Planktonic Foraminiferal Zones Research Articles

Correction to: Late Cretaceous–Early Paleogene tectonic events at Farafra-Abu Minqar Stretch, Western Desert, Egypt: results from calcareous plankton

This work depends on integrated high-resolution calcareous plankton nannofossil and foraminiferal biostratigraphic analyses for three Upper Cretaceous-Lower Paleogene successions at Farafra-Abu Minqar area, Western Desert, Egypt. These sections are distributed in a north-south geologic profile as follows: El Aqabat, North Gunna, and Abu Minqar. Lithostratigraphically, four formations are recorded in the study area, namely, Khoman (at base), Dakhla, Tarawan, and Esna (at top). In the north at El Aqabat section, Khoman Formation (carbonate facies) is only represented which changes partially toward the south to Dakhla Formation (siliciclastic facies). In the extreme south at Abu Minqar section, it changes completely into siliciclastic facies of Dakhla Formation. Biostratigraphically, seven calcareous nannofossil and eleven planktonic foraminiferal zones represent the Late Cretaceous-Early Paleogene are identified. Based on the occurrence or missing of these zones accompanied with the field criteria resulted in detecting four tectonic events. These tectonic events took place at the Cretaceous/Paleogene (K/Pg), the Danian/Selandian (D/S), the Selandian/Thanetian (S/T), and the Paleocene/Eocene (P/E) boundaries. These tectonic events are related to the impact of the Syrian Arc System. Four sequence boundaries (SB1, SB2, SB3, and SB4) are defined in the Late Cretaceous-Early Paleogene sequence in the Farafra-Abu Minqar area.

Revision of the planktonic foraminiferal biostratigraphy of the Voirons Flysch (Chablais Prealps, Haute-Savoie, France)

The ages obtained from planktonic foraminiferal assemblages retrieved from two exposures in the Gurnigel Flysch and from the re-examination of similar material gathered by previous researchers from the Voirons Flysch reveal only minor discrepancies with previous studies based on nannofossil biostratigraphy. In contrast, major divergences between this work and previous studies on the Voirons Flysch also based on planktonic foraminifera have been identified. They are generally related to distinct approaches in species classification and the use of different zonal schemes. Based on our data, the age of the Voirons Flysch extends from the Early Eocene (planktonic foraminiferal zone P7) to the Middle Eocene (planktonic foraminiferal zone P12). Contrasting with claims made in earlier studies, no specimen of Late Eocene or Early Oligocene age has been observed in the revised material. However, we cannot exclude a younger age (possibly Late Eocene) for the upper portion of this flysch from which we did not revise any sample. Thus, more research and sampling are needed to resolve this question. The palaeogeographic origin of the Voirons-Wagital complex as well as the sedimentation history of these flyschs need now to be re-evaluated in light of this revised biostratigraphic data.

Morphologic change and evolution of Acarinina sibaiyaensis and its descendants during the earliest Eocene CIE/PETM interval in southern Egypt

Acarinina sibaiyaensis is a very distinctive and short-lived planktonic foraminiferal taxon that is restricted to the temporally short Carbon Isotope Excursion (CIE) interval characteristic of the Paleocene-Eocene Thermal Maximum (PETM) event. It is confined to the planktonic foraminiferal Zone E1 which in southern Egypt corresponds to the Dababiya Quarry Member (DQM). This member yields a complete record of the biotic changes induced by the intense warming during the basal Eocene.Although this distinctive taxon is widely distributed throughout the tropic to the temperate regions, its morphologic changes and phylogenetic relations during the CIE/PETM interval have not yet been documented. The present study discusses and documents the morphologic changes which affected the short-lived Ac. sibaiyaensis probably caused by the extreme warming during the very brief (175–200 ka) CIE/PETM interval in southern Egypt. These morphologic variations are particularly well developed in the middle phosphatic phase (Beds 2 and 3 of the DQM), in which the CIE curve shows its maximum negative shift. The origin, morphology, wall texture, coiling direction and their changes during ontogeny and evolution of Ac. sibaiyaensis during the CIE-PETM interval at Qreiya, Gebel Abu Had, northeast Qena (southern Nile Valley) and Darb Gaga (southeast of Kharga Oasis, southern Western Desert) are described, interpreted and illustrated. During the PETM, numerous intraspecific varieties of Ac. sibaiyaensis are recorded. Several evolutionary lineages are delineated; some of them stay within the morphologic range of Ac. sibaiyaensis, whereas others lead to other excursion taxa i.e. Acarinina africana and Morozovella allisonensis. In addition, forms transitional to taxa which appear in younger horizons than the PETM (younger than Zone E1) are recorded, described and illustrated.

