Littérature scientifique sur le sujet « Coniacian-Santonian »

Abstract. Three new calcareous dinoflagellate species from the Middle Coniacian to Upper Santonian chalks of Lägerdorf (northern Germany) are formally described: Calcicarpinum macrogranulum n. sp., Pirumella fragilis n. sp. and Ruegenia quinqueangulata n. sp. The species show differing vertical distribution patterns which might result from local sea-level changes: P. fragilis and R. quinqueangulata are restricted to the possibly transgressive upper Mid-Coniacian to Lower Santonian interval and C. macrogranulum occurs consistently only in the probably regressive lower Mid-Coniacian and Middle to Upper Santonian intervals.

Kinematics of gravity-driven normal faults exerts a critical control on petroleum systems in deltaic settings but to date has not been extensively examined. The Ceduna Sub-basin (CSB) is a passive margin basin containing the White Pointer (Albian-Cenomanian) and Hammerhead (Campanian-Maastrichtian) delta systems that detach on shale layers of Albian-Cenomanian and Turonian-Coniacian ages, respectively. Here we present evidence for spatially variable fault growth styles based on interpretation of the Ceduna 3D seismic survey and fault kinematic analyses using displacement–distance, displacement–depth and expansion index methods. We identified faults that continuously grew either between the Cenomanian–Santonian or Santonian and the Maastrichtian located throughout the study area and faults that exhibit growth between the Cenomanian–Maastrichtian that are geographically separated into three areas according to their evolution histories: (i) Northern CSB faults exhibit constant growth between the Cenomanian and Maastrichtian. (ii) Central CSB faults show two dip-linkage intervals between (a) Cenomanian and Coniacian–Late Santonian, (b) Coniacian–Late Santonian and Late Santonian–Maastrichtian segments, respectively. (iii) Central and southern CSB faults exhibit dip-linkage intervals between Cenomanian–early Santonian and Late Santonian–Maastrichtian segments. Our study demonstrates a relationship between the location of the Cenomanian–Maastrichtian faults and their evolution history suggesting constant growth evolution at north and dip linkage at the central and south areas.

The ammonite faunas from the Amager Limestone and Bavnodde Greensand Formations of the island of Bornholm, Denmark are described. The Amager Limestone at its type locality has yielded five species, including the age diagnostic Scaphites (Scaphites) kieslingswaldensis kieslingswaldensis · Langenhan & Grundey, 1891 and Peroniceras tridorsatum (Schliiter, 1867). The Bavnodde Greensand has yielded seven species, including Scaphites (Scaphites) kieslingswaldensis fischer Riede!, 1931, which firs! appears in the Lower Santonian elsewhere in Europe. The age of the two formations is discussed. The Amager Limestone Formation is in part at least Middle Coniacian on ammonite evidence, Lower Coniacian on inoceramid bivalve evidence, while foraminifera suggest thai the formation spans most of the Coniacian. Tue Bavnodde Greensand Formation is referable to the upper Coniacian-Lower Santonian on the basis of ammonites, belemnites, and inoceramid bivalves.

The inoceramid bivalve faunas from the Arnager Greensand, Arnager Limestone, and Bavnodde Greensand Formations of the island of Bornholm, Denmark are described. The fauna from the basal part of the Arnager Greensand s. str. is from the Lower Middle Cenomanian and includes Inoceramus crippsi Mantell, /. crippsi hoppenstedtensis Trager, and I. schoendorfi Heinz. The Arnager Limestone at its type locality immediately west of Arnager yielded a diverse fauna, including /. waltersdorfensis cf. hannovrensis Heinz, /. lusatiae Andert, I. cf. rotundatus Fiege, /. striatoconcentricus Gumbel, I. (Heroceramus) cf. hercules Heinz, I. cf. wandereri Andert, I. cf. annulatus Goldfuss, I. cf. renngarteni Bodilevski & Schulgina, and/. (Mytiloides) incertus Jimbo. This fauna is Lower Coniacian. I. cf. lusatiae and /. cf. guerichi Heinz are recorded from the top part of the formation east of Horsemyre Odde, which is Lower Coniacian. /. (Cremnoceramus) schloenbachi Bohm from the upper Lower Coniacian is reported from the Arnager Limestone Formation at Muleby. /. (Volviceramus) koeneni Muller and /. (V.) alievimussensis lvannikov occur in 4 the top part of the Arnager Limestone Formation at Stampe A; this fauna is probably Lower Middle Coniacian. The fauna of the Bavnodde Greensand Formation at the type locality consists of /. (Sphenoceramus) pachti cf. pachti Arkhangelsky and /. (S.) cardissoides Goldfuss which are Lower, but not lowest, Santonian. At Risenholm, the formation yielded I. (S.) subcardissoides Schluter, I. (S.) cardissoides, I. (S. ?) bornholmensis n. sp., /. (S.) sp. ex gr. pachtilcardissoides, and incomplete, poorly preserved inoceramids possibly belonging to the I. (Magadiceramus) subquadratus group; this fauna is basal Santonian. The fauna of the formation at Jydegard comprises I. (S. ?) bornholmensis n. sp. and /. (S.) sp. ex gr. pachti/cardissoides, and the formation here is lowest Santonian and possibly highest Coniacian. The Cenomanian-Santonian lithostratigraphic formations of Bornholm are reviewed and their ages are discussed with regard to various fossil groups, including inoceramid bivalves, ammonites, belemnites, and foraminifera. Locality details are given.

