Tethyan Ammonites Research Articles

New biostratigraphical data (calcareous nannofossils, ammonites) and Early to Late Barremian transition in the Urgonien Jaune facies and Marnes de la Russille complex of the Swiss Jura Mountains

In the central Jura Mountains (Western Switzerland), the Urgonien Jaune (UJ) facies with the Marnes de la Russille beds (MRu) have provided very rich nannofloras associated with very rare Tethyan ammonites. A late Early Barremian nannoflora of the Mid-Barremian Event (MBE, following a regional tectonic event of an earliest Barremian synsedimentary tectonic crisis) was found in MRu of the lower UJ and includes 42 genera with 90 species. Among them, Biscutum jurensis De Kaenel, n. sp., Flabellites eclepensensis De Kaenel, n. sp., Palaeopontosphaera giraudii De Kaenel, n. sp., Rhagodiscus buisensis De Kaenel, n. sp., and Vagalapilla rutledgei De Kaenel, n. sp., are recognized as five new species. This nannoflora is a mixture of Boreal and Tethyan taxa with 20 nannofossil markers (Assipetra terebrodentarius, Broinsonia galloisii, Calcicalathina oblongata, Cyclagelosphaera rotaclypeata, Diloma placinum, Ethmorhabdus hauterivianus, Flabellites eclepensensis, Gorkaea pseudoanthophorus, Nannoconus abundans, Nannoconus pseudoseptentrionalis, Palaeopontosphaera giraudii, Palaeopontosphaera pinnata, Placozygus howei, Placozygus reticulatus, Reinhardtites scutula, Rhagodiscus buisensis, Rhagodiscus eboracensis, Tegulalithus septentrionalis, Tubodiscus jurapelagicus, Zeugrhabdotus moulladei) indicating very precisely the nannofossil Zones LK19 (Boreal)–NC5D (Tethyan) as well as the Elegans (Boreal) and Moutonianum (Tethyan) ammonite Zones of the latest Early Barremian. The ammonites in the basal UJ facies of Early Barremian age are reworked Lyticoceras claveli (Nodosoplicatum Zone, Early Hauterivian) and reworked Cruasiceras cf. cruasense (Sayni Zone, early Late Hauterivian), and Pseudometahoplites sp. juv. (Compressissima to Vandenheckii Zones, Early to Late Barremian transition) from the basal MRu. The new palaeontological and sequential results of this study allow a revision of previous data from Godet et al. (2010) precisely assigning a Barremian age to the MRu of the central Jura Mountains (Tethyan Compressissima to lower Sartousiana and Boreal uppermost Fissicostatum to middle Denckmanii ammonite Zones, Boreal LK20B-LK19-LK18 and Tethyan NC5D nannofossil Zones), within the Early to Late Barremian UJ (Tethyan Hugii to lower Sartousiana and Boreal Rarocinctum to middle Denckmanii ammonite Zones, Boreal LK20C to LK18 and Tethyan NC5C-NC5D nannofossil Zones) and below the Late Barremian Urgonien Blanc facies (Tethyan Sartousiana ammonite Zone).

The Aucellina biostratigraphy of the Upper Albian (Early Cretaceous) of the Kirchrode I cored borehole, Hannover-Kirchrode, northern Germany

