Rotalipora Cushmani Zone Research Articles

Quantitative analysis and paleoenvironmental reconstruction of the middle Cenomanian deposits from southern Bellezma-Batna Mountains (northeastern Algeria)

The middle Cenomanian deposits of the southern part of the Bellezma-Batna Mountains, northeastern Algeria, have been investigated to evaluate the response of Foraminifera to variations of paleo-bathymetry, oxygen, and salinity. The Djebel Azeb section, with a thickness of 40 m, is composed of a clay-marl mass interspersed with lumachellic limestone layers. It makes up the middle part of the ‘’Marnes de Smail’’ Formation. The Turrilites acutus Subzone of the upper part of the Acanthoceras rhotomagense Zone corresponds to the Aspidiscus cristatus Total Range Zone, and the Rotalipora cushmani Zone was recognized based on the study of ammonites, scleractinian and planktic foraminifera in this section. The statistical analysis of the foraminifera yielded only one assemblage of planktic foraminifera with globular chambers and trochospiral test belonging to the Cenomanian–Turonian; no association is typically restricted to the middle Cenomanian. The benthic foraminifera are poorly represented, belonging to the orders Textulariina, Lituolina, Trochamminina, Verneuilinina, Loftusiina, Orbitolinina, Miliolina, and Rotaliina. These foraminifera assemblages indicate that the bottom-water conditions during the middle Cenomanian were characterized by periodic changes in the oxygen and salinity. All planktic foraminifera species are opportunists related to poorly oxygenated, eutrophic conditions interspersed by a short interval of well-oxygenated environment with Planolites. The maximum abundance of Whiteinella and Muricohedbergella and the minimum amount of Planoheterohelix species within the Cenomanian of Djebel Azeb reflect dwindling palaeosalinity during this time, except for a slight increase in the middle of the section. Keywords: Foraminifera, corals, biostratigraphy, oxygen, salinity, Cretaceous.

Planktonic foraminiferal biostratigraphy and palaeobiogeography of the Albian–Turonian succession from the Sulaiman Range, Pakistan

Detailed taxonomy and biostratigraphy of the limestone, shale‐rich Cretaceous Goru Formation within the western Sulaiman Range refer to diverse and well‐preserved planktonic foraminifera. The age‐diagnostic planktonic foraminifera encountered are; Biticinella breggiensis (middle Albian), Rotalipora ticinensis (late Albian), Rotalipora appenninica (latest Albian), Rotalipora brotzeni (early Cenomanian), Rotalipora cushmani (late Cenomanian), Whiteinella archeocretacea (latest Cenomanian–Earliest Turonian), Helvetoglobotruncana helvetica (early to middle Turonian), and Marginotruncana sigali (late middle to late Turonian). Based on the recovered planktonic foraminifera a middle Albian–late Turonian age has been assigned to the studied formation. The Rotalipora reicheli (middle Cenomanian) Zone was not identified as the First Appearance Datum of the nominal taxa present within the Rotalipora cushmani Zone. The planktonic foraminiferal assemblage characteristics suggest that the bioprovince of the Cretaceous Goru Formation belongs to the subtropical, warm water environment belonging to the Cretaceous Tethyan Realm and the palaeobiogeographic reconstruction suggests that the Neotethys was well‐connected during the Albian–Turonian time interval.

Benthonic foraminiferal response to the Cenomanian-Turonian boundary event in the Ganuza section, northern Spain.

The studied interval comprises a 26.5 m thick section of the uppermost Cenomanian strata representing the uppermost Rotalipora cushmani and lowermost Whiteinella archaeocretacea Zones. Changes in the foraminiferal assemblages recorded in this interval may be summarized as follows: l. P/B ratio fluctuates throughout the section; the highest values (78 %) are recorded in the lowermost part of the Whiteinella archaeocretacea Zone. 2. Benthonic diversity in the Ganuza section varíes from 9 to 27 with decreasing tendency up the section. Highest number of species (16-27) in the studied interval is observed in the Rotalipora cushmani Zone while 9 to 14 species are found in the Whiteinella archaeocretacea Zone. 3. Stepped extinctions of foraminiferal species were recorded - two planktonic Rotalipora greenhomensis and R. cushmani and several benthonic, e.g. Gavelinella baltica, Conorbina sp., rosalinids, Gubkonella graysonensis and Textularia chapmani went extinct during latest Rotalipora cushmani and earliest Whiteinella archaeocretacea chrons; several species disappeared temporarily, e.g. Praebulimina elata; they reappeared in the Lower Turonian; sorne others e.g. Lingulogavelinella globosa, Gavelinella plummerae appeared after the extinction of Rotalipora greenhomensis and become very abundant in the upper part of the studied interval; there is also a group of species present in the entire section which dominated assemblages in the middle and upper part of the studied section, e.g. Gaudryinella pusilla, Lenticulina rotulata or Gavelinella berlhelini.