Resolution enhancement of foraminiferal biostratigraphy of the Campanian-Maastrichtian interval: A case study from the Eastern Desert, Egypt

The Campanian-Maastrichtian (C-M) rocks exposed at the Southern Galala Plateau, North Eastern Desert of Egypt are represented by Sudr Formation, which consists of snow white chalky limestone, rich in planktonic and benthonic foraminifera. The major C-M transgression resulted in a deposition of Sudr Formation in outer neritic environment with high diversity and abundance of species, which led to defining nine planktonic foraminiferal zones and establishing the stage boundaries. In comparison with the foraminiferal zones of the GSSP of the C/M boundary, the lowest occurrence of Rugoglobigerina scotti is here considered to be the only marker for this boundary. In contrast, the other species (e.g. Contusotruncana contusa) that used to define this boundary at the GSSP is a diachronous and not save to depend on it in definition of the C/M boundary. Therefore, the present study helps in refinement of the C/M boundary definition not only in the study area, but also elsewhere.

A strontium isotopic, petrographic, and Ostracoda biostratigraphic study of Middle-Late Miocene sequences: implications of record in the Silifke–Erdemli/Mersin, southern Turkey

In this paper, we present new data on Ostracoda micropaleontology, strontium isotopic ages, and petrology of the Miocene sequences in the Silifke–Erdemli area (Mersin/S. Turkey). Ostracods were investigated in the Middle and Late Miocene units, which are composed of clayey limestone and marl levels, reef limestones, and clay. Fifty-six ostracod species were identified, and a total of two initial levels were defined, one beginning in the Langhian stage, and the second at the end of the Serravallian and beginning of the Tortonian stage. The initial level of the Langhian stage is represented by the Carinocythereis, and the end of the Serravallian–beginning of the Tortonian stage is characterized by the initial level of Cyprideis. These levels have also been compared with other regions in the same stratigraphic levels in Turkey (Adana, Antakya, Mut, Denizli, and Antalya regions) and in areas around Turkey (Egypt, Italy, Greece, Croatia, and other Tethys–Paratethys regions). In addition, the levels identified in this study were also correlated to the planktonic foraminiferal zones identified for this region. The ostracod species identified are Carinocythereis at the initial level and subsequently, Cytherella postdenticulata Oertli, Grinioneis haidingeri minor (Ruggieri), Pokornyella deformis minor (Moyes), Carinocythereis antiquata (Baird), and Paracypris polita Sars; also, the other ostracod species are an initial level of Cyprideis followed by Cyprideis seminulum (Reuss), C. torosa (Jones), Cytheridea acuminata acuminata Bosquet, Miocyprideis sarmatica (Zalanyi), Neomonoceratina interiecta Bonaduce, Ruggieri, Russo and Bismuth, Schneidrella dromas (Schneider), and Krithe monosteracensis (Sequenza). Detailed petrographic analyses were carried out on the studied units. This analysis revealed that the reef limestones are composed of sandy intraclast-biomicrites, intra-packed biosparite, intra-packed biomicrite, microintra-packed micrite, and bioclastic-intramicrites; clayey limestones were rare clayey biomicrites and clayey intraclast-biomicrites. The main purpose of the study was to evaluate micropaleontological samples from the Miocene sequence based on ostracods and strontium dating to determine the precise age ranges. The 87Sr/86Sr ratios obtained from three samples of the limestones range between 0.708849 and 0.708902 and between 0.708868 and 0.708902, respectively. The Miocene sequences have been calibrated to range in age from 9.7 to 11.4 Ma via the strontium isotope ratio.

A new species of Cretalamna sensu stricto (Lamniformes, Otodontidae) from the Late Cretaceous (Santonian-Campanian) of Alabama, USA.