Abstract The Aucellina biostratigraphy of the Upper Albian Kirchrode Marls Member succession in the Kirchrode I (1/91) cored borehole is described and the fauna illustrated. The borehole commenced at an unknown depth below the Early Cenomanian marls of the Bemerode Member, but higher beds of the Kirchrode Marls and the basal beds of the Bemerode Member were exposed in the Mittellandkanal and its Stichkanal extension at Misburg. The borehole and surface exposures permit a virtually complete Late Albian succession of Aucellina species to be observed. Published Aucellina range data from the borehole are reassessed and it is suggested that the lower part of the recorded range is based partly on misidentifications of fragments of thin-shelled bivalves such as Syncyclonema and Amussium. Aucellina appears in the borehole succession within the upper part of the Callihoplites auritus ammonite Subzone (Mortoniceras inflatum Zone) and continues to the top of the borehole succession within the Preaeschloenbachia briacensis ammonite Subzone (Stoliczkaia spp. Zone). Aucellina from higher in the briacensis Subzone collected from the Misburg Mittellandkanal section are also discussed and illustrated. There is some evidence that Aucellina occurs typically at levels in the borehole containing predominantly Boreal European Province ammonites, supporting the general inference that Aucellina lived in cooler northern waters. In contrast, Aucellina is poorly represented in intervals with Tethyan ammonites and thin-shelled inoceramids (e.g. the Mortoniceras (Durnovarites) perinflatum Subzone, Stoliczkaia spp. Zone). The briacensis Subzone, with an admixture of Tethyan (Stoliczkaia) and Boreal ammonites contains a distinctive, taxonomically highly diverse Aucellina assemblage. Relevant taxonomic research on European Late Albian and Early Cenomanian Aucellina faunas is reviewed. The Late Albian Aucellina succession in the borehole differs from that established from partially correlative successions in England.

Changes in paleo-circulation and the distribution of ammonite faunas at the Coniacian–Santonian transition in central Poland and western Ukraine

AbstractAmmonite distribution patterns and carbon and oxygen stable isotopes from the Lipnik-Kije (Poland) and Dubovcy (Ukraine) sections allow us to propose a model of sea water paleo-circulation in central Europe for the Coniacian- Santonian interval. The tectonic evolution of the south-eastern part of Poland, and expansion of the Krukienic Island areas, appears to have been one of the most important factors affecting paleotemperatures and the distribution of ammonite faunas in the shallow, epicontinental sea in this part of Europe. In the Lipnik-Kije section, low-latitude Tethyan ammonites, especially of the genera Nowakites, Parapuzosia and Saghalinites, are mixed with the cold water loving ammonite genus Kitchinites in the Lower Santonian. In the Dubovcy section (western Ukraine), Tethyan ammonites disappear abruptly in the earliest Santonian, giving place to temperate ammonites of the Kitchinites group in the early Early Santonian and to Boreal belemnites of the genus Gonioteuthis in the Middle and Late Santonian. Despite evidence for the effects of diagenesis in both sections, bulk-rock δ18O records from the limestones support higher seawater paleotemperatures in the Polish sea and cooler conditions in the western Ukraine.The proposed paleo-circulation model and paleotemperature distribution across Europe is supported independently by changes in faunal and nannoflora evidence (ammonites, foraminifera and nannoplankton), and rather unexpectedly with the bulk δ18O data. These data allow the recognition of the end-Coniacian-Early Santonian cooling event, resulting from cold currents flowing from the north, which is traceable, with different magnitude, in several European sections.Facies changes in both sections are related to the input of terrigenous material, and linked to Subhercynian tectonic movements which affected the eastern (Ukrainian) and central (Holy Cross) segment of the Mid Polish Trough at different times. Uplift and sediment input moved westwards through time. Clastic input is detectable at the Coniacian-Santonian boundary in the Ukrainian segment. Similar facies changes reached the Holy Cross segment in Poland distinctly later, somewhen in the Middle Santonian. It is likely that tectonics together with paleo-circulation changes markedly restricted or even cut-off the western Ukraine area from Tethyan ocean influences in the Early Santonian.

Organic matter production and preservation in the Lusitanian Basin (Portugal) and Pliensbachian climatic hot snaps

