High Productivity Events Research Articles

Seasonal potential fishing zone model in the regional fisheries management of Indonesia (WPP-RI) 716 based on remote sensing satellite data

The variability of atmosphere-ocean interactions highly influences the distribution of fishing zones in the surrounding Indonesia Through Flow (ITF) channel, such as the WPP-716 region. Therefore, the seasonal determination of the fishing zone is crucial in this zone as one of the regional fisheries managements in Indonesia. This study aims to create a potential fishing zone (PFZ) model in the Regional Fisheries Management of Indonesia (WPP-RI) 716 based on the remote sensing satellite data. This study used the daily SST data extracted from the Suomi-National Polar-Orbiting Partnership-Visible Infrared Imaging Radiometer Suite (SNPP-VIIRS) image Level 2 from 2018 to 2019. A Single Image Edge Detection (SIED) method is applied to determine the PFZ points. Supporting data, such as sea current patterns, chlorophyll-a, fish-catching zones and Catch per Unit of Effort (CpUE), are also considered to bolster this study's findings. The models were validated and compared with the results established by central authority fish catch data. Of particular concern, the highest detection of PFZ is observed during the second transitional season, reaching 1835 points scattered all over the study area. The frequently detected PFZ is identified in northern Sulawesi and Sangihe Islands, where the circular eddy current observed during the second transitional season, ranging from 0.6 to 0.8 m/s, indicating upwelling (high productivity) events proven by the variability of surface temperature and chlorophyll-a and aligned with the high value of CpUE (ranging from 20 to 28 ​kg/GT/day). The developed model is expected to be a basis for further decision-making regarding fishery resources management in the study area.

Ocean acidification induces distinct metabolic responses in subtropical zooplankton under oligotrophic conditions and after simulated upwelling

Ocean acidification (OA) is one of the most critical anthropogenic threats to marine ecosystems. While significant ecological responses of plankton communities to OA have been revealed mainly by small-scale laboratory approaches, the interactive effect of OA-related changes on zooplankton metabolism and their biogeochemical implications in the natural environment still remains less well understood. Here, we explore the responses of zooplankton respiration and ammonium excretion, two key processes in the nutrient cycling, to high pCO2 levels in a 9-week in situ mesocosm experiment conducted during the autumn oligotrophic season in the subtropical northeast Atlantic. By simulating an upwelling event halfway through the study, we further evaluated the combined effects of OA and nutrient availability on the physiology of micro-and mesozooplankton. OA conditions generally resulted in a reduction in the biomass-specific metabolic and enzymatic rates, particularly in the mesozooplankton community. The situation reversed after the nutrient-rich deep-water addition, which initially promoted a diatom bloom and increased heterotrophic activities in all mesocosms. Under high pCO2 conditions (>800 μatm), however, the nutrient fertilization triggered the proliferation of the harmful alga Vicicitus globosus, with important consequences for the metabolic performance of the two zooplankton size classes. Here, the zooplankton contribution to the remineralization of organic matter and nitrogen regeneration dropped by 30% and 24%, respectively, during the oligotrophic period, and by 40% and 70% during simulated upwelling. Overall, our results indicate a potential reduction in the biogeochemical role of zooplankton under future ocean conditions, with more evident effects on the large mesozooplankton and during high productivity events.