Decades of collecting from exposures of the Upper Cretaceous Tombigbee Sand Member of the Eutaw Formation and Mooreville Chalk in Alabama, USA has produced large numbers of isolated Cretalamna (sensu stricto) teeth. Many of these teeth had formerly been assigned to the extinct Late Cretaceous shark Cretalamna appendiculata (Agassiz, 1843), a taxon that is now considered largely restricted to the Turonian of Europe. Recent studies have shed light on the diversity of Late Cretaceous Cretalamna (s.s.) taxa, and here we recognize a new species from Alabama, Cretalamna bryanti. The teeth of C. bryanti sp. nov. appear aligned with the members of the Cretalamna borealis species group, but can be distinguished from these other species by a combination of the following: anterior teeth with a more pronounced and triangular lingual root protuberance, broader triangular cusp, and a taller root relative to the height of the crown; anteriorly situated lateroposterior teeth have a distally inclined or hooked main cusp and more than one pair of lateral cusplets; and lateroposterior teeth have a strong distally hooked main cusp and a root that is largely symmetrical in basal view. At present, C. bryanti sp. nov. is stratigraphically confined to the Santonian/Campanian Dicarinella asymetrica Sigal, 1952 and Globotruncanita elevata Brotzen, 1934 Planktonic Foraminiferal Zones within the Tombigbee Sand Member of the Eutaw Formation and Mooreville Chalk, and teeth have been collected from only four counties in central and western Alabama. The recognition of C. bryanti sp. nov. in Alabama adds to our knowledge on the diversity and distribution of Late Cretaceous otodontids in the region.

Seafloor topography, paleodepth and bottom water conditions in the Miocene Cipero Formation, Southern Trinidad, SE Caribbean Sea

Six well logs and two seismic lines are used to reconstruct the paleo-seafloor surface onto which was deposited the Middle Miocene age Golconda Marl Member (Globorotalia fohsi peripheroronda to G. fohsi robusta planktonic foraminiferal Zones, = Zones N9/M6 to N12/M9) of the Cipero Formation of Trinidad, western tropical Atlantic Ocean, The reconstruction reveals five N-S oriented, south-vergent, reverse thrust fault sheets within the underlying Princes Town Marl Member (Catapsydrax dissimilis through Globigerinatella insueta Zones, N5/M2 – N7/M4) and Retrench Sandstone Member (Globigerinatella insueta planktonic foraminiferal Zone, N7/M4) onto which the Golconda Marl Member was deposited. The occurrence of sandy sections, determined from well-log signatures and illustrated on the reconstructed surface, can be used as an aid in locating potential hydrocarbon reservoirs within the Golconda Marl Member. Micropaleontology is used to infer (a) paleodepth and (b) changing paleoenvironmental conditions throughout the Cipero Formation. Foraminiferal investigation of 21 Cipero Formation samples collected at the La Fortune Anticline (LFA) places the Golconda Marl Member of the Cipero Formation at this site in the Globorotalia fohsi peripheroronda planktonic foraminiferal Zone (N9/M6). Planulina wuellerstorfi, recovered in abundance, places the LFAsection and remaining Golconda Member at water depths >700 m. The statistical similarity of the benthic foraminiferal assemblages in the >63 um and >106 um fractions suggests winnowing of the LFA section, which is thus hypothesized to comprise a contourite. The statistical similarity of previously published data from Zones N6/M3 and N12/M9 (Shannon’s H, the Berger-Parker Dominance Index, Evenness E, a Nutrient Flux Index [NFI = sum of proportional abundances of Bolivina + Bulimina + Uvigerina], and the Benthic Foraminiferal Dissolved-Oxygen Index [BFOI]) suggests that these were deposited in comparable paleoenvironments with, in contrast to Zone N9/M6 at the LFA, relatively little bottom current action.

Tethyan plankton bioevents calibrated to stable isotopes across the upper Santonian–lower Campanian transition in north-western Tunisia