Latest Albian-earliest Turonian deep-water agglutinated foraminifera in the Bottaccione section (Gubbio, Italy) - Biostratigraphic and palaeoecologic implications.

Using semi-quantitative methods, the distribution of deep-water agglutinated foraminifera (DW AF) was analyzed within the Latest Albian-earliest Turonian pelagic limestones of the famous Bottaccione standard section. The characteristic bathyal communities include forms of purely agglutinated "flysch-lype" assemblages and elements which are typical of Upper Cretaceous abyssal environments of the North Atlantic. Well-established planktonic foraminiferal and calcareous nannofossil zonations allowed to directly gauge the stratigraphic ranges of DW AF, contributing to a better chronostratigraphic calibration of a deep-water agglutinated foraminiferal zonation. Differences in ranges of sorne biostratigraphic marker species were observed. The distribution of morphogroups enabled us to interpret levels of oxygenation and organic input. The effects of the Cenomanian-Turonian boundary event (here represented by the ichtyolithic-bituminous-radiolaritic Livello Bonarelli) on the DW AF were explored in detail. A major faunal change in agglutinated foraminiferal communities consisting of a marked decrease in faunal density and species richness was recognized in the middle of the Rotalipora cushmani Zone coinciding with a marked change in sedimentary regimes and related to extensive oxygen depletion on the sea bottom.

BIOSTRATIGRAPHY AND SEDIMENTARY ENVIRONMENTS OF THE LOWER/UPPER CRETACEOUS BOUNDARY DEPOSITS BY SMALL FORAMINIFERA (PIENINY KLIPPEN BELT, UKRAINIAN CARPATHIANS)

The Pieniny Klippen Belt extends 600 km from the Slovakian Carpathians to the Romanian Carpathians. The Pieniny KIippen Belt narrows in the Ukrainian Carpathians. It is called the Pieniny Zone here. The Cretaceous succession of the Pieniny KIippen Belt in the Ukrainian Carpathians consists of the upper part of the Svalyava Formation (Titonian- Neocomian), Tyssalo Formation (Aptian-Senomanian), Puchov Formation (Turonian-Maastrichtian) and Yarmuta Formation (Maastrichtian). This succession is overlapped by the Eocene Vylhivchyk Formation with angular uncomformity. The Lower/Upper Cretaceuous boundary sediments of the Pieniny KIippen Belt in the Ukrainian Carpathians is located in the Tyssalo Formation. The paper presents the results of the analysis of foraminifera from the marls of the Tysalo Formation developed in the Tysalo tract, in the sections of the Tereblya and Luzhanka rivers, in the quarries of Perechyn and Pryborzhavske villages (Transcarpathians region). 27 species of foraminifera were identified in this study in the age range of Late Albian — earliest Turonian including 15 planktonic species and 4 benthic species. The biostratigraphic succession of foraminiferal subdivisions ranging from late Albian to Senomanian is identified. Upper Albian-Senomanian sediments of the Tyssalo Formation are divided into three lithological members. The lower member consists of black limestones and marls with dark grey limestones which correspond to early Late Albian. The middle member is represented by gray and gray-green marls with gray siltstones and sandstones which correspond to middle Late Albian. The upper member consists of light green-gray marls with pink marls which correspond to late Late Albian-Senomanian. The Hedbergella gaultina Zone (late Late Albian), Pseudothalmanninella ticinensis Zone (middle Late Albian) and Parathalmanninella appeninica Zone (late Late Albian) were identified in the Tyssalo Formation both by previous researchers and in the material presented. The layers with Thalmanninella globotruncanoides (early Senomanian), Thalmanninella reicheli Zone (middle Senomanian) and Rotalipora cushmani Zone (later Senomanian) are established in the Tyssalo Formation for the first time. The Lower/Upper Cretaceous boundary corresponds to the boundary between the Parathalmanninella appeninica Zone and the layers with Thalmanninella globotruncanoides, which are not found in the same section due to the intense deformation of the deposits in the Pieniny KIippen Belt. Changes in the generic composition of planktonic foraminifera in the boundary deposits of the Lower and Upper Cretaceous of the Tysalo Formation are gradual, from the dominance of small Biglobigerinella, Globigerinelloides, Hedbergella, Ticinella in the Upper Albian to the bloom of large complex-built Pseudothalmanninella, Rotalipora, Thalmanninella, Parathalmanninella, Praeglobotruncana Pseudothalmanninella, Rotalipora, Thalmanninella, Parathalmanninella, Praeglobotruncana in the Senomanian. The black marls of the lower member contain pyritized foraminifers, so it can be assumed that they were formed in oxygen-deficient botton-water conditions (early Late Albian). In the middle member change in the color of sediments from black to gray and green and the presence of calcareous benthic foraminifera belonging to genera Parella, Anomalina, Pleurostomella, Gavelinella indicate an improvement in oxygen conditions in bottom waters (middle Late Albian). The marl of the upper member is dominated by (70-100% of associations) planktonic foraminifera mainly from the genera Parathalmanninella, Rotalipora, Thalmanninella, Praeglobotruncana, which indicates the depth of the middle batial (late Late Albian-Senomanian).

