Academic literature on the topic 'Calcareous nannofossil'

Calcareous nannofossils, mineralogical and geochemical investigations are carried out on the Cenomanian-Turonian boundary of the Gulneri Formation in the Azmir, Dokan and Degala sections, northern Iraq. Regarding the calcareous nannofossil data CC11 and CC12 biozones were identified. A detailed investigation was carried out to identify calcareous nannofossils species. On the basis of their stratigraphic distribution, two biozones were proposed in this study; Quadrum gartneri Interval Biozone (CC11) part and Lucianrhabdus maleformis Interval Biozone (CC12) part. Correlation with other calcareous nannofossils biozones from regional schemes led to conclude that the age of the Gulneri Formation in the studied sections is the early Turonian. Mineralogical (X-ray diffraction XRD) and trace elements geochemistry (X-ray fluorescence XRF) data along with the dominance of calcareous nannofossil Watznauria that indicates warm and arid climatic condition prevailing in the Cenomanian-Turonian transition.

Abstract We obtained material from the Puerto Escano section (southern Spain) to study the Jurassic/Cretaceous (J/K) boundary interval. The same samples had already been processed for magnetostratigraphic studies and biostratigraphic zonation based on calpionellids and ammonites (Pruner et al. 2010), but not for calcareous nannofossils. The aim of this study was to process the samples using micropalaeontological analysis and to compare and calibrate results for calcareous nannofossils with existing magnetostratigraphic and other biostratigraphic data. The calcareous nannofossil assemblage was dominated by the genera Watznaueria, Cyclagelosphaera, Nannoconus, Conusphaera and Polycostella. Several nannofossil bioevents were recorded on the basis of the distribution of stratigraphically important taxa, including zonal and subzonal markers. Based on the lowest occurrences (LO) of M. chiastius, N. globulus minor, N. wintereri, N steinmanii minor, N. steinmannii steinmannii, N. kamptneri minor and N. kampteri kamptneri, two nannofossil subzones (NJT 15b, NJT 17a) and two nannofossil zones (NJT 16, NK-1) were recognized. The paper introduces new palaeoecological data based on geochemical analysis and macrofauna occurrences.

The presence of calcareous nannofossils in samples of the Post-Gondwana sequences (Kolbano and Viqueque sequence) gives guidance about the relative age of the study area located in the Outer Banda Arc, namely Timor, Rote, and Sawu Island. The study was carried out on six traverses, Timor Island traverse (Baun and Camplong), Rote Island traverse (Termanu and Central Rote), and Sawu Island traverses (West Sawu and East Sawu). There is 29 outcrop sample prepared using the smear slide method and observed using a polarizing microscope with 1000x magnification. The results of the study showed the presence of Cretaceous, Paleogene, and Neogen-Quarternary calcareous nannofossil. There are 82 species from 14 families identified in the post-Gondwana sequence. The results showed that the assemblage of calcareous nannofossil in Cretaceous characterized by the presence of Watznaueria fasciata, Watznaueria cynthae, Cyclagelosphaera brezae, Orastrum campanensis, and Micula concava. The assemblage of Paleogene calcareous nannofossil characterized by the presence of Coccolithus staurion, Chiasmolithus solitus, Discoaster minimus, Tawelus (?) magnicrassus, Chiasmolithus bidens, Prinsius africanus, Cyclicargolithus luminus, Spenolithus elongatus, Reticulofenestra umbilica, Cruciplacolithus vanheckae, and Helicospharea seminulum, and the assemblage of Neogene calcareous nannofossil characterized by the presence of Reticulofenestra pseudoumbilica, Discoaster quinqueramus, Helicosphaera princei, and Discoaster pansus. Quarternary calcareous nannofossil characterized by the presence of Ponthospaera indooceanica.

Biostratigraphic studies of the Baghamshah Formation from the Birg section in the northwest of Birjand (Lut Block) are done here for the first time based on the calcareous nannofossils. In the studied section, 82 samples were taken, and smear slides were prepared. The examination of the collected samples resulted in the identification of 65 calcareous nannofossil and 11 didemnid ascidian spicules species belonging to 38 genera corresponding from CC1 to CC4b biozones with the age of early Berriasian to early Hauterivian, according to the Sissingh biozonation. The calcareous nannofossil assemblages are dominated by the following genera: Watznaueria, Nannoconus, Conusphaera, and Cyclagelosphaera. Keywords: Birjand, Baghamshah Formation, biozonation, Biostratigraphy, Early Berriasian, Early Hauterivian.

The Indo-Burmamountain range represents an accretionary wedge which resulted from subduction of the Indian plate beneath the Eurasian plate. It is situated between the eastern Himalayan Namche Barwa syntaxis and the Sumatra–Andaman subduction zone.The rocks exposed in the Mizo Hills form a part of the Indo-Burma range. Although the geology of theMizo Hills has been studied for decades, fundamental aspects of age and paleoenvironment remain debatable. In this study, calcareous nannofossils have been used for refining the biostratigraphy and paleoenvironment of the Upper Bhuban Formation (UBF) of a part of Mizoram. A calcareous nannofossil assemblage comprising eleven species of eight genera have been recognized. Though the nannofossil yield is poor with a moderate to low preservation, their study is significant in determination of age and paleoenvironment. By integrating the calcareous nannofossil and known foraminiferal assemblage data, we constrain the studied succession to Calcareous Nannofossil Zone CNM7 of Backman et al. 2012 which is equivalent to early part of the middle Miocene. The relatively good abundance of Helicosphaera, presence of Discoasters and the published foraminiferal data indicate hemipelagic depositional setting for the UBF in Mizoram.

