Calcareous Nannoplankton Research Articles

Coccolithophore paleoproductivity since the Last Glacial Maximum in the Atlantic Ocean: Relationship with calcification and preservation variability

Paleoproductivity, calcification and preservation patterns are presented from calcareous nannoplankton paleo-assemblages records covering the last ∼25 kyr retrieved from Integrated Ocean Drilling Program Sites U1385 (37°34.285′N; 10°7.562′W) and U1313 (41°0.0′N; 32°57.4′W), located respectively along the Western Iberian Margin and in the North Atlantic Ocean. The main aim of the study is to provide paleoceanographic and paleoclimatic analyses together with an investigation of changes in coccolithophore calcification processes occurring in response to climate variability from the Last Glacial Maximum up to the Holocene. Coccolithophore calcification was investigated by comparing variations in coccolith thickness and total coccolith calcite; at the same time dissolution/preservation indices were used to better understand the response of coccolithophores to changes in environmental parameters.In general, the increasing CO2 recorded during the last 25 kyr has a negative effect on calcification, resulting in a reduction of the different species size-normalized thicknesses at both sites. However, differences between the responses at the two latitudes studied are identified, in particular during the Heinrich Stadials; in contrast, during both Younger Dryas and Holocene intervals, the different size-normalized species thicknesses show consistent patterns at the two sites. During the Last Glacial Maximum the influence of subtropical waters due to Azores Current recirculation leads to a moderate productivity, initially at Site U1385 and later at Site U1313. At the same time, temperature influences the calcification at both sites. At Site U1385, the temperature is the main parameter affecting the paleoproductivity during Heinrich Stadial events; in addition, during Heinrich Stadial 1 alone, it also affects the calcification. At Site U1313 the calcification processes during Heinrich Stadial events are apparently hampered by an increasing water turbidity, caused by icebergs acting as ice rafted debris transporters, which affects light filtration in the water column. Light availability is an important calcification-influencing factor. At Site U1313 during Heinrich Stadial 1 and at the Last Glacial Maximum inception, dissolution, a consequence of increased CO2 solubility in the colder ice-age ocean, has a negative influence on calcification. Furthermore, at Site U1313, in contrast to Site U1385, the continually increasing CO2 concentration recorded during the Bølling-Allerød hampers both calcification and preservation.

Radiolarian size and silicification across the Paleocene-Eocene boundary and into the early Eocene

The Paleocene-Eocene Thermal Maximum (PETM) was a major environmental perturbation that drove range shifts, adaptation, and faunal turnover in marine and terrestrial clades. Open ocean planktonic responses—including body size trends—have been characterized for calcareous nannoplankton, dinocysts, and planktonic foraminifera. Relatively little, however, is known about the response of radiolarians, which share life modes and phylogenetic history with planktonic foraminifera but make their tests (i.e., ‘shells’) out of silica rather than calcium carbonate. Here, we compare radiolarian assemblage changes in the Southwest Pacific with assemblages from Atlantic and Indian Ocean sites. We also measured radiolarian test size before, during, and after the PETM in a pelagic sedimentary succession at Mead Stream, South Island, New Zealand. Our results show a substantial positive shift in mean radiolarian test size at Mead Stream at the assemblage level concurrent with the onset of the PETM, primarily due to an increase in the size and relative abundance of spumellarian radiolarians. We investigate oligotrophy, elevated seawater silica concentration, and redeposition as potential drivers for this size shift. Mead Stream radiolarians remain large for 1.3 Myr, long past the recovery of the carbon isotope excursion and a return to baseline in terrigenous sedimentation, bioturbation, and benthic foraminifera diversity, leaving the ultimate cause of the observed changes in test size uncertain. We find little evidence for a uniform morphological response to the event or its aftermath across sites, particularly as relates to the relative extent of silicification of different groups of radiolarians.