Palaeoecology and facies analysis of benthic communities in mid-Cretaceous successions in the Sinai platform, Egypt

Within the Aptian-Cenomanian formations of Sinai successions in Egypt, lateral and vertical changes occur in the numerous benthic communities. Microbenthos such as Orbitolina foraminifera and calcareous algae are widespread in the Aptian-Albian deposits in North Sinai, whereas oysters and gastropods are common in the Cenomanian siliciclastic deposits in South Sinai. In order to establish the biostratigraphy, 90 benthic and planktonic foraminifera species have been identified from the studied succession. Based on the stratigraphic distribution of the identified species the studied succession could be subdivided into three planktonic foraminiferal zones: Pseudothalmanninella ticinensis zone (Late Albian), Rotalipora cushmani zone (Middle-Late Cenomanian), and Whiteinella archaeocretacea zone (Late Cenomanian-Early Turonian). This work discusses the first record of the Albian dasycladalean alga Holosporella sugdeni (Elliott) from Sinai and reports on Montiella elitzae (Bakalova) from the Albian Risan Aneiza Formation. The occurrence of Orbitolina (Conicorbitolina) conica distinguished the Albian-Cenomanian boundary in the North Sinai sequences. The benthic communities of the studied successions indicated a faunal shift from an algal-orbitolinid foraminifera community around the Aptian-Early Albian to a rudist community during the Middle Albian and an oyster-gastropod community during the Cenomanian. This faunal shift coincided with the major sea transgression that covered North Sinai until the Middle Albian and reached South Sinai during the Cenomanian. The identified Cenomanian gastropods included Neoptyxis olisiponensis, Nerinea gemmifera, and Tylostoma bussoni. Many oyster species distinguished the Cenomanian deposits, such as Ceratostreon flabellatum, Rhynchostreon mermeti, Rhynchostreon suborbiculatum, and Costagyra olisiponensis. Identifying the benthic fauna and facies indicated a shallow inner to middle ramp environment. Stable carbon and oxygen isotope data from the Cenomanian oyster shells indicate an inner ramp environment. Comparing the carbon isotope values of the oysters with those previously recorded from the rudists may explain the different trophic levels of both groups.

Cenomanian and lower Turonian relative chronology and palaeoenvironmental framework of the Nouader site (Aures Basin, Northeastern Algeria)

AbstractThe lower–upper Cenomanian boundaries interval of the Nouader site in the Aures Basin (NE Algeria) has been studied for the first time using the association of two particularly effective taxonomic groups, one macrofossil (ammonites), and the other microfossil (foraminifera). The study section is divided into two formations (Fahdene and Bahloul) and one member (Annaba). Biostratigraphicaly, six ammonite biozones and five foraminiferan biozones were identified and calibrated. The ammonite fauna allows recognition of the lower CenomanianMantelliceras mantelliZone, the upper lower CenomanianMantelliceras dixoniZone, the succeeding lower middle CenomanianCunningtoniceras inermeZone, theAcanthoceras rhotomagenseZone and its subzones ofTurrilites costatusandTurrilites acutus, followed by the upper middle CenomanianAcanthoceras amphibolumZone, the lower upper CenomanianEucalycoceras pentagonumZone and finally the lower TuronianPseudaspidoceras flexuosumZone. The foraminiferan biozones are respectively:Thalmanninella brotzeniZone,Thalmanninella reicheliZone,Rotalipora cushmaniZone,Whiteinella archaeocretaceaZone andHelvetoglobotruncana helveticaZone. Among 14 ammonite zones in the Tethyan domain versus 11 in the Boreal domain, seven are common to both domains. For the planktonic foraminifera the Tethyan domain has five zones, the Boreal domain also has five, with five in common. The succession of index species occurs in the same order in both Tethyan (NE Algeria and Central Tunisia) and Boreal realms (East and NW Europe). Furthermore, the supposed depositional setting is interpreted as a calm and relatively deep environment which can be located around the middle to the external platform.

