Fluvial dynamics and 14C-10Be disequilibrium on the Bolivian Altiplano

Determining sediment transfer times is key to understanding source-to-sink dynamics and the transmission of environmental signals through the fluvial system. Previous work on the Bolivian Altiplano applied the in situ cosmogenic ¹⁴C-¹⁰Be-chronometer to river sands and proposed sediment storage times of ~10–20 kyr in four catchments southeast of Lake Titicaca. However, the fidelity of those results hinges upon isotopic steady-state within sediment supplied from the source area. With the aim of independently quantifying sediment storage times and testing the ¹⁴C-¹⁰Be steady-state assumption, we dated sediment storage units within one of the previously investigated catchments using radiocarbon dating, cosmogenic ¹⁰Be-²⁶Al isochron burial dating, and ¹⁰Be-²⁶Al depth-profile dating. Palaeosurfaces appear to preserve remnants of a former fluvial system, which has undergone drainage reversal, reduction in catchment area, and local isostatic uplift since ~2.8 Ma. From alluvium mantling the palaeosurfaces we gained a deposition age of ~580 ka, while lower down fluvial terraces yielded ≤34 ka, and floodplains ~3–1 ka. Owing to restricted channel connectivity with the terraces and palaeosurfaces, the main source of channel sediment is via reworking of the late Holocene floodplain. Yet modelling a set of feasible scenarios reveals that floodplain storage and burial depth are incompatible with the ¹⁴C-¹⁰Be disequilibrium measured in the channel. Instead we propose that the ¹⁴C-¹⁰Be offset results from: (i) non-uniform erosion whereby deep gullies supply hillslope-derived debris; and/or (ii) holocene landscape transience associated with climate or human impact. The reliability of the ¹⁴C-¹⁰Be chronometer vitally depends upon careful evaluation of sources of isotopic disequilibrium in a wide range of depositional and erosional landforms in the landscape. © 2018 John Wiley & Sons, Ltd.     

A continuous tephrostratigraphic record from the Labrador Sea spanning the last 65 ka

Volcanic ash preserved in marine sediment sequences is key for independent synchronization of palaeoclimate records within and across different climate archives. Here we present a continuous tephrostratigraphic record from the Labrador Sea, spanning the last 65–5 ka, an area and time period that has not been investigated in detail within the established North Atlantic tephra framework. We investigated marine sediment core GS16-204-22CC for increased tephra occurrences and geochemically analysed the major element composition of tephra shards to identify their source volcano(es). In total we observed eight tephra zones, of which five concentration peaks show isochronous features that can be used as independent tie-points in future studies. The main transport mechanism of tephra shards to the site was near-instantaneous deposition by drifting of sea ice along the East Greenland Current. Our results show that the Icelandic Veidivötn volcanic system was the dominant source of tephra material, especially between late Marine Isotope Stage (MIS) 4 and early MIS 3. The Veidivötn system generated volcanic eruptions in cycles of ca. 3–5 ka. We speculate that the quantity of tephra delivered to the Labrador Sea was a result of variable Icelandic ice volume and/or changes in the transportation pathway towards the Labrador Sea.     

Controllability,observability and identifiability in single-phase porous media flow

Over the past few years, more and more systems and control concepts have been applied in reservoir engineering, such as optimal control, Kalman filtering, and model reduction. The success of these applications is determined by the controllability, observability, and identifiability properties of the reservoir at hand. The first contribution of this paper is to analyze and interpret the controllability and observability of single-phase flow reservoir models and to investigate how these are affected by well locations, heterogeneity, and fluid properties. The second contribution of this paper is to show how to compute an upper bound on the number of identifiable parameters when history matching production data and to present a new method to regularize the history matching problem using a reservoir’s controllability and observability properties.     

