Rapid and cyclic aeolian deposition during the Last Glacial in European loess: a high-resolution record from Nussloch, Germany

This paper reports the results of an investigation of the Weichselian Upper Pleniglacial loess sequences of Nussloch (Rhine Valley, Germany) based on stratigraphy, palaeopedology, sedimentology, palynology, malacology and geochemistry (δ¹³C), supported by radiocarbon, TL and OSL dating. Grain-size and magnetic susceptibility records are taken at 5 cm intervals from the Upper Pleniglacial (UPG) loess. The data indicate cyclic variations in loess deposition between ca 34 and 17 ka, when the sedimentation rate is especially high (1.0–1.2 m per ka for more than 10 m). The grain-size index (GSI: ratio of coarse silt versus fine silt and clay) shows variations, which are assumed to be an indirect measurement of wind intensity. The sedimentation rate, interpreted from the profiles, indicates high values in loess (Loess events LE-1 to LE-7) and low or negligible values in tundra gley horizons G1 to G8. OSL ages from the loess and ¹⁴C dates from organic matter in the loess show that loess deposition was rapid but was interrupted by shorter periods of reduced aeolian sedimentation. Comparison between the data from Nussloch and other European sequences demonstrates a progressive coarsening of the loess deposits between ca 30 and 22 ka. This coarsening trend ends with a short but major grain-size decrease and is followed by an increase to a new maximum at 20 ± 2 ka (“W” shape). Correlation between the loess GSI and the Greenland ice-core dust records, suggests a global connection between North Atlantic and Western European global atmospheric circulation and wind regimes. In addition, the typical Upper Pleniglacial loess deposition begins at ca 30–31 ka, close to Heinrich event (HE) 3, and the main period of loess sedimentation at about 25 ± 2 ka is coeval to HE 2. Correlation of magnetic susceptibility and grain-size records shows that the periods, characterised by high GSI, coincide with an increase in the amount of ferromagnetic minerals reworked from the Rhine alluvial plain. They suggest enhancement in the frequency of the storms from N–NW. These results are integrated within a palaeogeographical model of dust transport and deposition in Western Europe for the Weichselian Upper Pleniglacial (or Late Pleniglacial).     

Presolar silicate and oxide abundances and compositions in the ungrouped carbonaceous chondrite Adelaide and the K chondrite Kakangari: The effects of secondary processing

Abstract– Although it has been suggested that the ungrouped carbonaceous chondrite Adelaide and the K chondrite Kakangari could be considered highly primitive, our study of their presolar grain abundances shows that both have experienced more secondary processing than other primitive chondrites with high presolar grain abundances. Presolar grains are rare in Kakangari and are present in reduced abundances in Adelaide (approximately 70 ppm for O‐anomalous grains). Thermal annealing has led to widespread crystallization of their fine‐grained matrices, and accounts for the partial to complete destruction of presolar grains. In addition, presolar silicates in Adelaide show elevated Fe abundances and Fe‐rich rims indicative of infiltration of Fe into the grains from the surrounding matrix. This process probably also took place during annealing, most likely in the solar nebula, in a region with an enhanced dust‐to‐gas ratio. The most primitive meteorites, with the highest presolar grain abundances, appear to be those whose matrices contain abundant amorphous material that has escaped any significant thermal or aqueous alteration.     

Evolution of the winonaite parent body: Clues from silicate mineral trace element distributions

Abstract— We have measured the trace element compositions of individual plagioclase, pyroxene, and olivine grains in 6 different winonaites that span the range of textures and mineralogies observed in these meteorites. Textural evidence in these meteorites, including the presence of a plagioclase/clinopyroxene‐rich lithology and coarse‐grained olivine lithologies, suggests that they may have experienced some silicate partial melting. However, trace element distributions in these lithologies do not show any clear signatures for such an event. Pyroxene trace element compositions do exhibit systematic trends, with abundances generally lowest in Pontlyfni and highest in Winona. The fact that the same trends are present for both incompatible and compatible trace elements suggests, however, that the systematics are more likely the result of equilibration of minerals with initially heterogeneous and distinct compositions, rather than partial melting of a compositionally homogeneous precursor. The winonaites have experienced brecciation and mixing of lithologies, followed by varying degrees of thermal metamorphism on their parent body. These factors probably account for the variable bulk rare earth element (REE) patterns noted for these meteorites and may have led to re‐equilibration of trace elements in different lithologies.     

