Long‐term Holocene groundwater fluctuations in a chalk catchment: evidence from Rock‐Eval pyrolysis of riparian peats

The depositional history of peat‐dominated wetlands can be used to understand palaeoclimate and palaeohydrology and also constrain the impacts of future climate change. However, in chalkland valleys, seasonal water table fluctuations and a high alkalinity have diminished key environment indicators such as pollen, and there is a need for alternative investigative techniques. The method of Rock‐Eval pyrolysis can track changes in organic matter source and degradation, potentially relating to historic changes in vegetation cover. This is the first Rock‐Eval on cores from a groundwater‐dependent riparian chalk valley wetland combined with radiocarbon dating. The dating showed that the cores represented approximately 4000 years of depositional history. Changes in hydrocarbon chemistry including normal alkane composition of the peat indicated shifts of around 500 to 1000 years between terrestrial and more aquatic species, relating to periods of climate wetness. These climatic shifts are broadly consistent with other evidence from ombrotrophic peatland and lacustrine sediments across northwest Europe. However, the connection between climate wetness and groundwater dependent chalkland wetlands is complicated by external anthropogenically driven factors relating to land use and vegetation cover changes in the catchment. Nonetheless, this study suggests that Rock‐Eval pyrolysis is a useful and cost‐effective tool that can provide evidence for long‐term Holocene groundwater fluctuations. Copyright © 2016 British Geological Survey.     

A contribution to Pleistocene chronology in southeast Essex,England

Parallel to the Essex coast north of the mouth of the Thames, a series of gravel spreads ranging in altitude from near sea level westward to more than 200 ft O.D. (mean sea level) proved to be the remnants of an abandoned Thames/Medway terrace system, rather than a series of “raised” beaches, as their location had suggested. The seaward side of the ancient river valley has subsequently been “captured” by subsidence.Evidence is given for five terraces, with surface levels between 5 and 75 ft O.D. Because of subsidence of the Essex coast, the terrace levels are not easily correlatable with either the Thames or Medway terrace levels. Temporal placement is attempted on the basis of one site in the 25 ft Barling terrace, which yielded a Middle Acheulian archaeological assemblage associated with a cool temperate fauna including an early form of mammoth. An ice wedge cast in the Barling terrace was filled with floodloam which weathered to a parabraunerde soil during an interglacial climate warmer than now. For these reasons man is thought to have lived on the floodplain of the Barling terrace either at the onset of the Wolstonian (Riss) glacial or during an interstadial of that stage. The question of possible linkages between Swanscombe and Clacton terraces is discussed.     

A review and assessment of tributyltin contamination in the North Sea,based on surveys of butyltin tissue burdens and imposex/intersex in four species of neogastropods

It is evident from measures of butyltin tissue burdens and imposex or intersex in neogastropods that tributyltin (TBT) contamination of coastal waters and open parts of the North Sea is now low. It has been declining for at least the past decade. This is probably due to two measures. First, regulations prohibiting the use of TBT-based paints on small boats and fish farms have reduced inputs of TBT from these sources so that they are now negligible (except possibly where the regulations are flaunted). Second, there is evidence from sites, where commercial vessels are the sole source of TBT, that the adoption of TBT SPC paints has been effective in reducing environmental levels of these contaminants. However, poor dockyard practices, allowing TBT-contaminated wastes, including paint flakes, to accumulate in sediments have left a legacy of hot-spots of contamination in some ports. The impact is localised so that TBT contamination is low in coastal areas immediately adjacent to ports.     

Field measurements of shear strength of an underconsolidated marine clay

This paper presents the observations of cone penetration testing (CPT), in situ vane shear testing and undrained triaxial testing of underconsolidated marine clay in the Craney Island Dredged Material Management Area (CIDMMA), Norfolk, VA. Comparison of vane shear measurements, taken during 1981–1983, to CPT measurements, taken during 1993, indicates a change in undrained shear strength. Both the vane shear and cone penetration resistances are lowest at the mid-heights of the clay layers and the excess pore water pressures are highest at the mid-height of the clay layers, indicating that the clay layer is underconsolidated.     

The potential and actual primary productivity of southern Ontario's agro-ecosystem

There is a generally accepted assumption that the primary productivity of the natural vegetation cover of an area is the most appropriate indicator of the level of primary productivity that may be attained by agricultural systems in the same area. However, this relationship is not clearly understood. This paper assesses the potential rate of primary productivity for southern Ontario and compares these results with the equivalent values for the agro-ecosystems. Analysis is conducted at the level of the county. Climatically determined potential (natural) primary productivity values are adjusted by a soil performance index yielding a range of values from 986 g m^?2 y^?1 to 44 g m^?2 y^?1. The actual primary productivity for agriculture ranges from 3593 g m^?2 y^?1 to 515 g m^?2 y^?1. Over southern Ontario actual (agricultural) productivity exceeds potential (natural) productivity by an average of 2.6. The variations about this mean are examined. The results indicate where, and by which agricultural processes, the humanized landscape can improve the organic resource base.     

The decay of torque free toroidal magnetic fields confined beneath the solar convection zone

Calculation similar to those of Mestel and Moss (1983) are performed to investigate the decay of a toroidal field through configurations satisfying the torque free condition, imposed by the presence of a poloidal field of dipolar form confined beneath the solar convection zone. It is found that initially stable field configurations diffuse into unstable configurations on time-scales of order a few x 10⁸ yr. The results are similar to those of Tayler (1982) for a simpler field model without any dynamical constraints.     

The oscillation frequencies of magnetic stellar models

A first-order perturbation theory method developed by Goossens to determine the perturbation to the eigenfrequencies of stellar models caused by the presence of a magnetic field is modified slightly, and applied to models with toroidal and poloidal fields. Some limitations of the analysis are pointed out.     

Fatigue effects in quartz sand grains

Particles of quartz sand from a stream draining granite were found to exhibit noteworthy effects of fatigue. Both repeated static loading and collective movement in water weakened the particles markedly. This weakening must have significance in nature, where repeated stressing occurs in many environments, particularly in soils and during bed-load motion in both air and water. Tectonic movements may also create fatigue effects in sand grains. Fatigue effects appear also to be sufficiently pronounced to be significant in some industrial processes involving the use of sand.