Spine-like structures in Paleogene muricate planktonic foraminifera

Muricate planktonic foraminifera comprise an extinct clade that was diverse and abundant in the Paleogene oceans and are widely used in palaeoclimate research as geochemical proxy carriers for the upper oceans. Their characteristic wall texture has surface projections called “muricae” formed by upward deflection and mounding of successive layers of the test wall. The group is generally considered to have lacked “true spines”: that is, acicular calcite crystals embedded in and projecting from the test surface such as occur in many modern and some Paleogene groups. Here we present evidence from polished sections, surface wall scanning electron microscope images and test dissections, showing that radially orientated crystalline spine-like structures occur in the centre of muricae in various species of Acarinina and Morozovella and projected from the test wall in life. Their morphology and placement in the wall suggest that they evolved independently of true spines. Nevertheless, they may have served a similar range of functions as spines in modern species, including aiding buoyancy and predation and especially harbouring algal photosymbionts, the function for which we suggest they probably first evolved. Our observations strengthen the analogy between Paleogene mixed-layer-dwelling planktonic foraminifera and their modern spinose counterparts

North Atlantic Drift Sediments Constrain Eocene Tidal Dissipation and the Evolution of the Earth-Moon System

Cyclostratigraphy and astrochronology are now at the forefront of geologic timekeeping. While this technique heavily relies on the accuracy of astronomical calculations, solar system chaos limits how far back astronomical calculations can be performed with confidence. High-resolution paleoclimate records with Milankovitch imprints now allow reversing the traditional cyclostratigraphic approach: Middle Eocene drift sediments from Newfoundland Ridge are well-suited for this purpose, due to high sedimentation rates and distinct lithological cycles. Per contra, the stratigraphies of Integrated Ocean Drilling Program Sites U1408–U1410 are highly complex with several hiatuses. Here, we built a two-site composite and constructed a conservative age-depth model to provide a reliable chronology for this rhythmic, highly resolved (<1 kyr) sedimentary archive. Astronomical components (g-terms and precession constant) are extracted from proxy time-series using two different techniques, producing consistent results. We find astronomical frequencies up to 4% lower than reported in astronomical solution La04. This solution, however, was smoothed over 20-Myr intervals, and our results therefore provide constraints on g-term variability on shorter, million-year timescales. We also report first evidence that the g4–g3 “grand eccentricity cycle” may have had a 1.2-Myr period around 41 Ma, contrary to its 2.4-Myr periodicity today. Our median precession constant estimate (51.28 ± 0.56″/year) confirms earlier indicators of a relatively low rate of tidal dissipation in the Paleogene. Newfoundland Ridge drift sediments thus enable a reliable reconstruction of astronomical components at the limit of validity of current astronomical calculations, extracted from geologic data, providing a new target for the next generation of astronomical calculations

Zero to eight : young children and their internet use

EU Kids Online has spent seven years investigating 9-16 year olds’ engagement with the internet, focusing on the benefits and risks of children’s internet use. While this meant examining the experiences of much younger children than had been researched before EU Kids Online began its work in 2006, there is now a critical need for information about the internet-related behaviours of 0-8 year olds. EU Kids Online’s research shows that children are now going online at a younger and younger age, and that young children’s “lack of technical, critical and social skills may pose [a greater] risk” (Livingstone et al, 2011, p. 3).peer-reviewe

Characterization of early Eocene hyperthermals using benthic foraminiferal assemblages and stable isotopes

The aim of this project is to evaluate the short-and long-term effects of multiple subsequent global warming events on the marine biosphere in the earliest Eocene, about 56 to 52 million years ago (Ma). By studying the response of ecosystems to these transient warming events, or hyperthermals, an assessment of biogeosphere dynamics in an early Eocene greenhouse world setting can be made. More specifically, the objective is to improve our understanding of the response of deep-sea benthic ecosystems to hyperthermals using foraminiferal assemblages and stable carbon and oxygen isotopes (δ13C and δ18O). Deep-sea benthic communities may track changes in temperature, ocean circulation and stratification, pH and organic fluxes, and thus reflect the environmental changes during the non-catastrophic Eocene Thermal Maximum 2 (ETM2; ~54 Ma) hyperthermal. In the context with the (semi-) catastrophic effects of the Paleocene-Eocene Thermal Maximum (PETM; ~56 Ma), this study provides additional tiepoints in the assessment of benthic ecosystem sensitivity. Although the Eocene greenhouse world differs significantly from the present day in a number of ways (e.g. continent configuration and mountain ranges, ocean circulation, atmospheric CO2 concentrations and latitudinal global temperature gradients), this research is still relevant in the debate on anthropogenic global warming, as it may show how (in)sensitive the marine biosphere is to abrupt global warming.nrpages: 227status: publishe

Deep-sea benthic foraminiferal turnovers in the early Eocene: the role of the PETM and ETM2

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The demise of the early Eocene greenhouse - Decoupled deep and surface water cooling in the eastern North Atlantic

Early Paleogene greenhouse climate culminated during the early Eocene Climatic Optimum (EECO, 50 to 53 Ma). This episode of global warmth is subsequently followed by an almost 20 million year-long cooling trend leading to the Eocene-Oligocene glaciation of Antarctica. Here we present the first detailed planktic and benthic foraminiferal isotope single site record (d13C, d18O) of late Paleocene to middle Eocene age from the North Atlantic (Deep Sea Drilling Project Site 401, Bay of Biscay). Good core recovery in combination with well preserved foraminifera makes this site suitable for correlations and comparison with previously published long-term records from the Pacific Ocean (e.g., Allison Guyot, Shatsky Rise), the Southern Ocean (Maud Rise) and the equatorial Atlantic (Demerara Rise). Whereas our North Atlantic benthic foraminiferal d18O and d13C data agree with the global trend showing the long-term shift toward heavier 18O values, we only observe minor surface water 18O changes during the middle Eocene (if at all) in planktic foraminiferal data. Apparently, the surface North Atlantic did not cool substantially during the middle Eocene. Thus, the North Atlantic appears to have had a different surface ocean cooling history during the middle Eocene than the southern hemisphere, whereas cooler deep-water masses were comparatively well mixed. Our results are in agreement with previously published findings from Tanzania, which also support the idea of a muted post-EECO surface-water cooling outside the southern high-latitudes.publisher: Elsevier articletitle: The demise of the early Eocene greenhouse – Decoupled deep and surface water cooling in the eastern North Atlantic journaltitle: Global and Planetary Change articlelink: http://dx.doi.org/10.1016/j.gloplacha.2016.08.010 content_type: article copyright: © 2016 Elsevier B.V. All rights reserved.status: publishe