment. Absence of primary cement suggests that silicification took place early in diagenesis. The silicified, and therefore more resistant material from the original Cenomanian sequence was reworked and redeposited with the Cenozoic sediments. The age, indicated by the ammonites, suggests that the original deposition was related to the global late Cenomanian—early Turonian sea-level rise.     

Confirmation of an Early Cretaceous age for the Qihulin Formation in eastern Heilongjiang Province, China: constraints from a new discovery of radiolarians

The coal-bearing, alternating marine and non-marine Longzhaogou Group in eastern Heilongjiang, northeastern China, has long been considered as Jurassic, or mainly Jurassic, in age. However, recent studies have demonstrated that the ammonites and dinoflagellate cysts are of Early Cretaceous age. This has now been confirmed by new radiolarian evidence. The radiolarian fauna recovered from the upper Qihulin Formation of the Longzhaogou Group consists of nine poorly preserved species referable to nine genera. Novixitus is a Cretaceous genus, and the specimens of Archaeodictyomitra sp. and Xitus sp. recovered resemble A. vulgaris Pessagno and X. spicularius (Aliev), respectively.     

New data on ammonoids of the genus <Emphasis Type="Italic">Paraulacosphinctes</Emphasis> from the Upper Tithonian of the Mountainous Crimea

The Late Tithonian ammonites Paraulacosphinctes cf. transitorius (Oppel) and P. cf. senoides Tavera from the Feodosiya section boundary Tithonian-Berriasian beds of the Crimea are described. These species allow the correlation of the beds with P. cf. transitorius recognized in the Crimea with the Upper Tithonian Substage of the Western European scale. Based on magnetostratigraphic data, these beds supposedly correlate with the Durangites Zone.     

Ammonite <Emphasis Type="Italic">Fauriella boissieri</Emphasis> (Pictet), the index species of the Berriasian upper zone from the Crimean Mountains

Ammonite Fauriella boissieri (Pictet), the index species of the Berriasian upper zone, is described for the first time as taxon occurring in the Crimean Mountains. In the Berriasian sections of the central Crimea and Chatyr-Dag massif, species F. boissieri are encountered only in association with upper Berriasian ammonites. The Berriasian-Valanginian boundary has not been identified based on ammonites in the Crimean Mountains. Consequently, there is no reason to include the otopeta Zone into the boissieri Zone in the rank of its upper subzone.     

New ammonite zonation of the lower Callovian in North Siberia

The lower Callovian succession observable in cliffs of Anabar Bay and Bolshoi Begichev Island is described with consideration of zonal subdivisions and beds with ammonites. The unified summary biozonation suggested for North Siberia includes the Cadoceras elatmae Zone with C. frearsi and C. elatmae (instead former C. anabarense) subzones, subsequent C. tschernyschewi and C. tolype zones, and successive C. cf. sublaeve, Rondiceras milaschevici, and Cadoceras ex gr. durum (formerly part of the middle Callovian) beds. As in Siberia and East Europe there are species in common C. elatmae (Nik.), C. frearsi (Orb.), C. tolype Buck., and C. emelianzevi Vor.; certain ammonite zones of Siberian succession are directly correlated with the East European, East Greenland and standard zonations. It is concluded that the lower Callovian is completely represented in Siberia. The lower part of the interval, formerly attributed to the middle Callovian, represents the upper part of the lower Callovian Substage. Zones established in the lower Callovian succession of Siberia are contiguous, whereas equivalents of the Elatmae Subzone and Tschernyschewi Zone have not been distinguished in sections of East Greenland. Evolutionary trends of species in subfamily Cadoceratinae are preliminary discussed.     

Cephalopods of the ＂Falang Formation＂ （Triassic） from Guanling and Zhenfeng Counties, Guizhou Province, China

The “Falang Formation“ of western Guizhou was previously called the “Halobia Bed“ and considered to be Ladinian in age. It was subdivided upward into the Zhuganpo, Laishike and Longchang members based on ammonites and the Trachyceras multitubertulatum Zone of the Longchang Member was put in the Lower Camian. Here in the present paper, 4 genera and 9 species of ammonites and I nautiloid genus and species collected from the upper part of the “Falang Formation“ (i.e. the Wayao Formation used in this paper, equivalent to the Laishike Member from Guanling and Zhenfeng counties are described. The geological and geographical distribution of these cephalopods, as well as the co-existing conodonts, put the Wayao Formation to the late early Camian.     