The litostratigraphic subdivision includes the Kardif (Cenomanian?), Cerovska (Cenomanian, Turonian), Gradište (Coniacian, Santonian), Kubadin (Coniacian-Campanian), Sinemorec (Coniacian-Campanian), Izgrev (Coniacian-Campanian), Glušnik (Campanian), Konjovo (Campanian) and Dryankovec (Maastrichtian) Formations. The chronostratigraphy is based on microfaunistic (foraminifers) associations. The Cenomanian consists of limnic and coal-bearing undated rocks (Kardif Formation) or of shallow-marine dated clastic rocks and limestones (Cerovska Formation). The Turonian includes the upper part of the shallowwater rocks (Cerovska Formation). The Coniacian is represented by deep-marine graywacke-silstone flysch (Gradište Formation), limestones and arillaceous limestones (Kubadin Formation), tephroturbidite flysch (Sinemorec Formation) and volcanic tuffs (Izgrev Formation). The Santonian includes deepmarine rocks, which are similar to these of the Coniacian. The Campanian is represented by deepmarine limestones and argillaceous limestones (the upper part of Kubadin Formation), tephroturbidite flysch (Sinemorec Formation), limestones and argillaceous limestones (Glušnik Formation), volcanic tuffs (Izgrev Formation) and clastic-limestone flysch (Konjovo Formation). The Maastrichtian is characterized by shallow-marine limestones, sandstones and siltstones (Dryankovec Formation). The sedimentary environments had changed temporally: limnic (Cenomanian?); shallow epicontinental sea (Cenomanian, Turonian); deep-marine Sredna Gora intra-arc trough (Coniacian-Campanian); superimposed shallow epicontinental sea (Maastrichtian). The Early Subhercynian orogenic movements had occured between the Turonian and the Coniacian. The Late Subhercynian orogeny have caused a folding after the Campanian, but before the Maastrichtian.

The lithostratigraphic subdivision of the Upper Cretaceous in the Eastern Balkan Mountains includes the Balkanbas (Cenomanian?), Dobromir (Cenomanian, partly Turonian), Radova (partly Turonian – Santonian), Trânak (partly Turonian – Coniacian), Karaveljovo (Coniacian, Santonian) and Emine (partly Turonian – Maastrichtian) Formations. The chronostratigraphy is based on foraminiferal microfauna. The Cenomanian is represented by limnic conglomerates, sandstones, siltstones and shales with coals, as well as of shallow-marine clastic, argillaceous and calcareous rocks. The Turonian includes the upper part of the shallow-marine rocks and the lower part of the deep-marine Emine flysch. The Coniacian is represented by flysch consisting of alternation of graywackes, siltstones and shales or marls, clastic limestones, micritic limestones and argillaceous limestone ("marls") or of tephraturbidites, volcanic tuffs and effusive rocks. The Santonian is represented by flysch, analogical in composition to this of the Coniacian. The Campanian includes mainly clastic-limestone flysch, and locally, in the lower part a mixed flysch. The Maastrichtian consists mainly of clastic limestone flysch, locally (Emine Mountain) of mixed flysch. The boundary between the Maastrichtian an,d the Paleocene (Danian) is under discussion. Most probably it coincides with the boundary between the Emine and the lrakli flysch, where some shales occur. In the Emine back-arc marginal Sea (partly Turonian – Maastrichtian) through processes of normal sedimentation and resedimentation a flysch has been deposited. The Maastrichtian limestones are replaced by Paleocene clays.

U-Pb SHRIMP-dating of zircons from flora-bearing volcanic rocks of the Amka Formation stratotype (Ul'ya depression, Okhotsk-Chukotka volcanic belt) yield weighted mean 206Pb/238U age of 85.5 ±2 Ma (Santonian to Coniacian stage). This isotope dating is consistent with inferred Coniacian age of Ul’ya flora from the Amka Formation.