Early Jurassic coccolith diversification and response to pre-Toarcian environmental changes: A perspective from the Paris Basin

The early Jurassic saw large fluctuations in global temperature, sea-level and bottom-water oxic conditions prior to the Toarcian-Oceanic Anoxic Event (T-OAE), in several oceanic basins of NW Europe. Links between such changes, ocean nutrient concentrations and progressively increasing abundance and diversity of calcareous nannoplankton remain unclear. We have investigated the early Jurassic nannofossil assemblages of the Paris Basin across the mid-Sinemurian to lowermost Toarcian. Comparisons to geochemical proxy data let us decipher evolutionary trends from paleoenvironmental responses, test paleoecological affinities of coccolith species and improve our understanding of paleoenvironmental changes. Despite a strong evolutionary trajectory of the coccolith assemblages, multivariate analyses allowed to identify taxa indicating cold (Parhabdolithus, Crucirhabdus, Crepidolithus pliensbachensis), open ocean (Mitrolithus elegans, Mitrolithus lenticularis, Crepidolithus crassus sensu lato, Crepidolithus granulatus (both variants), Crepidolithus crucifer) and high fertility conditions (placoliths: Bussonius, Lotharingius, Similiscutum novum, Similiscutum finchii). Our data support that: (1) stable cool conditions persisted through the Upper Sinemurian, (2) progressive warming and high sea-levels onsetting across the Sinemurian/Pliensbachian transition, persisting to the lower margaritatus ammonite zone (AZ) may have favored the evolution of placoliths, (3) a first significant increase in abundance of placoliths was triggered in the stokesi ammonite subzone (ASz) by elevated fertility levels which preceded immediately the late Pliensbachian organic matter preservation interval (OMPI), (4) the OMPI and remaining subnodosus ASz were characterized by warm temperatures but low fertility surface waters, (5) another large increase in abundance of placoliths suggests again higher fertility levels across the uppermost margaritatus AZ, spinatum cold event and lowermost Toarcian.

An experimental study on post-mortem dissolution and overgrowth processes affecting coccolith assemblages: A rapid and complex process.

Coccolith dissolution together with post-mortem morphological features are immensely important phenomena that can affect assemblage compositions, complicate taxonomic identification as well as provide valuable palaeoenvironmental insights. This study summarizes the effects of pH oscillations on post-mortem coccolith morphologies and the abundances and compositions of calcareous nannoplankton assemblages in three distinct types of material-(i) Cretaceous chalk, (ii) Miocene marls, and (iii) late Holocene calcareous ooze. Two independent experimental runs within a semi-enclosed system setting were realized to observe assemblage alterations. One experiment was realized with the presence of bacteria and, in contrast, the second one inhibited their potential effect on the studied system. The pH was gradually decreased within the range of 8.3-6.4 using a reaction of CO2 with H2 O forming weak carbonic acid (H2 CO3 ), thereby affecting [ ]. Further, a subsequent overgrowth study was carried out during spontaneous degassing accompanied by a gradual pH rise. The experiment revealed that the process and intensity of coccolith corrosion and subsequent overgrowth build-ups are influenced by a plethora of different factors such as (i) pH and associated seawater chemistry, (ii) mineral composition of the sediment, (iii) the presence of coccoliths within a protective substrate (faecal pellets, pores, pits), and (iv) the presence/absence of bacteria. Nannoplankton assemblages with corroded coccoliths or with coccoliths with overgrowth build-ups showed that the observed relative abundances of taxa experienced alteration from the original compositions. Additionally, extreme pH oscillations may result in enhanced morphological changes that make coccoliths unidentifiable structures, and might even evoke the absence of coccoliths in the fossil record.

Shelf Ecosystems Along the U.S. Atlantic Coastal Plain Prior to and During the Paleocene‐Eocene Thermal Maximum: Insights Into the Stratigraphic Architecture

AbstractThe Paleocene‐Eocene Thermal Maximum (PETM) is the most pronounced global warming event of the early Paleogene related to atmospheric CO2 increases. It is characterized by negative δ18O and δ13C excursions recorded in sedimentary archives and a transient disruption of the marine biosphere. Sites from the U.S. Atlantic Coastal Plain show an additional small, but distinct δ13C excursion below the onset of the PETM, coined the “pre‐onset excursion” (POE), mimicking the PETM‐forced environmental perturbations. This study focuses on the South Dover Bridge core in Maryland, where the Paleocene‐Eocene transition is stratigraphically constrained by calcareous nannoplankton and stable isotope data, and in which the POE is well‐expressed. The site was situated in a middle neritic marine shelf setting near a major outflow of the paleo‐Potomac River system. We generated high‐resolution benthic foraminiferal assemblage, stable isotope, trace‐metal, grain‐size and clay mineralogy data. The resulting stratigraphic subdivision of this Paleocene‐Eocene transition is placed within a depth transect across the paleoshelf, highlighting that the PETM sequence is relatively expanded. The geochemical records provide detailed insights into the paleoenvironment, developing from a well‐oxygenated water column in latest Paleocene to a PETM‐ecosystem under severe biotic stress‐conditions, with shifts in food supply and temperature, and under dysoxic bottom waters in a more river‐dominated setting. Environmental changes started in the latest Paleocene and culminated atthe onset of the PETM, hinting to an intensifying trigger rather than to an instantaneous event at the Paleocene‐Eocene boundary toppling the global system.