Calcareous nannofossil and planktonic foraminifera biostratigraphic datums are correlated with carbon isotope stratigraphy across the upper Santonian–lower Campanian transition from Ain Zouakra outcrop (Ellès area) in north-western Tunisia. Twenty two calcareous microplankton bio-events are identified and discussed, including 11 planktonic foraminiferal and 11 nannofossil events. The studied upper Santonian–lower Campanian succession can be divided into five nannofossil zones (CC17/UC13 to CC21/UC15c) equivalent to three planktonic foraminiferal zones named Dicarinella asymetrica, Globotruncanita elevata, Globotruncana ventricosa. The Santonian/Campanian Boundary Event (SCBE) is characterized by a positive δ13C double peaks. The first peak (a) occurs within the uppermost CC17 Zone and Dicarinella asymetrica Zone. The second peak (b) directly occurs below the base of CC18 (FO of Bronsonia parca parca) and last occurrence (LO) of Dicarinella asymetrica. It is marked by several extinction bioevents of representatives of Whiteinella, Dicarinella and Sigalia and the gradual disappearance of species of Marginotruncana (all species except M. sinuosa and M. marginata). At the beginning of the Campanian a diversification of Globotruncanidae was noted.

1 喜界島・沖縄島・宮古島の島尻層群浮遊性有孔虫と島尻変動

1 喜界島・沖縄島・宮古島の島尻層群浮遊性有孔虫と島尻変動

Комплекси форамініфер палеоцену Північної України

Some modifications for Biostratigraphic Scheme of Paleocene deposits of the Northern Ukraine as result of examination of foraminifera assemblages of the Dnieper-Donets Depression and Ukrainian Shield are proposed. In the Northern Ukraine section sediments of Psolian regional stage (regiostage) contain the most representative assemblages of planktonic and benthic foraminifera. Two planktonic foraminifers’ zones Subbotina trivialis – Globoconusa daubjergensis – Globanomalina compressa and Praemurica inconstans established earlier by M.V. Jartseva (1972) characterize the Psolian regiostage. Subbotina trivialis – Globoconusa daubjergensis – Globanomalina compressa zone corresponding to Eoglobigerina taurica and Globoconusa daubjergensis zones of the Belokamenskian regiostage of the Southern Ukraine is correlated with Danian zone P1 Eoglobigerina edita of tropical planktonic foraminiferal biochronological zonation. Praemurica inconstans zone of the Northern Ukraine corresponds to south Ukraine zone of the same name and is correlated with zone P2 Praemurica uncinata of Danian too. Benthic foraminifers’ assemblages from Psolian deposits have been distinguished as Cibicides lectus zone corresponding to Anomalina danica s. l. and Pyramidina crassa interregional zones of Danian and Zelandian of the south Russia and adjacent regions. Reviewed in the article biostratigraphical characteristics of local stratigraphic units of Psolian regiostage: the Sumy Suite of the Dnieper-Donets Depression (zones Subbotina trivialis – Globoconusa daubjergensis – Globanomalina compressa, beds with Cibicidoides lectus, beds with Cibicidoides favorabilis of the central part of the Depression; Anomalina danica zone, Ceratolamarckina tuberculata local zone, beds with Parasubbotina pseudobulloides and beds with Globoconusa kozlowskii of the north-eastern part of the Depression), Strata of quartz-glauconitic sands of the Konka-Yalyn Depression (beds with Parasubbotina pseudobulloides, beds with Cibicidoides lectus), the Luzanovka Beds (beds with Parasubbotina pseudobulloides, beds with Globoconusa daubjergensis, beds with Elphidiella prima) and the Polesje Beds (beds with Parasubbotina pseudobulloides, beds with Cibicidoides lectus), the Rajgorod Suite (assemblage with Anomalina danica) of the Ukrainian Shield. Correlation of these Suites, Beds and Strata are given. The Merlian regiostage of the Northern Ukraine contains not numerous foraminifers. Benthic foraminifers’ associations from the Merlian and Irzhavets Suites of the Dnieper-Donets Depression have been distinguished as assemblage with Bolivinopsis spectabilis. Sediment containing this assemblage is of Thanetian age by dinocysts. Findings of sporadic planktonic foraminifers in the Merlian deposits do not contradict this.

