The nannoplankton research was conducted in the MH-2 well, Banggai-Sula Basin, Central Sulawesi. Thirty-four ditch-cutting samples were utilized to observe the Minahaki, Kintom, and Biak Formations. ...Age determination was carried out using biostratigraphy method and standard procedure for first and last occurrence of nannoplankton biodatum and had an absolute age, widely known as a zone indicator. This study aims to determine the age and nannoplankton biozonation of each geological formation in Banggai-Sula Basin. Based on the biostratigraphic analysis, 39 species from 14 genera with abundance frequencies ranging from rare to abundant were found in the MH-2 well. In this study, new results of the age of Banggai-Sula Basin areMiddle Miocene – Early Middle Pliocene (13,706 – 3,727 Ma), and can identify into six calcareous nannoplankton zones that are more detailed than previous researchers, Discoaster signus zone (NN5), Discoaster exilis zone (NN6-NN7), Discoaster berggrenii zone (NN11), Ceratolithus acustus zone (NN12), Helicosphaera sellii zone (NN13-NN15), and the Discoaster tamalis zone (NN16). Biostratigraphic data also shows new information for the first time, the absence of three zones from zone NN8 to zone NN10. This result indicates an unconformity in the Late Miocene age (10.606–8.20 Ma).
The Middle Pleistocene Transition (MPT) represents a major change in Earth's climate state, exemplified by the switch from obliquity-dominated to ∼100-kyr glacial/interglacial cycles. To date, the ...causes of this significant change in Earth's climatic response to orbital forcing are not fully understood. Nonetheless, this transition represents an intrinsic shift in Earth's response to orbital forcing, without fundamental changes in the astronomical rhythms. This study presents new high-resolution records of International Ocean Discovery Program (IODP) Site U1460 (eastern Indian Ocean, 27°S), including shallow marine productivity and organic matter flux reconstructions. The proxy series covers the interval between 1.1 and 0.6 Ma and provides insights into Pleistocene Leeuwin Current dynamics along the West Australian shelf. The large >45 m global sea level drop during the marine isotope stage (MIS) 22–24 is marked in our data, suggesting that the MPT led to large-scale changes in Indian Ocean circulation patterns and surface water conditions. We consider shelf exposure (and thus the “Sahul-Indian Ocean Bjerknes mechanism”) as a possible key process to increase the upwelling of nutrient-rich sub-Antarctic Mode waters through the Leeuwin Undercurrent along the Australian shelf. We conclude that the shoaling of nutrient-rich lower-thermocline waters enhanced mid-latitude productivity patterns in the eastern Indian Ocean across the 900-ka event.
•Organic carbon fluxes on the Australian Shelf increased after 900 ka BP.•Leeuwin Current intensity was tightly coupled to sea level in the middle Pleistocene.•Sea level changes decoupled alkenone/carbon and nannofossil fluxes on the shelf.•Spectral analyses indicate high latitude forcing increased after 900 ka BP.•Expanding sub-Antarctic mode waters forced productivity changes after 900 ka.
Coccolith compositions of surface sediment samples from the Southwestern Atlantic Ocean were analysed in relation with present-day surface-water environmental parameters (temperature, salinity, ...phosphate, and nitrate). This work is based on surface sediment data sets obtained from the Argentinean Continental Margin (40 – 55°S and 55 – 65°W). A multivariate ordination technique, Redundancy Analysis, was applied on the relative abundances of the most abundant taxa (Emiliania huxleyi, Gephyrocapsa muellerae, Calcidiscus leptoporus and Gephyrocapsa spp. small). The results of the analysis revealed the affinities of G. muellerae and Gephyrocapsa spp. small for high nutrient conditions. In contrast, E. huxleyi and C. leptoporus seem to be associated with high salinity and high temperature. Statistical analysis results revealed three Groups (I–III), nutrient content controlled. Group I lies within northern sites, is dominated by E. huxleyi and has a positive correlation with salinity and temperature. Conversely, Group II, located in Sloggett Canyon, is dominated by E. huxleyi and is not correlated to any environmental variables. Group III, is composed by E. huxleyi and G. muellerae, is geographically confined to the southeast area and has a positive correlation with phosphate and nitrate. There would be a moderate association of certain groups of coccolithophores (as Gephyrocapsa spp.) with nutrient-rich waters from the Malvinas Current, and Emiliania huxleyi strains more associated with relatively low nutrient content of waters from the northernmost part of Argentinean Continental Margin.
