Benthic foraminiferal turnover across the Cretaceous/Paleogene boundary at Agost (southeastern Spain): paleoenvironmental inferences

We studied Upper Cretaceous and Lower Paleogene benthic foraminifera from the Agost section (southeastern Spain) to infer paleobathymetrical changes and paleoenvironmental turnover across the Cretaceous/Paleogene (K/P) transition. Benthic foraminifera indicate uppermost bathyal depths at Agost during the Abathomphalus mayaroensis Biochron (from about 400 kyr before the K/P boundary) through the early Plummerita hantkeninoides Biochron (about 120–150 kyr before that boundary). The depth increased to middle bathyal for the remainder of the Cretaceous, and remained so for the Danian part of the studied section (Parasubbotina pseudobulloides Biochron, at least 200 kyr after the K/P boundary). There were no perceivable bathymetrical changes at the K/P boundary, where 5% of the species became extinct, and the species composition of the benthic foraminiferal fauna changed considerably. Below the boundary, infaunal morphogroups constitute up to 65–73% of the faunas. Directly above the boundary, in the black clays of the lower Guembelitria cretacea Biozone, benthic foraminifera are rare. Several opportunistic taxa (e.g. the agglutinant Haplophragmoides sp.) have short peaks in relative abundance, possibly reflecting low-oxygen conditions as well as environmental instability, with benthos receiving food from short-lived, local blooms of primary producers. Above the clays through the end of the studied interval, epifaunal morphogroups dominate (up to 70% of the assemblages) or there is an even mixture or epifaunal and infaunal morphogroups. Infaunal groups do not recover to pre-extinction relative abundances, indicating that the food supply to the benthos did not recover fully over the studied interval (about 200 kyr after the K/P boundary). The benthic foraminiferal faunal changes are compatible with the direct and indirect effects of an asteroid impact, which severely destabilized primary producers and the oceanic food web that was dependent upon them.     

Abyssal NE Atlantic benthic foraminifera during the last 15 kyr: Relation to variations in seasonality of productivity

Benthic foraminiferal faunas (> 63 μm) and stable isotopes from the last 15 kyr were studied in BENGAL programme (high-resolution temporal and spatial study of the BENthic biology and Geochemistry of a north-eastern Atlantic abyssal Locality) kasten core 13078#16 from the Porcupine Abyssal Plain, NE Atlantic (48°49.91 N, 16°29.94 W, water depth 4844 m). Changes occurred in the accumulation rates, species composition, diversity, and stable isotopes during the last 15 kyr. Today, the area is strongly influenced by seasonal inputs of phytodetritus following the spring blooms in surface water primary productivity. Variations in the relative abundance of the two most abundant species, Epistominella exigua and Alabaminella weddellensis, which today show significant increases in abundance with the presence of phytodetritus on the sea-floor, are interpreted as resulting from changes in the seasonality of productivity. Seasonal productivity was higher during the Holocene than during the last deglaciation and Younger Dryas, probably coinciding with the retreat of the polar front to higher latitudes. This hypothesis is consistent with simultaneous decreases in the percentage of the polar planktic foraminifera Neogloboquadrina pachyderma (s), and increases in the percentage of Globigerina bulloides, a warmer water planktic foraminifera indicative of phytoplankton blooms and enhanced productivity. The relative abundance of the ‘phytodetritus species’ (E. exigua and A. weddellensis) covary between 14.7 and 8.1 kyr, but not between 7.8 and 1.2 kyr. Major decreases in the numbers per gram and accumulation rates of planktic and benthic foraminifera occurred at ∼ 12–8.5 kyr and at ∼ 4 kyr which correspond to decreases in the % sediment coarse fraction and published data on inorganic carbon contents suggesting that dissolution may have increased at these times. Relationships between benthic foraminiferal faunas and benthic stable isotope records suggest no simple relationship between faunal abundances and test isotope chemistry. For example, the abundances of phytodetritus species do not show strong correlations with either the δ¹³C values of E. exigua or the Δδ¹³C _{E. exigua − P. wuellerstorfi} record, which have previously been suggested as indicative of seasonality of productivity.     

