Heterozoan carbonates from the equatorial rocky reefs of the Galápagos Archipelago

Strongly influenced by seasonal and interannual (i.e. El Niño‐Southern Oscillation) upwelling, the equatorial setting of the Galápagos Archipelago is divided into well‐defined temperature, nutrient and calcium carbonate saturation (Ω_aragonite) regions. To understand the relationship between oceanographic properties and sediment grain associations, grain size, carbonate content and components from sea floor surface samples were analysed, representing the main geographical regions of the Galápagos Archipelago. The shallow‐water rocky reefs of the Galápagos Archipelago are characterized by mixed carbonate–siliciclastic slightly gravelly sands. Despite minor differences in carbonate content, major differences exist in the distribution and composition of key carbonate producing biota. Halimeda is absent and benthic foraminifera occur in extremely low abundance. The western side of the Galápagos Archipelago is strongly influenced by nutrient‐rich, low‐Ω_aragonite, subtropical water, which generates a heterozoan carbonate biofacies in a tropical realm resembling cold‐water counterparts (i.e. serpulid, echinoderm, gastropod, barnacle and bryozoan‐rich facies). The Central East region is composed of a transitional‐heterozoan biofacies. Biofacies observed in the northern region have an increased occurrence of tropical corals, albeit with a minor overall contribution to the carbonate components. Although the temperature gradient would allow for a broader distribution of photozoan biofacies, the increased nutrient concentration and related reduced light penetration from the upwelled waters favour heterozoan carbonate factories, mimicking cool‐water, deeper or higher latitude environments. The recent sedimentary record of the Galápagos Archipelago presents a range of tropical heterozoan carbonate communities, responding to more than simply latitude or temperature but a much more complex mixture of physical, evolutionary and geological processes.     

Multiphase lattice Boltzmann simulations for porous media applications

Over the last two decades, lattice Boltzmann methods have become an increasingly popular tool to compute the flow in complex geometries such as porous media. In addition to single phase simulations allowing, for example, a precise quantification of the permeability of a porous sample, a number of extensions to the lattice Boltzmann method are available which allow to study multiphase and multicomponent flows on a pore scale level. In this article, we give an extensive overview on a number of these diffuse interface models and discuss their advantages and disadvantages. Furthermore, we shortly report on multiphase flows containing solid particles, as well as implementation details and optimization issues.     

A clear and present danger: Ladakh's increasing vulnerability to flash floods and debris flows

This preliminary investigation of the recent spate of deadly flash floods and debris flows in Ladakh (India) over the last decade identifies uncontrolled development in hazardous locations as an important factor contributing to loss of life and property damage in this high mountain desert. The sediments exposed in the channel banks and on the alluvial fans of several mountain streams in the area indicate a long history of flash floods and debris flows resulting from intense storms, which appear to have increased in frequency within the last decade. The signposts of these recurrent hazards are being ignored as a growing economy, which is boosted by a well‐established tourism industry, is now driving development onto lands that are susceptible to floods and debris flow hazards. In this science briefing we argue that the increasing vulnerability in Ladakh should be addressed with sound disaster governance strategies that are proactive, rather than reactionary. Copyright © 2016 John Wiley & Sons, Ltd.     

Seismic rupture during the 1960 Great Chile and the 2010 Maule earthquakes limited by a giant Pleistocene submarine slope failure

Determining factors that limit coseismic rupture is important to evaluate the hazard of powerful subduction zone earthquakes such as the 2011 Tohoku‐Oki event (Mw = 9.0). In 1960 (Mw = 9.5) and 2010 (Mw = 8.8), Chile was hit by such powerful earthquakes, the boundary of which was the site of a giant submarine slope failure with chaotic debris subducted to seismogenic zone depth. Here, a continuous décollement is absent, whereas away from the slope failure, a continuous décollement is seismically imaged. We infer that underthrusting of inhomogeneous slide deposits prevents the development of a décollement, and thus the formation of a thin continuous slip zone necessary for earthquake rupture propagation. Thus, coseismic rupture during the 1960 and 2010 earthquakes seems to be limited by underthrusted upper plate mass‐wasting deposits. More generally, our results suggest that upper plate dynamics and resulting surface processes can play a key role for determining rupture size of subduction zone earthquakes.     

Exploring possible connections between hydrological extreme events and climate change in central south Chile

Abstract

Motivated by recent extreme flow events in the Mataquito River located in the Mediterranean region of Chile, we performed a detailed trend analysis of critical hydroclimatic variables based on observed daily flow, precipitation and temperature within the basin. For the period 1976–2008, positive trends in temperature were observed, especially during spring and summer months. At the same time, we found negative trends in the frequency and intensity of precipitation, especially during spring months. We observed an increasing difference between average streamflow in the rainy season as compared to the snowmelt season. Part of this trend is caused by larger flows during autumn months, although no positive precipitation trends are observed for these months. Finally, significant reductions in minimum flow during spring/summer and a disproportionate concentration of high-flow events occurring in the last 10 years were also identified. These high-flow events tend to happen during autumn months, and are associated with high precipitation and high minimum temperatures. Based on a simple assessment of changes in irrigated agriculture and land use, we concluded that other non-climatic factors seem not to be as relevant to the detected flow trends. All these results are in accord with future climate change scenarios that show an increase in temperature, a reduction in average precipitation and a reduction in snow accumulation. Such future scenarios could seriously hamper the development of economic activities in this basin, exemplifying also a fate that may be shared by other similar basins in Chile and in other regions of the world.