Turonian microcrinoids from the lower Aruma Formation of Saudi Arabia

Pelagic microcrinoids assigned to the genus Roveacrinus identified in thin-sections of carbonates of the Turonian lower Aruma Formation of Saudi Arabia provide the first documented occurrence of these microfossils in the Arabian Peninsula. The species include Roveacrinus cf. alatus Douglas 1908, Roveacrinus sp., Roveacrinus geinitzi Schneider 1989, Roveacrinus cf. geinitzi, Roveacrinus aff. rugosus Douglas 1908, Roveacrinus sp. A., Roveacrinus aff. geinitzi Schneider 1989 and Roveacrinus cf. derdereensis. The Turonian range is based on the presence of planktonic foraminifera Heterohelix moremanni, H. globulosa and Marginotruncana sigali in the absence of Rotalipora spp., although possible Cenomanian forms are present within one deep marine microfacies assemblage. The biofacies containing the often abundant Roveacrinus fragments consists typically of abundant calcareous dinoflagellate cysts Calcisphaerula innominata with less common Pithonella ovalis, and rare Bonitocardiella conica, rare to common planktonic foraminifera and rare benthonic foraminifera including Marssonella turris and Gavelinella spp. This assemblage, within very fine-grained packstones, suggests a deep marine depositional environment with low energy, normal salinity conditions. Deep marine sediments, that include Heterohelix moremanni and forms that may be transitional to H. globulosa, include roveacrinids that compare with the Cenomanian species R. derdereensis and these may prove to be supplementary useful age indicators in such environments. Although their association with pelagic microfossils would suggest a planktonic lifestyle, a definite paleoenvironmental interpretation seems elusive by most authors although there is a direct association between the roveacrinoid abundance and flooding surfaces and high-productivity events. Roveacrinid fragments have been recovered from calcareous mudstones of the Ruwaydha and Tuwayil members of the Aruma Formation that overlie upper Cenomanian grainstones of the MishrifMember of theWasia Formation. A regionally significant unconformity separates the Mishrif Formation from the Aruma Formation, of which the basal Aruma represents a significant deep marine transgression. The episodic microcrinoid distribution potentially provides regionally correlative bioevents in addition to their possible relationship with the oceanic anoxic event OAE 2.

Influence of dominant wind patterns in a distal region of the NW Iberian Margin during the last glaciation

This work combines planktonic foraminiferal assemblages, stable isotope, transfer function estimated sea surface paleotemperatures (SST) and export productivity (Pexp) with sedimentological records from the PC7 core to document paleoclimatic and paleoceanographic changes on a distal region of the NW Iberian Margin since the last glaciation (<≈68 ka). Neodymium and strontium isotope data are also used to identify the provenance of ice rafted debris (IRD) during Heinrich event 5 (H5). Our results are compared and combined with previously published records and evidence that melt water and icebergs from the Canada, Greenland, Iceland and Europe ice sheets arrived to the NW Iberian Margin causing a significant decrease of SST during the last six Heinrich Stadials (HS) and some Dansgaard–Oeschger (D-O) stadial events. εNd and 87 Sr/ 86 Sr indicate that the studied locality mostly received sediments from European Ice Sheets (EIS) during H5. During the HS and D–O stadial events, SSTs were in general higher than in other cores collected in inner areas of the NW Iberian Margin. The presence and intensification of Portugal Current probably induced heat transfer to this distal region of the Iberian Margin. Our results also suggest the occurrence of high variability in the intensity and wind patterns during the last glaciation. In some periods, the intensity of northerly winds could have been very strong and contributed to a significant stimulation of ocean productivity in this distal area through the intensification of upwelling. In general, oceanic productivity decreased during the HS and D–O as the presence of cold and less saline water prevented nutrient rich waters from deep levels reaching the surface. The high productivity events were bracketed by periods characterized by the highest influence of the Azores Current eastern branch during which northerly winds and the oceanic productivity should have been weakened. Supplementary material: Geochemical and foraminiferal data analysed in this work as well as Pearson Correlations between the analysed data are available at https://doi.org/10.6084/m9.figshare.c.3931813

Zoonoses As Ecological Entities: A Case Review of Plague.

As a zoonosis, Plague is also an ecological entity, a complex system of ecological interactions between the pathogen, the hosts, and the spatiotemporal variations of its ecosystems. Five reservoir system models have been proposed: (i) assemblages of small mammals with different levels of susceptibility and roles in the maintenance and amplification of the cycle; (ii) species-specific chronic infection models; (ii) flea vectors as the true reservoirs; (iii) Telluric Plague, and (iv) a metapopulation arrangement for species with a discrete spatial organization, following a source-sink dynamic of extinction and recolonization with naïve potential hosts. The diversity of the community that harbors the reservoir system affects the transmission cycle by predation, competition, and dilution effect. Plague has notable environmental constraints, depending on altitude (500+ meters), warm and dry climates, and conditions for high productivity events for expansion of the transmission cycle. Human impacts are altering Plague dynamics by altering landscape and the faunal composition of the foci and adjacent areas, usually increasing the presence and number of human cases and outbreaks. Climatic change is also affecting the range of its occurrence. In the current transitional state of zoonosis as a whole, Plague is at risk of becoming a public health problem in poor countries where ecosystem erosion, anthropic invasion of new areas, and climate change increase the contact of the population with reservoir systems, giving new urgency for ecologic research that further details its maintenance in the wild, the spillover events, and how it links to human cases.