Biostratigraphy of Oligo-Miocene marine deposits of Central Iran basin based on calcareous nannoplanktons

Biostratigraphy of Oligo-Miocene marine deposits of Central Iran basin based on calcareous nannoplanktons

Weakening of the biological pump induced by a biocalcification crisis during the early Toarcian Oceanic Anoxic Event

Severe environmental changes during the early Toarcian (Early Jurassic; ∼182 Ma), comprising global warming, elevated pCO2, intensified continental weathering and a high amplitude sea level rise, led to the genesis of a Toarcian Oceanic Anoxic Event (T-OAE), expressed by the widespread occurrence of organic carbon (OC)-rich sediments (black shales) forming on anoxic epicontinental shelves. Here, we show that during the T-OAE black shales in some depocenters have formed under rather low organic carbon accumulation rates (OCAR). We explain this observation by a reduced export efficiency of OC to the sediment, caused by a drastic decline in the abundance of mineral ballast, due to a major biocalcification crisis and the demise of calcareous nannoplankton. The reduction of mineral ballast led to slowing of the sinking speed of particulate organic matter, which thus became more prone to biodegradation. A major sea level rise, accompanying the T-OAE, was associated with retrograding shorelines and shift of depocenters away from the basin centers to more coastal areas. This might have reduced nutrient fluxes to the distal depocenters and diminished surface productivity and export flux in the central basin. Moreover, during sea level rise reduced input of clastics from adjacent landmasses may have led to a decline in organic carbon dilution. A decline in both abundance and size is documented for faecal pellets in core FR-210-078 from the Lorraine Basin, substantiating the scenario of reduced marine primary productivity and organic matter transport efficiency. Accordingly, during the T-OAE low OCAR are here interpreted to reflect a weakening of the biological pump. These new data substantiate the role of organic matter preservation as major factor controlling the formation of black shales during the T-OAE. The Toarcian marine transgression led to an increase in the extent of shelf areas, accompanied by an expansion of oxygen-deficient conditions that favored the preservation of organic matter in shelf sediments. Consequently, despite low OCAR, net C-burial in shelf sea sediments increased during the T-OAE, which may have acted as negative feedback mechanism that caused global cooling in the aftermath of the event.

Middle Miocene (Serravallian; upper Badenian–lower Sarmatian) dinoflagellate cysts from Bad Deutsch-Altenburg, Vienna Basin, Austria

Middle Miocene (Serravallian; upper Badenian–lower Sarmatian) strata recovered in 10 cored boreholes (83 samples) from Bad Deutsch-Altenburg, Vienna Basin, Austria, were analysed palynologically for the first time. The strata belong to the Rabensburg Formation of the Baden Group. The lateral distribution of the boreholes in reference to a Mesozoic ridge makes this area interesting for studying various aspects such as distribution of deposits, stratigraphy and palaeoenvironmental reconstruction. A diverse and well-preserved in situ dinoflagellate cyst association has been identified. Middle Miocene age-diagnostic species including Cannosphaeropsis passio, Cerebrocysta poulsenii, Habibacysta tectata, Labyrinthodinium truncatum, Operculodinium? borgerholtense and Unipontidinium aquaeductum are recorded. Their occurrences allow correlation with dinoflagellate cyst biozonations on a regional scale. Based on the identified dinoflagellate cysts and by correlation with calcareous nannoplankton and ostracods, from the same set of samples, a Serravallian age – corresponding to a late Badenian and early Sarmatian age (regional Paratethys stages) – is confirmed. Reworked (Cretaceous and Paleogene) dinoflagellate cyst assemblages, also well preserved, were recorded abundantly from boreholes HA 521 and HA 573 (south-west of the Mesozoic ridge). In accordance with ostracods, the Badenian–Sarmatian boundary can be traced in the upper part of borehole HA 66 based on an abrupt change in the dinoflagellate cyst assemblages. The upper Badenian strata were deposited in a coastal to inner shelf environment with terrigenous (siliceous sand and clay) and carbonate sediments. The recorded dinoflagellate cysts reflect marine, tropical to warm-temperate climatic conditions. The composition of the recorded dinoflagellate cyst assemblages is very close to that of the Middle Miocene assemblages of the Mediterranean, indicating water exchanges between the Central Paratethys and the Mediterranean during the late Badenian (early Serravallian).