Editor Z.W. Kundzewicz

Citation Vicuña, S., Gironás, J., Meza, F.J., Cruzat, M.L., Jelinek, M., Bustos, E., Poblete, D., and Bambach, N., 2013. Exploring possible connections between hydrological extreme events and climate change in central south Chile. Hydrological Sciences Journal, 58 (8), 1598–1619.     

The loess sequence of Dolní Věstonice,Czech Republic: A new OSL‐based chronology of the Last Climatic Cycle

The Dolní Věstonice loess section in the Czech Republic is well known for its high‐resolution loess–palaeosol sequence of the last interglacial–glacial climatic cycle (Upper Pleistocene). The loess section is situated in a climatic transition zone between oceanic and continental climates and is therefore of great value in reconstructing past regional climate conditions and their interaction with climate systems, in particular that of the North Atlantic. Based on a combination of optically stimulated luminescence (OSL) ages, stratigraphic field observations and magnetic susceptibility measurements, a chrono‐climatic interpretation of the Dolní Věstonice loess section is presented. To establish a reliable Upper Pleistocene chronology, a quartz OSL approach was applied for equivalent dose (D_e) determination. Monomineralic quartz extracts of three distinct grain sizes, fine (4–11 μm), middle (38–63 μm) and coarse (90–200 μm), were used and compared. Within error limits, the calculated OSL ages are the same for the different grain sizes, and the OSL ages are in stratigraphic order. The established OSL chronology is in agreement with a Weichselian litho‐ and pedostratigraphy. The Dolní Věstonice loess section is characterized by four pedosedimentary subsequences. At the base of the profile, subsequence I is characterized by a distinct Early Glacial soil complex, OSL‐dated to c. 110 to 70 ka, representing one of the most complete records of environmental change in the European loess belt. Subsequence II is allocated to the Lower Pleniglacial and is characterized by laminated sandy loess. Middle Pleniglacial subsequence III is represented by a brown soil complex, and is followed by the uppermost subsequence IV, characterized by a thick body of laminated sandy loess, indicating strong wind activity and a high sedimentation rate of more than ～1 mm a^?1 during the Upper Pleniglacial. According to the OSL chronology, as well as to the sedimentological and palaeopedological investigations, it is likely that the sequence at Dolní Věstonice has recorded most of the climatic events expressed in the NGRIP δ¹⁸O reference record between 110 and 70 ka.     

Transnational entrepreneurs,global pipelines and shifting production patterns. The example of the Palanpuris in the diamond sector

Building on the buzz-and-pipelines model of regional clusters, the paper shows that transnational entrepreneurs play an important role in the construction of external cluster relations and hence influence both the dynamics of regional clusters and global production settings. Unlike most studies on the economic implications of transnational migrants, the paper deals with a labor intensive manufacturing sector. In detail, diamond dealers from the Indian city of Palanpur will be conceptualized as transnational entrepreneurs who, in the past, were able to cover certain locations of the diamond value added chain with family members. The global relations set up by these families at the same time formed business networks allowing for an intense global exchange of knowledge and artifacts (diamonds). In the long run, these patterns implied a change of the overall production structures: in Antwerp, a traditional diamond trading and cutting center, the Indian dealers developed to strong competitors in the smaller stones segment and as such contributed to the fading away of the historically grown industrial base. In addition, the institutional support structures were partly dismantled. On the other hand, in India, a new cluster in diamond cutting emerged. The findings suggest that transnational entrepreneurs can contribute to a weakening of traditional cluster structures and therefore call for a more differentiated view as evoked by the one-sided focus of studies on returnee migrants in the high-tech sector.     

Late Cretaceous extension overprinting a steep belt in the Northern Calcareous Alps (Schesaplana, R?tikon, Switzerland and Austria)

The Triassic to Cretaceous sediment succession of the Lechtal Nappe in the western part of the Northern Calcareous Alps (NCA) has been deformed into large-scale folds and crosscut by thrust and extensional faults during Late Cretaceous (Eoalpine) and Tertiary orogenic processes. The following sequence of deformation is developed from overprinting relations in the field: (D1) NW-vergent folds related to thrusting; (D2) N–S shortening leading to east–west-trending folds and to the formation of a steep belt (Arlberg Steep Zone) along the southern border of the NCA; (D3) E–W to NE–SW extension and vertical shortening, leading to low-angle normal faulting and recumbent “collapse folds” like the Wildberg Syncline. D1 and D2 are Cretaceous in age and predate the Eocene emplacement of the Austroalpine on the Penninic Nappes along the Austroalpine basal thrust; the same is probably true for D3. Finally, the basal thrust was deformed by folds related to out-of-sequence thrusting. These results suggest that the NCA were at least partly in a state of extension during the sedimentation of the Gosau Group in the Late Cretaceous.