Evidence for calcification depth change of Globorotalia truncatulinoides between deglaciation and Holocene in the Western Atlantic Ocean

Measurements of the δ¹⁸O in tests of planktonic and benthic foraminifera in the Florida Straits are used to reconstruct the properties of the water column through time over the last 12 ka (Lynch-Stieglitz et al., in press). The isotopic composition of the foraminifera largely reflects the vertical density gradient. We use this reconstruction and δ¹⁸O measurements on Globorotalia truncatulinoides in a nearby core to track the depth habitat of this species from the last deglaciation to 1.6 ka B.P. Around 9 ka, G. truncatulinoides was calcifying in much shallower water than during the late Holocene. The downward migration toward its modern habitat is a regional phenomenon over the western tropical Atlantic continental slope. The cause is still unclear but we hypothesize that the shallower calcification depth may be a response to the presence of glacial melt water or to circulation changes. This study points to the value of further study of the ecology, life cycle and calcification depth for G. truncatulinoides and other planktonic foraminifera that are used to reconstruct the history of the thermocline and upper water column structure.     

Benthic foraminiferal population fluctuations related to anoxia: Santa Barbara Basin

The pore-water geochemistry and benthic foraminiferal assemblages of sediments from two slope sites and within the central portion of the Santa Barbara Basin were characterized between February 1988 and July 1989. The highest foraminiferal numerical densities (1197 cm^–3 as determined by an ATP assay) occurred at a slope site in June 1988 (550 m) in partially laminated sediments. In continuously laminated sediments from the central basin, foraminifera were found living (as determined by ATP assay) in October 1988 to depths of 4 cm, and specimens prepared for transmission electron microscopy were found with intact organelles to 3 cm, indicating their inhabitation of anoxic pore waters. Ultrastructural data from Nonionella stella is consistent with the hypothesis that this species can survive by anaerobic respiration. However, the benthic foraminifera appear unable to survive prolonged anoxia. The benthic foraminiferal population was completely dead in July 1989 when bottom water O₂ was undetectable.     

Seasonal variations in foraminiferal flux in the Southern Ocean, Campbell Plateau, New Zealand

Time-incremental sediment trap moorings were deployed at two sites across Campbell Plateau, New Zealand; one in the relatively quiet waters of the plateau interior (Pukaki Rise) and the other at the Antarctic Circumpolar Current-swept margin (eastern Campbell flank). A continuous record of particle flux over 416 days identifies marked differences in faunal composition and seasonal occurrence in response to these two dynamically different Southern Ocean settings. In the shallow and thermally isolated interior of the Pukaki Rise site, the flux of foraminifera was closely linked to the austral spring pulse of primary production, at which time 97% of the total foraminiferal production for the year occurred. This seasonal flux of foraminifera at Pukaki Rise was dominated by the species Globorotalia inflata and Globigerina bulloides. The collapse of phytoplankton production at the end of spring was most likely a result of a co-limitation of iron and silicic acid. Over the deep and dynamic eastern flank of Campbell Plateau there were four seasonal pulses of foraminiferal flux, the largest in spring when almost half of the foraminiferal production occurred. Most of the spring flux at this site consisted of Globorotalia inflata and Globigerinita glutinata. Summer at eastern Campbell flank, exhibited the lowest flux of foraminifera, but the highest species diversity, while autumn and winter fluxes were dominated by the deep-dwelling Globorotalia truncatulinoides. Although there was only a single pulse of foraminiferal flux at Pukaki Rise, its mass (g m^{− 2}d^{− 1}) was still greater than that which occurred over the flank, summed across all four seasons. However, the overall standing stock (tests m^{− 2}d^{− 1}) on the flank was more than twice that which occurred at the Pukaki Rise site.An examination of core-top material taken from gravity cores collected in the vicinity of the sediment trap locations, revealed typical Southern Ocean foraminiferal assemblages that were markedly dissimilar in proportion to those observed in the sediment traps.     

The Impact of the Latest Danian Event on Planktic Foraminiferal Faunas at ODP Site 1210 (Shatsky Rise,Pacific Ocean)