Biostratigraphy and tectonically controlled sedimentation of the Maastrichtian in Israel and adjacent countries

Maastrichtian argillaceous chalks of the Ghareb Formation are widespread throughout Israel, both in exposures and in the subsurface. These strata contain a rich fauna of foraminifera and calcareous nannoplankton, allowing detailed biozonation of the sediments, which were deposited in a series of basins in an outer-shelf to upper-slope environment. The distribution of benthonic and planktonic foraminifera from a reference section in southern Israel is described. Three planktonic foraminiferal tethyan chronozones, the Globotruncana falsostuarti , Gansserina gansseri and Abathomphalus mayaroensis zones, are identified. The middle and upper parts of the Maastrichtian succession are fully recorded in the section. The common occurrence of Abathomphalus mayaroensis and Plummerita hantkeninoides at the top of the Maastrichtian strata indicate a continuous sedimentation till the Cretaceous/Tertiary boundary. The Maastrichtian beds in Israel vary in thickness from 0 to 200 m and reflect structures, controlled by the Syrian Are fold system, which evolved during pre- and syn-Maastrichtian times. Their isopach contours are in good agreement with present-day structural axes. The lithostratigraphy and tectonic events during the Maastrichtian in Israel are compared with those of other countries in the eastern Mediterranean

Belemnites and calcareous nannoplankton: Proxy tools for recognising of cryptic Jurassic geological history of Central Europe

Belemnites and calcareous nannoplankton: Proxy tools for recognising of cryptic Jurassic geological history of Central Europe

Nový výskyt příbojové facie u Ronova nad Doubravou (kolínský litofaciální vývoj, česká křídová pánev)

A rocky-coast facies in the Bohemian Cretaceous Basin (BCB) are developed mainly in the Kolín lithofacial area at its southern margin. Ronov – the newly described locality – is situated south of Ronov nad Doubravou, on the right bank of the Doubrava river near the St. Kříž church. The outcrop located in a ditch was partially excavated in order to study the character and extent of Cretaceous sediments (Beds No. 1–3; see Figs. 1–3). Bed 1 is composed of red clay with yellow streaks, representing lateritically weathered crystalline bedrock – likely amphibolites and garnet migmatites (Fig. 2). Overlying bed 2 consists of yellow to gray-green clay; in the lower part, the layer contains fragments of fossils that occur in the overlying layer, and sandy “intraclasts” interpreted as bioturbations. The most conspicuous bed 3 (25 cm in thickness) is represented by calcareous, coarse-grained sandstone to conglomerate with glauconite and abundant fauna (mainly fragmentary; Figs. 4 and 5). This type of rock in the wider area (between Ronov nad Doubravou and Žleby) was reported by Sejček (1982) who described three occurrences as scree or fragments on the surface but has not found any rock outcrops in situ despite excavation work. The individual layers were sampled for the study of foraminifers, calcareous nannoplankton and macrofauna. Shells of Rhynchostreon suborbiculatum, which are always disarticulated, often fragmented and bioturbated (Entobia exogyrarum), represent the most prominent element of macrofauna. In addition, Rastellum diluvianum and Amphidonte halitoidea, unspecified large colonies of bryozoans, spines of the echinoids Cidaris vesiculosa, complete shells of brachiopods Cyclothyris aff. difformis and tiny teeth of sharks Otodus rarely occur. Calcareous nannofossils were found only in bed 3. Isolated small, mostly difficult to identify fragments belong to long-range stratigraphic taxa (Fig. 6) and may indicate an interval from the uppermost Cenomanian to the lowermost Turonian. Similar poor nannofossil assemblages are known also in other rocky-coast facies of the BCB. The refining indicator of stratigraphic classification is thus macrofauna. Similar communities with Rhynchostreon suborbiculatum and echinoderms are known from Upper Cenomanian and Lower Turonian in the area of Heřmanův Městec, Čáslav and especially Kutná Hora. However, brachiopods Cyclothyris aff. difformis and oyster Amphidonte halitoidea recorded from Ronov are typical representatives of Upper Cenomanian “rocky-coast” faunas, whereas typically Lower Turonian elements such as the oyster Exogyra reticulata, Exogyra sigmoidea, or the spines of the Cidaris sorigneti are missing in the studied community. The study of macrofossil and nannofossil communities shows that the Upper Cretaceous rocks, represented by the calcareous glauconitic sandstones to conglomerates in Ronov locality, are most likely of the Upper Cenomanian age and represent the Korycany Member of the Peruc-Korycany Formation.