Nearly all iron dissolved in the ocean is complexed by strong organic ligands of unknown composition. The effect of ligand composition on microbial iron acquisition is poorly understood, but ...amendment experiments using model ligands show they can facilitate or impede iron uptake depending on their identity. Here we show that siderophores, organic compounds synthesized by microbes to facilitate iron uptake, are a dynamic component of the marine ligand pool in the eastern tropical Pacific Ocean. Siderophore concentrations in iron-deficient waters averaged 9 pM, up to fivefold higher than in iron-rich coastal and nutrient-depleted oligotrophic waters, and were dominated by amphibactins, amphiphilic siderophores with cell membrane affinity. Phylogenetic analysis of amphibactin biosynthetic genes suggests that the ability to produce amphibactins has transferred horizontally across multiple Gammaproteobacteria, potentially driven by pressures to compete for iron. In coastal and oligotrophic regions of the eastern Pacific Ocean, amphibactins were replaced with lower concentrations (1–2 pM) of hydrophilic ferrioxamine siderophores. Our results suggest that organic ligand composition changes across the surface ocean in response to environmental pressures. Hydrophilic siderophores are predominantly found across regions of the ocean where iron is not expected to be the limiting nutrient for the microbial community at large. However, in regions with intense competition for iron, some microbes optimize iron acquisition by producing siderophores that minimize diffusive losses to the environment. These siderophores affect iron bioavailability and thus may be an important component of the marine iron cycle.
The Late Triassic marks the inception of marine calcareous nannoplankton. However, calcareous nannofossil of this period have been found so far only in successions of the eastern Panthalassa Ocean, ...and from the western and southern Neo-Tethys Ocean. A new middle to late Norian (Late Triassic) calcareous nannofossil association is presented for the first time from Hongyan section at Baoshan block in the Palaeo-Tethys. Here, the calcareous nannofossils association is composed of Prinsiosphaera triassica, P. sp., and Orthopithonella geometrica and calcispheres. The assemblage is predominantly composed of Prinsiosphaera, accounting for >90% of the relative abundance, with a small amount of calcispheres and Orthopithonella geometrica. Similar to the western Tethys, Prinsiosphaera makes up 0.1–1.1% of the limestone volume in the Baoshan block. The mean diameter of Prinsiosphaera decreases from approximately 8.0 to 6.2 μm in the upper Norian (Sevatian), and average volume reduction of approximately 50%. The change in size is coeval with negative carbon and oxygen isotope excursions of the Norian, suggesting a temporal coincidence between C-cycle perturbations, global warming and a dwarfing of Prinsiosphaera.
•First report of Norian calcareous nannofossils from the eastern Tethys.•Prinsiosphaera dominates the calcareous nannofossil association in eastern Tethys.•A dwarfing of Prinsiosphaera during the Norian warming event is observed.•Prinsiosphaera susceptible to environmental changes and may adapted to an r-strategy.
The taxonomic composition and detailed stratigraphic distribution of the calcareous nannofossils from the Santonian and Campanian of the Crimea have been studied for the first time. The identified ...assemblage of calcareous nannofossils in the Alan-Kyr section consists of 85 species, including all primary and additional zonal markers. The following calcareous nannofossil zones and subzones have been recognised and correlated with planktonic (PF) and benthic (BF) foraminifera zones: transitional Santonian–Campanian CC17 or latest Santonian UC13 (Dicarinella asymetrica/D. concavata PFZone and the lower part of Globotruncanita elevata/stuartiformis PFZone), lower Campanian CC18a/UC14a, CC18b–c and CC19/UC14b–UC15a (Globotruncanita elevata/stuartiformis PFZone), lower Campanian CC20/UC15b (Contusotruncana plummerae/Globotruncana ventricosa PFZone), upper Campanian CC21/UC15c (Contusotruncana plummerae/Globotruncana ventricosa PFZone and Globotruncanella havanensis PFZone) and upper Campanian CC22/UC15d (Globotruncanella havanensis PFZone). Using magnetostratigraphic data as the primary source for definition of the base of the Campanian, we place the Santonian–Campanian boundary in the Alan-Kyr section at the level of the base of Chron C33r and inside the nannofossil transitional Santonian–Campanian CC17 or lower Campanian UC14 Zone and the planktonic foraminifera Santonian D. asymetrica/D. concavata Zone. This conclusion is supported by the relative position of other microfossil bioevents: the first occurrence of Broinsonia parca parca, which happens just above the highest occurrences of both Dicarinella asymetrica and D. concavata, as well as the lowest occurrence of the benthic foraminifera Neoflabellina asema.