Planktonic foraminifera biozones and isotope stratigraphy of the Cenomanian-Turonian boundary in the western part of the Kopet-Dagh Basin, NE Iran

A biostratigraphic study based on the planktonic foraminifera and isotope stratigraphy of the Cenomanian-Turonian interval has been undertaken in the western part of the Kopet-Dagh Basin (NE Iran). In this research, two stratigraphic sections including: Maraveh Tappeh and Qareh Galdy have been sampled and studied. Based on planktonic foraminifera, three biozones were assigned to this interval. These are the Rotalipora cushmani Zone, Whiteinella archaeocretacea Zone and Helvetoglobotruncana helvetica Zone, These biostratigraphic data confirm a gradual faunal turnover of planktonic foraminifera, at the Cenomanian-Turonian boundary in Whiteinella archaeocretacea Zone characterized by: absences, low abundance and disappearances of complex morphotypes. After this event, in Helvetoglobotruncana helvetica Zone, along with simple globular chamber morphotypes, single keeled and double-keeled morphotypes appeared and flourished.The carbon-isotope curves in both sections, record a negative shift values below the Aitamir-Abderaz formations boundary in Whiteinella archaeocretacea Zone, and then, a positive excursion of about 5.50‰, along with several fluctuations are well evident in both sections. The δ18O values show, from the bottom to the top, a gradual increase of averagely 2‰. Based on these results, the Cenomanian-Turonian succession in this part of the Kopet-Dagh Basin is continuous and corresponds to the siltstone and chalky limestone layers of the upper part of the Aitamir Formation and the lower part of the Abderaz Formation.

Integrated stratigraphy, facies analysis and correlation of the upper Albian–lower Turonian of the Esfahan area (Iran): Unravelling the conundrum of the so-called “Glauconitic Limestone”

The so-called “Glauconitic Limestone of Esfahan” is a thin (<4 m) but very conspicuous lithological unit that is well known for its late Albian to middle Cenomanian ammonite faunas. However, it consists of two genetically unrelated stratigraphical units: the lower part commonly comprises fine-grained bioclastic limestones that are poor in macrofossils and rest with a sharp basal surface on mid-upper Albian strata of the deep-marine Bazyab Formation; the microbiostratigraphy shows this part to be mid-late Albian in age (Pseudothalmanninella ticinensis Zone), thus constituting a lithostratigraphical equivalent of the lower Debarsu Formation. The upper part of the “Glauconitic Limestone” consists of a fossiliferous glauconitic conglomerate with large rounded limestone pebbles to boulders and phosphatized bio-/lithoclasts, yielding the famous ammonite faunas of the unit. It has a major erosional unconformity at its base that may cut out the Debarsu Formation over short distances and it shows a fining-upward trend grading into an overlying marl and argillaceous limestone unit. These observations demonstrate that the glauconitic conglomerate initiated a new depositional cycle and is thus genetically related to the overlying fine-grained strata. Consequently, the glauconitic conglomerate is regarded as the basal Takhte-Sheitan Member (new) of the Kolah-Qazi Formation (new), formalized herein. The matrix of the upper part of the Takhte-Sheitan Member could be dated as mid-late Cenomanian (upper Rotalipora cushmani Zone) and the overlying fine-grained offshore deposits of the Kolah Qazi Formation as latest Cenomanian to early Turonian by means of foraminifera, ammonites, inoceramid bivalves and carbon stable isotopes. Thus, the late Albian to middle Cenomanian phosphatized ammonites from the Takhte-Sheitan Member are derived, i.e., represent classic remanié faunas. The Takhte-Sheitan Member is regarded as a complex, condensed transgressive lag onlapping a considerable palaeotopography after a late mid- to early late Cenomanian tectonic event. The overlying marl and argillaceous limestones of the Kolah-Qazi Formation indicate a considerable deepening in response to a major eustatic sea-level rise and highstand across the Cenomanian–Turonian boundary associated by increased organic carbon burial related to the oceanic anoxic event (OAE) 2. The carbon stable isotope curve from the base of the Kolah-Qazi Formation (Takhte-Sheitan Member) up-section into the marls and argillaceous limestones shows the conspicuous structure of the major positive excursion of the OAE 2 and serves as precise tool for the high-resolution chemostratigraphic calibration of the Iranian sections. It provides a new reference curve for the OAE 2 in the Middle East.

