Downslope Displacement Rates of Ploughing Boulders in A Mid-Alpine Environment: Finse, Southern Norway.

Annual and seasonal displacements of ploughing boulders were investigated at Finse, southern Norway, by traditional surveying and differential carrier-phase global positioning system measurements. Annual displacement rates were mainly below 10 mm/year, although one particular season showed rates of 26 mm/year on average. There was a tendency for larger boulders to travel faster. Seasonal displacements were restricted to the annual freeze-thaw cycle. The frost heave seems to have a significant horizontal component, which does not necessarily point in the downslope direction. Thus, the concept of frost creep is not applicable to the investigated ploughing boulders. On the other hand, due to tilting of the boulders, a momentum may be gained during thaw consolidation that could induce downslope displacements. Such a process will work together with gelifluction.     

The Nama Group revisited

The Nama Group of southern Namibia is a candidate for the Terminal Proterozoic Global Stratotype Section and Point (GSSP). Desirable characteristics of a GSSP include a well-preserved index-fossil assemblage, little deformation or metamorphism. well-constrained isotopic ages, stable-isotope records and magnetostratigraphic control. The age of the Nama Group sediments is now constrained to between 570 and 510 Ma. Assuming the Gondwana assembly was nearly complete at this same time, there is a discrepancy between the previously published Nama poles, a revised 550-510 Ma apparent polar wander path for Gondwana and the preceding supercontinental assemblages of Rodinia and Panottia. For these reasons, the Nama Group sediments were resampled in an effort to evaluate the potential of detailing the magnetostratigraphy of the Nama Group and resolving the discrepancy between the Nama poles and the APWP of Gondwana. Collectively, both the previous studies of the Nama Group and this one show a complex series of overprints and no easily discernible primary direction of magnetization. We therefore urge caution in using the Nama Group poles in any tectonic models of the Neoproterozoic-Early Palaeozoic. Specifically, the N1 component of magnetization, previously identified as a primary magnetization, was discovered in a younger suite of samples. Therefore, previous tectonic models that used the N1 magnetization direction as representative of the time of Nama deposition should be revised in light of these recent findings.     

The key role of global solid‐Earth processes in preconditioning Greenland's glaciation since the Pliocene

After >500 Ma of absence, major Northern Hemisphere glaciations appeared during the Plio‐Pleistocene, with Greenland leading other northern areas. Here, we propose that three major solid‐Earth processes underpinned build‐up of the Greenland ice‐sheet. First, a mantle‐plume pulse, responsible for the North Atlantic Igneous Province at ~60 Ma, regionally thinned the lithosphere. Younger plume pulses led to uplift, which accelerated at ~5 Ma, lifting the parts of the East Greenland margin closest to Iceland to elevations of more than 3 km above sea level. Second, plate‐tectonic reconstruction shows a ~6° northward component of Greenland motion relative to the mantle since ~60 Ma. Third, a concurrent northward rotation of the entire mantle and crust towards the pole, dubbed True Polar Wander (TPW), contributed an additional ~12° change in latitude. These global geodynamic processes preconditioned Greenland to sustain long‐term glaciation, emphasizing the role of solid‐Earth processes in driving long‐term global climatic transitions.     

Turbidites in the Upper Carboniferous Ross Formation, western Ireland: reconstruction of a channel and spillover system

ABSTRACT The Upper Carboniferous deep‐water rocks of the Shannon Group were deposited in the extensional Shannon Basin of County Clare in western Ireland and are superbly exposed in sea cliffs along the Shannon estuary. Carboniferous limestone floors the basin, and the basin‐fill succession begins with the deep‐water Clare Shales. These shales are overlain by various turbidite facies of the Ross Formation (460 m thick). The type of turbidite system, scale of turbidite sandstone bodies and the overall character of the stratigraphic succession make the Ross Formation well suited as an analogue for sand‐rich turbidite plays in passive margin basins around the world. The lower 170 m of the Ross Formation contains tabular turbidites with no channels, with an overall tendency to become sandier upwards, although there are no small‐scale thickening‐ or thinning‐upward successions. The upper 290 m of the Ross Formation consists of turbidites, commonly arranged in thickening‐upward packages, and amalgamated turbidites that form channel fills that are individually up to 10 m thick. A few of the upper Ross channels have an initial lateral accretion phase with interbedded sandstone and mudstone deposits and a subsequent vertical aggradation phase with thick‐bedded amalgamated turbidites. This paper proposes that, as the channels filled, more and more turbidites spilled further and further overbank. Superb outcrops show that thickening‐upward packages developed when channels initially spilled muds and thin‐bedded turbidites up to 1 km overbank, followed by thick‐bedded amalgamated turbidites that spilled close to the channel margins. The palaeocurrent directions associated with the amalgamated channel fills suggest a low channel sinuosity. Stacks of channels and spillover packages 25–40 m thick may show significant palaeocurrent variability at the same stratigraphic interval but at different locations. This suggests that individual channels and spillover packages were stacked into channel‐spillover belts, and that the belts also followed a sinuous pattern. Reservoir elements of the Ross system include tabular turbidites, channel‐fill deposits, thickening‐upward packages that formed as spillover lobes and, on a larger scale, sinuous channel belts 2·5–5 km wide. The edges of the belts can be roughly defined where well‐packaged spillover deposits pass laterally into muddier, poorly packaged tabular turbidites. The low‐sinuosity channel belts are interpreted to pass downstream into unchannellized tabular turbidites, equivalent to lower Ross Formation facies.     

The potential of natural ecosystem self-purifying measures for controlling nutrient inputs

Most ecosystems have a certain assimilative capacity regarding plant nutrient or biodegradable organic matter. Knowledge of the metabolizing processes of different ecosystems enable the use of natural systems for pollution abatement from agricultural, domestic and industrial sources. Such ecologically engineered natural systems are often very cost efficient. At the Centre for Soil and Environmental Research (JORDFORSK) studies of degradation processes and the fate of plant nutrients in small streams, ponds, wetlands, vegetative filter strips and soil are being conducted in order to gain experience with and develop self purifying methods. Preliminary results show that denitrification in streams remove only a minor part of the annual nitrogen (N) transport (1–15%), but that this process can remove a considerable part of the N transport during summer. Constructed ponds and wetlands in streams draining agricultural areas showed 10–56% retention of soil particles, 23–40% of phosphorous (P) and 5–13% of N. Narrow ponds had a higher efficiency than wide ponds per unit surface area. Short-term experiments with vegetative strips treating agricultural runoff show a sediment removal of over 95%, a P removal from 80–90% and N removal between 60 and 75%. A multistage subsurface constructed wetland treating domestic waste-water removed an average of 97% P, 91% BOD, 80% of suspended solids, 55% N and 99.9% E. coli over the first 18 months of operation. Preliminary results from a multistage plant with constructed ponds and wetlands treating landfill leachate show high treatment efficiency for the same parameters. A rapid infiltration plant in northern Norway showed an average removal of 99% P, 90% COD and 73% N after 4 years of operation. These results show that self purifying measures offer potential for design of pollution abatement systems for agricultural as well as domestic purposes in the Norwegian climate.