Depositional conditions during the Lower Kellwasser Event (Late Frasnian) in the deep-shelf Łysogóry Basin of the Holy Cross Mountains Poland

Integrated biostratigraphical, microfacial and geochemical studies of the Lower Kellwasser Event in the Plucki succession (southern Poland) provide details about redox conditions during the deposition of this horizon in the deep-shelf Łysogory basin of the Holy Cross Mountains. The environment is characterized by calm sedimentation and soft, muddy carbonate substrate. However, microfacies changing from wackestones to grainstones, the presence of crushed or current-oriented nautiloid shells and the occurrence of redeposited material from shallow-water Dyminy Reef environments (such as calcispheroids, algae and girvanellid cyanobacteria) suggest episodes of a higher-energy regime. Uranium/thorium ratios indicate that bottom-water redox conditions changed periodically from being mainly anoxic in the middle part of the Lower Kellwasser Horizon to dysoxic in the lower and upper parts. During a short-term episode of bottom-water ventilation, the seafloor was rapidly colonized by a dense assemblage of opportunistic buchiolid bivalves, which suffered mass mortality upon the return to anoxic conditions. A very rich concentration of cephalopods and homoctenids may be regarded as reflecting a bloom of high-density populations during high-productivity events. Similarly, they suffered mass mortality when episodically increasing anoxia/euxinia reached the upper part of the water column. The Late Frasnian inorganic carbon isotope records in the Plucki section show a positive shift with a maximum amplitude of 3‰. This enrichment in δ13C can be correlated with the deposition of the Lower Kellwasser Horizon and reflects the expansion of anoxic and probably high-productivity regimes.

Proliferation of shallow-water radiolarians coinciding with enhanced oceanic productivity in reducing conditions during the Middle Permian, South China: evidence from the Gufeng Formation of western Hubei Province

The Middle Permian is a critical period when a possible cooling regime prevailed and massive deep-water cherty sediments were deposited in the South China Craton. An integration of radiolarian paleoecologic and geochemical studies from the Middle Permian Gufeng cherty succession of western Hubei Province, South China tests the relationships among oceanic productivity, redox conditions, and radiolarian responses as well as origin of the cherts. A total of 21 species and six undetermined species in 10 radiolarian genera are identified from the Gufeng Formation in the northern margin basin of the Yangtze Platform of the South China Craton. Three radiolarian Pseudoalbaillella globosa, Follicucullus monacanthus, and Follicucullus scholasticus zones were established and constrained the Gufeng Formation as Roadian to Middle Capitanian in age. The Gufeng cherts embrace a biologic and hydrothermal origin in the northern marginal basin and southern margin basin (the Nanpanjiang Basin) of the South China Craton, respectively. The high oceanic primary productivity in surface oceans resulted in the widespread reducing conditions in the bottom water column. Such high oceanic productivity event slightly predated the Middle Permian Kamura cooling event of the Panthalassian Ocean. Both the elevated continent weathering due to pre-eruptive crustal uplift of the Emeishan flood volcanism and active oceanic upwelling may have stimulated high oceanic productivity and facilitated the deposition of the Gufeng cherts. All radiolarians bloomed in relatively oxic conditions. Only shallow-water radiolarians, mainly spherical forms, proliferated in the reducing conditions, which also coincided with an enhanced oceanic productivity. The abundance of spherical radiolarians therefore is an ideal proxy indicating oceanic primary productivity.

Depositional history of the youngest strata of the Sassendalen Group (Bravaisberget Formation, Middle Triassic–Carnian) in southern Spitsbergen, Svalbard

The Bravaisberget Formation of southern Spitsbergen (the youngest formation of the Sassendalen Group; Middle Triassic–Carnian) comprises a succession of organic-rich and sandy phosphogenic deposits that developed in a marginal part of the Svalbard basin, in response to a high biological productivity event in the Barents Shelf. The basin margin was bounded on the southwest by the elevated structure of the SÝrkapp-Hornsund High. North of the high, the subsiding shelf bottom stretched from southern to western Spitsbergen. The organic-rich, fine-grained sedimentation that gave rise to the formation of the Passhatten Member extended southward after the Anisian transgression; it reached the topmost part of the SÝrkapp -Hornsund High during the maximum flooding of the basin in the early Ladinian. The sudden appearance of deltaic deposits of the Karentoppen Member directly after the maximum flooding was a consequence of short-lived tectonic activity of the SÝrkapp -Hornsund High and the adjacent land area. Reworking and redistribution of the deltaic sediments during the Ladinian brought about the formation of shallow-marine clastic facies of the Somovbreen Member. Decreasing depositional rates close to the Middle-Late Triassic boundary led to a regional hiatus and the formation of a condensed phosphorite horizon at the top of the Somovbreen Member. The sedimentation of the Bravaisberget Formation ended in the early Carnian. The youngest siliciclastic and spiculitic sediments of the Van Keulenfjorden Member were deposited in southern and western Spitsbergen in shallow- to marginal-marine environments.

