New constraints on the Messinian sealevel drawdown from 3D seismic data of the Ebro Margin,western Mediterranean

We present new 3D seismic and well data from the Ebro Margin, NW Mediterranean Sea, to shed new light on the processes that formed the Messinian Erosion Surfaces (MES) of the Valencia Trough (Mediterranean Sea). We combine these data with backstripping techniques to provide a minimum estimate of the Messinian sea level fall in the EBRO Margin, as well as coupled isostasy and river incision and transport modeling to offer new constraints on the evolution of the adjacent subaerial Ebro Basin. Four major seismic units are identified on the Cenozoic Ebro Margin, based on the seismic data, including two major prograding megasequences that are separated by a major unconfirmity: the MES. The 3D seismic data provide an unprecedented view of the MES and display characteristic features of subaerial incision, including a drainage network with tributaries of at least five different orders, terraces and meandering rivers. The Messinian landscape presents a characteristic stepped‐like profile that allows the margin to be subdivided in three different regions roughly parallel to the coastline. No major tectonic control exists on the boundaries between these regions. The boundary between the two most distal regions marks the location of a relatively stable base level, and this is used in backstripping analysis to estimate the magnitude of sea level drop associated with the Messinian Salinity Crisis on the Ebro Margin. The MES on the Ebro Margin is dominated by a major fluvial system, that we identify here as the Messinian Ebro River. The 3D seismic data, onshore geology and modeling results indicate that the Ebro River drained the Ebro Basin well in advance of the Messinian.     

A subaltern critical geopolitics of the war on terror: Postcolonial security in Tanzania

Currently, hegemonic geographical imaginations are dominated by the affective geopolitics of the War on Terror, and related security practice is universalised into what has been called “globalized fear” (Pain, 2009). Critical approaches to geopolitics have been attentive to the Westerncentric nature of this imaginary, however, studies of non-Western perceptions of current geopolitics and the nature of fear will help to further displace dominant geopolitical imaginations. Africa, for example, is a continent that is often captured in Western geopolitics - as a site of failed states, the coming anarchy, passive recipient of aid, and so on - but geopolitical representations originating in Africa rarely make much of an impact on political theory.This paper aims to add to critical work on the so-called War on Terror from a perspective emerging from the margins of the dominant geopolitical imagination. It considers the geopolitical imagination of the War on Terror from a non-Western source, newspapers in Tanzania.     

Erosion-driven drawdown of atmospheric carbon dioxide: The organic pathway

Rapidly eroding, coastal mountain belts, where steep rivers and submarine channels connect upland sources to nearby marine sinks are hotspots of organic carbon transfer from life biomass, soil and exhumed bedrock into geological storage. Using observations from the Southern Alps of New Zealand, and Taiwan, we have mapped this organic pathway to geological carbon sequestration, and can evaluate the magnitude and efficiency of transfers between sources and sinks. We demonstrate that POC is harvested by landsliding, but importantly also by common and widespread surface runoff on steep hillslopes. Although terrestrially sourced POC is found in many sedimentary environments associated with mountain belts and frontier basins, it appears to be most abundantly trapped and preserved in marine turbidites. The loss of all forms of POC in onward transport through short, steep routing systems to this repository is limited. This is in marked contrast to larger routing systems, in which only the most resilient forms of POC survive into long-term deposition.     

Heavy metals in surface sediments of Waiwhetu Stream,Lower Hutt,New Zealand

Abstract

Surface sediment samples (60 μm‐2 mm, and < 60 μm fractions) from the Waiwhetu Stream, Lower Hutt City, New Zealand, were leached with dilute HCl to remove the mobile heavy‐metal fraction. Cd, Cr, Cu, Pb, Zn, Al, Fe, and Mn analyses of the leachates show that sediments of the upper reaches area of the stream are generally uncontaminated. In contrast, sediments in the lower reaches area are highly contaminated, despite clean‐up measures in the late 1970s. Lead and Zn are the most significantly enriched metals with concentrations over 1000 mg kg^?1 adjacent to some drains. In the polluted zone, metals originate from either upward remobilisation from underlying sediment (contaminated in the early 1960s and 70s) or more recent industrial spillages. Similar trends exhibited by Cd, Cu, Cr, Zn, Pb, and Al indicate that a proportion of the metal enrichment downstream probably results from a naturally higher clay content of sediments near the mouth of the stream. Fe and Mn show reverse trends to the other metals, indicating that a high proportion of these two metals occurs in substrate different to that of the other metals. The orange brick‐coloured sediments of the upper reaches of the stream indicate oxides upstream; the black sediments in the lower reaches indicate sulphides downstream.     

Temperature extremes and wildfires in Siberia in the 21st century: the MGO regional climate model simulation

Possible changes in temperature extremes and wildfires in the 21st century in the regions of Russia are analyzed using a regional climate model (RCM) with high space-time resolution. The IPCC A2 scenario of greenhouse gas and aerosol concentration increase in the atmosphere is used. It is shown that changes in extreme wildfires appear to be in the 21st century most pronounced relative to changes in moderate and high wildfires. In some areas, along with decreased moderate and high wildfires, a significant increase in extreme wildfires is expected. Further studies should be associated both with RCM development, aimed at improving simulation of the wildfire atmospheric condition, and with enlarging the parameter set for wildfire analysis. Not only seasonal mean, but also monthly mean wildfire conditions should be studied, along with the use of statistical methods of model data interpretation to analyze intraseasonal and interannual variability of wildfire characteristics.     