Oceanic Anoxic Event 2 (OAE2) at the Cenomanian/Turonian Boundary (CTB: 93.9Ma) involved the global deposition of organic carbon-rich sediments, a distinctive positive shift in carbon isotope values, ...and significant species turnover, including changes in calcareous nannofossil assemblages. While it is thought that volcanism triggered organic C-rich sediment deposition during OAE2, it is unclear whether enhanced productivity, increased stratification, of some combination of the two increased organic matter preservation. Calcareous nannofossil assemblages have the potential to qualitatively assess changes in ocean nutrient and temperature conditions to disentangle such ecological dynamics during OAE2. Here we study an expanded section of the Tropic Shale in a drill core in southern Utah near the western margin of the Western Interior Seaway (WIS) to understand how circulation changed during the event and how this may have influenced primary productivity and organic carbon burial. Relative abundance data of well-preserved nannoplankton are complemented with measurements of trace metal, and organic carbon and carbonate concentrations to determine changes in temperature and water column structure, as well as controls on surface water productivity. Detailed statistical analysis helps refine species paleoecologies combined with information from planktic and benthic foraminiferal assemblages and organic biomarkers. Changes in calcareous nannofossil assemblages indicate that near the start of OAE2 the western WIS surface ocean actually cooled for a short time. Following this, surface waters became warmer and more stratified as a Tethyan water mass invaded the seaway. Assemblages suggest that warmth persisted for much of the OAE2 interval, while stratification waxed and waned. The local seaway cooled near the end of OAE2 as Boreal water masses streamed along the western margin. Variations, including the decrease in the abundance of Biscutum constans and short-lived peaks in the abundance of Eprolithus spp. are super regional or possibly global in extent. There is no correlation between calcareous nannofossil assemblages and trace metal concentrations, suggesting they were unaffected by volcanism-related nutrient inputs. Assemblages support other data that suggest increased stratification influenced organic carbon burial in the Western Interior Seaway, and possibly elsewhere, during OAE2.
The marine system of the Mediterranean-Paratethys region in the Middle Miocene was influenced by the global climatic changes corresponding to the Miocene Climate Optimum. The latter was characterized ...by global warming of deep oceanic waters succeeded by a decrease of wind activity and ocean water circulation together with a decline in oceanic productivity. This study provides a detailed paleoenvironmental and depositional history of the Middle Miocene deposits from Mt. Požeška Gora (the east part of Croatia). Stable carbon and oxygen isotope data with foraminiferal fauna coupled together with palynological data indicate both seasonal and long-term changes in surface water temperatures, nutrient contents, and salinity. Furthermore, it was possible to determine two phases of Middle Miocene flooding in the studied marine system: (a) a shallow, high nutrient marginal sea strongly affected by freshwater inputs corresponding to the thermal maximum and periods with enhanced precipitation during the Miocene Climate Optimum, and (b) a younger deeper marginal sea with a developed seasonal stratification, rather intermediate nutrient availability and reduced fresh-water inputs. Based on the microbiostratigraphy and strontium isotope stratigraphy (87Sr/86Sr) coupled with previously published high-precision geochronology, the timing of the first and second flooding can be correlated with the Langhian age - ≤15.4 Ma and 14.6 Ma, respectively Possibly, the properties of the surficial waters that were described as a part of the flooding phases in individual time intervals can indicate changes in circulation patterns as a result of potential influence of the open-sea water masses.