The marine ecosystem has been severely disturbed by several transient paleoenvironmental events (<200 kyr duration) during the early Paleogene, of which the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma) was the most prominent. Over the last decade a number of similar events of Paleocene and Eocene age have been discovered. However, relatively little attention has been paid to pre-PETM events, such as the “Latest Danian Event” ("LDE", ~62.18 Ma), specifically from an open ocean perspective. Here we present new foraminiferal isotope (δ¹³C, δ¹⁸O) and faunal data from Ocean Drilling Program (ODP) Site 1210 at Shatsky Rise (Pacific Ocean) in order to reconstruct the prevailing paleoceanographic conditions. The studied five-meter-thick succession covers ~900 kyr and includes the 200-kyr-lasting LDE. All groups surface dwelling, subsurface dwelling and benthic foraminifera show a negative δ¹³C excursion of >0.6‰, similar in magnitude to the one previously reported from neighboring Site 1209 for benthic foraminifera. δ¹⁸O-inferred warming by 1.6 to 2.8°C (0.4–0.7‰ δ¹⁸O measured on benthic and planktic foraminiferal tests) of the entire water column accompanies the negative δ¹³C excursion. A well stratified upper ocean directly before and during the LDE is proposed based on the stable isotope gradients between surface and subsurface dwellers. The gradient is less well developed, but still enhanced after the event. Isotope data are supplemented by comprehensive planktic foraminiferal faunal analyses revealing a dominance of Morozovella species together with Parasubbotina species. Subsurface-dwelling Parasubbotina shows high abundances during the LDE tracing changes in the strength of the isotope gradients and, thus, may indicate optimal living conditions within a well stratified surface ocean for this taxon. In addition, distinct faunal changes are reported like the disappearance of Praemurica species right at the base of the LDE and the continuous replacement of M. praeangulata with M. angulata across the LDE.     

The Late Glacial–Holocene record from Central Adriatic Sea: Paleoenvironmental reconstruction based on benthic foraminiferal assemblages

New micropaleontological data coming from three cores collected on the meso-Adriatic continental shelf (Vasto area) are studied. Comparisons to foraminiferal assemblages and radiocarbon dates previously collected from cores in the San Benedetto del Tronto and Tremiti areas allow the correlation of patterns observed in shallow water areas with those in deeper parts of the basin. We focused on the response of benthic foraminifera during the Holocene high-stand, corresponding to the installation of the recent sedimentary and trophic system. An influence of anthropogenic impacts cannot be ruled out; its effects consist of a depletion of oxygen level with a consequent modification of the structure of benthic foraminiferal assemblages. During the glacial/post glacial cycle, three phases, characterized by a total of six foraminiferal biofacies including different species assemblages were recognized. The first phase, from 14 kyr BP to 11 kyr BP, corresponds to the Bölling/Alleröd and Younger Dryas cold event, before the Holocene sea-level rise. During this phase, the continental shelf was characterized by an infralittoral environment with productive waters owing to the proximity of the Po river delta at the edge of the Mid-Adriatic Deep. The second phase, from 11 kyr BP to 4 kyr BP, represents the Holocene sea-level rise and is characterized by a condensed sedimentation spread over the entire basin. The third phase corresponds to the Holocene high-stand, during which time the modern current system became established. During this phase, the eastern portion of the shelf underwent to the central part of the mud-belt, corresponding to the sub-recent conditions. Recent eutrophication resulting from human activities over the last few centuries is evidenced by frequency fluctuations of typically opportunistic taxa such as Nonionella turgida and Epistominella vitrea.     

Palaeoenvironmental turnover across the Ypresian–Lutetian transition at the Agost section, Southastern Spain: In search of a marker event to define the Stratotype for the base of the Lutetian Stage