Biological productivity along Line P in the subarctic northeast Pacific: In situ versus incubation‐based methods

We compared net community production determined from an in situ O2/Ar mass balance (O2/Ar‐NCP) with incubation measurements of new and primary production in the subarctic northeast Pacific. In situ O2/Ar‐NCP was strongly correlated to new production from 24‐h15NO3− uptake integrated over the mixed layer (15N‐NewP), if measurements were separated into high and low‐productivity conditions. Under high‐productivity conditions, O2/Ar‐NCP estimates were similar to15N‐NewP, whereas under low productivity conditions O2/Ar‐NCP was up to two times higher than15N‐NewP. The relationship between O2/Ar‐NCP and 24‐h13C primary production (13C‐PP) was more variable, but with a consistent mean O2/Ar‐NCP:13C‐PP ratio of 0.52 ± 0.17 when only low‐productivity, summer measurements were considered. This relationship with primary production is perturbed by high productivity events such as a late‐summer, iron‐stimulated bloom observed at the offshore stations. Finally, we show that diapycnal mixing usually dominates the O2/Ar mass balance in winter in the subarctic Pacific, preventing the determination of NCP by the O2/Ar method at that time, except for one unusual stratification event in February 2007.

Dominant eukaryotic export production during ocean anoxic events reflects the importance of recycled NH 4 +

The Mesozoic is marked by several widespread occurrences of intense organic matter burial. Sediments from the largest of these events, the Cenomanian-Turonian Oceanic Anoxic Event (OAE 2) are characterized by lower nitrogen isotope ratios than are seen in modern marine settings. It has remained a challenge to describe a nitrogen cycle that could achieve such isotopic depletion. Here we use nitrogen-isotope ratios of porphyrins to show that eukaryotes contributed the quantitative majority of export production throughout OAE 2, whereas cyanobacteria contributed on average approximately 20%. Such data require that any explanation for the OAE nitrogen cycle and its isotopic values be consistent with a eukaryote-dominated ecosystem. Our results agree with models that suggest the OAEs were high-productivity events, supported by vigorous upwelling. Upwelling of anoxic deep waters would have supplied reduced N species (i.e., NH(4)(+)) to primary producers. We propose that new production during OAE 2 primarily was driven by direct NH(4)(+)-assimilation supplemented by diazotrophy, whereas chemocline denitrification and anammox quantitatively consumed NO(3)(−) and NO(2)(−). A marine nitrogen reservoir dominated by NH(4)(+), in combination with known kinetic isotope effects, could lead to eukaryotic biomass depleted in (15)N.

Diatom phytoplankton response to Holocene climate change in the Subpolar North Atlantic

A detailed investigation of marine core MD99-2251 from the Gardar Drift has been undertaken to examine the extent of Holocene climate variability reflected by changes in diatom floral abundances in the subpolar North Atlantic. The results from this study provide both an overview of climate variability for the entire Holocene and a decadal-scale study focussed around the 8.2 kyr event, where ice rafted debris also has been quantified. The changing composition of diatom assemblages indicates a highly unstable early Holocene from 11.5 to 9 kyr with switches in the dominance of cool Subarctic floras and warmer North Atlantic Current floras. The presence of high productivity events in the diatom floras during this interval suggests that the core location was, at times, in close proximity of the Subarctic Front. An expansion in the importance of cold Arctic/Greenland Current floras occurred from 9 to 7 kyr, followed by a switch to a well developed warm North Atlantic Current flora between 7 and 5 kyr and then more stable conditions during the Late Holocene. Changes in sea surface hydrography, especially the relative strength of the warm North Atlantic Current, are considered to have had the greatest influence on the composition of diatom floral assemblages. The 8.2 kyr event is not recognised as a discrete climate perturbation in the diatom assemblage data, but this event occurred within a broad cooling from 9 to 7 kyr, where the presence of sea-ice and cold water species indicate an increased incursion of the Arctic and Subarctic water masses between 8.8 and 7.8 kyr. The 8.2 kyr event also was not marked by any increase in the delivery of ice rafted debris over the Gardar Drift.