Molecular fossils and calcareous nannofossils reveal recurrent phytoplanktonic events in the early Toarcian

During the early Toarcian (Early Jurassic, ~183 Ma) global climate and environmental change profoundly impacted biogeochemical cycles and marine ecosystems culminating in the early Toarcian Oceanic Anoxic Event (T-OAE). The T-OAE exhibited a global temperature rise and carbon cycle perturbation that manifested in a stepwise negative Toarcian carbon isotope excursion. While the response of marine invertebrates towards early Toarcian environmental change is well documented, that of marine primary producers is only poorly constrained and is mainly inferred from changes in algae groups producing hard parts, such as calcareous nannoplankton and organic-walled dinoflagellates. Both biotic groups, however, represent only a small part of the marine phytoplankton, the majority of which lack parts with preservation potential in the geosphere. In order to obtain a holistic view on the response of marine primary producers towards the early Toarcian environmental perturbation, we here conducted a high-resolution study based on the combined application of molecular fossils (biomarker) and calcareous nannofossils. Upon the climax of the T-OAE our data indicate that the marine phytoplankton community structure was dominated by eukaryotic algae, which experienced at least five distinct paleoecological events. Each of these was characterized by a demise of red algae groups and shallow- and deep-dwelling calcareous nannoplankton, and a contemporaneous proliferation of opportunistic green algae groups. An increase of poorly developed coccoliths (resembling protococcoliths) during each phytoplankton event attests to periodically harsh environmental conditions in surface waters. Each phytoplankton event was followed by a recovery of pre-event algal communities, indicative of a cyclicity in unstable and fluctuating environmental conditions. During the onset of the T-OAE, phytoplankton events align with negative δ 13 C shifts, suggesting that changes in the global carbon cycle and the climate system impacted on marine primary producers. Phytoplankton events, particularly during the onset of the T-OAE, were accompanied by recurrent freshening of surface waters during warming periods, suggesting these were the most important ecological drivers. Cyclicity in phytoplankton events followed the short eccentricity (100 kyr) orbital frequency, emphasizing the role of orbital forcing in early Toarcian environmental change and ecosystem disturbances. Ecosystem change and extinction were not driven by a single event, but resulted from multiple disturbances that occurred superimposed onto long-term environmental change and culminated in the early Toarcian ecosystem crisis. • Biomarker and calcareous nannofossils reveal recurrent phytoplankton events. • Phytoplankton events record shift from red to green algae communities. • Phytoplankton events forced by high SST, surface water freshening and stratification. • Environmental change and phytoplankton events were paced by orbital cycles.

Early Maastrichtian-Early Eocene Biostratigraphy of El Hasana Area, Central Sinai, Egypt

ABSTRACT Ten calcareous nannofossils and ten planktic foraminiferal biozones were recognized from two sections measured in El Hasana area, in Central Sinai, Egypt. In the West El Hasana section, an early Maastrichtian/early Paleocene (K/Pg) unconformity was recorded due to the absence of the planktic foraminiferal Gansserina gansseri, Abathomphalus mayaroensis, and Globigerina eugubina Zones and the calcareous nannoplankton Micula prinsii and Markalius inversus Zones. The early Paleocene is represented by two biozones, Morozovella pseudobulloides (P1b) and Morozovella trinidadensis (P1c) that correlate with the Cruciplacolithus tenuis Zone (NP2), Chiasmolithus danicus Zone (NP3), and Ellipsolithus macellus Zone (NP4). In both sections, during the middle Paleocene three biozones were recorded: Morozovella uncinata (P2), the lower part of P3 Morozovella angulata, and Planorotalites pusilla pusilla (upper part of P3). The first and second biozones are equated with the upper two thirds of Ellipsolithus macellus (NP4), while the third one is correlated with Fasciculithus tympaniformis Zone (NP5). In the West El Hasana section, the Planorotalites pseudomenardii Zone (P4) ends the measured section. A small hiatus was observed across the late Paleocene/early Eocene (P/E) boundary in the East El Hasana section. This hiatus is due to the absence of the Planorotalites pseudomenardii Zone (P4), Morozovella velascoensis Zone (P5), M. edgari Zone (lower part of P6) and Heliolithus kleinpellii Zone (NP6), Discoaster molheri Zone (NP7), Heliolithus riedelli/Discoaster nobilis Zone (NP8), and Discoaster spp. (e.g., D. araneus) Subzone NP9a. The P/E boundary in East El Hasana section is delineated with the appearance of Rhomboaster spp. (e.g., Rhomboaster bitrifida) NP9b Subzone that coincides with the appearance of the planktic foraminiferal Morozovella subbotinae Zone (upper part of P6).