Marker events to define the stratotype for the base of the Lutetian Stage are poorly defined. To elucidate such markers and characterize palaeoenvironmental turnovers, we conducted an integrated study of the Ypresian–Lutetian (Y–L; early-middle Eocene) transition at the continuous Agost section (southeastern Spain). This 115-m-thick section, which consists of hemipelagic marls intercalated with hemipelagic limestones and turbidity sandstones, spans from planktic foraminiferal Zones P9 to P12 (E7 to E10) and calcareous nannofossil Zones CP11 to CP14a (NP13 to NP16). We report quantitative analyses of planktic and benthic foraminifera and characterization of trace fossil assemblages that are integrated with mineralogical analyses.Relative to benthic forms, planktic foraminifera constitute more than 80% of the foraminiferal assemblage. We found that the most abundant planktic species belong to the genera Acarinina, Morozovella, Subbotina, and Pseudohastigerina. Benthic foraminiferal assemblages are strongly dominated by calcareous taxa, with bolivinids being the most abundant group. Trace fossils showed the succession Nereites–Zoophycos–Cruziana ichnofacies throughout the Agost section. In addition to changes in palaeobathymetry, we deduced that quantity and quality of organic matter flux influenced by turbidity currents are the main factors controlling benthic assemblages. We distinguished several mineralogical boundaries at the Agost section, each associated with lithological facies changes suggesting a change in provenance rather than changes in weathering conditions. We made three observations that indicate an increase in sea water temperatures or a possible hyperthermal event related to the first occurrence (FO) of hantkeninids (i.e., the P9/P10 boundary): 1) a distinct peak in abundance of the benthic foraminifera Aragonia aragonensis; 2) the low-diversity of benthic foraminiferal assemblages; and 3) the occurrence of the planktic foraminifera Clavigerinella eocenica and Clavigerinella jarvisi. Benthic foraminiferal and trace fossil assemblages also suggest an associated relative fall of sea level from upper-middle bathyal to sublittoral depths. These characteristic indicators point to this boundary as a promising feature for defining the Global Stratotype Section and Point (GSSP) for the base of the Lutetian Stage. However, complementary magnetobiostratigraphic studies carried out at the Agost section point to the FO of calcareous nannofossil Blackites inflatus (base of CP12b), which occurred 3–5 Myr before the P9/P10 boundary, as the most suitable primary marker event. Whatever the marker event chosen, all the successive events recognized at the Agost section allow a complete characterization of the Y–L transition, and thus this section may be a suitable candidate to locate the GSSP for the Ypresian/Lutetian boundary.     

Paleoenvironmental change in the middle Okinawa Trough since the last deglaciation: Evidence from the sedimentation rate and planktonic foraminiferal record

Well-dated, high-resolution records of planktonic foraminifera and oxygen isotopes from two sediment cores, A7 and E017, in the middle Okinawa Trough reveal strong and rapid millennial-scale climate changes since ∼ 18 to 17 thousand years before present (kyr B.P.). Sedimentation rate shows a sudden drop at ∼ 11.2 cal. kyr B.P. due to a rapid rise of sea level after the Younger Dryas (YD) and consequently submergence of the large continental shelf on the East China Sea (ECS) and the retreat of the estuary providing sediment to the basin. During the last deglaciation, the relative abundance of warm and cold species of planktonic foraminifera fluctuates strongly, consistent with the timing of sea surface temperature (SST) variations determined from Mg/Ca measurements of planktonic foraminifera from one of the two cores. These fluctuations are coeval with climate variation recorded in the Greenland ice cores and North Atlantic sediments, namely Heinrich event 1 (H1), Bølling–Allerød (B/A) and YD events. At about 9.4 kyr B.P., a sudden change in the relative abundance of shallow to deep planktonic species probably indicates a sudden strengthening of the Kuroshio Current in the Okinawa Trough, which was synchronous with a rapid sea-level rise at 9.5–9.2 kyr B.P. in the ECS, Yellow Sea (YS) and South China Sea (SCS). The abundance of planktonic foraminiferal species, together with Mg/Ca based SST, exhibits millennial-scale oscillations during the Holocene, with 7 cold events (at about 1.7, 2.3–4.6, 6.2, 7.3, 8.2, 9.6, 10.6 cal. kyr BP) superimposed on a Holocene warming trend. This Holocene trend, together with centennial-scale SST variations superimposed on the last deglacial trend, suggests that both high and low latitude influences affected the climatology of the Okinawa Trough.     

Response of deep-sea benthic foraminifera to Miocene paleoclimatic events, DSDP Site 289

Changes in the Miocene deep-sea benthic foraminifera at DSDP Site 289 closely correlate to the climatically induced variations in deep and bottom waters in the Pacific Ocean. In early Miocene time, oxygen and carbon isotopes indicate that bottom waters were relatively warm and poorly oxygenated. Benthic foraminiferal assemblages are characterized by various species inherited from the Oligocene. Expansion of the Antarctic icecap in the early middle Miocene, 14–16 m.y. ago, increased oxygen isotope values, produced cold, more oxygenated bottom waters and lead to a turnover in the benthic foraminifera. An Oligocene—early Miocene assemblage was replaced by a cibicidoid-dominated assemblage. Some species became extinct and benthic faunas became more bathymetrically restricted with the increased stratification of deep waters in the ocean. In mid-Miocene time, Epistominella exigua and E. umbonifera, indicative of young, oxygenated bottom waters, are relatively common at DSDP Site 289. Further glacial expansion 5–9 m.y. ago lowered sealevel, increased oceanic upwelling and associated biological productivity and intensified the oxygen minima. Abundant hispid and costate uvigerines become a dominant faunal element at shallow depths above 2500 m as E. umbonifera becomes common to abundant below 2500 m. By late Miocene time, benthic faunas similar in species composition and proportion to modern faunas on the Ontong-Java plateau, had become established.     