Molecular isotopic evidence of environmental and ecological changes across the Cenomanian–Turonian boundary in the Levant Platform of central Jordan

We evaluated the structure of planktonic communities and paleoenvironmental conditions throughout the Cenomanian–Turonian Oceanic Anoxic Event (OAE2) by studying bulk geochemical properties and the molecular isotopic composition of source-specific hydrocarbons from organic-rich sediments deposited in an intrashelf basin at the Levant Platform, central Jordan. High concentrations of desmethyl and 4-methylsteranes as well as dinosteranes indicate that marine algae including dinoflagellates were the main primary producing organisms. The presence of 2-methylhopanes and 13C-enriched hopanes, in addition to isotopically enriched aryl isoprenoids, evidenced the contribution of cyanobacteria and green sulfur bacteria, respectively. Additionally, variable but fairly low δ 15N values during OAE2 suggest the occurrence of diazotrophy as a likely important process fueling primary production during OAE2 in this stratified/anoxic continental platform. Variations in the relative contribution of biomarkers revealed changes in planktonic communities associated with sea level change and water column stratification. OAE2 was characterized by strong stratification, anoxic bottom waters and a deep chemocline, as evidenced by high gammacerane and homohopane indices and the absence of photic zone euxinia (PZE) markers, respectively. However, the presence of isorenieratane and its derivatives in post-OAE black shales points to a shoaling of the chemocline and to PZE. This interval was also characterized by an exceptionally high abundance of chlorophyll-derived pristane and phytane (up to 2 mg g −1 TOC), likely as a result of highly enhanced primary production and organic matter preservation. Remarkably, this high productivity event co-occurs with an exceptionally high abundance of calcispheres reported elsewhere to be part of a global bio-event.

Organic-carbon deposition and coastal upwelling at mid-latitude during the Upper Ordovician (Late Katian): A case study from the Welsh Basin, UK

A lack of stratigraphical, sedimentological and geochemical data for sediment accumulation rates and indicators of productivity and anoxia means that causative models for ancient black shales are largely inferred from modern settings. Coastal upwelling has been suggested as a general hypothesis for Ordovician black shale deposition within the Iapetus Ocean, but has not been directly tested. Despite anchizone metamorphism we utilize a suite of geological and geochemical environmental proxy data (TOC wt.%, δ 13C org, Ba/Al, P) to elucidate the mechanism for the origin of a single grey-black shale cycle within the upper Katian succession of the Welsh Basin. Here we interpret organic carbon (OC)-rich deposition to be suggestive of a period of high photic productivity (higher TOC wt.%), with 12C and Ba enrichment, comparable to high productivity events in modern coastal upwelling systems. Productivity proxy values are consistent with those from margins where sedimentation rates are high (e.g. Gulf of California). Inter-bedded grey shales have low TOC wt.% more positive δ 13C org and marginally lower Ba and are interpreted as low productivity events. Thalassinoides, Planolites and Chondrites ichnofacies indicate changing seafloor oxygen levels. These show predominantly dysoxic conditions even during the deposition of OC-poor grey shales. During an OC-rich laminated hemipelagite event, oxygen levels declined at the sea floor before the deposition of the OC-rich layers. Full anoxia was established early on in the deposition of OC-rich layers and the return to more oxic conditions was rapid though fluctuating and coincident with the return of grey shale deposition. This pattern suggests OC accumulation at the seafloor resulted from a complex interaction of productivity and preservation. None of the widely used trace element redox proxies are reliable in anchizone metamorphic rocks. Climate sensitive detrital proxies (K/Al and Ti/Al) indicate arid–temperate conditions in the basin hinterland during the deposition of the OC-rich layers. The Welsh Basin was situated on the southern margin of the Iapetus Ocean in (30°S) beneath the prevailing SE trade winds. We interpret the occurrence of OC-rich laminated hemipelagite events to represent the intensification of upwelling, prior to the Hirnantian glaciation, possibly having resulted from a strengthening of the trade winds, associated with stepped changes in ice volume, and a more arid local climate.