Calcareous nannofossils are used here for the first time in order to establish a precise biostratigraphic framework for the Kermanshah Radiolarite Formation, an outcropping in Western Iran. The new data presented here challenge the previous tentative age interpretations (Pliensbachian to early Toarcian) based upon radiolarians. Calcareous nannofossil assemblages and events unequivocally indicated that the pelagic limestones and marls are late Sinemurian in age (NJT 3b nannofossil subzone), and that these are thrusted over shales and cherts dated as uppermost Sinemurian (NJT 3b-c nannofossil subzone) and lowermost Pliensbachian (NJT 4 nannofossil zone). This result leads not only to reconsideration of the age of the radiolarite formations, which are widespread in the Zagros orogenic system, but also a better understanding of the stratigraphic relationships between the various lithological units known in the area. Besides these new stratigraphic inferences, the calcareous nannofossil assemblages of the uppermost Sinemurian–lowermost Pliensbachian successions revealed the common presence of new morphologies of the Mitrolithus genus, never described before. These findings allow for the description of three new species, M. montgolfieri, M. pseudonannoconus, and M. tethysiensis, and reveal the existence of homeomorphy between the spine structure of conical Lower Jurassic coccoliths and the widespread Cretaceous nannoconids.

The variations in assemblages of calcareous nannofossils are tracked in the Dakhla and Tarawan Formations exposed at Gebel Nezzazat (central Sinai, Egypt). Five calcareous nannofossil biozones, namely NP2/3, NP4, NP5, NP6, and NP7/8 are identified. A distinct marker bed related to the Latest Danian Event (LDE) occurs within the Dakhla Fm. The earliest representative of fasciculiths, Lithoptychius schmitzii, first occurs just below the LDE distinct bed and is followed by the Los of Diantholitha alata, D. mariposa, L. varolii, L. felis, and L. collaris. The abundance of calcareous nannofossils drops within the LDE distinctive bed. The base of Selandian Stage is here approximated at the base of Zone NP5 in concurrence with a sudden drop in the abundance of calcareous nannofossils. No considerable lithological changes are noted across this transition. The absence of subsequent occurrences of L. ulii, L. janii, L. billii, and L. stegostus suggest inconsistent lowest occurrences (Los) of these taxa, insufficient sampling resolution, and/or a hiatus. The base of Thanetian is approximated with the base of Zone NP7/8 in the topmost of Dakhla Fm. No considerable changes in calcareous nannofossil assemblages are associated in correspondence to this transition except the LO of D. mohleri, lowest continuous occurrence (LctO) of Bomolithus megastypus, and the increase in abundance of Heliolithus kleinpellii as well as a sudden drop in abundance within Zone NP7/8. The variations in calcareous nannofossil assemblages at Gebel Nezzazat suggest prevailing warm-water and oligotrophic conditions during the Paleocene and particularly along the Danian Stage that are interrupted by minor fluctuations in paleoclimatic conditions. In particular, the Danian–Selandian transition marks a decrease in warm and oligotrophic conditions that persisted along the Selandian Stage. The Selandian–Thanetian transition shows an increase of warm and oligotrophic conditions prevailed in the Thanetian record. The sudden decrease in abundance of calcareous nannofossils in both the Selandian and Thanetian is likely resulted from an increase in dissolution of carbonates rather than variations in the paleotemperature and/or paleofertility.

Calcareous nannofossils are very small microfossils composed of calcium carbonate. They are very good biostratigraphic markers within marine sediments by covering the Jurassic to present. The standard preparation of a sample for nannofossil analysis requires the collection of the largest quantity and the best fossils. Sample preparation accords to the following steps: i. Pounding sample; ii. Eliminating organic matter; iii. Washing sample; iv. Filter sample through the sieve; v. Eliminating clay; vi. Drying sample in an incubator; vii. Packing sample. Sample analysis accords to the following steps: i. Preparation of smear - slide; ii. Observation of morphology; iii. Determination; iv. Taking photo; v. Evaluating overall preservation and abundance of fossils; vi. Making analysis result sheet. This process is applied to study calcareous nannofossils within marine sediments in Soc Trang province. It makes much clear to understand middle Pleistocene-early Holocene ecosystem of calcareous nannofossil. In conclusion, this assemblage belongs to NN21 zone by the present of Emiliania huxleyi and Gephyrocapsa oceanica.

Nannofossil biostratigraphy of the Lower Cretaceous Shadui Formation (Northern Tethyan Himalayas, Southern Tibet)Calcareous nannofossils of Aptian-Albian age were found in the basal part of the Shadui Formation, Northern Tethyan Himalayas, Southern Tibet. The predominantly shale strata are exposed near the northeastern tip of Yamdrock Tso Lake at the locality of Bangbu and they were previously considered to be of Late Cretaceous age. Occurrence of the nannofossil speciesPrediscosphaera columnataandCribrosphaerella ehrenbergiiindicates the Upper Aptian-Lower Albian Zone BC23. Nannofossil species of Late Albian, Cenomanian or younger Cretaceous age were not present in the studied part of the Shadui Formation. Nannofossils are badly preserved and hardly identifiable probably as a result of strong post mortem etching and dissolution during burial. The depositional setting of the Shadui Formation is interpreted as hemipelagic to pelagic. A horizon of dark shale in the lower part of the Shadui Formation may be stratigraphically correlated with ocean anoxic event OAE1b. The discovery of calcareous nannofossils at the Bangbu locality increases the stratigraphic precision in the correlation of Cretaceous strata between hemipelagic-pelagic facies and shelf depositional areas in the Tibetan Tethyan Himalayas.