Frequency Domain Electromagnetic Induction Sounding Surveys for Landfill Site Characterization Studies

A frequency domain electromagnetic induction sounding survey (FDEM) was conducted on a landfill in northern Illinois to determine the depth of fill, locate areas of drum disposal, and locate areas of heavy metal sludge disposal. Sketchy information obtained from interviews of the site personnel identified specific exploration targets and areas of concern. The results of the geophysical survey verified much of the reported disposal history and identified areas suspected to contain hazardous waste.
Based on the results of the survey, the thickness of fill was estimated and two areas with highly conductive fill were located. These areas could represent leachate pockets or sludge disposal areas. An area in which the fill appears to be thicker than expected was identified. This area is thought to represent industrial sludge disposal in trenches excavated into the existing fill and underlying soils. An area with several linear in-phase, quadrature, and conductivity highs was detected. A subsequent magnetometer survey detected linear magnetic anomalies that are believed to be caused by parallel trenches filled with steel drums. This area is believed to be a previously unreported hazardous waste drum disposal cell excavated into the native soil.
As of this writing, the results of this survey have not been verified by traditional intrusive methods. When these investigations begin, we expect that information provided by the FDEM survey will reduce project costs by directing subsequent investigations, thereby reducing the number of borings and test pits required to characterize the site. While there is an unavoidable margin of error and uncertainty in remote sensing methods, the subsurface coverage provided by this geophysical survey could not have been reproduced by traditional methods without substantial expense. This paper presents the results of the survey and discusses application of the FDEM method on landfills.     

Particle energization in galactic centre ejections

For ejections in the galactic centre (the galactic centre lobe, the galactic centre jet, and the low-energy jet), which were discovered recently, the efficiency of two low plasma- electron re-acceleration processes (Alfvén resonance heating and dissipation by magnetic non-equilibrium) considered recently by one of us (T.M.K.) are discussed and order of magnitude calculations for the dissipated power are given.     

Comparing analytical and numerical approaches to meteoroid orbit determination using Hayabusa telemetry

Fireball networks establish the trajectories of meteoritic material passing through Earth's atmosphere, from which they can derive pre‐entry orbits. Triangulated atmospheric trajectory data require different orbit determination methods to those applied to observational data beyond the Earth's sphere of influence, such as telescopic observations of asteroids. Currently, the vast majority of fireball networks determine and publish orbital data using an analytical approach, with little flexibility to include orbital perturbations. Here, we present a novel numerical technique for determining meteoroid orbits from fireball network data and compare it to previously established methods. The re‐entry of the Hayabusa spacecraft, with its known pre‐Earth orbit, provides a unique opportunity to perform this comparison as it was observed by fireball network cameras. As initial sightings of the Hayabusa spacecraft and capsule were made at different altitudes, we are able to quantify the atmosphere's influence on the determined pre‐Earth orbit. Considering these trajectories independently, we found the orbits determined by the novel numerical approach to align closer to JAXA's telemetry in both cases. Using simulations, we determine the atmospheric perturbation to become significant at ~90 km—higher than the first observations of typical meteorite dropping events. Using further simulations, we find the most substantial differences between techniques to occur at both low entry velocities and Moon passing trajectories. These regions of comparative divergence demonstrate the need for perturbation inclusion within the chosen orbit determination algorithm.     

Predicting riverine dissolved silica fluxes to coastal zones from a hyperactive region and analysis of their first-order controls