Reconstruction of Indian monsoon variability over the past 230,000 years: Planktic foraminiferal evidence from the NW Arabian Sea open-ocean upwelling area

We determined the faunal composition and total number of tests (#/g) of planktic foraminifera (> 125 μm) in core KH00-05 GOA 6 near Oman in order to decipher monsoon-induced variability of oceanographic productivity in the open-ocean upwelling area in the northwest Arabian Sea. The core contains a continuous record of sedimentation over the last 230 kyr, with the age model based on oxygen isotope and accelerator mass spectrometry 14C dates. We focused on species ( Globigerina bulloides and Globigerinita glutinata) typical for SW monsoonal upwelling and species typical for NE monsoon conditions ( Neogloboquadrina incompta, Neogloboquadrina dutertrei, Globigerinoides ruber, and Globigerinoides sacculifer). The changes in relative abundance of these monsoonal indicators suggest that the open-ocean upwelling area was dominated by the SW monsoon during interglacial periods, but by the NE monsoon during glacial periods. Increases in total test abundance during glacial periods confirmed that the NE monsoon rather than SW monsoon contributes largely to planktic foraminiferal productivity in this area. We argue that three types of circumstances resulted in high productivity, with nine high productivity events occurring at a 23-kyr frequency. The first type caused high productivity events at 102 and 199 ka (interglacial periods), characterized by the dominance of upwelling species, indicating high productivity during strong SW monsoons, correlated with high July insolation at 45° N. An exceptional high productivity event occurred at 37 ka during interglacial marine isotope stage (MIS) 3, with contributions from both SW and NE monsoons. The second type of high productivity event occurred at 61, 147, and 175 ka, during glacial periods, characterized by dominance of NE monsoon species, and correlated with low January insolation at 45° N. In addition, a high productivity event at 85 ka (interglacial period) also was induced by enhanced NE monsoons. The last two high productivity events occurred during transitional periods from glacial to interglacial (MIS 6/5.5 and 2/1), were characterized by the replacement of NE monsoon species with upwelling species, and corresponded to abrupt climate warming, suggesting that they are related to both accelerated SW monsoon systems and reduced NE monsoon systems.

A unique carbon isotope record across the Guadalupian–Lopingian (Middle–Upper Permian) boundary in mid-oceanic paleo-atoll carbonates: The high-productivity “Kamura event” and its collapse in Panthalassa

Middle to Upper Permian shallow marine carbonates in the Kamura area, Kyushu (SW Japan), were derived from a paleo-atoll complex developed on an ancient seamount in mid-Panthalassa. The Capitanian (Upper Guadalupian) Iwato Formation (19 m-thick dark gray limestone) and the conformably overlying Wuchiapingian (Lower Lopingian) Mitai Formation (17 m-thick light gray dolomitic limestone) are composed of bioclastic limestone of subtidal facies, yielding abundant fusulines. A secular change in stable carbon isotope ratio of carbonate carbon ( δ 13C carb) was analyzed in the Kamura section in order to document the oceanographic change in the superocean Panthalassa with respect to the mass extinction across the Guadalupian–Lopingian boundary (G–LB). The Iwato Formation is characterized mostly by unusually high positive δ 13C carb values of + 4.9 to + 6.2‰, whereas the Mitai Formation by low positive values from + 1.9 to + 3.5‰. The negative excursion occurred in three steps around the G–LB and the total amount of the negative shifts reached over 4‰. A remarkably sharp drop in δ 13C carb values, for 2.4‰ from 5.3 down to 2.9‰, occurs in a 2 m-thick interval of the topmost Iwato Formation, after all large-shelled fusulines and bivalves disappeared abruptly. Such a prominent high positive δ 13C carb plateau interval in the end-Guadalupian followed by a large negative shift across the G–LB was detected for the first time, and this trend in the mid-superoceanic sequence is correlated chemostratigraphically in part with the GSSP (Global Stratotype Section and Point) candidate for the G–LB in S. China. The present results prove that the end-Guadalupian event was doubtlessly global in context, affecting circum-Pangean basins, Tethys, and Panthalassa. The end-Guadalupian interval of a high positive plateau in δ 13C carb values over + 5‰ is particularly noteworthy because it recorded an unusually high bio-productivity period that has not been known in the Permian. This end-Guadalupian high-productivity event, newly named “Kamura event”, suggests burial of a huge amount of organic carbon, draw-down of atmospheric CO 2 and resultant global cooling at the end of Guadalupian, considerably after the Gondwana glaciation. The low temperatures during the Kamura event may have caused the end-Guadalupian extinction of large-shelled Tethyan fusulines and bivalves adapted to warm climate. On the other hand, the following event of ca. 4‰ negative shift in δ 13C carb values across the G–LB indicates a global warming in the early Lopingian. This may have allowed radiation of the new Wuchiapingian fauna, and this trend appears to have continued into the Mesozoic. These observations are in good agreement with the global sea-level curve in the Middle–Late Permian. The smooth and gradual pattern of the negative shift suggests that the causal mechanism was not of catastrophic nature (e.g. bolide impact, sudden melting of methane hydrate) but was long and continuous.