Abstract Studies, based on calcareous nannofossils, proved that the level of reworked microfossils had so far been underestimated. More recently detailed quantitative studies of calcareous nannoplankton of the Magura, Malcov, Zawada and Kremna formations from the Magura Nappe in Poland documented a degree of nannofossil recycling among those formations. In the Late Eocene-Early Oligocene pelagic Leluchów Marl Member of the Malcov Formation the level of redeposition is very low (0-3.80 %), however, in the flysch deposits of the Malcov Formation reworking increased to 31.4 %. Late Oligocene through Early Miocene “molasse” type deposits of the Zawada and Kremna formations contain 43.7-69.0 % of reworked nannofossils. Quantitative analyses of the reworked assemblages confirmed the domination of Paleogene nannofossil species over Cretaceous ones. The most abundant, reworked assemblages belong to the Early- Middle Eocene age.

In my PhD project, I’ve studied calcareous nannofossil assemblages from three different sites during the Middle Eocene Climatic Optimum (MECO). The MECO is a global transient short-lived hyperthermal episode characterized by a global prominent perturbation both in oxygen and carbon stable isotopes, it occurred at Chron C18r-C18n transition (ca. 40 Ma) and lasted ca. 500-600 kyr (Bohaty et al., 2009). It represents a significant climate reversal during the Middle-Late Eocene long-term cooling trend. The MECO event is one of several hyperthermal events occurred in the Paleogene, after the well known Paleocene Eocene Thermal Maximum (Kennett and Stott, 1991). Actually, interest in these issues is raising because they are considered potential analogues in the past of the expected global warming we are going to experience in the next future. The most accredited hypothesis regarding the onset of the MECO warming involves a huge CO2 degassing event, linked to major plate tectonic reorganization, occurred during the Eocene (Bohaty et al., 2009). The study sections are located in different depositional settings and geographical areas. In particular, the first study succession, the Alano section, is set in north-eastern Southern Alps of the Veneto region and spans the middle to late Eocene. From a paleogeographic point of view, the section has a paleodepth of 600-1000 m and belongs to the Belluno Basin in the central-western Tethys; the second study section was recovered from IODP Site 1333 during Exp.320 in the Equatorial Pacific. The paleodepth estimate for this Site is ca. 3800 m, while the modern water depth is ca. 4800. The third study section was recovered during ODP Leg 171B located in the Blake Nose (NW Atlantic) with a paleodepth of ca. 1500 m. The first aim of this study is to verify if there is a unique and global change of calcareous nannofossil assemblages in response to the MECO event. A wide spectrum of paleodepositional settings and locations (Alano section, Site 1051A and U1333C) has been analyzed during this extreme paleoclimatic phase eventually providing paleoenviromental reconstructions based on modifications observed in calcareous nannofossil assemblages. The second aim of this study is focused on biostratigraphic and biochronologic issues related to Middle Eocene to Early Oligocene interval, with a special emphasis on the MECO. Standard and additional biohorizons have been tested and compared with previous data available from literature, providing estimates of the degree of reliability of considered bioevents and of their calibrations. The first chapter of this thesis is a brief general overview of the early Paleogene paleoclimatic evolution, followed by a description of the study materials and common methods and strategies adopted in this work. In the second chapter of this thesis, a high resolution study on calcareous nannofossil across the MECO event is presented. Our data from the middle-bathial Alano section indicate that the MECO interval seems to coincide with significant changes in calcareous nannofossil assemblages. Eutrophic/cold taxa and reworked specimens show an overall increase in abundance during the warming event. Conversely, oligotrophic/warm taxa are characterized by a peculiar anticovariant trend with respect to meso-eutrophic taxa, decreasing significantly during the MECO and post-MECO intervals. These results are interpreted as a transient enrichment in dissolved nutrients in warmer sea surface waters and suggest that the enhanced availability of nutrient in the water column overrides other environmental factors in the make-up of calcareous nannofossil assemblage. Morevover, the increase in reworking is consistent with an augment in terrigenous input, likely due to accelerated chemical weathering triggered by the enhanced hydrological cycle. In the third chapter of this thesis, I provide results of sediments recovered from IODP Exp. 320 (U1333C - Pacific Equatorial Ocean) in a time interval comprised from the Middle Eocene to Early Oligocene. These data show dramatic changes in preservation state, with the number of specimens counted on a specific area (1 mm2) virtually collapsing to zero during the MECO event. In the same interval, we also observed changes in calcareous nannofossil assemblages that are consistent with strong dissolution phenomena. As already said, a strong decrease of specimens/mm2 is clear, but a even stronger argument for pervasive dissolution conditions is based on the fact that if we consider the relative abundance (%) of the most resistant genus, Discoaster, there is a remarkable increase of this taxon, as it is expected if the pristine assemblages were altered/biased by preferential dissolution. At Site U1333C, the MECO can be considered a semi-barren interval and thus any paleoenviromental inference is definitively hindered. For this reason, I decided to focus on a longer interval with the purpose of providing biostratigraphic and biochronologic datums from one of the rare carbonate successions available for the Middle Eocene to Early Oligocene in the Equatorial Pacific. We used this refined framework to analyze the mode and tempo of evolution of some calcareous nannofossil taxa (i.e., sphenoliths and Dictycoccites). The fourth chapter of this thesis provides a highly resolved documentation of the MECO as recorded from the ODP Site 1051A (NW Atlantic). Our results evidence changes in calcareous nannoflora assemblages during this transient episode of global warming that are consistent with an increase in nutrient availability. Small reticulofenestrids, typically thriving in eutrophic environments and stressed conditions, show a long-term gradual increase in their relative abundance thus suggesting increased nutrient availability of the sea surface waters at ODP Site 1051A. A similar trend is also recorded by eutrophic large Dictyococcites which sharply increase in abundance at the same stratigraphic level (LCO) providing a further evidence of a shift toward more eutrophic conditions. This scenario is also supported by the slight decline showed by Sphenolithus and Discoaster. These genera are considered as k-specialist warm-oligotrophic taxa and their decrease in abundance during a phase of gradual warming is clearly related to an increase of nutrient availability. Finally, if we go into detail on genus Sphenolithus, a profound reorganization was found to take place: S. furcatolithoides goes extinct, S. predistentus and S. obtusus firstly appear and most of the other species temporary increase/decrease their abundance. Overall, our data from ODP Site 1051A indicate that changes in calcareous nannofossil assemblages started well after the onset of the MECO and before the peak warming following two different modes, a first type has been defined as abrupt (e.g., the LCO of Dictyococcites, the HO of S. furcatolithoides) while the second as gradual (the increase of small Reticulofenestra).