Silicate weathering and resulting transport of dissolved matter influence the global carbon cycle in two ways. First by the uptake of atmospheric/soil CO₂ and second by providing the oceanic ecosystems via the fluvial systems with the nutrient dissolved silica (DSi). Previous work suggests that regions dominated by volcanics are hyperactive or even “hot spots” concerning DSi-mobilization. Here, we present a new approach for predicting DSi-fluxes to coastal zones, emphasizing “first-order” controlling factors (lithology, runoff, relief, land cover and temperature). This approach is applied to the Japanese Archipelago, a region characterized by a high percentage of volcanics (29.1% of surface area). The presented DSi-flux model is based on data of 516 catchments, covering approximately 56.7% of the area of the Japanese Archipelago. The spatial distribution of lithology—one of the most important first order controls—is taken from a new high resolution map of Japan. Results show that the Japanese Archipelago is a hyperactive region with a DSi-yield 6.6 times higher than the world average of 3.3 t SiO₂ km⁻² a⁻¹, but with large regional variations. Approximately 10% of its area exceeds 10 times the world average DSi-yield. Slope constitutes another important controlling factor on DSi-fluxes besides lithology and runoff, and can exceed the influence of runoff on DSi-yields. Even though the monitored area on the Japanese Archipelago stretches from about 31° to 46°N, temperature is not identified as a significant first-order model variable. This may be due to the fact that slope, runoff and lithology are correlated with temperature due to regional settings of the Archipelago, and temperature information is substituted to a certain extent by these factors. Land cover data also do not improve the prediction model. This may partly be attributed to misinterpreted land cover information from satellite images. Implications of results for Earth System and global carbon cycle modeling are discussed.     

Young-of-the-year oyster,Crassostrea virginica,reproduction in coastal Georgia

Young-of-the-year (YOY) oysters (Crassostrea virginica) in the Gulf of Mexico mature sexually and spawn in their first year. This study determined whether YOY oysters in the southeastern United States also mature and spawn in their first year. In 1991 and 1993, 300 YOY oysters were marked in May and 20–30 were sampled in subsequent months along with 20 adult controls. Two sites were chosen in 1991 (House Creek and Skidaway River) and one in 1993 (Skidaway River). At House Creek, YOY oysters were mature and spawned in September. YOY oysters at Skidaway spawned in October. Adult oysters did not appear to spawn in 1991. In 1993, the adult oysters spawned in August and September whereas, the YOY oysters spawned heavily in October. Oyster recruitment in coastal Georgia extends through October. The potential contribution of YOY oysters to this late season set is substantial, given that the YOY oysters are relatively large (≈4 cm) and are found in greater numbers than the adults. Oysters are capable of having two, if not more, generations within one year, prior to exposure of disease-causing organisms. Also, this particular reproductive strategy would increase the oysters suitability as a test subject in population genetic studies.     

Application of array data processing techniques to a network of ordinary seismograph stations

Summary Array data processing techniques, which are based upon signal similarity between the stations, offer important tools in seismic signal analysis.P waves recorded in the Fennoscandian network in general exhibit the signal resemblance required for applying array processing methods. The largest station separation in this network is about 1800 km, and the site structures range from sedimentary rocks in Denmark to the homogeneous crust of the Baltic shield. Inother words, we can consider the Fennoscandian station network as a super-large aperture seismic array (SLASA). An analysis of the background noise shows that application of even very simple processing techniques results in very effective noise suppression.A general adaptation of array processing techniques to ordinary seismograph stations is considered possible. Such methods will greatly improve our ability to extract reliable information from ordinary seismograms. Although theC-D (compression-dilatation) readings are usually correct, they often do not refer to the very first signal onset. Records of nuclear explosions from stations all over the world exhibit a high degree of signal similarity.     

Application of array data processing techniques to the swedish seismograph stations

Summary An efficient tool in seismic signal analysis is offered by the array data processing techniques which are based upon similarity of pulse shapes between stations. Records at the six Swedish stations in general exhibit the signal resemblance required by the array methods. By applying a simple processing technique, the signal-to-noise ratio is increased by a factor of about 2, and the accuracy ofP-wave readings is improved. High similarity is found not only between the same phase (P, pP) at different stations, but also between different phases (P, pP) at the same or different stations. Altogether, records of eleven earthquakes were investigated in detail. The Swedish station network can be considered as a super-large aperture seismic array (SLASA), despite some differences in instrumental equipment. A general adaptation of array techniques to SLASA systems is discussed. Such methods will greatly improve the seismological information which can be extracted from ordinary station records, provided the stations are located on geologically homogeneous ground.