The Pliensbachian (Early Jurassic) hemipelagic carbonate series of the Lusitanian Basin (Portugal) are of major importance as this basin is located at a key position between the Tethyan and Boreal (North European) realms. One of the most conspicuous features of this basin is the organic-rich nature of most of the Margaritatus Chronozone hemipelagic deposits, with the occurrence of several well-defined regional black shales. The analysis of selected redox sensitive elements (V, Cr, Co, Ni, Mo, and U) from the worldwide reference section of Peniche indicates that in this basin most of the organic-rich facies of the Ibex–Margaritatus chronozones were deposited under an oxic–dysoxic regime, while the rare centimetre thick well-defined black shales were deposited and preserved under suboxic–anoxic, intermittently euxinic conditions. Based on the integration of sedimentological, biostratigraphical, geochemical, and organic petrographic evidence we suggest that these basinwide black shales, corresponding to widespread mucilage and microbial outbreaks, were driven by extreme climate warming coupled with high oceanic productivity and intermittently stratified epeiric seas. Regionally, these “hot snaps” may have promoted the observed rapid but short-lived expansion of Tethyan ammonites into Boreal domains or led to decrease benthic diversity. Ensuing cooling during the Margaritatus Chronozone was accompanied by southwards influx of northwards ammonite fauna or radiation of cyst forming dinoflagellates.Worldwide preservation of organic matter during the Late Pliensbachian seems to have resulted in decreased atmospheric CO2 levels through geological storage of carbon, triggering and/or amplifying the Spinatum Chronozone icehouse event. Ultimately, this cooling event may have led to the occurrence of permafrost and/or methane gas hydrates in locations easily disturbed by the subsequent Early Toarcian warming, or/and volcanic activity driven by crustal unloading due to deglaciation.

Climatic events during the late Pleistocene in New Zealand

The Pliensbachian (Early Jurassic) hemipelagic carbonate series of the Lusitanian Basin (Portugal) are of major importance as this basin is located at a key position between the Tethyan and Boreal (North European) realms. One of the most conspicuous features of this basin is the organic-rich nature of most of the Margaritatus Chronozone hemipelagic deposits, with the occurrence of several well-defined regional black shales. The analysis of selected redox sensitive elements (V, Cr, Co, Ni, Mo, and U) from the worldwide reference section of Peniche indicates that in this basin most of the organic-rich facies of the Ibex–Margaritatus chronozones were deposited under an oxic–dysoxic regime, while the rare centimetre thick well-defined black shales were deposited and preserved under suboxic–anoxic, intermittently euxinic conditions. Based on the integration of sedimentological, biostratigraphical, geochemical, and organic petrographic evidence we suggest that these basinwide black shales, corresponding to widespread mucilage and microbial outbreaks, were driven by extreme climate warming coupled with high oceanic productivity and intermittently stratified epeiric seas. Regionally, these “hot snaps” may have promoted the observed rapid but short-lived expansion of Tethyan ammonites into Boreal domains or led to decrease benthic diversity. Ensuing cooling during the Margaritatus Chronozone was accompanied by southwards influx of northwards ammonite fauna or radiation of cyst forming dinoflagellates.Worldwide preservation of organic matter during the Late Pliensbachian seems to have resulted in decreased atmospheric CO2 levels through geological storage of carbon, triggering and/or amplifying the Spinatum Chronozone icehouse event. Ultimately, this cooling event may have led to the occurrence of permafrost and/or methane gas hydrates in locations easily disturbed by the subsequent Early Toarcian warming, or/and volcanic activity driven by crustal unloading due to deglaciation.

Upper Coniacian, Santonian, and lowermost Campanian ammonites of the Lipnik-Kije section, central Poland—taxonomy, stratigraphy, and palaeogeographic significance