Late Quaternary deep and surface water mass evolution in the northeastern Indian Ocean inferred from carbon and oxygen isotopes of benthic and planktonic foraminifera

New planktonic and benthic foraminiferal stable isotope records from core YDY05 (northeastern Indian Ocean) provide new insights into paleoceanographic changes in the northeastern Indian Ocean since the last glacial period. The distinct δ¹⁸O decrease was observed since the beginning of the deglaciation to the mid-Holocene (∼8–6 kyr BP), possibly reflecting a reduction in surface salinity in the central Bay of Bengal (BoB) water, which probably resulted from strengthened precipitation, concurrent enhanced river discharge and rising sea-level, related to the intensification of Indian Summer Monsoon (ISM). Variations in benthic δ¹³C and δ¹³C_{Planktonic-Benthic} in our core site reflect significant variations in source water characteristics over the LGM-Holocene. The large δ¹³C_{Planktonic-Benthic} offset during the glacial period suggests a more sluggish deep water circulation, and lower δ¹³C_{Planktonic-Benthic} from the deglaciation to the Holocene suggests an enhanced deep water circulation in the central BoB. The drastic depletion in benthic δ¹³C during the glacial period suggests a significant reduction of North Atlantic Deep Water (NADW) intrusion and a progressive influx of Antarctic Bottom Water (AABW) and ¹²C-rich Circumpolar Deep Water (CDW) into the central BoB. In contrast, since the deglaciation, the central BoB experienced a drastically increased intrusion of better ventilated and ¹³C-rich NADW. The differences in benthic δ¹⁸O between the LGM section and the Holocene exceeds the ice volume effect by ∼0.5‰, providing further evidence that the deep water mass of the central BoB was influenced by the less dense NADW, instead of the AABW, since the last deglaciation.     

Paleoceanographic implications of smaller benthic and planktonic foraminifera from the Eocene Pazin Basin (Coastal Dinarides,Croatia)

Summary Smaller benthic and planktonic foraminifera from the clastic sediments of the Pazin Basin (Istria, Croatia) were studied in order to obtain more data about paleoceanographic conditions that existed in the Middle Eocene Dinaric foreland basin. The succession investigated corresponds to the Middle Eocene planktonic foraminiferal zones Globigerapsis kugleri/Morozovella aragonensis (P11), Morozovella lehneri (P12), and Globigerapsis beckmanni (P13). Benthic foraminiferal assemblages from the clastic succession are dominated by epifaunal trochospiral genera suggesting oligotrophic to mesotrophic conditions and moderately oxygenated bottom waters. Planktonic foraminiferal assemblages indicate mesotrophic to eutrophic conditions of the surface waters, with increased eutrophication in the upper part of the section. Water depth, based on the ratio between planktonic and epifaunal benthic foraminifera and on the recognized species of cosmopolitan benthic foraminifera, was estimated to have been between about 900 and 1200 m. The basin was elongated and open to marine currents on both sides allowing good circulation and ventilation of the bottom water.     

Glacial Holocene environment of the southeastern Okhotsk Sea: evidence from geochemical and palaeontological data

Environmental conditions and productivity changes in the southeastern Okhotsk Sea have been reconstructed for the last 20 ka using planktonic and benthic foraminiferal oxygen isotope records and calcium carbonate, organic carbon and opal content data from two sediment cores. Species variability in benthic foraminiferal and diatom assemblages provides additional palaeoceanographic evidence. AMS radiocarbon dating of the sediments and oxygen isotope stratigraphy serve as the basis for the age models of the cores for the last 20 ¹⁴C kyr and for correlation between environmental variations in the Okhotsk Sea, and regional and global climate changes. Benthic foraminiferal assemblages in the two cores (depth 1590 and 1175 m) varied with time, so that we could recognise seven zones with different species composition. Changes in the benthic foraminiferal assemblages parallel major environmental and productivity variations. During the last glaciation, fluxes of organic matter to the sea floor showed strong seasonal variations, indicated by the presence of abundant A. weddellensis and infaunal Uvigerina spp. Benthic foraminiferal assemblages changed with warming at 12.5–11 and 10–8 ¹⁴C kyr BP, when productivity blooms and high organic fluxes were coeval with global meltwater pulses 1A and 1B. Younger Dryas cooling caused a decline in productivity (11–10 kyr BP) affecting the benthic faunal community. Subsequent warming triggered intensive diatom production, opal accumulation and a strong oxygen deficiency, causing significant changes in benthic fauna assemblages from 5.26–4.4 kyr BP to present time.     