Durante il mio progetto di dottorato ho studiato le associazioni a nannofossili calcarei provenienti da tre siti nell’intervallo corrispondente al Middle Eocene Climatic Optimum (MECO). Il MECO è un episodio ipertermale transitorio e di breve durata, caratterizzato da un’importante perturbazione a livello globale degli isotopi stabili sia dell’ossigeno che del carbonio, osservato alla transizione tra Chron C18r-C18n (ca. 40 Ma) ha una durata di circa 500-600 kyr (Bohaty et al., 2009). Esso rappresenta un’inversione significativa del clima durante il trend di raffreddamento di lunga durata dell’Eocene medio e superiore. Il MECO è uno tra gli eventi ipertermali, assieme al meglio conosciuto Paleocene Eocene Thermal Maximum, riconosciuti nel Paleogene (PETM, Kennett and Stott, 1991). Attualmente l’interesse verso questi argomenti è crescente perché essi sono considerati potenziali analoghi nel passato dell’atteso riscaldamento globale che sarà in atto nel prossimo futuro. L’ipotesi più accreditata riguardo le cause del MECO è connessa ad un enorme evento di degassazione di CO2, legato a una importante riorganizzazione delle placche tettoniche avvenuta durante l’Eocene (Bohaty et al., 2009). Le sezioni studiate sono situate in diversi setting deposizionali e aree geografiche. In particolare la prima successione, la sezione di Alano, è localizzata nelle Alpi nord orientali del Veneto e comprende l’Eocene medio e superiore. Dal punto di vista paleogeografico, la sezione ha una paleoprofondità di 600-1000 m ed è parte del bacino di Belluno, entro la Tetide centro occidentale; la seconda sezione di studio è stata recuperata nell’IODP Site 1333 durante l’Exp.320 svoltasi nel Pacifico Equatoriale. La paleoprofondità stimata per questo Site è di 3800 m, mentre la profondità attuale è ca. 4800 m. La terza sezione di studio è stata recuperata dal Leg ODP 171B nell’area del Blake Nose (Atlantico nord occidentale) ed ha paleoprofondità stimata di ca. 1500 m. Il primo obiettivo di questo studio è verificare se c’è un cambiamento unico e globale nelle associazioni a nannofossili calcarei in risposta al MECO. Un ampio spettro di setting paleodeposizionali e aree diverse (sezione di Alano, Site 1051A and U1333C) è stato analizzato durante questa fase paleoclimatica estrema e sono state fornite ricostruzioni paleoambientali basate su modificazioni osservate nelle associazioni a nannofossili calcarei. Il secondo obiettivo di questo studio è centrato sulla biostratigrafia e biocronologia dell’intervallo Eocene medio a Oligocene inferiore, con particolare attenzione al MECO. Biorizzonti standard e addizionali sono stati testati e confrontati con dati precedenti presenti in letteratura, fornendo stime del grado di affidabilità dei bioeventi considerati e delle loro calibrazioni. Il primo capitolo della tesi è una breve presentazione generale dell’evoluzione paleoclimatica del Paleogene inferiore, seguita dalla descrizione dei materiali di studio e dei metodi e strategie adottate in questo lavoro. Nel secondo capitolo di questa tesi viene presentato uno studio sui nannofossili calcarei ad alta risoluzione attraverso il MECO. I nostri dati dalla sezione medio batiale di Alano indicano che l’intervallo riguardante il MECO sembra coincidere con cambiamenti significativi nelle associazioni a nannofossili calcarei. Taxa che preferiscono acque eutrofiche/fredde e forme rimaneggiati mostrano un aumento nelle abbondanze durante l’evento ipertermale. Al contrario, taxa con preferenze per acque oligotrofiche/calde mostrano un trend peculiare anticovariante rispetto ai taxa meso-eutrofici, diminuendo in modo significativo durante gli intervalli del MECO e post-MECO. Questi risultati possono essere interpretati come un arricchimento temporaneo dei nutrienti disciolti nelle acque più calde superficiali, e suggeriscono che la aumentata disponibilità di nutrienti nella colonna d’acqua ricopre un’importanza maggiore rispetto ad altri fattori ambientali nel determinare l costituzione dell’associazione a nannofossili calcarei. Inoltre il maggior rimaneggiamento è coerente con un aumentato input di terrigeno, probabilmente dovuto all’accelerato weathering (alterazione) chimico, scatenato dall’aumentato ciclo idrologico. Nel terzo capitolo di questa tesi, fornisco i risultati dei sedimenti recuperati dall’IODP Site 1333 durante l’Exp.320 nel Pacifico Equatoriale, in un intervallo di tempo compreso tra l’Eocene medio e l’Oligocene inferiore. Questi dati evidenziano un importante cambiamento nello stato di preservazione, con il numero di individui contati entro un’area specifica (1 mm2) che si avvicinano allo zero durante il MECO. Nello stesso intervallo abbiamo osservato modifiche nelle associazioni a nannofossili calcarei coerenti con un evento di intensa dissoluzione. Oltre alla evidente forte diminuzione di individui/mm2 già citata, un argomento ancora più forte a favore di condizioni di dissoluzione pervasiva è basato sul fatto che, se consideriamo l’abbondanza relativa (%), Discoaster, il genere più resistente, aumenta considerevolmente, come atteso nel caso in cui l’associazione originaria sia alterata da dissoluzione preferenziale. Al Site U1333C, il MECO si può considerare un intervallo semi sterile, quindi nessuna interpretazione paleoambientale è possibile. Per questo motivo ho deciso di focalizzarmi su un intervallo più lungo, con l’obiettivo di ottenere dati biostratigrafici e biocronologici da una delle rare successioni carbonatiche disponibili dall’Eocene medio all’Oligocene inferiore nel Pacifico equatoriale. Abbiamo usato questo modello per analizzare il modo e tempo dell’evoluzione di alcuni taxa di nannofossili calcarei (i.e., sfenoliti e Dictycoccites). Il quarto capitolo della tesi fornisce una serie di dati ad alta risoluzione del MECO, ottenuti dal Site 1051A (Atlantico nordoccidentale). I nostri risultati evidenziano cambiamenti nelle associazioni a nannofossili calcarei durante questo episodio transitorio di riscaldamento globale coerenti con un aumento nella disponibilità di nutrienti. I reticulofenestridi di piccole dimensioni, che tipicamente prosperano in ambienti eutrofici e in condizioni di stress, mostrano un aumento graduale di lunga durata nelle loro abbondanze relative, suggerendo quindi una aumentata disponibilità di nutrienti nelle acque superficiali dell’ODP Site 1051A. Un andamento simile si registra anche nei Dictyococcites di grandi dimensioni, eutrofici, che aumentano bruscamente in abbondanza allo stesso livello stratigrafico (LCO), fornendo una ulteriore evidenza di uno shift verso condizioni più eutrofiche. Questo scenario è supportato anche dal lieve declino che si evidenza in Sphenolithus e Discoaster. Questi generi sono considerati taxa di acque calde ed oligotrofiche, K-specialisti, e la loro diminuzione in abbondanza durante una fase di graduale riscaldamento è chiaramente correlabile ad un aumento dei nutrienti disponibili. Infine, entrando all’interno del genere Sphenolithus, si è osservata una profonda riorganizzazione, S. furcatolithoides si estingue, S. predistentus e S. obtusus fanno la loro prima comparsa, e molte delle altre specie subiscono aumenti o diminuzioni temporanee delle loro abbondanze. Nel complesso, i dati provenienti dal Site ODP 1051A indicano che i cambiamenti nelle associazioni a nannofossili calcarei sono iniziati molto dopo l’inizio del MECO e prima del picco di riscaldamento, presentando due diversi andamenti: un primo tipo può essere definito brusco (ad es. la LCO di Dictyococcites, la HO di S. furcatolithoides), mentre un secondo tipo è graduale (ad es. l’aumento delle Reticulofenestra di piccole dimensioni).