New insights into the Barremian–lower Aptian calcareous nannofossils of the Mediterranean Tethys: Chronostratigraphic and paleobiogeographic implications

A detailed study of calcareous nannofossil assemblages from twelve uppermost lower Barremian–lower Aptian sections in the Subbetic Domain of the Betic Cordillera was performed. Seven new nannofossil species (Crucibiscutum bastetanum, Crucibiscutum gracile, Chiastozygus lamprostauros, Cyclagelosphaera platyaspis, Lithraphidites aichmoides, Lithraphidites pugio, and Rhagodiscus sicutclipeus) are described, one species is emended (Lithraphidites magnus) and the taxonomic concept of the marker species Hayesites irregularis is discussed and clarified. The detailed stratigraphic ranges of the new species, together with those of other relevant taxa, are determined and correlated to standard ammonite biostratigraphy. Age estimates of biostratigraphically relevant calcareous nannofossil biohorizons are calculated using astrochronologically tuned cyclostratigraphic data. Five new calcareous nannofossil subzones are proposed which enhance upper Barremian biostratigraphic resolution at a regional scale and are directly correlated with respect to the standard Tethyan ammonite zonation. Two of the new species described here are used as biostratigraphic markers for the newly proposed subzones. The duration of each subzone is provided through astrochronological calibration. This study allows the refinement of the calcareous nannofossil zonation for the Mediterranean–Atlantic province of the Tethyan Realm. The implications of these new results are discussed regarding the extant definition and use of the Barremian/Aptian boundary. The morpho-evolutionary trends of selected nannofossil groups are reviewed in relation to the latest Barremian–Aptian paleogeographic changes, showing these were a prominent factor controlling calcareous nannoplankton evolution and biogeographical distribution in the west European-Atlantic region.

Pollen Record Of Early/ Middle Miocene Boundary In The South Sumatra Basin

Early to Middle Miocene sediment obtained from three wells drilled in South Sumatera area has been evaluated for its micropaleontological content including foraminifera, calcareous nannoplankton and palynomorph. The boundary of Early/ Middle Miocene is clearly represented by zone N8/ N9 boundary based on foraminiferal analysis and zone NN4/ NN5 boundary on the basis of calcareous nannoplankton analysis. The rich assemblage of foraminifera and calcareous nannoplankton indicates the occurrence of marine sediment within the well sections. In addition, environmental markers of benthonic foraminifera suggest the occurrence of inner to middle neritic along the studied sections. Palynological analysis however, proves the high occurrence of pollen and spore along the marine successions situated in Early/ Middle Miocene boundary which is the first time to yield a good quality of palynological record. The Early/ Middle Miocene boundary is marked by low sea level in global sea level curve as indicated by significant decrease of foraminifera and calcareous nannoplankton. In addition, palynological record reflects climatic changes over N8/ N9 sediment marking Early/ Middle Miocene boundary with the declines of pollen assemblage suggesting seasonal/ dry climate condition. N8 sediment shows high abundance and diversity of palynomorphs including those of wet climate markers. Palynological assemblage drops gradually approaching foram zone N9/ N8 boundary, whilst seasonal climate indicators increase. On the other hand, palynological record recovers its assemblage over N9 sediment.