Tasman Front shifts and associated paleoceanographic changes during the last 250,000 years: foraminiferal evidence from the Lord Howe Rise

The paleoceanography of the Tasman Sea over the past 250,000 years was studied using benthic (>75 μm size fraction) and planktonic foraminifera (>149 μm size fraction) from three cores collected along 162°E traverse between 25°S and 30°S on the Lord Howe Rise. Planktonic foraminiferal oxygen isotope stratigraphy dates the cores between OIS 1 and 11. R-mode cluster and Q-mode factor analyses were carried out on benthic foraminiferal faunas, and Q-mode factor analysis and the modern analog technique (MAT) were used in analyzing planktonic foraminiferal faunas. Distinct benthic faunas across latitude from north (25°S) to south (30°S and 35°S) reflects the difference in primary productivity level in the overlying surface water. The MAT result is thought to express latitudinal shifts of the Tasman Front over the last 250,000 years with: (1) the Tasman Front at 35°S during the oxygen isotope stage (OIS) 1 (post-glacial period); (2) migration of the front nearby 25°S during the last glacial period (OIS 2–OIS 4) and slightly northward of its present position during the penultimate glacial period (OIS 6); and (3) a return of the front to near 35°S during OIS 5 and OIS 7. Based on time-series and spatial variations of benthic foraminiferal factor typified by Pseudoparrella exigua and Uvigerina peregrina and one variety, southern-winter mixing and convection along the Tasman Front may have strengthened during the interglacial OIS 7 in particular.     

Perturbation at the sea floor during the Paleocene–Eocene Thermal Maximum: Evidence from benthic foraminifera at Contessa Road, Italy

Detailed analyses of the benthic foraminiferal assemblages extracted with the cold acetolyse method together with high resolution geochemical and mineralogical investigations across the Paleocene/Eocene (P/E) boundary of the classical succession at Contessa Road (western Tethys), allowed to recognize and document the Paleocene–Eocene Thermal Maximum (PETM) interval, the position of the Benthic Extinction Event (BEE) and the early recovery of benthic faunas in the aftermath of benthic foraminiferal extinction. The stratigraphical interval spanning the P/E boundary consists of dominantly pelagic limestones and two prominent marly beds. Benthic foraminifera indicate that these sediments were deposited at lower bathyal depth, not deeper than 1000–1500 m. The Carbon Isotope Excursion (CIE) interval is characterized by high barite abundance with a peak at the base of the same stratigraphic interval, indicating a complete, although condensed record of the early CIE. A succession of events and changes in the taxonomic structure of benthic foraminifera has been recognized that may be of use for supra-regional stratigraphic correlation across the P/E boundary interval. The composition of the benthic foraminiferal assemblages, dominated by infaunal taxa, indicates mesotrophic and changing conditions on the sea floor during the last  45 kyr of the Paleocene. The BEE occurs at the base of the CIE within the lower marly bed and it is recorded by the extinction of several deep-water cosmopolitan taxa. Then, the lysocline/CCD rose and severe carbonate dissolution occurred. Preservation deteriorated, the faunal density and simple diversity dropped to minimum values and a peak of Glomospira spp. has been observed. Stress-tolerant and opportunistic groups, represented mainly by bi-and triserial taxa, dominate the low-diversity post-extinction assemblages, indicating a benthic foraminiferal recovery under environmental unstable conditions, probably within a context of sustained food transfer to the bottom. A three-phase pattern of faunal recovery is recognizable. At first the lysocline/CCD started to descend and then recovered. Small-sized “Bulimina”, Oridorsalis umbonatus, and Tappanina selmensis rapidly repopulated the severely stressed environment. Later on, Siphogenerinoides brevispinosa massively returns, dominating the assemblage together with other buliminids, Nuttallides truempyi, and Anomalinoides sp.1. Finally, a marked drop in abundance of S. brevispinosa is followed by a bloom of the opportunistic and recolonizer agglutinated Pseudobolivina that, for the first time, is recorded within the main CIE. A second interval of dissolution, but less severe than the previous one, has been recognized within the upper marly bed (uppermost part of the main CIE interval) and it is interpreted as a renewed, less pronounced shoaling of the lysocline/CCD that interrupted the recovery of benthic faunas. This further rise likely represents a response to persistent instability of ocean geochemistry in this sector of the Tethys before the end of the CIE. In the CIE recovery and post CIE intervals, the composition of the benthic foraminiferal assemblages suggests mesotrophic and unstable conditions at the sea floor. According to the geochemical proxy for redox conditions, the deposition of the PETM sediments at Contessa Road occurred in well-oxygenated waters, leading out a widespread oxygen depletion as major cause of the BEE. Changing oceanic productivity, carbonate corrosivity and global warming appear to have played a much more important role in the major benthic foraminiferal extinction at the P/E boundary.     