Abstract Calcareous nannoplankton appeared in the Late Triassic and rapidly evolved during the Jurassic and Cretaceous, reaching a diversity maximum in the Late Cretaceous. The widespread distribution, the high abundance and assemblage diversity of Late Cretaceous nannofloras make calcareous nannofossils a very effective biostratigraphic tool for high-resolution dating and correlations. This study is focused on the revision of nannofossil biostratigraphic events in the Upper Cretaceous. The major objective is to refine the biostratigraphic schemes available for the latest Albian-earliest Campanian time interval by the investigation of eight selected sections. These are located in different sedimentary basins in order to assess nannofossil bioevents in different paleoceanographic regimes and/or latitudes and evaluate the applicability of the three major nannofossil zonations. Sites and sections studied are: DSDP Site 463 (Mid-Pacific Mountains – Pacific Ocean), ODP Site 763 (Exmouth Plateau – Indian Ocean), ODP Site 1138 (Kerguelen Plateau – Indian Ocean), ODP Site 1261 (Demerara Rise – Atlantic Ocean), Monte Petrano (Umbria-Marche Basin – Italy), Clote de Chevalier (Vocontian Basin – France), Rock Canyon, Pueblo (Western Interior Basin – Colorado), Tarfaya Core (Tarfaya Basin – Morocco). Biostratigraphic investigation was performed on a total of 564 smear slides analyzed using standard light microscope techniques under cross polarizers and transmitted light, at 1250X magnification. I produced semi-quantitative range charts of all taxa providing information on their preservation, total and single taxon abundance. Taxonomic revision was applied to cases of potential misidentification and discrepant attribution. Taxonomic notes and remarks based on personal observation are provided. Also, photographic plates illustrate all zonal/subzonal markers and some other common species. The results were compared to those from other sections published in literature to test reliability of biozonations and discriminate global, regional or local events. Nannofossil biohorizons were also examined in the context of stage boundary definition. More specifically, for each stage boundary the data documented for GSSP sections and/or presented for GSSP proposals were analyzed and the result of my investigation were used to provide information about the applicability of nannofossil events. Adopting the three zonations, a total of 17 zonal and 4 subzonal markers were recognized as potentially cosmopolitan biohorizons. The achieved resolution is comparable for the three biozonations and higher subdivision is possible only at regional level and in restricted time intervals. Moreover, nannofossil events were proved to be extremely useful to biostratigraphically constrain paleoceanographic events of the Late Albian-Early Turonian interval. Namely, Oceanic Anoxic Event 1d, the Mid-Cenomanian Event and Oceanic Anoxic Event 2 were successfully characterized in the studied sequences.