Anatomy of a mountain: The Thebes Limestone Formation (Lower Eocene) at Gebel Gurnah, Luxor, Nile Valley, Upper Egypt

We present a detailed geologic study of the Thebes Formation at Gebel Gurnah in its locus typicus on the West Bank (opposite Luxor) of the Nile River in the Upper Nile Valley, Egypt. This is the first detailed measurement and lithologic description of the ∼340 m thick (predominantly) carbonate section. The Thebes Formation is divided into thirteen major lithic units (A to M). We interpret data on the lithologic succession and variations, whole rock/clay mineralogy, and macro/micropaleontology in terms of deposition on a shallow carbonate platform episodically influenced by continental runoff, and describe six depositional sequences that we place in the global framework of Lower Eocene (Ypresian) sequence stratigraphy. We note however significant incompatibilities between the Thebes depositional sequences and the global sequences. We emend the definition of the Thebes Formation by defining its top as corresponding to level 326 m at the top of Nodular Limestone ‘L’ (NLL), and assigning the overlying beds to the Minia Limestone Formation. New biostratigraphic data and revision of previous studies establish the direct assignment of the Thebes Formation to planktonic foraminiferal Zones E4/P6b (upper part), E5/P7 and (indirectly) Zone E6/P8, and (probably, indirectly) Zone E7a/”P9”, and to calcareous nannofossil Zone NP12 and lower Zone NP13 of the Lower Eocene (Ypresian) and provide a temporal framework spanning ∼ 2.8 Myr from <52.45 to ∼49.6 Ma for the deposition of the Thebes Formation prior to the prominent sea level fall (∼49.6 Ma) towards the end of the Early Eocene. Dominantly carbonate deposition, with a strongly reduced detrital influx, occurred on a very wide shelf (probably) at least ∼ 100 km from the coastline. The thick sedimentary succession and the marked vertical lithologic variations are interpreted as resulting from sea level fluctuations imprinted on a long-term decrease in sea-level associated with rapid subsidence reflecting tectonic relaxation after the major Late Paleocene tectonic reorganization of the Syrian Arc.

Integrated stratigraphy of the Priabonian (upper Eocene) Urtsadzor section, Armenia

The transition from the Bartonian to the Priabonian, as traditionally understood, has long been associated with a series of extinctions and originations in several microfossil groups. The planktonic foraminifer genus Morozovelloides and large species of Acarinina suffered a rapid global extinction, as did many radiolarians. Calcareous nannofossils show several assemblage changes including the acme beginning of Cribrocentrum erbae and the lowest and highest occurrences of Chiasmolithus oamaruensis and C. grandis respectively. In shallow water environments, larger foraminifera also show an extinction among large species of Nummulites, as well as the first occurrences of the stratigraphically important genus Spiroclypeus. However, the correlation between shallow and deep water records remains uncertain, as do the mechanisms driving these biotic events. Here we present the results of a new integrated stratigraphical study (calcareous nannofossils, planktonic foraminifera, larger benthic foraminifera, and low-resolution magnetostratigraphy) of the Urtsadzor section in south-western Armenia which appears to be continuous through this interval. The Urtsadzor section consists of calcareous siltstones rich in micro- and nannofossils, with interbedded limestones containing abundant larger benthic foraminifera. Our new data enable us to correlate larger foraminiferal events with global plankton biostratigraphy, in a section outside of southwest Europe where most previous correlations have been based. At Urtsadzor, the large Nummulites species of N. millecaput-group are present throughout the whole section but decrease in abundance toward the top. The first occurrence of Spiroclypeus, also occurs in the upper part of the section, marking the SBZ 18/19 boundary. These events are associated with the phylogenetic development of the Nummulites fabianii and Heterostegina reticulata lineages. However, the calcareous plankton biostratigraphy indicates the section is well within the Priabonian; within planktonic foraminiferal Zones E14 and E15 and calcareous nannoplankton Zones CNE 18 and CNE 19. These results indicate larger foraminiferal events occur well above the planktonic foraminiferal extinction level and nannofossil assemblage changes indicating the events are not synchronous across groups, with implications for biostratigraphy and recognition of the basal Priabonian in different depositional settings and regions.

Late Cretaceous - Early Paleogene bio- and sequence stratigraphy of west-central Sinai, Egypt

