Mid‐Holocene environmental changes in the Bay of Skaill,Mainland Orkney,Scotland: an integrated geomorphological,sedimentological and stratigraphical study

A detailed multidisciplinary investigation of intertidal freshwater sediments exposed in the north of the Bay of Skaill, Mainland Orkney, Scotland, have revealed a complex sedimentary sequence. This provided evidence for dynamic coastal environmental changes in the area since the mid‐Holocene. Freshwater ponds developed on glacial sediments ca. 6550 ± 80 yr BP (cal. bc 5590–5305). From ca. 6120 ± 70 yr BP (cal. bc 5040–4855), these were infilled by blown sand from the distal edge of a dune ridge located to the west. Thereafter, a series of sand‐blow events alternating with periods of quiescence occurred until ca. 4410 ± 60 yr BP (cal. bc 3325–2900). Between ca. 5240 ± 160 and 4660 ± 80 yr BP (cal. bc 4370–3115), pollen and charcoal records show evidence of anthropogenic activities, associated with the nearby Neolithic settlement of Skara Brae. Agriculture was probably affected by recurrent sand movement and widespread deposition of calcium carbonate in the hinterland of the bay. Machair development between ca. 6100 and 5000 yr BP (cal. bc 5235–3540) corresponds to a mid‐Holocene phase of dune formation recorded elsewhere in northwest Europe. The more recent and progressive formation of the bay has probably been related to increasing external forcing via storminess, long‐term relative sea‐level change and sediment starvation within this exposed environment. Copyright © 2000 John Wiley & Sons, Ltd.     

Combining IR and X‐ray microtomography data sets: Application to Itokawa particles and to Paris meteorite

In the near future, a new generation of sample return missions (Hayabusa2, OSIRIS‐REx, MMX, etc.) will collect samples from small solar system bodies. To maximize the scientific outcome of laboratory studies and minimize the loss of precious extraterrestrial samples, an analytical sequence from less destructive to more destructive techniques needs to be established. In this work, we present a combined X‐ray and IR microtomography applied to five Itokawa particles and one fragment of the primitive carbonaceous chondrite Paris. We show that this analytical approach is able to provide a 3‐D physical and chemical characterization of individual extraterrestrial particles, using the measurement of their 3‐D structure and porosity, and the detection of mineral and organic phases, and their spatial co‐localization in 3‐D. We propose these techniques as an efficient first step in a multitechnique analytical sequence on microscopic samples collected by space missions.     

Considerations on the squat of unevenly trimmed ships

In existing publications about empirical studies of ship squat trim is only dealt with implicitly by focussing the concern on the maximum squat. This restriction is only sufficient if a non-zero static trim is always increased dynamically, which, however, turns out to be wrong. Instead of maximum squat, we suggest a more suitable definition of the quantity relevant for under-keel clearance. In an example, it is shown that a non-zero static trim can actually be reduced dynamically, indicating a possible optimisation of trim. For a correct estimation of the squat effect on under-keel clearance, trim must be treated as an explicit parameter. Our arguments are based on full-scale experiments as well as results from numerical simulations.     

Grazing impact of mesozooplankton in an upwelling region off northern California, 2000–2003

Mesozooplankton (>200 μm) grazing impact (% phytoplankton standing crop consumed d⁻¹) was determined by the gut fluorescence method during three springs (2000, 2001 and 2002) and two winters (2002 and 2003) in a coastal upwelling region off northern California. Wind events, in terms of both magnitude and duration, varied inter-annually and seasonally and included both upwelling-favorable and relaxation events. Grazing impact of mesozooplankton also varied inter-annually and seasonally, and was highest during June 2000 (mean=129% of standing crop d⁻¹), a prolonged period of wind “relaxation” and phytoplankton bloom. In contrast, mean grazing impact was lower during periods of stronger, more persistent winds, more active upwelling, greater cross-shelf transport, and lower chlorophyll concentration (25% and 38% in May–June 2001 and 2002, respectively). Wintertime conditions (January 2002 and 2003) were characterized by weakly upwelling or downwelling-favorable winds, low chlorophyll concentration, and lower mean mesozooplankton grazing impact (13% and 12%, respectively). The larger (>500 μm) size class contributed proportionally more to total mesozooplankton (>200 μm) grazing impact than the smaller (200–500 μm) size class during all sampling periods except spring 2002. These results suggest that mesozooplankton grazing impact is higher in spring than in winter, and that during the spring upwelling season, grazing is higher during periods of wind relaxation (weak upwelling) than during periods of stronger upwelling. Further, these results suggest an important role of mesozooplankton grazers on phytoplankton dynamics in the upwelling region off northern California.     

The opposition surge of Enceladus: HST observations 338-1022 nm

Hubble Space Telescope (HST) Wide-Field Planetary Camera (WFPC2) observations at phase angles in the range α=0.26°-6.4° obtained at every opposition and near quadrature between October 1996 and December 2002 reveal the opposition effect of Enceladus. We present a photometric analysis of nearly 200 images obtained through the five broadband UVBRI filters (F336W, F439W, F555W, F675W, and F814W) and the F785LP and F1042M filters from which we generate mutually consistent solar and rotational phase curves. Our solar phase curves reveal a dramatic, sharp increase in the albedo (from 0.11 mag in the F675W filter to 0.17 mag in the F785LP filter) as phase angles decrease from 2° to 0.26°. A slight opposition effect is evident in data from the F1042M filter (λ_eff=1022 nm); however, the smallest phase angle currently available for observations from this filter is α=0.58°. With the addition of data from the F255W filter we demonstrate the wavelength dependence of the albedo of the trailing hemisphere from 275 to 1022 nm. Our rotation curves show that the trailing hemisphere is ∼0.06 mag brighter than the leading when observed at wavelengths between 338 and 868 nm and 0.11 mag brighter than the leading at 1022 nm. We have supplemented the phase curve from the F439W filter (λ_eff=434 nm) with Voyager clear filter (λ_eff=480 nm) observations made at larger phase angles (α=13°-43°) to produce a phase curve with the most extensive phase angle coverage possible to date. This newly expanded range of phase angles enhances the ability of the Hapke photometric model (Hapke B., 2002, Icarus 157, 523-534) to relate physical characteristics of the surface of Enceladus to the manner in which incident light is reflected from it. We present Hapke 2002 model fits to solar phase curves from each UVBRI filter as well as from the F785LP and F1042M filters. Geometric albedos derived from these model fits range from p=0.92±0.01 at 1022 nm to p=1.41±0.03 at 549 nm, necessitating an increase of about 20% from previously derived values. Our Hapke fits demonstrate that the opposition surge of Enceladus is best described by a model which combines both moderate shadow-hiding and narrow coherent backscattering components.     

Environmental Geology

The mining environment, medical geology and urban geochemistry form a group of related scientific disciplines that have developed strongly during recent years in the Nordic countries. Modern legislation controls the environmental issues. Close co-operation of researchers and legislators has improved the quality and safety of life in the societies of the Nordic countries. In mining environmental studies, methods that are suitable in Arctic conditions have been developed; in medical geology, the input from the Nordic countries has made it an appreciated scientific discipline throughout the world, and in the case of the urban environment, methods developed by our geochemists have especially improved the health conditions, particularly of children.