Oligocene Palynology Of On-Shore West Java

Compared to its counterpart in the off-shore area (including Northwest Java and Northeast Java), the Oligocene sediment of on-shore West Java provides low pollen assemblages. In addition, superwet elements of Dacrydium and Casuarina commonly occurred in off-shore area are less represented in the on-shore area. However, it is believed that the study area still experienced wet climate condition as proved by common occurrence of rattan pollen Dicolpopollis spp. indicating a thick growth of swamp forest under moist climate. Unlike its counterpart in the off-shore North West Java, the studied sediment rarely yields lacustrine elements suggesting the disappearance of lake deposit. The Oligocene sediment of on-shore West Java is defi ned by the regular appearance of Oligocene marker of pollen Meyeripollis naharkotensis. The last occurrence of this pollen marks the top Oligocene age. In fact, the appearance of pollen M. Naharkotensis is obviously used to separate Oligocene age from Miocene age in the off-shore area. Moreover, marine micropaleontology analysis on foraminifers and calcareous nannoplankton confi rms this age. The studied sediment was deposited in the transition to shallow marine environment as indicated by rare occurrence of marine microfossils. The common brackish pollen of Zonocostites ramonae (Rizophora) and Spinizonocolpites echinatus (Nypa) indicates mangrove/ back-mangrove environment. Moreover, the domination of shallow water benthonic over the planktonic forms suggests shallow marine setting.

Paleoenvironment, sequence stratigraphy and source rock potentiality of the Cenomanian-Turonian boundary sediments of Southern Tethys

The Abu Qada Formation is a reference interval for the Cenomanian–Turonian boundary event in the northeastern margin of Africa. In this paper, geochemical, biostratigraphical, and carbon isotope ratio studies are presented using high-resolution well data yielded from the Gulf of Suez, Egypt to evaluate the paleoenvironmental condition, sequence stratigraphy and source rock potential of the Upper Cenomanian/Lower Turonian Abu Qada Formation. A total of 12 core samples and 4 ditch cuttings were collected from OCT-A8St1 well in the October Oil Field for geochemical, palynological and calcareous nannoplankton analyses. Cyclostratigraphic analysis was prepared to characterize the electrofacies change along the Cenomanian/Turonian boundary interval including the Oceanic Anoxic Event 2 (OAE2). The Predictive Error Filter Analysis (PEFA) patterns and Integrated Predictive Error Filter Analysis (INPEFA) curves found 3rd order cycle of the OAE2 within the global third-order cycle Ce5. A stable carbonate isotope analyses with total organic carbon (TOC) resulted in a remarkable positive excursion δ13Ccarb (3.67‰) associated with change in the TOC content. The quantitative analysis of calcareous nannofossils indicates the high productiveness of nannoplankton around the Cenomanian/Turonian boundary interval. The high abundance of the Discorhabdus genus proves the paleoenvironmental change during the OAE2 interval. The palynofacies interpretation indicates the lower part of Abu Qada Formation to be deposited in a slightly reducing conditions at the inner neritic setting, while the upper part of Abu Qada to lower part of Wata formations were deposited in deeper marine setting under anoxic conditions. These changes in the overall depositional conditions are documented by the remarkable change in palynofacies and organic carbon content (TOC). Dark gray shale and carbonate sediments are interpreted to be a good source rock potential by kerogen quantified palynofacies analysis indicating oil and gas prone producing materials (Kerogen types II and II/III). The best source rock quality is associated with the Abu Qada Formation's OAE2 record. These criteria allow us to identify the occurrence of OAE2 record in the Gulf of Suez petroleum province as a useful tool for high-resolution chronostratigraphic analysis.

Sequence stratigraphy of the Miocene siliciclastic–carbonate sediments in Sadat Area, north‐west of Gulf of Suez: Implications for Miocene eustasy

The Miocene sequences in the north‐west of the Gulf of Suez represent transition zones between carbonate‐dominated and siliciclastic‐dominated strata. These rocks were greatly influenced by the Gulf of Suez rifting, which resulted in lateral variations of facies and hence presented a complicated stratigraphic setting. Here, we interpret the sequence stratigraphy of the Sadat Area to the north‐west of the Gulf of Suez by integrating biostratigraphic data and microfacies analysis to contribute primarily to the geology of the studied successions and incorporate the existing knowledge of syn‐rift deposition. We determined the ages of the studied formations by biostratigraphic examination of the integrated calcareous nannoplankton, planktic, and benthic foraminifera. Our results distinguish four genetic Miocene sequences. These sequences are defined by four major sequence boundaries that outline sedimentation cycles and were chiefly deposited in a lagoon to outer‐shelf settings. The proposed Miocene eustacy is well‐correlated with global curves, implying a rise in sea level in the lower parts of Zones M4, M5, and M8. In contrast, the reduction of sea‐level rise resulted in the decrease of accommodation space in the upper part of Zone M5. The studied Miocene deposits mainly formed in a shallower marine environment, as shown by a comparison between data from the eastern side of the Gulf of Suez and the data presented in this paper. Furthermore, we demonstrate that the local tectonic activity linked with the Gulf of Suez rifting and the eustatic sea‐level changes were significant factors in the deposition of the Miocene in the studied successions.