This thesis presents a new calcareous nannofossil based zonation scheme for Iraq based upon the examination of 515 drill cutting, conventional core and bit samples from both southern and northern Iraq. This zonation consists of 13 zones and 7 subzones covering the Late Cretaceous to Early Miocene. To date no detailed nannofossil zonation scheme was available for Iraq and therefore the nannofossil zonation presented here breaks new ground. The new zonation scheme has also been successfully correlated with the established global calcareous nannofossil zonation schemes of Martini (1971), Okada and Burky (1980) and Varol (1989). In addition, this zonation has been correlated with nannofossil zonation schemes applied in other Middle Eastern countries. These correlations have enabled Iraq to be put into a global and regional stratigraphic framework. The new zonation scheme has also been integrated with global planktonic foraminiferal zonation schemes and both planktonic and benthonic foraminiferal zonation schemes previously produced for Iraq. This was done to assess the dates previously assigned to the formations being analysed during this study. The new nannofossil scheme has also been correlated with the magnetobiostratigraphic timescale so that the timing of tectonic events, the duration of hiatuses and sedimentation rates could be assessed for the study area. This information has been used to refine the existing sediment deposition models believed to be active in Iraq during the time period studied. Finally, concentrations of certain nannofossil groups noted in the study area during particular time periods are explained with reference to regional and global environmental conditions associated with local salinity changes and global warming and cooling.

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.
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.