Planktonic foraminiferal biostratigraphy and assemblage composition across the Cenomanian–Turonian boundary interval at Clot Chevalier (Vocontian Basin, SE France)

The Cenomanian–Turonian boundary interval is generally considered a critical time for planktonic foraminifera due to the environmental perturbations associated with Oceanic Anoxic Event 2. However, only the rotaliporids became extinct at the onset of the event, whilst several lineages evolved and/or diversified. This remarkable morphologic plasticity is often overlooked in the literature, partly because a number of stratigraphic sections have only been studied in thin-section due to the degree of lithification of the samples. Improved documentation of the morphological variability of planktonic foraminifera and better defined species concepts are required in order to improve biostratigraphy, particularly as Helvetoglobotruncana helvetica is an unreliable marker for the base of the Turonian. At the same time, detailed study of the planktonic foraminiferal response to OAE 2 demands a more profound knowledge of the assemblage composition.We present new biostratigraphic, taxonomic, and quantitative data for planktonic foraminiferal species from the Clot Chevalier section (Vocontian Basin, SE France), with the aim of (1) providing a detailed biostratigraphic analysis of the section, (2) documenting the morphological plasticity of specimens in this time interval and stabilizing species concepts, and (3) identifying promising markers to improve the resolution of the present biozonation and allow regional correlation. Samples were processed with acetic acid to extract isolated planktonic foraminifera. Assemblages were assigned to the upper Cenomanian Rotalipora cushmani Zone and to the uppermost Cenomanian–lowermost Turonian Whiteinella archaeocretacea Zone. Planktonic foraminiferal bioevents and assemblage composition identified at Clot Chevalier are compared with the well-studied Pont d'Issole section located ca. 15 km to the NE, highlighting similarities and differences in the species occurrences that may complicate the stratigraphic correlation between the two sections.The results of our study support the validity and common occurrence of species that have been misidentified and/or overlooked in the literature (i.e., Dicarinella roddai, Praeglobotruncana oraviensis, Marginotruncana caronae) and indicate that primitive marginotruncanids evolved before the onset of OAE 2, although species diversification occurred only after the event. Moreover, we believe that the first appearance of P. oraviensis might represent a promising bioevent for approximating the Cenomanian/Turonian boundary, after calibration with bio- and chemostratigraphically well-constrained sections. Finally, we describe three new trochospiral species, named “Pseudoclavihedbergella” chevaliensis, Praeglobotruncana pseudoalgeriana and Praeglobotruncana clotensis.

EVOLUTION AND PHYLOGENY OF MID-CRETACEOUS (ALBIAN-CONIACIAN) BISERIAL PLANKTIC FORAMINIFERA

Research Article| January 01, 2015 EVOLUTION AND PHYLOGENY OF MID-CRETACEOUS (ALBIAN–CONIACIAN) BISERIAL PLANKTIC FORAMINIFERA Shannon J. Haynes; Shannon J. Haynes 3 1Department of Geological Sciences, University of Missouri, 101 Geology Building, Columbia, MO 65211, USA 3Correspondence author. E-mail: sjh2c4@mail.missouri.edu Search for other works by this author on: GSW Google Scholar Brian T. Huber; Brian T. Huber 2Department of Paleobiology, MRC 121, Smithsonian Museum of Natural History, Washington, D.C. 20013, USA Search for other works by this author on: GSW Google Scholar Kenneth G. Macleod Kenneth G. Macleod 1Department of Geological Sciences, University of Missouri, 101 Geology Building, Columbia, MO 65211, USA Search for other works by this author on: GSW Google Scholar Journal of Foraminiferal Research (2015) 45 (1): 42–81. https://doi.org/10.2113/gsjfr.45.1.42 Article history received: 04 Nov 2013 accepted: 18 Aug 2014 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Shannon J. Haynes, Brian T. Huber, Kenneth G. Macleod; EVOLUTION AND PHYLOGENY OF MID-CRETACEOUS (ALBIAN–CONIACIAN) BISERIAL PLANKTIC FORAMINIFERA. Journal of Foraminiferal Research 2015;; 45 (1): 42–81. doi: https://doi.org/10.2113/gsjfr.45.1.42 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyJournal of Foraminiferal Research Search Advanced Search Abstract In this paper we critically examine the biostratigraphy and systematics of late Albian–Coniacian biserial planktic foraminifera using measurements and qualitative observations from SEM and X-radiograph images of exquisitely preserved specimens from hemipelagic sediments of southeast Tanzania, augmented by analogous observations of selected Ocean Drilling Program samples and holotypes and paratypes of nearly all species. We document interspecific differences and intraspecific variability, and propose a revised phylogeny for Cretaceous biserial planktic foraminifera placed within a refined biostratigraphic framework. Taxonomic emendations are proposed for the genera ProtoheterohelixGeorgescu & Huber, 2009, and PlanoheterohelixGeorgescu & Huber, 2009, and for the species Pr. washitensis (Tappan, 1940), Pr. obscuraGeorgescu & Huber, 2009, Pl. moremani (Cushman, 1938), Pl. reussi (Cushman, 1938), and Laeviheterohelix reniformis (Marie, 1941). In addition, a neotype is designated for Pl. globulosa (Ehrenberg, 1840), and Pl. praenuttalli n. sp. is described. Biserial speciation events are recognized in the planktic foraminiferal Rotalipora cushmani Zone (latest Cenomanian), Helvetoglobotruncana helvetica Zone (early Turonian), and at the Helvetoglobotruncana helvetica-Marginotruncana schneegansi zonal boundary (middle Turonian). You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The stratigraphic setting of cretaceous volcanic rocks in Crimea and in the North Caucasus