The ammonites from upper Coniacian through basal Campanian of the Lipnik-Kije section (Lipnik-Kije Basin), southwestern margin of the Holy Cross Mountains, central Poland, are described in the context of its inoceramid bivalve zonation. Nineteen species-level ammonite taxa assigned to twelve genera ( Gaudryceras, Saghalinites, Parapusozia, Kitchinites, Nowakites, Eupachydiscus, Protexanites, Texanites, Hyphantoceras, Glyptoxoceras, Neocrioceras, and Scaphites) are recognized. Three ammonite interval zones are distinguished. The upper Coniacian is assigned to the Paratexanites serratomarginatus and Texanites pseudotexanus zones. The lower and middle Santonian interval is assigned to a Kitchinites emscheris– Nowakites savini Zone, which is characterized by a mixed desmoceratid and pachydiscid assemblage. The upper Santonian ammonites belong to long-ranging taxa and assignment to an ammonite zone is not possible. The lower Santonian ammonite assemblages are compared with those from the Münsterland Cretaceous Basin in northern Germany and the Corbières in southern France. The co-occurrence in the Lipnik-Kije section of faunal elements from both the Boreal Realm (Münsterland Cretaceous Basin) and the Tethyan Realm (the Corbières) makes it an important section for correlation of European Santonian successions. The occurrence of Tethyan ammonites, particularly Saghalinites and Nowakites, could perhaps be explained by an incursion of warmer water masses from the Tethyan Realm into the Lipnik-Kije Basin. This suggestion is supported by unpublished oxygen stable isotope investigations of the Lipnik-Kije section which indicate relatively high sea water palaeotemperatures.

Representatives of the Neocosmoceras (Neocomitidae, Ammonoidea) genus from the Berriasian of the Crimean Mountains and their stratigraphic significance

The genus Euthymiceras is considered as the junior synonym of the genus Neocosmoceras. Four species N. euthymi, N. cf. transfigurabilis, N. minutus sp. nov., and N. giganteus sp. nov. from the Berriasian deposits of the Crimean Mountains are described for the first time. The biostratigraphic unit formerly termed the “Euthymiceras-Neocosmoceras Beds” is ranked now as the Neocosmoceras euthymi Subzone with a synonymous index species. The subzone is correlated to the following biostratigraphic units: the synonymous subzone of the northern Caucasus, the Neocosmoceras-Septaliphoria semenovi (upper part) and Buchia volgensis local zones of Mangyshlak, the upper part of the Riasanites rjasanensis Zone in the East European platform, and the paramimounum Subzone of the boissieri Zone in the standard zonation of the Tethyan ammonites.

Stratigraphy of the Bathonian-Callovian boundary deposits in the Prosek section (Middle Volga Region). Article 1. Ammonites and infrazonal biostratigraphy

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 Bathonian-Callovian boundary are difined more carefully. 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 ammonite assemblages occurring in lower part of the Elatmae Zone, the breve, frearsi, quenstedti, and elatmae biohorizons are identified. The joint occurrence of Boreal, Subboreal, and Tethyan ammonites in the section facilitate its correlation with the other sections of the Panboreal paleobiogeographic superrealm.

A Valanginian (Early Cretaceous) ‘boreal nannoplankton excursion’ in sections from Romania

In order to resolve both sea-level and palaeoclimatic signals for the earliest Cretaceous, 161 calcareous nannofossil samples of Berriasian to Valanginian age have been studied from Romania. These samples are derived from three biostratigraphically well-dated sections of Tethyan litho- and biofacies. The nannofossil assemblages recorded are of high diversity, reflecting stable warm water conditions typical for the earliest Cretaceous of the Tethys. The floras are characterised by abundant Watznaueria spp. and Nannoconus spp., whereas other taxa are less common. Long term trends on the scale of 1–4 my are reflected by shifts from Watznaueria spp. dominated assemblages in the Lower Berriasian to Nannoconus spp. assemblages in the Middle-Upper Berriasian, back to Watznaueria spp. in the Upper Berriasian–Lower Valanginian and again to Nannoconus spp. in the Upper Valanginian. These changes are thought to be caused by palaeoclimatic shifts. Periods, with a dominance of cosmopolitan eurytopic Watznaueria are thought to reflect cooler, humid conditions and well mixed surface waters, those with a dominance of Nannoconus warmer conditions and a rather stabile surface water stratification. Crucibiscutum salebrosum, very common at high latitudes, is extremely rare in the Romanian samples. It occurs only at one specific interval of early Late Valanginian age ( Saynoceras verrucosum ammonite Zone), associated with other rare Boreal taxa, also restricted to this particular level. This ‘boreal nannoplankton excursion’ is believed to be controlled by sea-level rather than by climate, since simultaneously Tethyan ammonites found their way into the Boreal Realm.

