Sedimentological interpretation of an Ediacaran delta: Bonney Sandstone,South Australia

The type section of the late Ediacaran (ca 565 Ma) Bonney Sandstone in South Australia provides an opportunity to interpret a succession of Precambrian clastic sediments using physical sedimentary structures, lithologies and stacking patterns. Facies models, sequence stratigraphic analysis, and process-based architectural classification of depositional elements were used to interpret depositional environments for a series of disconformity-bounded intervals. This study is the first detailed published work on the Bonney Sandstone, and provides additional context for other Wilpena Group sediments, including the overlying Rawnsley Quartzite and its early metazoan fossils. Results show that the ～300 m-thick section studied here shows a progressive change from shallow marine to fluvially dominated sediments, having been deposited in storm-dominated shelf and lower shoreface environments, lower in the section, and consisting primarily of stacked channel sands, in a proximal deltaic environment near the top. Based on the degree of influence of wave, tidal or fluvial depositional processes, shallow marine sediments can be classified into beach, mouth bar, delta lobe and channel depositional elements, which can be used to assist in predicting sandbody geometries when only limited information is available. Sediments are contained within a hierarchical series of regressive, coarsening-upward sequences, which are in turn part of a larger basin-scale sequence that likely reflects normal regression and filling of accommodation throughout a highstand systems tract. Paleogeographic reconstructions suggest the area was part of a fluvially dominated clastic shoreline; this is consistent with previous reconstructions that indicate the area was on the western edge of the basin adjacent to the landward Gawler Craton. This research fills in a knowledge gap in the depositional history of a prominent unit in the Adelaide Rift Complex and is a case study in the interpretation of ancient deposits that are limited in extent or lacking diagnostic features.     

The effect of changes in tidal range on a sublittoral macrotidal sequence,bay of fundy,Canada

Independent evidence of changes in sea level and tidal range in the Bay of Fundy during the last 9000 years is used to evaluate the lithologies in 17 cores from the sublittoral part of Chignecto Bay. The composite tidal sequence identified is complex because of changes from microtidal through mesotidal to macrotidal conditions associated with changing water depths. Despite the complex stratigraphy, lithology correlates well with the depositional environment on a bed-by-bed basis. We postulate that such variations in tidal range are important to the interpretation of tidalite deposits from the geologic record.     

The settling behavior and benthic transport of fish feed pellets under steady flows

Settling and erosion experiments were carried out on a size range of fish feed pellets using an annular flume. A strong positive correlation was observed between settling rate and pellet dimension (pellet length, pellet dimeter, and equivalent sedimentation diameter). Erosion thresholds also showed a strong positive correlation with pellet dimensions. Experiments were also carried out to examine the effect of the number of pellets on erosion threshold of two sizes. The results show an asymptotic increase in erosion threshold with increasing number of pellets present, possibly due to sheltering effects. The chemical composition of the pellets was analyzed in terms of water and organic, carbon, and nitrogen contents as well as stable carbon and nitrogen isotopes. The results arising from this study will provide, information regarding potential tracers of waste feed material and help validate model predictions associated with dispersal of waste material.     

Estuarine mud flocculation properties determined using an annular mini-flume and the LabSFLOC system