Riassunto L’Evento Anossico Oceanico del Toarciano Inferiore (T-OAE) è stato associato ad una delle maggiori perturbazioni del ciclo del carbonio degli ultimi 250 Ma. Questo drammatico episodio di alterazione climatica e riscaldamento globale, anossia oceanica ed anomalie geochimiche è avvenuto durante un momento cruciale per la diversificazione del nannoplancton calcareo dal momento che un importante episodio di speciazione si è verificato nell’intervallo Pliensbachiano Superiore-Toarciano Inferiore. Nuovi generi e specie sono apparsi e si sono evoluti velocemente permettendo lo sviluppo di una biostratigrafia ad alta risoluzione per questo intervallo di tempo e anche del T-OAE sulla base delle prime ed ultime comparse. Inoltre, all’interno dei nannofossili calcarei, drastiche variazioni nelle abbondanze di alcuni taxa sono associate alle perturbazioni registrate durante il T-OAE. In questa tesi di dottorato viene presentata la biostratigrafia a nannofossili calcarei ad alta risoluzione di tre sezioni carotate nel Bacino Lombardo (Carota Sogno) e nel Bacino della Bassa Sassonia (Carote L1 e Schandelah), contenenti l’espressione litologica del T-OAE nei domini, rispettivamente, Tetideo e Boreale. Gli eventi a nannofossili riconosciuti nella Carota Sogno hanno permesso la distinzione di tre biozone/sottozone (NJT5a, NJT5b e NJT6) mentre quelli riconosciuti nelle Carote L1 e Schandelah hanno permesso l’identificazione di tre zone/sottozone (NJ5b, NJ6 e NJ7). Questi risultati sono stati confrontati con i dati di letteratura in modo da valutare la riproducibilità dei singoli eventi primari e secondari caratterizzanti l’intervallo del Pliensbachiano Superiore/Toarciano Inferiore con particolare interesse rivolto al limite Pliensbachiano/Toarciano ed al T-OAE nei domini Tetideo e Boreale. Per le sezioni Tetidee (Italia, Spagna del sud e dell’est, Francia del sud, Grecia ed Ungheria) gli eventi primari includono le prime comparse di Lotharingius sigillatus, Carinolithus poulnabronei, Lotharingius crucicentralis, Carinolithus superbus sceptrum, Watznaueria sp. 1, Discorhabdus striatus, la crisi di Schizosphaerella ed ultima comparsa di Mitrolithus jansae mentre le prime comparse di Lotharingius velatus e Discorhabdus ignotus sono considerate come eventi secondari. Allo stesso modo, per il dominio Boreale (Francia centrale e del nord, Inghilterra e Germania), sulla base della mia analisi critica si propone la separazione di eventi primari, comprendenti le prime comparse di Crepidolithus impontus, L. sigillatus, C. superbus sceptrum, D. striatus e le ultime comparse di Crucirhabdus primulus e Biscutum finchii e di eventi secondari, che includono le prime comparse di L. crucicentralis, L. velatus, D. ignotus, C. poulnabronei, Watznaueria sp. 1, la crisi di Schizosphaerella ed ultime comparse di Crepidolithus granulatus, Parhabdolithus liasicus e Biscutum grandis. Il mio studio ha rivelato che la prima comparsa di C. superbus sceptrum è l’unico evento riproducibile a scale sopraregionale e ha confermato che il limite Pliensbachiano/Toarciano è approssimato dalle prime comparse di L. sigillatus (top Pliensbachiano) e C. poulnabronei (Toarciano basale) nel dominio Tetideo mentre è identificato dall’ultima comparsa di C. primulus nel Boreale. Alle basse latitudini (Italia, Spagna del sud e dell’est, Francia del sud, Grecia ed Ungheria), il T-OAE è ben definito dalla prima comparsa di C. superbus sceptrum e dalla crisi di Schizosphaerella all’inizio e dall’ultima comparsa di M. jansae alla fine. Questi eventi sono riproducibili in Portogallo, con l’aggiunta della prima comparsa comune di D. ignotus determinante la fine dell’evento. Alle alte altitudini (Francia centrale e del nord, Spagna del nord, Inghilterra e Germania) l’inizio del T-OAE è definito dalla prima comparsa di C. superbus sceptrum. Eventi secondari, non riproducibili in Spagna del nord, sono la crisi di Schizosphaerella all’inizio del T-OAE e le ultime comparse di C. granulatus, B. finchii, P. liasicus e B. grandis all’interno dell’escursione negativa del carbonio caratterizzante il T-OAE. Sono state inoltre condotte analisi morfometriche su esemplari di Carinolithus superbus e Carinolithus magharensis che hanno permesso di chiarire le discrepanze tassonomiche riguardanti i due taxa. Due nuove sottospecie, Carinolithus superbus sceptrum e Carinolithus superbus superbus ed una nuova specie, Carinolithus premaghaarensis, sono state istituite mentre la specie C. magharensis è stata emendata. Studi qualitativi effettuati su foto al microscopio ottico del taxon Carinolithus cantaluppii hanno dimostrato che si tratta di un artefatto diagenetico del genere e che, quindi, questa specie deve essere rigettata. Implicazioni per la biostratigrafia ed i trend evolutivi del genere Carinolithus rappresentano un ulteriore oggetto di discussione.
Abstract The Early Toarcian Oceanic Anoxic Event (T-OAE), in the Early Jurassic Period, was associated with one of the largest perturbations of the carbon cycle in the past 250 Ma. This dramatic episode of ecosystem adjustments, global warming, oceanic anoxia and altered chemistry occurred during a crucial time for calcareous nannoplankton diversification as a major speciation episode took place in the Late Pliensbachian – Early Toarcian time interval. New genera and species appeared and quickly evolved allowing a high-resolution biostratigraphy of the onset and the termination of the T-OAE based on first and last occurrences. Moreover, drastic drops in abundance of some taxa are associated to the paleoenvironmental perturbations recorded across the T-OAE. In this PhD thesis I present a high-resolution calcareous nannofossil biostratigraphy of three cores drilled in the Lombardy Basin (Sogno Core) and in the Lower Saxony Basin (L1 and Schandelah Cores), covering the lithological expression of the T-OAE in the Tethyan and Boreal realms. Events recognized across the Sogno Core allow the detection of three biozones (NJT5a, NJT5b and NJT6) whereas those recognized in the L1 and Schandelah Cores result in the identification of three zone/subzones (NJ5b, NJ6 and NJ7). These results are integrated with data from literature in order to derive a solid framework of primary and secondary events characterizing the upper Pliensbachian/lower Toarcian interval with a special focus on the Pliensbachian/Toarcian boundary and the characterization of the T-OAE in the Tethyan and Boreal realms. For the Tethyan sections (Italy, South-East Spain, South France, Greece and Hungary) the primary events include the FOs of Lotharingius sigillatus, Carinolithus poulnabronei, Lotharingius crucicentralis, Carinolithus superbus sceptrum, Watznaueria sp. 1, Discorhabdus striatus, Schizosphaerella crisis and LO of Mitrolithus jansae while the FOs of Lotharingius velatus and Discorhabdus ignotus are considered within the secondary ones. Likewise, for the Boreal Realm (sections in Central-North France, England and Germany), my synthesis resulted in the separation of primary events including the FOs of Crepidolithus impontus, L. sigillatus, C. superbus sceptrum, D. striatus and LOs of Crucirhabdus primulus and Biscutum finchii from the secondary ones comprising the FOs of L. crucicentralis, L. velatus, D. ignotus, C. poulnabronei, Watznaueria sp. 1, Schizosphaerella crisis and LOs of Crepidolithus granulatus, Parhabdolithus liasicus and Biscutum grandis. My study revealed that the FO of C. superbus sceptrum is the only event reproducible at a supraregional level and confirmed that the Pliensbachian/Toarcian boundary is approximated by the FOs of L. sigillatus (slightly below) and C. poulnabronei (slightly above) in the Tethyan Realm and by the LO of C. primulus in the Boreal. At lower latitudes (sections in Italy, South-East Spain, South France, Greece and Hungary), my study revealed that the T-OAE is well constrained by the FOs of C. superbus sceptrum and the “Schizosphaerella crisis” at the onset and by the LO of M. jansae at its termination. These events are reproducible in Portugal, with the addition of the FCO of D. ignotus marking the termination of the event. At higher latitudes (sections in Central-North France, North Spain, England and Germany) my study confirms that the onset of the T-OAE is constrained by the FO of C. superbus sceptrum. Secondary events, not reproducible in North Spain, are the “Schizosphaerella crisis” at the onset of the T-OAE and the LOs of C. granulatus, B. finchii, P. liasicus and B. grandis within the carbon isotope excursion characterizing the T-OAE. Morphometric analyses conducted on Carinolithus superbus and Carinolithus magharensis specimens allow to clarify taxonomic discrepancies regarding the two taxa. Qualitative investigations performed on Carinolithus cantaluppii revealed that this taxon is a diagenetic artefact of the genus and, therefore, that this species must be rejected. Implications for biostratigraphy and evolutionary trends are discussed.