“Cretaceous black flysch” in the Pieniny Klippen Belt, West Carpathians: a case of geological misinterpretation

This is a critical assessment of the paper by Oszczypko et al. (2004: Cretaceous Research 25, 89–113), in which they tried to prove a mid-Cretaceous age for the Szlachtowa (“black flysch”) and Opaleniec Formations, in the Pieniny Klippen Belt, West Carpathians, both of which had previously been shown to be of Jurassic age. We argue that the mid-Cretaceous age assignment is a misinterpretation, primarily resulting from their field samples having been collected from some Cretaceous lithostratigraphic units, tectonically associated with the Jurassic formations, and/or from tectonic contact-breccias involving Jurassic and Cretaceous strata. In addition, we suggest that they have overlooked a number of significant palaeontological papers, published since 1962, which record the presence of in situ ammonites, aptychi, belemnites, thin-shelled bivalves (Bositra), gryphaeids, foraminifera, and ostracod assemblages, all indicating a Jurassic (mainly Aalenian), and not a Cretaceous, age for the Szlachtowa Formation, and also the in situ Jurassic (Bajocian) ammonites and thin-shelled bivalves (Bositra), Bositra-microfacies, and age-diagnostic foraminiferal assemblages of the Opaleniec Formation.Our presentation here of recently published dinocyst data from well-preserved assemblages further supports the Jurassic ages for the Szlachtowa (“black flysch”) and Opaleniec Formations.     

The Volgian Praechetaites exoticus Zone: Geochronological range, stratigraphic position and interregional correlation (a Response to the Paper by S.V. Meledina et al. “On the Position of the Praechetaites exoticus Zone in the Volgian Stage”)

The Praechetaites exoticus Zone is characterized; its definition, geographical range and correlation in the Panboreal Superrealm are discussed. New evidence supports the Middle Volgian age of the Exoticus Zone. It is shown that the presence of the characteristic ammonoid assemblage allows the recognition of this zone in the sections of North Siberia and Spitzbergen. The suggested key characters defining the zone include the appearance of the ammonites from the P. exoticus group at the lower boundary and Craspedites ex gr. okensis at the upper boundary. The stratigraphic distribution of boreal genera of ammonites at the Middle-Upper Volgian boundary is discussed.     

Cephalopods of the “Falang Formation” (Triassic) from Guanling and Zhenfeng Counties, Guizhou Province, China

The "Falang Formation" of western Guizhou was previously called the "Halobia Bed" and considered to be I .adinian in age. It was subdivided upward into the Zhuganpo, Laishike and Longchang members based on ammonites and the Trachyceras multitubertulatum Zone of the Longchang Member was put in the Lower Carnian. Here in the present paper, 4 genera and 9 species of ammonites and 1 nautiloid genus and species collected from the upper part of the "Falang Formation" (i.e. the Wayao Formation used in this paper, equivalent to the Laishike Member from Guanling and Zhenfeng counties are described. The geological and geographical distribution of these cephalopods, as well as the co-existing conodonts, put the Wayao Formation to the late early Carnmian.     

Marine connections in North America during the late Maastrichtian: palaeogeographic and palaeobiogeographic significance ofJeletzkytes nebrascensisZone cephalopod fauna from the Elk Butte Member of the Pierre Shale, SE South Dakota and NE Nebraska

The Elk Butte Member of the Pierre Shale of southeast South Dakota and northeast Nebraska yields a late Maastrichtian cephalopod fauna of nautiloids, belemnites and ammonites of theFeletzkytes nebrascensisZone, best known from the near-shore facies of the Fox Hills Formation. ThenebrascensisZone is the highest distinct marine assemblage that can be recognised in the Western Interior, although ammonites occur as rarities high in the Lance Formation in Wyoming. Elements of the fauna occur in the Gulf Coast and Atlantic Seaboard, and extend into the highest Maastrichtian nannofossil Subzone CC26b, ofMicula prinsii, in Texas. These occurrences point to the existence of a southerly marine route for migration into and out of the northern Interior during the late late Maastrichtian. An analysis of Maastrichtian ammonite occurrences in West Greenland reveals no evidence for a marine link to the western Interior at this time, but rather indicates an open marine link to the North Atlantic region.The presence of upper upper Maastrichtian Pierre Shale in southeast South Dakota and northeast Nebraska, deposited in water depths that are conservatively estimated at 100-200 m, suggests that marine conditions (evidence for which has been removed by post-Cretceous erosion) may have extended well to the north of the shoreline position indicated in recent palaeogeographic reconstructions.     