Regional record of a global oceanic anoxic event: OAE1a on the Apulia Platform margin, Gargano Promontory, southern Italy

The Gargano Promontory of southern Italy, located on the eastern margin of the Apulia Platform, represents a peculiar Tethyan area where the transition between carbonate platform and adjacent basins is exposed on land. The Aptian stratigraphic record, represented in shallow-water, slope and deep-water deposits, provides a good opportunity to investigate the regional response to the worldwide documented climatic, biotic and palaeoceanographic changes related to Oceanic Anoxic Event 1a (OAE1a). A synthesis of data previously published (Ischitella and Coppitella sections), together with original data (Val Carbonara and Coppa della Guardia sections), from four stratigraphic sections from different depositional settings (proximal to distal) is provided, using an integrated, high-resolution micropalaeontological (planktonic foraminifera and calcareous nannofossils) and, for one section, geochemical (stable carbon and oxygen isotopes) approach. Organic matter preservation is confined to the more distal areas and consists of two thin intervals of black shales in the Aptian portion of the Marne a Fucoidi Formation. Biostratigraphic data assign the older black shale (5 cm thick) to the Selli Level equivalent (OAE1a, Lower Aptian); this carbon-rich interval is immediately followed by another black shale (7–10 cm thick) of early Late Aptian age. OAE1a is generally interpreted as a high-productivity event during a warming interval, followed by a cooling trend. In the Gargano Promontory, although the oxygen isotope curve indicates the above-mentioned climatic evolution, the micropalaeontological data do not support high fertility of the surface water, whereas micropalaeontological and geochemical data for the younger black shale do record high productivity (radiolarian increase in overall abundance, low nannofossil and foraminiferal species richness, increase in abudance of nannofossil fertility indices) associated with a cooling trend. The carbon and oxygen isotope record is in line with evidence from the curves documented elsewhere, whereas, among the biotic events, only the “nannoconid crisis” preceding OAE1a is revealed to be globally correlable. Environmental models for the two episodes of organic matter preservation are proposed, taking into account both global and local controlling factors.

Comparative high-resolution chemostratigraphy of the Bonarelli Level from the reference Bottaccione section (Umbria–Marche Apennines) and from an equivalent section in NW Sicily: Consistent and contrasting responses to the OAE2

The Bonarelli Level (BL) from the upper Cenomanian portion of the reference Bottaccione section (central Italy) is characterized by the presence of black shales containing high TOC concentrations (up to 17%) and amounts of CaCO 3 near to zero. In the absence of carbonate and, consequently, of relative carbon- and oxygen-isotopic data, the elemental geochemistry revealed to be a very useful tool to obtain information about the palaeoclimatic and palaeoceanographic evolution of the Tethys Ocean during the OAE2. Based on several geochemical proxies (Rb, V, Ni, Cr, Si, Ba), the BL is interpreted as a high-productivity event driven by increasingly warm and humid climatic conditions promoting an accelerated hydrological cycle. The enrichment factors of peculiar trace metals (Zn, Cd, Pb, Sb, Mo, U) provide further insight about the H 2S activity at the seafloor during the organic-rich sediment deposition and permitted us to evaluate the use of Ba as palaeoproductivity tracer in conditions of high rate of sulphate reduction. By comparing geochemical records from the reference Bottaccione section (central Italy) with those previously obtained for the coeval Calabianca section (northwestern Sicily), different degrees of oceanic anoxia were delineated and ascribed to different abundance and type (degradable or refractory) of organic matter, which are limiting factors in the bacterial sulphate reduction reactions and in subsequent euxinic conditions at seafloor in the Tethys realm. Based on a ciclostratigraphic approach, consistent fluctuations at 100 ky scale in the chemostratigraphic signals from the two sections are inferred to be expression of a strong orbital-climatic forcing driving changes in the oceanic environment during the BL deposition.