[Truncated abstract] The Northern Bonaparte Basin and adjacent Darwin Shelf form part of a major petroleum province on the northwestern margin of Australia. The middle to Late Cretaceous Bathurst Island Group consists of siliciclastic and pelagic carbonate strata that form the regional seal to underlying Upper Jurassic and Lower Cretaceous reservoir sandstones. The Bathurst Island Group has previously been subdivided into four stratigraphic sequences or ‘play intervals’ bound by regional disconformities in the Valanginian (KV horizon), Lower Aptian (KA horizon), upper Lower Cenomanian (KC horizon), Middle Campanian (KSC horizon), and at the CretaceousPaleocene boundary (T horizon). Correlation of these sedimentary packages and stratigraphic surfaces requires high-resolution calcareous microfossil biostratigraphy, while palaeobathymetric determinations based on benthonic foraminiferal assemblages are important for determining the subsidence history of the area and relative sea-level changes. This study presents the first detailed stratigraphic distributions, taxonomic lists and illustrations of foraminifera and calcareous nannofossils from the Bathurst Island Group of the Northern Bonaparte Basin and Darwin Shelf. A biostratigraphic framework has been constructed for the study area incorporating ‘standard’ (Tethyan) Cretaceous planktonic foraminiferal and calcareous nannofossil events where applicable, and integrating locally defined events where necessary. This framework allows Cretaceous strata to be correlated regionally across the study area and to the global chronostratigraphic scale. Correlation of the Northern Bonaparte Basin and Darwin Shelf strata to the Cretaceous Stages and international time scale is based on recent ties of nannofossil and foraminiferal events to macrofossil zones and palaeomagnetic polarity chrons at ratified and proposed Global Stratotype Sections and Points (GSSPs). Calcareous nannofossil events recorded in the study area that are critical for defining stage boundaries include the lowest occurrences of Prediscosphaera columnata, Micula decussata, Lithastrinus grillii, and Aspidolithus parcus parcus, and the highest occurrences of Helenea chiastia, Lithastrinus moratus, Aspidolithus parcus constrictus, and Eiffellithus eximius. Important planktonic foraminiferal events for correlation include the lowest occurrences of Rotalipora gr. globotruncanoides, and Dicarinella asymetrica, and the highest occurrences of Planomalina buxtorfi, Rotalipora cushmani, and Dicarinella asymetrica. During the middle to Late Cretaceous the Northern Bonaparte Basin and Darwin Shelf occupied mid-high palaeolatitudes between 35ºS to 45ºS. These palaeolatitudes are reflected in the transitional character of the planktonic microfossil assemblages, which combine elements of the low-latitude, warm-water Tethyan Province to the north and the cool-water high-latitude Austral Province to the south. ‘Standard’ Tethyan zonations are most applicable for uppermost AlbianMiddle Campanian strata because equator-to-pole temperature gradients were weakly developed, and global climate was warm and equable during this interval. These conditions resulted in broad latitudinal distributions for Tethyan marker species, and consequently most UC calcareous nannofossil zones and European-Mediterranean planktonic foraminiferal zones are recognised. In contrast, the EarlyLate Albian and the late Middle CampanianMaastrichtian were intervals of greater bioprovinciality and stronger palaeotemperature gradients. In these intervals application of the Tethyan zonations is more difficult, and a number of the Tethyan biostratigraphic markers are absent from the study area (e.g. Ticinella species in the Albian and Radotruncana calcarata in the Late Campanian). Cretaceous palaeobathymetric reconstruction of the study area is based on comparison of the foraminiferal assemblages with those of previous Cretaceous palaeobathymetric studies. Marginal marine assemblages consist solely of low diversity siliceous agglutinated foraminifera (e.g. Trochammina). Inner and middle neritic water depths (0-100 m) contain rare to common planktonic foraminifera (mainly globigerine forms), robertinids (e.g. Epistomina), siliceous agglutinates, lagenids, buliminids (e.g. Neobulimina), and rotaliids. The outer neritic zone (100-200 m water depth) contains abundant planktonic foraminifera (keeled and globigerine), calcareous agglutinates (e.g. Dorothia), and diverse lagenids, buliminids, and rotaliids. Upper-middle bathyal water depths (200-1000 m) are characterised by abundant planktonic foraminifera, common siliceous agglutinated taxa (e.g. Glomospira), rare to common Osangularia, and globular species of Gyroidinoides, Pullenia, and Paralabamina.