A Decline in Benthic Foraminifera following the Deepwater Horizon Event in the Northeastern Gulf of Mexico

Sediment cores were collected from three sites (1000–1200 m water depth) in the northeastern Gulf of Mexico from December 2010 to June 2011 to assess changes in benthic foraminiferal density related to the Deepwater Horizon (DWH) event (April-July 2010, 1500 m water depth). Short-lived radioisotope geochronologies (²¹⁰Pb, ²³⁴Th), organic geochemical assessments, and redox metal concentrations were determined to relate changes in sediment accumulation rate, contamination, and redox conditions with benthic foraminiferal density. Cores collected in December 2010 indicated a decline in density (80–93%). This decline was characterized by a decrease in benthic foraminiferal density and benthic foraminiferal accumulation rate (BFAR) in the surface 10 mm relative to the down-core mean in all benthic foraminifera, including the dominant genera (Bulimina spp., Uvigerina spp., and Cibicidoides spp.). Cores collected in February 2011 documented a site-specific response. There was evidence of a recovery in the benthic foraminiferal density and BFAR at the site closest to the wellhead (45 NM, NE). However, the site farther afield (60 NM, NE) recorded a continued decline in benthic foraminiferal density and BFAR down to near-zero values. This decline in benthic foraminiferal density occurred simultaneously with abrupt increases in sedimentary accumulation rates, polycyclic aromatic hydrocarbon (PAH) concentrations, and changes in redox conditions. Persistent reducing conditions (as many as 10 months after the event) in the surface of these core records were a possible cause of the decline. Another possible cause was the increase (2–3 times background) in PAH’s, which are known to cause benthic foraminifera mortality and inhibit reproduction. Records of benthic foraminiferal density coupled with short-lived radionuclide geochronology and organic geochemistry were effective in quantifying the benthic response and will continue to be a valuable tool in determining the long-term effects of the DWH event on a larger spatial scale.     

Foraminiferal response to Holocene environmental changes of a tidal estuary in Victoria, southeastern Australia

The Holocene strata in the Anderson Inlet area in Victoria can be stratigraphically divided into four units, Unit I, Unit II, Unit III, and Unit IV. Unit I and Unit IV lack fossils and were deposited in non-marine, probably fluvial environments. Unit II and Unit III contain abundant foraminifera with molluscs, ostracods and bryozoans. Foraminiferal analysis suggests that Unit III was formed in a partially sheltered marine environment, while the high plankton content and relatively high diversity of benthic species in Unit II indicate that this unit was deposited in an open bay at water depths possibly less than 5 m. The foraminiferal data are integrated with radiocarbon dates to arrive at the following Holocene palaeoenvironmental history in this area: (1) low alluvial plain stage (10,000–7000 yr B.P.); (2) open bay environment stage (7000–5500 yr B.P.); (3) partially sheltered marine environment stage (5500–4500 yr B.P.); (4) alluvial plain and coastal lagoon environment stage (since about 4500 yr B.P.). The foraminiferal fauna show a clear response to these palaeoenvironmental changes. Globigerina bulloides can be used as an indicator for cold water marine environments. The high concentration of this species in these middle Holocene sediments shows a strong cold water influence on the coastal environments which reduced the effect of regional warm currents during this period. The Holocene palaeoenvironmental changes in the area were controlled by the Holocene sea-level fluctuations associated with the deglaciation history during this period. Similar integrated studies of shallow to marginal marine strata in southern Africa, America and New Zealand will lead to a better understanding of Holocene relative sea-level change and the interplay between Holocene cold and warm water regimes in the Southern Hemisphere.     