Abstract Ammonite 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.

Il Cretacico si caratterizza per la presenza di diversi intervalli di alterazione del sistema climatico-oceanico a scala globale responsabili della deposizione di black-shale marini ricchi di carbonio, definiti come Eventi Anossici Oceanici (OAEs). L’OAE3 rappresenta l’ultimo episodio di diffusa anossia durante l’intervallo Coniaciano-Santoniano. Rispetto ai precedenti eventi anossici, l’OAE3 ha una estensione regionale, ma non globale, poiché risulta essere confinato all’Oceano Atlantico sud-equatoriale e ad alcuni bacini limitrofi (es: Bacino Caraibico, Bacino del Western Interior). Altre importanti differenze fra l’OAE3 e i precedenti eventi anossici consistono nell’assenza di una anomalia del δ13C, ma piuttosto il verificarsi durante il Coniaciano-Santoniano di una serie di escursioni isotopiche sia positive che negative di piccola entità. Inoltre la deposizione di sedimenti ricchi di materia organica (black shales) sembra essere diacrona anche all’interno dello stesso Atlantico centro-meridionale. I principali obiettivi di questa tesi sono la ricostruzione di eventuali cambiamenti paleoceanografici avvenuti durante l’OAE3 in base alle variazioni di abbondanza e composizione delle associazioni a nannofossili calcarei. Il mio progetto di dottorato si è concentrato sulla biostratigrafia e paleoceanografia a nannofossili calcarei per l’intervallo compreso tra il tardo Turoniano e il Campaniano inferiore (Cretacico Superiore) e in particolare sul Coniaciano-Santoniano. La studio delle associazioni a nannofossili calcarei sia in termini semiquantitativi che quantitativi ha permesso di ottenere una biostratigrafia di dettaglio utile a datare e correlare le variazioni del nannoplancton calcareo durante l’OAE3. Lo studio è stato condotto sia su siti oceanici carotati nell’ambito dei progetti Deep Sea Drilling Project (DSDP) e Ocean Drilling Program (ODP) che su sezioni continentali, situate nell’Atlantico sud-equatoriale, in Oceano Indiano e nel Bacino Anglo-Parigino. I risultati ottenuti sono stati poi integrati con dati di letteratura al fine di ottenere una successione di eventi per il Coniaciano-Santoniano e fornire una caratterizzazione paleoceanografica dell’OAE3. È stata realizzata una dettagliata revisione tassonomica per risolvere alcune incongruenze tassonomiche e ottenere una terminologia aggiornata e unificata. Questa è stata la base per una biostratigrafia coerente, ad alta risoluzione delle successioni studiate, e stabilire una datazione e correlazione a scala sovra-regionale. Sono state applicate le quattro biozonazioni standard proposte per il Cretacico Superiore per ottenere la massima risoluzione e testare la loro applicabilità nei diversi bacini e contesti oceanografici. Le analisi quantitative delle associazioni a nannofossili calcarei hanno permesso di caratterizzare la distribuzione dei nutrienti prima, durante e dopo l’OAE3. La distribuzione dei taxa indicativi di più alta fertilità mostra caratteristiche diverse per le varie successioni, suggerendo che l’OAE3 non è stato caratterizzato da un episodio globale di fertilizzazione. Infatti, la fertilità rimane in genere bassa ad eccezione delle aree di upwelling che sono caratterizzate da condizioni meso-eutrofiche anche negli intervalli che precedono e seguono l’OAE3. Le analisi quantitative condotte in questo studio hanno evidenziato la presenza di ampie fluttuazioni di abbondanza dei generi Micula e Marthasterites durante il Coniaciano-Santoniano. Questi picchi di abbondanza possono essere correlati con eventi analoghi descritti in letteratura, anche se con valori di incremento differenti nei vari siti. Durante l’OAE3 sono stati individuati due distinti picchi di abbondanza di Marthasterites (M. furcatus) e cinque di Micula (M. staurophora). L’affinità paleoecologica di Micula, e in particolare M. staurophora, così come quella del genere Marthasterites rimane poco chiara, pertanto le cause dei loro picchi di abbondanza devono essere individuate. Tuttavia, le fluttuazioni nelle associazioni a nannofossili calcarei indicano un profondo cambiamento paleoceanografico durante il Coniaciano-Santoniano. L’inizio dell’OAE3 coincide con un elevato aumento in abbondanza (e localmente dominanza) di M. furcatus, che suggerisce il rapido instaurarsi di nuove e peculiari condizioni paleoceanografiche ad ampia scala. Le condizioni paleoceanografiche più alterate sono raggiunte nella parte centrale dell’OAE3 con un picco di abbondanza (climax) di M. staurophora sincrono a scala globale. Oltre al loro valore per le ricostruzioni paleoambientali, i picchi di abbondanza di Micula and Marthasterites si sono rilevati estremamente utili per complementare/implementare la caratterizzazione biostratigrafica dei limiti Turoniano/Coniaciano, Coniaciano/Santoniano e Santoniano/Campaniano. Questi picchi di abbondanza potrebbero dunque essere introdotti come eventi addizionali in future zonazioni a nannofossili calcarei del Cretacico Superiore.