ON THE PERILS OF PERCEIVING PERCEPTION

The emergence of man\u27s perception of his environment within the discipline of geography as a suitable topic of pursuit is a most wholesome development. The recently articulated views of Saarinen through the publications of the Commission on College Geography provide an admirable springboard for those interested in pursuing the topic and obtaining an overview of what has already been pursued.\u27 But geography teachers have, for years, been intuitively doing the same thing by discovering through their classroom contacts the correct and incorrect perceptions of students and teaching concepts based upon this knowledge. Although few of these have been conducted as controlled experiments and found their way in print the mechanisms have been operating at a highly subjective level

A xandarellid artiopodan from Morocco – a middle Cambrian link between soft-bodied euarthropod communities in North Africa and South China

NB. A corrigendum [correction] for this article was published online on 09 May 2017; this has been attached to this article as an additional file. This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ © The Author(s) 2017. The attached file is the published version of the article

Physical mixing effects on iron biogeochemical cycling: FeCycle experiment

The effects of physical processes on the distribution, speciation, and sources/sinks for Fe in a high-nutrient low-chlorophyll (HNLC) region were assessed during FeCycle, a mesoscale SF6 tracer release during February 2003 (austral summer) to the SE of New Zealand. Physical mixing processes were prevalent during FeCycle with rapid patch growth (strain rate γ = 0.17–0.20 d−1) from a circular shape (50 km2) into a long filament of ∼400 km2 by day 10. Slippage between layers saw the patch-head overlying noninfused waters while the tail was capped by adjacent surface waters resulting in a SF6 maximum at depth. As the patch developed it entrained adjacent waters containing higher chlorophyll concentrations, but similar dissolved iron (DFe) levels, than the initial infused patch. DFe was low ∼60 pmol L−1 in surface waters during FeCycle and was dominated by organic complexation. Nighttime measurements of Fe(II) ∼20 pmol L−1 suggest the presence of Fe(II) organic complexes in the absence of an identifiable fast Fe(III) reduction process. Combining residence times and phytoplankton uptake fluxes for DFe it is cycled through the biota 140–280 times before leaving the winter mixed layer (WML). This strong Fe demand throughout the euphotic zone coupled with the low Fe:NO3 − (11.9 μmol:mol) below the ferricline suggests that vertical diffusion of Fe is insufficient to relieve chronic iron limitation, indicating the importance of atmospheric inputs of Fe to this region

International Symposium on the Ediacaran–Cambrian Transition (ISECT) 2017

Research into the long-recognized ‘Cambrian Explosion’ of animal life (e.g., Lipps and Signor, 1992; Briggs, 2015) has, in recent decades, increasingly sought to resolve the interplay between evolutionary, geochemical and environmental changes that occurred over an extended Ediacaran to Cambrian transitional interval. This wider interval encompasses several significant geological events, including large-scale glaciations, supercontinental reorganization, global marine transgression, and perturbations in oxygen levels, other isotope proxies, and UV-B radiation (summarised in Narbonne et al., 2012; Meert et al., 2016). These events occurred contemporaneously with evolutionary developments including the radiation of macroscopic eukaryotes, the appearance of the extant animal phyla, the onset of burrowing and biological sediment processing, and the evolution of biomineralization (e.g., Kouchinsky et al., 2012; Mángano and Buatois, 2016; Cunningham et al., 2017). Biological and geological phenomena are widely considered to have been linked during the Ediacaran to Cambrian transition (e.g., Canfield et al., 2007; Sperling et al., 2013; Boyle et al., 2014; Herringshaw et al., 2017; Shields, 2017), and their interaction across this interval is an area of considerable scientific interest. Stratigraphic correlation and subdivision of Ediacaran and Cambrian sections worldwide has been identified as a key objective in order to better understand the co-evolution of the Earth and life systems, and in recent years there have been substantial advances in discussions relating to this challenge (Narbonne et al., 2012; Peng et al., 2012; Landing et al., 2013b; Babcock et al., 2014; Xiao et al., 2016)

Reconstructing the reproductive mode of an Ediacaran macro-organism.

Enigmatic macrofossils of late Ediacaran age (580-541 million years ago) provide the oldest known record of diverse complex organisms on Earth, lying between the microbially dominated ecosystems of the Proterozoic and the Cambrian emergence of the modern biosphere. Among the oldest and most enigmatic of these macrofossils are the Rangeomorpha, a group characterized by modular, self-similar branching and a sessile benthic habit. Localized occurrences of large in situ fossilized rangeomorph populations allow fundamental aspects of their biology to be resolved using spatial point process techniques. Here we use such techniques to identify recurrent clustering patterns in the rangeomorph Fractofusus, revealing a complex life history of multigenerational, stolon-like asexual reproduction, interspersed with dispersal by waterborne propagules. Ecologically, such a habit would have allowed both for the rapid colonization of a localized area and for transport to new, previously uncolonized areas. The capacity of Fractofusus to derive adult morphology by two distinct reproductive modes documents the sophistication of its underlying developmental biology.This work has been supported by the Natural Environment Research Council [grant numbers NE/I005927/1 to C.G.K., NE/J5000045/1 to J.J.M., NE/L011409/1 to A.G.L. and NE/G523539/1 to E.G.M.], and a Henslow Junior Research Fellowship from Cambridge Philosophical Society to A.G.L.This is the author accepted manuscript. The final version is available from NPG via http://dx.doi.org/10.1038/nature1464

Terminology of Geological Time: Establishment of a Community Standard

It has been recommended that geological time be described in a single set of terms and according to metric or SI (“Système International d’Unités”) standards, to ensure “worldwide unification of measurement”. While any effort to improve communication in scientific research and writing is to be encouraged, we are also concerned that fundamental differences between date and duration, in the way that our profession expresses geological time, would be lost in such an oversimplified terminology. In addition, no precise value for ‘year’ in the SI base unit of second has been accepted by the international bodies.Under any circumstances, however, it remains the fact that geological dates – as points in time – are not relevant to the SI. Known dates may define durations, just as known durations may define dates, or dates may simply be punctual references that support historical narratives, but dates are not quantities. Furthermore, dates, as datum points, belong to a specific type of guiding information that is in constant use not only by the disciplines that explore the unwritten past, but in the physical sciences and engineering as well. Accordingly, we recommend a new standardization of the distinction between geohistorical date, in years before present expressed in ‘annus’, symbol ‘a’,with the multiples ‘ka’, ‘Ma’, and ‘Ga’ for thousands, millions and billions of years ago, according to a convention that has been very widely adopted during the last 30 years, and geohistorical duration, expressed in ‘year’, symbol ‘yr’, with multiples ‘kyr’, ‘Myr’ and ‘Gyr’, respectively, as the most appropriate among the various formats in the current literature. Agreement on these two sets of terms throughout the wide community that deals with paleochronology would remove a false impression of improvisation and uncertainty as to appropriate terminology, and would lead to more effective communication in areas where a simplified but needlessly SI-conisistent terminology would be less, not more useful