Molecular evidence for an independent origin of modern triserial planktonic foraminifera from benthic ancestors

Gallitellia vivans is the only Recent representative of the triserial planktonic foraminiferal family Guembelitriidae. The origin and evolution of this interesting albeit poorly known family are enigmatic. To elucidate the phylogenetic relationships between G. vivans and other planktonic foraminifera, we sequenced the small subunit ribosomal DNA (SSU rDNA) for comparison to our extensive database of planktonic and benthic species. Our analyses suggest that G. vivans represents a separate lineage of planktonic foraminifera, which branches close to the benthic rotaliids Stainforthia and Virgulinella. Both genera resemble Gallitellia in general morphological appearance, having elongate triserial tests at least in their early ontogenic stages. The divergence time of G. vivans is estimated at ca. 18 Ma (early Miocene), suggesting an origin independent from the Cretaceous and Paleogene triserial planktonic foraminifera. Our study thus indicates that modern triserial planktonic foraminifera are not related to the Cretaceous–Paleogene triserial species, and that the sporadic occurrences in the fossil record are not the result of poor preservation, but reflect multiple transitions from benthic to planktonic mode of life.     

Impacts of storms on Recent planktic foraminiferal test production and CaCO3 flux in the North Atlantic at 47 °N, 20 °W (JGOFS)

Planktic foraminiferal assemblages are well known to vary in accordance with seasonal fluctuations in ocean properties, periodic reproduction cycles, and variations between water masses. Here we report that storms also can significantly influence foraminiferal assemblages. During the RV Meteor cruise 21 to the Northeast Atlantic Ocean ( area), from March to May 1992, planktic foraminifera were sampled using a multiple opening-closing net. While sampling, two storms with wind forces up to 12 Beaufort caused intensified surface layer mixing with shifts in the depth of the upper ocean mixed-layer from 20–40 m to 170–240 m. Subsequently, planktic foraminiferal growth rates increased, resulting in an elevated quantity of small (100–150 μm) tests (Phase 1). When the wind strength increased a second time, the mixed-layer deepened to a depth below the former position of the pycnocline, and again the abundance of small tests increased (Phase 2). During Phase 2, the weight of calcite in specimens of the productive zone reached its maximum. In the export zone, an associated increase in empty tests occurred with a lag time depending on the test sinking velocity. In the upper export zone, down to 700 m water depth, CaCO₃ flux increased from 9.3 to 49.8 mg CaCO₃ m⁻² d⁻¹ after the first storm and from 8.9 to 19.9 mg CaCO₃ m⁻²d⁻¹ after the second storm. In the 700 to 2500 m depth interval, the flux increased from 5.1 mg CaCO₃ m⁻² d⁻¹ to about 9.2 mg CaCO, m⁻² d⁻¹. Thus, the standing stock of living foraminifera and export of empty tests from the productive zone increased after the storms, leading to pulses of CaCO₃ exported from the surface to deep water.     

Foraminiferal turnover across the Eocene–Oligocene transition at Fuente Caldera, southern Spain: No cause–effect relationship between meteorite impacts and extinctions

We studied planktic and small benthic foraminifera from the Fuente Caldera section, southern Spain, across the Eocene–Oligocene transition. Benthic foraminifera indicate lower bathyal depths for the late Eocene and earliest Oligocene. Detailed high-resolution sampling and biostratigraphical data allowed us to date precisely layers with evidence for meteorite impact (Ni-rich spinel), which occur in the lower part of the planktic foraminiferal Globigerapsis index Biozone and in the middle part of the small benthic foraminiferal Cibicidoides truncanus (BB4) Biozone (middle Priabonian, late Eocene). Major turnovers of foraminifera occur at the Eocene/Oligocene boundary, only. The impact did not occur at a time of planktic or benthic foraminiferal extinction events, and the late Eocene meteorite impacts did thus not cause extinction of foraminifera. The most plausible cause of the Eocene/Oligocene boundary extinctions is the significant cooling, which generated glaciation in Antarctica and eliminated most of the warm and surface-dwelling foraminifera.