The Upper Bajocian-Lower Bathonian boundary section in the outskirts of Saratov: Molluscan characteristics and biostratigraphy

The analysis of all available data on the structure of the Bajocian-Bathonian boundary section in the outskirts of Saratov (Sokur quarry) and the taxonomic composition of its ammonites, belemnites, and bivalves revealed a continuous succession of the Pseudocosmoceras michalskii (Upper Bajocian), Oraniceras besnosovi, and Arcticoceras ishmae (Lower Bathonian) zones. In connection with the critique by Meledina et al. (2009), correlation of Bajocian and Bathonian boundary strata of the Central Russia and Northern Siberia is discussed. The inconsistency of Siberian bivalve and belemnite assemblages with Central Russian ammonite zones is explained by heterochronous invasions of different molluscan groups.     

The Pliensbachian ammonites of the Algarve Basin (Portugal) and their palaeobiogeographical significance for the “Iberia-Newfoundland” conjugate margins

A review of the Pliensbachian ammonite faunas of the Algarve Basin is given covering their taxonomy, stratigraphy and palaeobiogeography (palaeobiodiversity). This review is based on both an extensive revision of the previously collected and/or published material and on new finds precisely located within the ammonite succession. This new material allows us to clarify the variations within the most abundant species—a new species Reynesocoeloceras elmii nov. sp. is described—and to improve our understanding (palaeobiodiversity, palaeobiogeography and bio- or chrono-stratigraphy) of the two single known Pliensbachian fossiliferous assemblages in the Algarve Basin. The first of these assemblages is relatively diverse and is ascribed to the upper half of the Luridum Subchronozone. The second assemblage is less diversified and probably partly condensed. It is broadly attributed to the upper half of the Stokesi Subchronozone. Despite the newly collected ammonites and extensive prospecting, our knowledge of the Pliensbachian ammonite faunas of the Algarve remains fragmentary. Therefore, it is difficult to propose an incontrovertible extensive palaeobiogeographical interpretation for these faunas, but it seems that Tethyan (Mediterranean) affinities were of major importance whereas there were probably no NW European influences via the Lusitanian Basin.     

The upper Cenomanian (Cretaceous) ammonite Neolobites vibrayeanus () in the Middle East: taxonomic and palaeoecologic remarks

In the Middle East and Africa, the Cenomanian ammonite genus Neolobites occurs, partly in great abundance, in shallow marine shelf settings. The genus includes several species but it has remained uncertain to what extent these species reflect biospecies, chronospecies or morphological variants. Based on material from Jordan and Egypt, the morphological variation of Neolobites vibrayeanus is described and discussed. From the several species of Neolobites described in the literature, only N. vibrayeanus, N. fourtaui and N. peroni appear to deserve specific separation. Sedimentological and lithological data, notably the common occurrence in strata that were possibly deposited above storm wave base, suggest that Neolobites was able to inhabit shallow marine settings. In these settings, it seems to form a distinct assemblage with the nautiloid Angulithes. Although N. vibrayeanus shows morphological variability between distinct populations, local N. vibrayeanus assemblages seem to develop morphologically stable populations that show only a little morphological overlap with those of other areas. This may be the reason for the earlier taxonomic splitting. The occurrence in habitats in which other stratigraphically significant ammonites are often missing may be the reason for the previous poor dating of Neolobites assemblages.     