The ages of volcanic activity in the Crimea and North Caucasus are reported in this paper. The age estimation of the described ranges is based on the results of micropaleontological analysis (planktonic Foraminifera) with account for the data on other groups, mostly Ammonites and Inoceramids. Volcanic rocks are related to the Upper Albian (Thalmanninella appenninica Zone), Lower Cenomanian (Thalmanninella globotruncanoides Zone) deposits, boundary deposits of the Lower and Middle Cenomanian (Thalmanninella deeckey Zone), and Middle-Upper Cenomanian (Rotalipora cushmani Zone). Volcanic activity was found for the Campanian Stage (Globotruncanita elevate and Globotruncana ventricosa) as well.

Siliceous and organic-rich sedimentation during the Cenomanian–Turonian Oceanic Anoxic Event (OAE2) on the northern margin of Africa: an evidence from the Bargou area, Tunisia

The late Cenomanian–early Turonian deposits in Tunisia recording the OAE2 event are commonly attributed to the Bahloul Formation. These deposits are composed of dark clayey limestone and organic-rich black shales with abundant planktic foraminifera. At the Bargou area, Oued Kharroub section, these organic-rich deposits include siliceous beds with abundant radiolarians recalling the “Livello Bonarelli”. A total of 25 radiolarian species are identified with a maximum of 18 species per sample. Moreover, the species skeleton preservation is usually poor to moderate in the most studied samples [estimated preservation index (PI) values ranging between 4 and 6]. Two successive assemblages are distinguished. The oldest one (RI) is dominated by nassellarians, which includes mainly Stichomitra, Pseudodictyomitra and Rhopalosyringium genera. It is included within the upper part of foraminiferal Rotalipora cushmani Zone and lower part of Whiteinella archaeocretacea zone. In contrast, the youngest assemblage (RII), which belongs to the upper part of the W. archaeocretacea zone and the earliest Turonian Watinoceras ammonite assemblage, is dominated by spumellarians and includes mainly Archaeocenosphaera, Cavaspongia, Pseudoeucyrtis and Pyramispongia genera. In addition, major and trace elements are analysed to test whether the geochemical record was synchronous to the biotic event or not. Thus, selected crossplots, Al2O3 vs. SiO2 and Al2O3 vs. TiO2, are used to evaluate the detrital input, and V/Cr vs. V/(V + Ni) and U/Th vs. V/(V + Ni) are used to evaluate the bottom redox conditions and the primary productivity within the Bahloul Formation. A strong Si/Al increase is marked in the lower part of the siliceous and organic-rich Bahloul Formation that could be explained by a local increase in upwelling-related biogenic SiO2 (silica-secreting organisms). Relative low abundance of terrigenous-related Ti/Al and K/Al ratios and enrichment of some productivity proxies such as Ba (organic matter related trace elements) suggests that the Bahloul was of relatively elevated primary productivity and minimal detrital input. Enrichments in redox-sensitive trace metals U and V in the Bahloul Formation deposits and redox indices, such as V/(V + Ni), U/Th and V/Cr, indicate that oxygen-restricted conditions prevailed during the late Cenomanian–earliest Turonian times and correlate well with relative abundances of some radiolarian and foraminiferal paleo-environmental indicators. In addition, indicators of detrital flux variations are used. Al2O3 shows a slight positive correlation with TiO2 and a less distinct correlation with SiO2.

Stratigraphy of the Dokan Formation (Upper Cretaceous) JebelAzmer- Sulaimaniya Area, Northeastern Iraq

Contrary to the present opinion regarding the Balambo Formation exposed in Jebel Azmer, Sulaimaniya area, northeastern Iraq, this study shows that the upper part (63 m) of the Balambo succession actually belongs to the Dokan Formation. The major hiatus between the lower part of the succession which represents the Balambo Formation and the upper part of the succession which we claim to represent the Dokan Formation together with the lithological differences give strong reason to characterize the studied section as the Dokan Formation. Dokan Formation in the studied section consists of light brown and white massive not well bedded limestone. Nineteen planktonic foraminiferal species have been identified from this section. The age of the Dokan Formation in the Jebel Azmer area is Middle - Late Cenomanian and is assigned to Rotalipora cushmani Zone; this indicates a major hiatus between the Dokan Formation and the older Balambo Formation of Middle-Late Albian age in this area.