<br>The Late Cretaceous was punctuated by several periods of global perturbations of the climate-ocean system that lead to widespread organic carbon-rich marine black shale deposition, termed Oceanic Anoxic Events (OAEs). The OAE3 represents the last episode of anoxia dated as Coniacian-Santonian. Compared to previous anoxic events, OAE3 has a regional extension, rather than a global significance, since it is confined to the equatorial-south Atlantic Ocean and adjacent basins (e.g. Caribbean Basin, Western Interior Basin). Another major difference of OAE3 relative to previous OAEs resides in the absence of a prominent δ13C anomaly, but the occurrence of several minor positive and negative excursions in the Coniacian-Santonian interval. Moreover, the deposition of organic carbon-rich sediments (black shales) seems to be diachronous even in the central-south Atlantic Ocean. This PhD project focused on calcareous nannofossil biostratigraphy and paleoceanography of the Late Turonian to Early Campanian time interval (Late Cretaceous), and specifically of the Coniacian-Santonian. Nannofossil assemblages were investigated semiquantitatively and quantitatively to obtain a detailed biostratigraphic framework for assessing the paleoenvironmental changes across OAE3. The study was performed on Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) sites and on-land sections, situated in the equatorial and south Atlantic Ocean, the Indian Ocean and the Anglo-Paris Basin. The results of my investigation were integrated with data from literature in order to achieve a solid framework of events for the Coniacian-Santonian time interval and provide a paleoceanographic characterization of OAE3. A detailed revision of the taxonomy was accomplished for solving a few taxonomic incongruities and obtain a unified updated nomenclature. This was the basis for the coherent high-resolution biostratigraphy of the selected sites, in order to establish dating and correlations at supra-regional scale. The four standards biozonation schemes available for the Upper Cretaceous were applied to attain the maximum resolution and test their individual applicability in different oceanic basins and oceanographic settings. The major objective of this PhD thesis was the reconstruction of presumed paleoceanographic changes across OAE3 as recorded by abundance and composition of calcareous nannofossil assemblages. Quantitative analyses of calcareous nannofossil assemblages allowed the characterization of paleotemperature and nutrient changes prior, during and after OAE3. Nannofossil-based paleotemperature obtained in this study and documented in the literature do not show significant changes in the studied successions, perhaps due to unresolved unambiguous temperature-related taxa in the Late Cretaceous and/or minor (subtle) temperature changes across OAE3. As far as paleofertility isconcerned, the nannofossil taxa indicative of higher nutrient content display very different patterns at the various sites, suggesting that OAE3 was not characterized by a global fertilization episode. Indeed, fertility remained globally low with the exception of upwelling areas characterized by meso-eutrophic conditions also in the intervals preceding and following OAE3. The quantitative analyses conducted in this study pointed out relatively large fluctuations in abundance of genera Micula and Marthasterites in the Coniacian-Santonian interval. These abundance peaks could be correlated with analogous events described in the literature, even if with different values of abundance at the various sites/sections. Two Marthasterites (M. furcatus) abundance peaks and five Micula (M. staurophora) abundance peaks were distinguished across OAE3. The paleoecological affinity of Micula, and specifically M. staurophora, as well as that of genus Marthasterites remains unexplained, so the causes of their abundance peaks continue to be elusive. However, the distinctive fluctuations in nannofossil assemblages indicate profound paleoceanographic changes during the Coniacian-Santonian. The onset of OAE3 coincides with a major increase in abundance (and locally dominance) of M. furcatus suggesting the rapid establishment of new and peculiar paleoceanographic conditions at widespread to global scale. The most altered paleoceanographic conditions were reached in the core of OAE3 with the synchronous maximum abundance (climax) of M. staurophora at global scale. In addition to their value for paleoenvironmental reconstructions, the identified Micula and Marthasterites abundance peaks turned out to be extremely useful for complementing/implementing the biostratigraphic characterization of the Turonian/Coniacian, Coniacian/Santonian and Santonian/Campanian boundaries and might be introduced as additional events in future nannofossil zonations for the Late Cretaceous.