Short-range variations in the micromorphology of a palaeosol from Wivenhoe in southeast England

The pedogenic histories of four adjacent profiles of a polygenetic palaeosol developed on a Middle Pleistocene terrace of the proto-Thames from Wivenhoe in southeast England are reconstructed on the basis of superposition of key micromorphological features. Despite a considerable variation in macromorphology, partly resulting from large-scale periglacial features, three of the profiles have similar micromorphological records in that they retain evidence for two phases of clay illuviation separated by a period of periglacial disruption. This reconstruction, however, seems to be incomplete because the fourth profile contains micromorphological evidence for a further illuviation–disruption cycle. The extent of this variation suggests that soil micromorphology should be used only with care to reconstruct pedogenic or pedosedimentary histories of complex polygenetic palaeosols, or to compare such palaeosols on different surfaces of chronosequences spanning periods of major climatic change. The variable and possibly limited resolution of micromorphology, together with the current uncertainty over the exact environmental signifiance of illuvial clay features, means that inferred pedogenic phases should be correlated with specific climatic stages only with considerable caution. © 1998 John Wiley & Sons, Ltd.     

Modeling an irrigation ditch opens up the world. Hydrology and hydraulics of an ancient irrigation system in Peru

Ancient Peruvian irrigation systems have been studied extensively, but much remains unknown about technical and hydrological aspects of these irrigation systems. The Pampa de Chaparrí irrigation system in Peru is used as an example to show how modeling approaches for hydrological and hydraulic features of irrigation can yield results to improve our understanding of irrigation in the area. Analysis focuses on water availability compared demand, the way available water may have been applied to crops and whether the water needed could be delivered through the canal system. Results suggest that on the Pampa some 2500 hectares may have been cultivated within certain security limits for acceptable yields. The rhythm with which the irrigation requirement was applied to crops most likely influenced yields and thus food security. Furthermore, the influence of groundwater on crop growth may have been considerable. The hydraulic behavior of the irrigation system suggests that it should not be taken for granted that theoretically required water flows could actually be diverted and/or distributed to water users. The many questions coming out of the results define important items for a joint research agenda of archeologists and irrigation scientists.     

Environmental governance through information: China and Vietnam

In the field of environmental governance information is starting to become increasingly important, not least because of globalization and the information and communication technologies revolution. The notion of informational governance is a recent coinage that acknowledges the (partial) switch from regulatory‐based forms of governance to information‐based modes. In the information‐rich centres and nodes of the network society, where information is widely produced, disseminated and accessible, this might prove analytically useful. But what are the contours of informational governance in information‐poor environments? This paper looks into the (limited) emergence of informational governance arrangements in environmental protection in two cases characterizing the informational periphery: China and Vietnam.     

Towards a critical analysis of fictive geographies

Summary The recent 'culture turn' in geography has generated a good deal of interest in the structure of scientific knowledge and modes of writing, but there has less attention to the construction of other forms of knowledge and writing. While humanistic and regional geographers have referred to literature on the whole without comment on genre, mode of production or range of consumption, more recent critical geographers have regarded literature as a material artefact which fulfils a role designated by its position in various social and economic processes. This paper critiques both positions as offering a limited vision of the relationship between geography and literature and attempts to offer an engagement with literary fiction which analyses the content and form of the text, but also leaves room for its distinctive voice.     

Colloidal Control on the Distribution of Rare Earth Elements in Shallow Groundwaters

A 7-year monitoring period of rare earth element (REE) concentrations and REE pattern shapes was carried out in well water samples from a 450 m long transect setup in the Kervidy/Coët-Dan experimental catchment, France. The new dataset confirms systematic, topography-related REE signatures and REE concentrations variability but challenges the validity of a groundwater mixing hypothesis. Most likely, this is due to REE preferential adsorption upon mixing. However, the coupled mixing–adsorption mechanism still fails to explain the strong spatial variation in negative Ce anomaly amplitude. A third mechanism—namely, the input into the aquifer of REE-rich, Ce anomaly free, organic colloids—is required to account for this variation. Ultrafiltration results and speciation calculations made using Model VI agree with this interpretation. Indeed, the data reveal that Ce anomaly amplitude downslope decrease corresponds to REE speciation change, downhill groundwaters REE being mainly bound to organic colloids. Water table depth monitoring shows that the colloid source is located in the uppermost, organic-rich soil horizons, and that the colloid input occurs mainly when water table rises in response to rainfall events. It appears that the colloids amount that reaches groundwater increases downhill as the distance between soil organic-rich horizons and water table decreases. Topography is, therefore, the ultimate key factor that controls Ce anomaly spatial variability in these shallow groundwaters. Finally, the <0.2 μm REE fraction ultimately comes from two solid sources in these groundwaters: one located in the deep basement schist; another located in the upper, organic-rich soil horizon.