Lower Berriasian of Southern Primorye (Far East Russia) and the problem of Boreal–Tethyan correlation

Jurassic/Cretaceous boundary deposits in the Far East of Russia are characterized by fauna of a mixed type, including Tethyan ammonites and Boreal species of Buchia. In the north of the region (Western Okhotsk area), the middle Volgian deposits comprise the upper Tithonian Durangites. In Southern Primorye, the lower Berriasian ammonites Pseudosubplanites cf. grandis, P. aff. combesi, Berriasella ex gr. jacobi, Dalmasiceras etc. occur on the Ussuri Bay coast, together with upper Volgian Buchia species. Hence, the notion of non-correspondence between the Tithonian and Volgian is confirmed, as well as that a part of the Volgian belongs to the Cretaceous. A description of the lower Berriasian ammonites and the upper Volgian Buchia is given, including one new ammonite species: Dalmasiceras orientale sp. nov.

Palaeobiogeography of Tethyan ammonites during the Tithonian (latest Jurassic)

This study deals with the palaeobiogeographic distribution of Tethyan ammonites in the Tithonian. In particular, the relationships between ammonites of the Mediterranean Tethys, East Africa, Caribbean and Southeast Pacific areas are discussed. The study of palaeobiogeographical raw data allows one to recognize palaeobiogeographic patterns and delimit provinces and to infer palaeobiogeographical processes and, in some cases, palaeogeographical (geological) processes. Biological and physical factors affecting the palaeobiogeographic distribution of the ammonites are reviewed prior to a discussion of the distributional patterns. The analysis is constrained by different factors such as taxonomy, sample size, accuracy of the biostratigraphic information, etc. The highly problematic taxonomy of the family Ataxioceratidae hampers the use of quantitative analyses, only allowing `phenetic' definitions of provinces. Some of the Tethyan palaeobiogeographic provinces already known in the literature are dealt with further. In particular the subdivision into Mediterranean and Sub-Mediterranean provinces (or sub-provinces), that is quite clear at the scale of the entire Jurassic period, is rejected in the Tithonian though a phase of faunal separation is recorded during the transition between the early and late Tithonian. The ammonite assemblages in the shelves were less diverse and different from those of the distal, pelagic areas. Dispersal is recognized as an important process in ammonite palaeobiogeography although objective location of centres of origin is impossible. Vicariant phenomena certainly occurred but in marine environments barriers that separate areas of distribution instead of portions of space cannot be delimited objectively. The `barrier' is certainly represented by the different palaeoenvironmental contexts (shelf or pelagic habitats). The palaeobiogeographic distributions observed were produced by a complex of concurrent biogeographic processes.

Lower Jurassic-Lower Cretaceous belemnite biogeography and the development of the Mesozoic Boreal Realm

The distribution of Lower Jurassic-Lower Cretaceous belemnites is reviewed in the light of recent taxonomic and biogeographic studies and it is seen that belemnite provinciality developed in the late Lower Jurassic, when distinct Arctic taxa are first recognised. In the Middle Jurassic, Boreal and Tethyan belemnite realms are apparent, the Boreal Realm being divisable into informal Boreal-Atlantic and Arctic provinces, which can be recognised up into the Lower Cretaceous. In the Upper Jurassic and Lower Cretaceous distinct Arctic belemnites are found in association with Tethyan ammonites in California, and it is this factor, in association with an observed increase in belemnite diversity northwards from the Boreal-Atlantic to the Arctic provinces that suggests that latitudinal temperature gradients were not the overall control influencing the development of Boreal and Tethyan belemnite realms. Instead, the hostile environment of the Boreal-Atlantic area (the European Archipelago) is seen as an effective barrier to the migration of Tethyan belemnites to the Arctic, and vice versa. However, high sea level stands may have helped blur these distinctions, as in the late Valanginian-Hauterivian, when Arctic taxa invaded Europe, and Tethyan taxa the periphery of the Arctic basin.