•Determination of two transgressive pulses of the Middle Miocene flooding in the Paratethys.•(1) shallow marginal sea strongly affected by freshwater input.•(2) deeper marginal sea with a developed seasonal stratification.•Plankton biostratigraphy coupled with geochronology/SIS (87Sr/86Sr) - the timing of individual floodings.•Flooding phases - indicative of changes in circulation + sea-level changes.
New biostratigraphic investigations based on palynomorphs (mainly dinoflagellate cysts), foraminifera and calcareous nannoplankton recovered from eight geological sections indicate that the Hangu ...Formation near the Pluton-Pipirig area (Tarcău Nappe, Eastern Carpathians, Romania), previously assigned to the Senonian–Paleocene interval, includes only uppermost Cretaceous deposits. The palynological assemblages are moderately rich, with a total of 167 well-preserved taxa. The marine palynomorphs – essentially consisting of dinoflagellate cysts (dinocysts) – are dominated by peridinioid taxa, mainly recorded in upper Upper Campanian–lower Maastrichtian deposits, and by a high-diversity assemblage of gonyaulacoid taxa during the late Maastrichtian. Marine algae and dinogymnioid dinocysts were less common. The terrestrial palynoflora is dominated by fern spores and angiosperm pollen, with subordinate gymnosperm pollen. The foraminiferal assemblages include an assortment of well-preserved agglutinated forms, present mainly in the upper Maastrichtian deposits, whereas calcareous benthics and planktonic foraminifera are rare and poorly preserved. Calcareous nannoplankton assemblages are also rare, often represented by two taxa (Micula staurophora and Watznaueria barnesiae); certain important biostratigraphic markers were found to be reworked in the analyzed deposits. Age assignments for the studied sections were mainly provided by dinocysts, through the identification of significant marker taxa and comparisons with well-calibrated Campanian–Maastrichtian dinocyst assemblages from well-dated sections and stratotypes, located mostly in the Northern Hemisphere.
Indices such as particulate organic matter (POM) composition, the relative abundance of dinocyst eco-groups, as well as agglutinated foraminiferal morphogroups, were used to reconstruct the depositional environments of the Hangu Formation from the studied area. The upper Upper Campanian–lower Maastrichtian deposits from the Pluton-Pipirig sections were mainly deposited in neritic marine conditions, although occasional redeposition of the sediments transported by turbidity currents towards deeper water settings is not excluded, either. The depositional environments evolve towards outer neritic to distal (bathyal) during the late Maastrichtian, as indicated by palynofacies constituents and by high frequencies of gonyaulacoid dinocysts and deep-water benthic foraminifera.
•Upper Campanian–Maastrichtian microfossils, Eastern Carpathians, Romania, are studied.•Palaeoenvironmental and palaeoecological conditions are discussed.•A new detailed geological map for the studied area was proposed.
How much temporal recurrence is present in microbial assemblages is still an unanswered ecological question. Even though marked seasonal changes have been reported for whole microbial communities, ...less is known on the dynamics and seasonality of individual taxa. Here, we aim at understanding microbial recurrence at three different levels: community, taxonomic group and operational taxonomic units (OTUs). For that, we focused on a model microbial eukaryotic community populating a long‐term marine microbial observatory using 18S rRNA gene data from two organismal size fractions: the picoplankton (0.2–3 µm) and the nanoplankton (3–20 µm). We have developed an index to quantify recurrence in particular taxa. We found that community structure oscillated systematically between two main configurations corresponding to winter and summer over the 10 years studied. A few taxonomic groups such as Mamiellophyceae or MALV‐III presented clear recurrence (i.e., seasonality), whereas 13%–19% of the OTUs in both size fractions, accounting for ~40% of the relative abundance, featured recurrent dynamics. Altogether, our work links long‐term whole community dynamics with that of individual OTUs and taxonomic groups, indicating that recurrent and non‐recurrent changes characterize the dynamics of microbial assemblages.
see also the Perspective by Moreira and López‐García
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