Substrate of Bivalve Borers as Recorded on Phosphatic Fills of Gastrochaenolites, Palaeoenvironmental Context (Bohemian Cretaceous Basin, Czech Republic)

Phosphatized Gastrochaenolites fills, derived from the rocky-coast facies of the Late Cenomanian age of the Bohemian Cretaceous Basin, comprised specimens with smooth and ribbed surfaces and with Fremdskulpturen. The ribbing may be simple or complex and its origin interpreted as a function of substrates. Close examination of accessible substrates indicates that oyster and/or gastropod shells are the most probable hosts of respective tracemakers. The formation of borings preceded a phosphogenic episode and subsequent destruction of bored substrates and a release and reworking of phosphatized fills. This scenario functioned during the Rotalipora cushmani Zone or a little earlier, and in part anew during the Praeactinocamax plenus Zone of the Late Cenomanian. Phosphatized fills thus represent the reworked relics of phosphogenic products preserved in basal parts of two successive transgressive sets of sediments that followed the settings with phosphogenesis.

Yaxcopoil-1 and the Chicxulub impact

CSDP core Yaxcopoil-1 was drilled to a depth of 1,511 m within the Chicxulub crater. An organic-rich marly limestone near the base of the hole (1,495 to 1,452 m) was deposited in an open marine shelf environment during the latest Cenomanian (uppermost Rotalipora cushmani zone). The overlying sequence of limestones, dolomites and anhydrites (1,495 to 894 m) indicates deposition in various carbonate platform environments (e.g., sabkhas, lagoons). A 100-m-thick suevite breccia (894–794 m) identifies the Chicxulub impact event. Above the suevite breccia is a dolomitic limestone with planktic foraminiferal assemblages indicative of Plummerita hantkeninoides zone CF1, which spans the last 300 ky of the Maastrichtian. An erosional surface 50 cm above the breccia/dolomite contact marks the K/T boundary and a hiatus. Limestones above this contact contain the first Tertiary planktic foraminifera indicative of an upper P. eugubina zone P1a(2) age. Another hiatus 7 cm upsection separates zone P1a(2) and hemipelagic limestones of planktic foraminiferal Zone P1c. Planktic foraminiferal assemblages of Zone Plc to P3b age are present from a depth of 794.04 up to 775 m. The Cretaceous carbonate sequence appears to be autochthonous, with a stratigraphic sequence comparable to late Cretaceous sediments known from outside the Chicxulub crater in northern and southern Yucatan, including the late Cenomanian organic-rich marly limestone. There is no evidence that these sediments represent crater infill due to megablocks sliding into the crater, such as major disruption of sediments, chaotic changes in lithology, overturned or deep dipping megablocks, major mechanical fragmentation, shock or thermal alteration, or ductile deformation. Breccia units that are intercalated in the carbonate platform sequence are intraformational in origin (e.g., dissolution of evaporites) and dykes are rare. Major disturbances of strata by the impact therefore appear to have been confined to within less than 60 km from the proposed impact center. Yaxcopoil-1 may be located outside the collapsed transient crater cavity, either on the upper end of an elevated and tilted horst of the terrace zone, or even outside the annular crater cavity. The Chicxulub site thus records a large impact that predates the K/T boundary impact and mass extinction.

Cenomanian–Turonian and δ13C, and δ18O, sea level and salinity variations at Pueblo, Colorado

Stable isotopes of the surface dwelling planktic foraminifera Hedbergella planispira, its abundance variations, and mineralogical analysis of the Cenomanian–Turonian at Pueblo, CO, reveal cyclic variations in surface salinity due to changes in precipitation, freshwater influx, marine incursions and long-term sea-level fluctuations. Hedbergella planispira is a proxy for salinity variations, as indicated by 2–4‰ more negative δ 18O values in intervals of peak abundances as compared to intervals with reduced populations. Negative δ 18O values reflect periods of brackish surface waters caused by freshwater influx during wet humid periods, accompanied by increased clastic transport. More positive δ 18O values reflect more normal marine salinities as a result of arid periods and/or marine incursions and correlate with intervals of increased biogenic carbonate deposition. The magnitude of salinity variations during the low sea-level of the Hartland Shale is twice that during the sea-level transgression of the Bridge Creek Limestone. The rapid positive δ 13C shift that marks the onset of Oceanic Anoxic Event 2 (OAE 2) at Pueblo occurred over a period of about 100 ky (93.90–94.00 Ma), and coincided with the major sea level transgression that culminated in the deposition of the basal Bridge Creek Limestone. A positive δ 13C shift also occurred in the Rotalipora cushmani zone prior to OAE 2 and coincided with a sea level rise and enhanced preservation of terrestrial organic matter. The likely cause for OAE 2 is depletion of 12C in the water column as a result of high primary productivity, whereas an earlier R. cushmani zone event was primarily caused by increased input of terrigenous organic matter. Both δ 13C events are associated with enhanced organic matter preservation and anoxic or dysoxic bottom waters.