Biostratigraphy and sequence stratigraphy of the deep offshore Niger Delta and implications for future hydrocarbon exploration in the Paleogene sequences

The Niger Delta Deep Offshore Basin has been the latest frontier within the Niger Delta for hydrocarbon exploration and production activities. Until the onset of drilling activities in the early 1990s, little was known about the biostratigraphy of this frontier setting. Thus, uncertainties existed in the ages ascribed to the various stratigraphic sequences. Presently, several wells have been drilled in the deep offshore Niger Delta and three-pronged biostratigraphic data and some sequence stratigraphic interpretations have become available. We have integrated biostratigraphic data comprising palynological, foraminiferal, and calcareous nannoplankton zonation and biofacies, wireline log information, and regional-3D seismic data, with simple basic sequence stratigraphic analysis for a detailed well correlation, regional mapping of hydrocarbon-bearing intervals, and evaluation of the thicknesses of promising stratigraphic intervals. Results indicate a significant effect on not only the earlier conceptualized age of the deepest prospective reservoirs, but also the ages of possible source rocks in the Paleogene of the Niger Delta offshore sequence. Our findings will help in the realistic assumptions of source rock characterization, charge modeling/prediction, and the stratigraphic thicknesses of the offshore sequences and their reservoirs. We examine the specific derivable age interpretations from the integration of at least six wells, biostratigraphic data with seismic, and the implications of these interpretations for hydrocarbon prospectivity of the Paleogene sequences. Furthermore, we document the biostratigraphy work done in the area, in all the structural belts where drilling has occurred including the deepest well drilled in the deep offshore Niger Delta, Bosi-006. The results of this study have a critical impact on the current regional geologic understanding of the deep offshore Niger Delta.

Вік та умови нагромадження палеоценових відкладів Скибового покриву Карпат на основі мікропалеонтологічних та седиментологічних даних

The results of micropaleontological and sedimentological studies of the Paleocene sediments such as the Upper Member of the Stryi Formation and the Yamna Formation located in the Skyba Nappe in the Ukrainian Outer (Flysh) Carpathians are represented. Sedimentological features of the flysch successions (including the sedimentary succession along the Prut River in the city of Yaremche) proved that the Upper Member of the Stryi Formation is represented mainly by turbidites; the lower part of the Yamna Formation (variegated Yaremcha Horizon) is composed of red and green clay hemipelagites and turbidites, and the upper part of the Yamna Formation (Yamna sandstone) consists of deposits of high-density turbidite currents and grain flows. The calcareous nannoplankton: NP1, NP2, NP3 and NP4 zones as well as the foraminifera: planktonic Globoconusa daubjergensis Zone (Danian Stage) and benthic Rzehakina epigona Subzone of Rzehakina fissistomata Zone, s. l. (the early Paleocene) are identified in the Upper Member of the Stryi Formation. The calcareous nannoplanktonic NP4, NP5, NP6 zones are distinguished in the Yaremcha Horizon and NP6, NP8, NP9 zones are identified in the Yamna sandstone. The agglutinated foraminifera including Rzehakina fissistomatа, Rz. epigona, Caudammina ovula, Hormosina velascoense, Glomospirella grzybowskii, Saccammina placenta, Paratrochamminoides irregularis are dominated in the Yamna Formation. The age of the Stryi Formation (Upper Member) is established as Danian–partly Zealandian, and the age of the Yamna Formation is Zealandian–Thanetian based on nannoplankton and foraminifera data. Deep-water agglutinated foraminifera (DWAF) belonging to the genera Rhabdammina, Hyperammina, Dendrophrya, Ammodiscus, Glomospira, Hormosina, Reophax, Haplophragmoides, Recurvoides, Trochamminoides, Paratrochamminoides, Spiroplectammina, Karreriella are dominated in the background hemipelagic clay deposits and make up to 100% of the tests in the microfaunal associations, that suggests the lower bathyal-abyssal depths of the sedimentary paleobasin The channel deposits (Yamna sandstone) and interchannel sediments (Upper Member of the Stryi Formation) of the ancient deep-sea fan are identified in the Paleogene flysch.