Most entrained estuarine sediment mass occurs as flocs. Parameterising flocculation has proven difficult as it is a dynamically active process dependent on a set of complex interactions between the sediment, fluid and the flow. However the natural variability in an estuary makes it difficult to study the factors that influence the behaviour of flocculation in a systematic manner. This paper presents preliminary results from a laboratory study that examined how floc properties of a natural estuarine mud from the Medway (UK), evolved in response to varying levels of suspended sediment concentration and induced turbulent shearing. The experiments utilised the LabSFLOC floc video camera system, in combination with an annular mini-flume to shear the suspended sediment slurries. The flows created in the mini-flume produced average shear stresses, at the floc sampling height, ranging from 0.01 N m⁻² to a peak of 1.03 N m⁻². Nominal suspended particulate matter concentrations of 100, 600 and 2000 mg l⁻¹ were introduced into the flume. The experimental runs produced individual flocs ranging in size from microflocs of 22.2 μm to macroflocs 583.7 μm in diameter. Average settling velocities ranged from 0.01 to 26.1 mm s⁻¹, whilst floc effective densities varied from 3.5 up to 2000 kg m⁻³. Low concentration and low shear stress were seen to produce an even distribution of floc mass between the macrofloc (>160 μm) and microfloc (<160 μm) fractions. As both concentration and stress rose, the proportion of macrofloc mass increased, until they represented over 80% of the suspended matter. A maximum average macrofloc settling velocity of 3.3 mm s⁻¹ was attained at a shear stress of 0.45 N m⁻². Peak turbulence conditions resulted in deflocculation, limiting the macrofloc fall velocity to only 1.1 mm s⁻¹ and placing over 60% of the mass in the microfloc size range. A statistical analysis of the data suggests that the combined influence of both suspended concentration and turbulent shear controls the settling velocity of the fragile, low density macroflocs.     

Continental Oxygen Isotopic Record of the Last 170,000 Years in Jerusalem

A long radiometrically dated oxygen isotopic record of continental climatic variations since the penultimate glaciation was obtained from a stalagmite deposited in a sealed cave in Jerusalem. This record shows that speleothems have the potential of assigning dates to long- and short-term climatic events, with possible refining of Milankovitch tuning of ice and marine records which themselves are not datable. Short-term (1000-yr) events are very significant in the region, reaching 50% of glacial/interglacial fluctuations. The Mediterranean Sea was the most probable source of local precipitation throughout the last glacial cycle.     

Reactive Transport Modeling of ZVI Column Experiments for Nickel Remediation

MIN3P, a multicomponent reactive transport model for variably saturated porous media, is used to simulate the outputs of column tests carried out using zero valent iron (ZVI) for nickel contaminated groundwater remediation. The objective of this study is to investigate the main chemical reactions involved in contaminant removal and the main causes of the reactivity decline of ZVI over time. According to the results of the model the major causes of ZVI reactivity loss is identified in the mineral precipitation of α‐FeOOH on iron surface that probably caused ZVI passivation and led to a decline of the electron transfer rate. An existing empirical relationship between mineral precipitation and the reactivity loss of ZVI, included in the model, reproduced the changes in nickel removal observed during different laboratory column tests.     

Fluvial flood risk in Europe in present and future climates

In this work we evaluate the implications of climate change for future fluvial flood risk in Europe, considering climate developments under the SRES A2 (high emission) and B2 (low emission) scenario. We define flood risk as the product of flood probability (or hazard), exposure of capital and population, and vulnerability to the effect of flooding. From the European flood hazard simulations of Dankers and Feyen (J Geophys Res 114:D16108. doi:, 2009) discharges with return periods of 2, 5, 10, 20, 50, 100, 250 and 500 years were extracted and converted into flood inundation extents and depths using a planar approximation approach. Flood inundation extents and depths were transformed into direct monetary damage using country specific flood depth-damage functions and land use information. Population exposure was assessed by overlaying the flood inundation information with data on population density. By linearly interpolating damages and population exposed between the different return periods, we constructed damage and population exposure probability functions under present and future climate. From the latter expected annual damages (EAD) and expected annual population exposed (EAP) were calculated. To account for flood protection the damage and population exposure probability functions were truncated at design return periods based on the country GDP/capita. Results indicate that flood damages are projected to rise across much of Western Europe. Decreases in flood damage are consistently projected for north-eastern parts of Europe. For EU27 as a whole, current EAD of approximately €6.4 billion is projected to amount to €14–21.5 billion (in constant prices of 2006) by the end of this century, depending on the scenario. The number of people affected by flooding is projected to rise by approximately 250,000 to 400,000. Notwithstanding these numbers are subject to uncertainty, they provide an indication of potential future developments in flood risk in a changing climate.