A sequence biostratigraphic analysis has been done for the Upper Cretaceous-Lower Paleogene sedimentary outcrops at Wadi Raha, Sudr El-Hetan and Wadi El-Giddi areas in west-central Sinai. The sequences are subdivided into four carbonate rock units; from base to top: the Wata, Themed, Sudr and Waseiyit formations.The biostratigraphic analysis of the studied samples led to the identification of two main planktonic foraminiferal zones, three benthic foraminiferal zones with the ammonite zone.Eleven microfacies associations are recorded in the rock units. Nine constitutes a limestone facies with one constitutes a dolostone facies and one a claystone facies. The stratigraphic data, and the facies study support the identification of three major breaks (sequence boundaries) and four depositional sequences. The depositional sequences are subdivided into four supercycles and seven cycles of 3rd order.The oldest break (∼90-88.5Ma.) exists at the top of the Wata Formation coincides with the intra Turonian drop in the global sea level with the initiation of the Syrian Arc inversion phase. The second major break (85 - ∼75Ma.) coincides with the major inversion phase and the evolution of the doubly plunging anticlines. The third major break (∼68 through ∼53Ma.) represents the last phase of the Syrian Arc inversion and complete the missing of Paleocene sequences.

The formation placement and palaeoenvironment of the Middle Miocene Los Atajos Member, Trinidad

The age, palaeoenvironment and formation placement of the conglomeratic Los Atajos Member of central Trinidad have long been unclear. Seven samples (four from calcareous silts near the member's base exposed by building work at the Los Atajos Community Centre, and three from the underlying calcareous claystones of the Brasso Formation) were examined for calcareous microfossils. These indicate a conformable succession encompassing an overall regression. The oldest of the claystone samples, of uppermost early Middle Miocene Globorotalia fohsi fohsi Zone age (N11), contained an upper bathyal benthic foraminiferal assemblage, while the younger claystone samples yielded abundant, shallow neritic Hanzawaia carstensi. The recovery of the planktonic foraminifera Globorotalia mayeri but absence of Globigerinoides subquadratus suggest a Middle Miocene age (Globorotalia mayeri planktonic foraminiferal Zone; N14) for both the uppermost Brasso claystone sample and the Los Atajos Member. The benthic foraminiferal fauna in the Los Atajos is dominated by Rosalina subaraucana, with subdominant Cibicides ex gr. aknerianus and C. floridanus sensu Galloway and Heminway, and common Elphidium spp. This faunal succession has a close affinity with that of parts of the Lower to Middle Miocene Brasso Formation, especially the N10 Guaracara Limestone Member and the clays on which it sits. However, the Los Atajos Member assemblage differs markedly from that of the overlying Late Miocene San José Calcareous Silt Member of the Manzanilla Formation, from which the Los Atajos is separated by an unconformity of Globorotalia menardii (N15) Zone age. On these grounds, the Los Atajos Member is here placed within the Brasso Formation. The low diversity, high dominance benthic foraminiferal fauna and the associated ostracod assemblage in the Los Atajos are indicative of inner to shallower middle neritic palaeodepths in a carbonate-prone palaeoenvironment with marine vegetation and strong current action. It is concluded that the Los Atajos was deposited prior to the Late Miocene diversion of the palaeo-Orinoco River towards Trinidad, which is marked by the Manzanilla Formation.

PLANKTON BIOSTRATIGRAPHY AND PALEOCLIMATIC IMPLICATIONS OF AN EARLY LATE MIOCENE SEQUENCE OF LEVKAS ISLAND, IONIAN SEA, GREECE

Planktonic foraminiferal biostratigraphy is carried out in an Early Tortonian tectonically active setting, located in the Pre-Apulian Foreland Basin in Levkas Island. The studied section (Manassi section) is composed of hemipelagic silty clays and turbidite sandstones, reflecting sedimentation as a result of thrust activity. The distributional pattern of biostratigraphical significant species suggests that the Manassi section has been deposited during the time interval that Globigerinoides obliquus occurs regularly, the neogloboquadriniids are present in low percentages and Paragloborotalia siakensis is continuously present. The correlation with astronomical tuned sections allowed dating the studied section as ranging between 11.54Ma to 11.2Ma, having a lower Tortonian age, above the Serravallian/Tortonian boundary (Paragloborotalia siakensis planktonic foraminiferal zone). On the basis of the obtained palaeoclimatic curve, a series of palaeoclimatic events are recognized. The faunal composition suggests a cooling trend in the lower part which has been correlated with the Mi5 event. This cooling is followed by a warm-temperate phase, punctuated by several negative peaks in the palaeoclimatic curve. The palaeoclimatic evolution of the study area generally corresponds to the global palaeoclimatic trend with some subtle differences, supporting that the regional climate of this area was not merely controlled by global changes in climate.