The Cenomanian–Turonian extinction and oceanic anoxic event: evidence from southern Tibet

Deep shelf locations on the Perigondwanan margin of southern Tibet record a major extinction of foraminifera and calcareous nannoplankton in the latest Cenomanian (top of the Rotalipora cushmani Zone). This is followed by a low diversity survival interval that straddles the Cenomanian–Turonian boundary ( Whiteinella archaeocretacea Zone) during which only low diversity, surface water-dwelling foraminifera and nannoplankton and ‘microfilaments’ are present. Rapid recovery in the early Turonian saw the appearance of new species, the reappearance of many Lazarus species and the reestablishment of a diverse community of planktonic foraminifera that included a range of shallow to deep-water column dwellers. The extinction and survival intervals coincide with the development of dysaerobic facies characterised by small-sized burrows and moderately large-sized framboid pyrite populations. At no time does the water column appear to have become sulfidic. This study indicates that the end-Cenomanian oceanic anoxic and extinction events were also manifested in moderately high southerly palaeolatitudes on the southern margin of the Tethyan Ocean, thereby increasing the known extent of this global event, albeit with the proviso that the ‘anoxic event’ was a dysoxic one.

The mid-Cenomanian Event: prelude to OAE 2

A detailed synthesis of litho- and biostratigraphic investigations of the Cenomanian pelagic limestones of the Scaglia Bianca Formation in the Umbria–Marche Basin shows that the Bonarelli Level, which is the regional sedimentary expression of the OAE 2, represents the climax of a ∼2 Myr-long cycle of black shale deposition that began in the mid-Cenomanian planktonic foraminiferal Rotalipora cushmani Zone. This long-term cycle began with a prominent short-term event, named mid-Cenomanian Event (MCE), which is associated with several changes in the biotic and abiotic records. In particular, a comparison of the available litho-, bio-, and chemostratigraphic data from the Umbria–Marche Basin allows recognition of the MCE based on: (a) a significant change in the sedimentary and tectonic regimes; (b) a reorganisation of planktonic foraminiferal assemblages; (c) a major change in benthic foraminifera; (d) a major turnover in the radiolarian assemblages; (e) a 0.7‰ positive shift in the carbon isotope values; and (f) a positive shift of carbonate Sr/Ca ratio. Moreover, the MCE is preceded (∼400 kyr) by a short-term 0.5‰ negative excursion in the oxygen isotope record. The above mentioned changes in carbon and oxygen isotope values can be confidently correlated over different basins and oceans and seem to occur in correspondence with a major sea-level fall. These lines of evidence define the MCE as an outstanding event associated with large-scale changes in the oceanic structure and palaeoclimate. The MCE and the subsequent cyclical deposition of organic-rich beds serve as a case study to better understand differences and similarities between Mesozoic black shales and Cenozoic sapropels and related palaeoceanographic changes controlled by orbital climate cycles.

Benthonic foraminiferal mass extinction and survival assemblages from the Cenomanian-Turonian Boundary Event in the Menoyo Section, northern Spain

Abstract Foraminiferal response to the Cenomanian-Turonian Boundary Event was studied from a 50 m thick section in Menoyo, northern Spain, representing the uppermost Rotalipora cushmani and Whiteinella archaeocretacea Zones. Taxonomic and stratigraphic studies on benthonic foraminiferal assemblages indicate that the studied section represents mass extinction and survival intervals, with the mass extinction boundary in the lowermost part of the Whiteinella archaeocretacea Zone. Stepped extinction within benthonic foraminifers was observed in the uppermost Rotalipora cushmani Zone. In the late phase of mass extinction several species became extinct (e.g. Gavelinella intermedia-cenomanica-baltica group, Tritaxia pyramidata (Reuss)), some others temporarily disappeared; Lazarus taxa (e.g. Tritaxia tricarinata (Reuss), nodosariids) and progenitor (e.g. Globoratalites sp. 1) taxa appeared. Disaster (e.g. Praebulimina elata ) species along with opportunistic taxa (e.g. Gyroidinoides praestans (Magniez-Jannin), Ammobaculites parvispira Ten Dam) colonized vacated ecospace in the middle part of the survival interval, i.e. in the topmost part of the Rotalipora cushmani Zone. Opportunistic taxa dominated assemblages in the Whiteinella archaeocretacea Zone, i.e. in the higher part of the survival interval. The recorded changes in benthonic foraminiferal assemblages most likely reflect the decline in oxygenation level of the bottom waters at the end of the Rotalipora cushmani Zone and the persistence of these unfavourable conditions in the Whiteinella archaeocretacea Zone.