Global and regional palaeoceanographic changes as recorded in the mid-Cretaceous (Aptian–Albian) sequence of the Ionian zone (NW Greece)

Micropalaeontological and chemostratigraphic results from the mid-Cretaceous ‘upper siliceous zone’ of the Ionian zone, studied in two localities of NW Greece (Paliambela and Panaya), provide new insights into the palaeoceanographic evolution of Tethys and better correlation with well-studied Italian successions. δ 13 C carbonate and organic-carbon isotope stratigraphy allows an improved correlation of the early Aptian Fourcade Level with Oceanic Anoxic Event 1a. Calcareous nannofossils point to intervals of reduced sedimentation within the late Aptian part of the limestones overlying the Fourcade Level. Combined calcareous nannofossil, radiolarian and planktonic foraminiferal biostratigraphy suggests that the overlying radiolarites (named herein the ‘Dercourt Member’) are essentially mid-Albian in age. Radiolarites of this age and thickness have not been identified in the well-explored Italian sections or in southern Albania. It is therefore likely that the Dercourt radiolarites reflect a high-productivity event localized in the Greek area of the Ionian zone, possibly caused by a bathymetrically induced upwelling of intermediate to deep waters that entered the Ionian trough following the opening of new oceanic gateways in the Eastern Mediterranean Tethys.

High-resolution geochemical and biotic records of the Tethyan ‘Bonarelli Level’ (OAE2, latest Cenomanian) from the Calabianca–Guidaloca composite section, northwestern Sicily, Italy

High-resolution micropalaeontological and chemostratigraphic records for the upper Cenomanian portion of the Calabianca–Guidaloca composite section (NW Sicily) provide new insight into the palaeoclimatic and palaeoceanographic evolution of the Tethys Ocean. The Bonarelli Level equivalent was identified on the basis of lithology and well constrained by calcareous plankton biostratigraphy and radiolarian assemblages, as well as by the δ 13C curve showing a marked positive excursion (up to 4.7‰). The Bonarelli Level equivalent deposition is characterized by highly eutrophic conditions as testified by radiolarian proliferation. Black shale samples from the Calabianca–Guidaloca composite section contain very high TOC (up to 26%) and moderate to high amounts of CaCO 3 (on average 20%). Among the planktonic foraminifera, hedbergellids and globigerinelloids tolerated the environmental stress induced by the Oceanic Anoxic Event 2 (OAE2). The occurrence of some benthic foraminifera testifies to dysoxic rather than completely anoxic conditions at the sea floor during the deposition of some portions of the Bonarelli Level equivalent. Based on micropalaeontological results and geochemical proxies ( δ 13C, D*, Rb, Ti, V, Ni, Ba, Si, Cr), the Bonarelli Level equivalent is interpreted as a high-productivity event driven by increasingly warm and humid climatic conditions promoting an accelerated hydrological cycle. We propose that periodically increased riverine influxes, triggered by enhanced humidity, resulted in a sluggish circulation mode and consequent anoxic/euxinic conditions favouring the preservation of organic matter at the sea-floor. Spectral analyses performed on selected geochemical signals reveal within the main high productivity event a strong orbital–climatic forcing represented by a long-term eccentricity-steered humidity cyclicity that amplifies a short-term precession-controlled productivity fluctuation.

Influence of northwest Pacific productivity on North Pacific Intermediate Water oxygen concentrations during the Bølling-Ållerød interval (14.7–12.9 ka)

Elevated productivity in the northwest Pacific is suggested as a new possible control driving past intervals of low-O2 intermediate water along the western continental margin of North America. According to this mechanism, O2 consumption would occur near the site of formation of North Pacific Intermediate Water (NPIW), due to increased respiration of organic carbon in response to a high-productivity event. Evidence is provided for such a productivity increase during the Bolling-Allerod interval (14.7–12.9 ka), a time when laminated sediments were deposited along the northern California margin. By this mechanism, low-O2 events in intermediate waters off the western North American margin could occur without significant changes in the rate of NPIW ventilation.