Campanian–Maastrichtian foraminiferal stratigraphy and palaeoenvironment of the Lower Tar Member in the Wadi Tar section, Western Sirte Basin (Libya)

Upper Campanian–Maastrichtian sections on the western flank of the Hun Graben in the Western Sirte Basin (WSB) are displaying two major type facies based on the foraminiferal assemblages. The first one indicates open-marine to outer-shelf conditions, and is represented by numerous bathy-pelagic planktonic foraminiferal species referable to the Radotruncana calcarata, Globotruncana aegyptiaca and the lower part of the Gansserina gansseri Zone (all late Campanian).The second type facies indicates an inner-shelf environment and is represented in the middle-upper part of the Gansserina gansseri Zone (early Maastrichtian) and Racemiguembelina fructicosa (late Maastrichtian) dominated by epi-pelagic planktonic and large benthic foraminifers. Large benthic foraminiferal index species Siderolites calcitrapoides Lamarck and Omphalocyclus macroporus (Lamarck) occur in abundance by the middle–late Maastrichtian. Correlation between planktonic foraminiferal zonation and large benthic foraminiferal zonation is given. An open-marine to outer-shelf environment passed into shallower marine conditions during the late Campanian–early Maastrichtian to late Maastrichtian, then a slight deepening and again shallowing is noticed.

Planktonic foraminiferal zonation and sea-level changes in the upper Maastrichtian-middle Danian successions of Meghalaya, India

The biostratigraphic study of the upper Maastrichtian- middle Danian shelf successions of Therriaghat and Mahadeo in Meghalaya, India allowed for the identification of sixty seven species of planktonic foraminifera and recognized the following four zones and eleven subzones: in upperMaastrichtian, Racemiguembelina fructicosa, Pseudoguembelina hariaensis, Pseudoguembelina palpebra and Plummerita hantkeninoides Subzones within the Abathomphalus mayaroensis Zone; in lower-middle Danian Hedbergella holmdelensis and Parvularugoglobigerina longiapertura Subzones within the Guembelitria cretacea Zone, Eoglobigerina fringa and Eoglobigerina praeedita Subzones within the Parvularugoglobigerina eugubina Zone and Parasubbotina pseudobulloides Subzone, Subbotina triloculinoides and Globanomalina compressa Subzones within the uppermost Eoglobigerina edita Zone. The sections are biostratigraphically continuous across the Cretaceous-Paleogene boundary, but the tectonic development of the unstable Therriaghat and Mahadeo blocks caused local tectono-eustatic differences between the two blocks in litho- and biostratigraphy, foraminiferal dispersal, sea-level changes and depositional environments. The succession of the Therriaghat block,where 4 zones and 11 subzoneswere identified, is more complete than the succession of theMahadeo block, which comprises 3 zones and 6 subzones. The ratio of planktonic to benthic foraminifera allowed for the recognition of five transgressive-regressive cycles, most of which have subcycles and pulses. These cycles were calibrated using the planktonic foraminiferal zonation, allowing for detailed documentation of the local history of sea-level change. The extra-basinal tectono-thermal influence, frequent local sea-level changes, suspended clay and microspherules, and greenhouse effect of volcanism caused an increase of temperature and biotic stress in the shelf waters and consequently turnover in the planktonic foraminiferal assemblages, occasional migration and re-appearance, widespread predation, morphological aberrations, dwarfed and anomalous tests, abraded forms andmorphogroups. These paleoenvironmental changesmay have modified the local range of taxa, and the extension of biozones, so that some of the recognized subzones can be local, such as Eoglobigerina fringa and Eoglobigerina praeedita Subzones. Nonetheless, the planktonic foraminiferal assemblages that maintained usual trend of evolution are useful to unravel the complexities of local eustatic history.