Valanginian perisphinctid ammonites from the Kisújbánya Basin (Eastern Mecsek Mts., Hungary)

The most complete Hungarian Valanginian perisphinctid ammonite fauna of the Mecsek Mountains (South Hungary) consists of 14 species is reported. Thurmanniceras sp. aff. otopeta, Fuhriella michaelis, F. cf. hoheneggeri, Sarasinella cf. ambigua, Neocomites (Neocomites) subtenuis, Neocomites (Eristavites) platycostatus are reported for the first time from Hungary. The fauna comprises 23 ammonite species and is reported from Valanginian tuffaceous marl, alternating marl–limestone beds and loose limestone blocks. Two studied sections represent the Lower Valanginian Thurmanniceras pertransiens and partly the Busnardoites campylotoxus Zones while ammonites from loose blocks indicate the latter and possibly the Upper Valanginian Saynoceras verrucosum Zone. Variations in the faunal composition of the marl beds and the limestone blocks respectively, refer to the contrast between the ammonite ecological demands. Phylloceratid and lytoceratid ammonites prevail the marl beds, while olcostephanid and neocomitid ammonites prevail the shallower platform-like limestones. Sediment accumulation rate in that palaeo volcano related environment was high and bottom currents frequently washed together ammonite shells or filled their body chambers with smaller ammonite shell fragments. Due to the fast sedimentation the sections represent only partially the recognized ammonite zones therefore long-term or even infra-regional correlation was not possible. Palaeobiogeographically, the ammonite fauna has Mediterranean character and it shows close relationships to the Valanginian faunas of the Bakony Mts. (Hungary), Western Carpathians (Slovakia), Northern Calcareous Alps (Austria), and SE Spain. The presence of Fuhriella species is remarkable and enlarges our knowledge on the distribution of this enigmatic ammonite taxon adding new data to its Valanginian stratigraphic position and geographic distribution.     

Ammonite biostratigraphy of the Albian in the Kirchrode II borehole, Hannover, Germany

The ammonite biostratigraphy of the 279.35 m of sediments of mid-Late Albian–Early Albian age traversed by the Kirchrode II (1/94) boring is described. The borehole was drilled in the Hermann-Löns Park, Kirchrode (Hannover), northwest Germany, in the central region of the Lower Saxony sedimentary basin. The core commenced within the Kirchrode Mergel Member of the Gault Formation in sediments of Callihoplites auritus Subzone age and showed a Late Albian ammonite zonal succession similar to that previously described by Wiedmann and Owen from the lower part of the nearby Kirchrode I (1/91) core, with which it is correlated. The thick underlying clay sediments of the Minimus Ton Member (Middle Albian–late Early Albian) provided a relatively sparse ammonite fauna. In the Middle Albian part of the sediment succession, several hiatuses are present and only sediments of the lower Euhoplites loricatus Zone (Anahoplites intermedius Subzone) and the Hoplites dentatus Zone (Hoplites spathi Subzone) have been identified. This is followed downward by a thick sedimentary succession through the upper part of the Early Albian Douvilleiceras mammillatum Superzone (Otohoplites auritiformis Zone). Earlier mammillatum and perhaps latest Leymeriella tardefurcata Zone portions of the core straddling the Minimus Ton/Schwicheldt Ton boundary, did not yield ammonites. The underlying sediments at the top of the Schwicheldt Ton Member, consist of dark clays and mudstones with a good representation of the Leymeriella (Neoleymeriella) regularis Subzone and the uppermost part of the Leymeriella acuticostata Subzone (Leymeriella tardefurcata Zone). Of particular importance is the succession through the sediments of the L. (N.) regularis Subzone, hitherto poorly known in north Germany. A brief comparison and correlation is made with other surface and borehole sections in northern Germany and elsewhere. The Boreal and more cosmopolitan Tethyan elements of the fauna are indicated and discussed. An appendix of ammonites obtained from the Mittellandkanal section at Misburg of latest Albian, Arraphoceras (Praeschloenbachia) briacensis Subzone age, completes the study.     

Mineralogy of fossilized ammonites

The composition and structure of mineral substance in shells of three Jurassic ammonites (Cadoceras elatmae) from the Makar’ev South outcrop in Kostroma oblast, Russia, have been studied. The studied shells differ in degree of preservation. The shell of one ammonite with partly retained internal structure has been replaced with quartz, carbonate-bearing apatite-(CaF), and newly formed aragonite. Other shells without retained internal structure underwent phosphatization rather than replacement with quartz. This difference serves as the basis for a discussion on fossilization conditions. Silicification of the shell supports preservation of its wall and elements of the internal structure. It is suggested that quartz might be biogenic in origin and was formed in cavities of phosphate substance, which had replaced the soft tissue of ammonites.