MARC: a robust method for multiple-aspect trajectory classification via space,time, and semantic embeddings

ABSTRACT

The increasing popularity of Location-Based Social Networks (LBSNs) and the semantic enrichment of mobility data in several contexts in the last years has led to the generation of large volumes of trajectory data. In contrast to GPS-based trajectories, LBSN and context-aware trajectories are more complex data, having several semantic textual dimensions besides space and time, which may reveal interesting mobility patterns. For instance, people may visit different places or perform different activities depending on the weather conditions. These new semantically rich data, known as multiple-aspect trajectories, pose new challenges in trajectory classification, which is the problem that we address in this paper. Existing methods for trajectory classification cannot deal with the complexity of heterogeneous data dimensions or the sequential aspect that characterizes movement. In this paper we propose MARC, an approach based on attribute embedding and Recurrent Neural Networks (RNNs) for classifying multiple-aspect trajectories, that tackles all trajectory properties: space, time, semantics, and sequence. We highlight that MARC exhibits good performance especially when trajectories are described by several textual/categorical attributes. Experiments performed over four publicly available datasets considering the Trajectory-User Linking (TUL) problem show that MARC outperformed all competitors, with respect to accuracy, precision, recall, and F1-score.     

GIS research to address tensions in geography

The rise of Geographic Information Systems (GIS) technologies has been producing powerful tools for spatial data processing, management, analysis, modeling, and visualization. While supporting many tasks, GIS technologies have evoked new thinking and advanced intellectual inquiries in geography. Technological advances in other fields often stimulate new research questions and lead to revolutionary discoveries. The Hubble telescope revolutionizes our understanding of the universe, and 3D digital microscopes transform our knowledge of the coordination among biological, neurological, and physiological systems in living organisms. Can GIS claim similar revolutionary effects on geography? The answer is much up for debate. With GIS technologies, geographic studies can explore a broader extent across multiple scales in space and time and tackle problems through increasingly complex spatial statistics, visual analytics, computation, simulation, machine learning, and artificial intelligence. Both the Hubble telescope and 3D digital microscope were built based on scientific research that subserves the technological advances for inquiries into space and life systems. Likewise, GIScience research innovates GIS methods that enable novel geographic investigations and therefore contribute to geographic knowledge production. For the sake of simplicity, the term GIS used here represents both GIScience and GIS technologies. This essay attempts to clarify the intellectual contributions of GIS to geography on the following two questions: (1) What novel geographic thinking is driven by GIS? (2) How may GIS provoke new geographic inquiries and knowledge? Building on Nystuen's notion of four tensions that trigger geographic questions, the essay discusses how GIS innovations mediate historical tension, space‐time tension, dimensional tension and scale tensions.     

Green growth machines? Competing discourses of urban development in Playa Vista,California

Playa Vista is a massive mixed-use development built on coastal wetlands in west Los Angeles. Its land use story illustrates how strategically constructed discourses shape contested urban spaces. Through an analysis of newspaper reporting and government documents, this paper traces how pro-Playa Vista interests changed their growth discourses rationalizing the development between 1979 and 2015. Findings suggest that pro-growth coalitions are resilient when they modify their discourses to negotiate new regulatory and political contexts, specifically pursuing sustainability fixes. They are not dogmatic in their adherence to orthodoxies of private property rights and “highest and best use” of land but rather continually reconstruct growth discourses incorporating enough of the values of their opponents (i.e. “green” values such as growth management and smart growth) that some environmental and homeowner citizens’ groups join the growth coalition, forming a “green growth machine” that not only profitably builds on the land but finances ecological restoration.     

Large-Scale and Mesoscale Distribution of Plankton Biomass and Metabolic Activity in the Northeastern Central Atlantic

Plankton biomass and indices of metabolism and growth [electron transport system (ETS), glutamate dehydrogenase (GDH) and aspartate transcarbamylase (ATC) activities] were studied over a 2,800 km east-west section of the tropical North Atlantic Ocean (21°N) in <200, 200–500 and >;500 µm size classes. On the large-scale, zooplankton (>;200 µm) enzymatic activities increased westward in the study section, where large cyanobacteria chains (Trichodesmium spp.) were observed. Parallel to it, an increase in medium calanoids (1–2 mm length) was observed towards the western part of the transect, whereas small calanoids (<1 mm) were dominant throughout the boundary area of the subtropical gyre. Microplankton ETS and mesoplankton ETS and ATC activities seemed to match the wave length of low frequency waves. Our results suggest that such waves are related to the observed enhancement of metabolic activity of micro- and mesoplankton. The large-scale and mesoscale variability observed give evidence of the inadequacy of assuming a steady-state picture of the euphotic zone of tropical and subtropical waters.