Cenomanian–turonian stable isotope signatures and depositional sequences in northeast Egypt and central Jordan

Lithostratigraphic, biostratigraphic and microfacies studies of two Cenomanian-Turonian shallow-marine, siliciclastic-carbonate successions at Gebel Ekma plateau (southwestern Sinai, Egypt) and Wadi Karak section (central Jordan) are calibrated with δ13C-, profiles to reveal relative sea-level changes within a sequence stratigraphic framework. The study provides significantly enhanced stratigraphic resolution and key sections for regional correlation. Lithofacies are dominated by well-developed peritidal to subtidal facies associations indicating deposition in a rimmed carbonate shelf setting. Biostratigraphic analysis indicates the presence of 6 ammonite zones, 3 calcareous nannofossil zones and 3 planktonic foraminiferal zones within the Cenomanian to Turonian succession. Six, third-order depositional sequences, bounded by correlatable sequence boundaries can be traced across the African-Arabian platform. Comparison with δ13C records in deeper water pelagic sequences help to improve the resolution of the boundaries of each depositional sequence. Recognition of time gaps at the sequence boundaries on the platform, recorded in different parts of African-Arabian platform, is attributed to local tectonic activity, associated with the change from passive to active margins, which are overprinted by the global eustatic signature.

Early Eocene planktonic and benthic foraminifera from the Khangiran formation (northeast of Iran)

The Kopet-Dagh sedimentary basin is located in northeast of Iran and southeast of Turkmenistan in the Middle East. The Khangiran formation represents the last marine deposition in the Kopet-Dagh sedimentary basin. The early Eocene planktonic and benthic foraminifera from the Khangiran formation which belongs to the lower 376 m thickness of this formation are identified and biostratigraphically evaluated. Due to rarity of Morozovella species, planktonic foraminiferal zonation was difficult to determine in this formation. The determination of upper part of the late Paleocene for the lower 124 m of this formation is according to the lowest occurrence of Acarinina sibaiyaensis species. From E5 to near middle of E7 biozone, increasing trend of Acarinina frequency and a peak in Morozovella species and decreasing trend of frequency of Subbotina and Pseudohastigerina species indicate the warm and oligotrophic condition of the seawater during sedimentation of the studied interval. Toward the Ypresian-Lutetian boundary, the increasing trend of Pseudohastigerina and Subbotina species and decreasing in frequency of Acarinina species suggest the low-oxygen level, eutrophic and intermediate condition of the seawater. In this formation, the high abundance of the epifaunal taxa such as Anomalinoides spp., Cibicidoides spp., Gyroidinoides spp., and Lenticulina spp. from the base (late Paleocene sediments) up to E6 biozone reflects oligotrophic and oxic shallow water conditions. The occurrence of several peaks in abundance of Bulimina and Uvigerina species at the Ypresian/Lutetian boundary suggests eutrophic condition. These paleoecological conditions could be correlated with fluctuations in the numbers of the planktonic foraminifera.

The Chicxulub impact is synchronous with the planktonic foraminifera mass extinction at the cretaceous/paleogene boundary: New evidence from the Moncada section, Cuba

The Moncada section, western Cuba, is one of the few sections across the Cretaceous/Paleogene (K/Pg) boundary in the Gulf of Mexico and Caribbean where an Ir anomaly has been identified toward and above the top of a clastic unit, locally called the Moncada Formation (Fm.). The Moncada Fm. is enriched in ejecta (altered glass spherules, shocked quartz, melt rock fragments, etc.) and represents the local Complex Clastic Unit (CCU) linked to the Chicxulub impact event. This CCU is overlain by a 2-3cm thick bed of Ir-rich, dark, calcareous claystone which represents the “K/T Boundary Clay” at Moncada. All lowermost Danian Planktonic Foraminiferal zones and Acme-Stages (PFAS) were identified, suggesting stratigraphic continuity across the Danian and indicating that the Moncada Fm. is K/Pg boundary in age. High-resolution biostratigraphic data suggest that the mass extinction event of planktonic foraminifera at the K/Pg boundary was more severe than previously suggested. The absence of cosmopolitan, generalist Cretaceous species in the Danian deposits of Moncada supports the hypothesis that only Guembelitria survived the mass extinction triggered by the Chicxulub impact event. The high Ir-concentration and the ejecta-rich clay laminations identified in the lowermost Danian of Moncada (Ancon Fm.) are explained partly as the redeposition of ejecta material eroded and reworked from higher topographic levels, still contaminated by toxic trace elements ( e.g. , Cu and Ni) of meteoritic origin. These pollutants of meteoritic origin could have affected the ecological conditions of the pelagic environment for thousands of years after the K/Pg boundary, being particularly intense just after the Chicxulub impact. The ecological stress due to the pollutants partly explains the catastrophic mass extinction of planktonic foraminifera at the K/Pg boundary and their subsequent evolutionary radiation