Inversions in sub-potassic nephelines

Sub-potassic nephelines in the system NaAlSiO₄(Ne)-KAlSiO₄(Ks) were synthesized under a variety of conditions and studied at room temperature and up to 1000 °C using an X-ray powder diffractometer. At low temperatures they do not have the hexagonal structure determined by Hahn and Buerger (1955) for natural nepheline. Samples with 0.7 to 2.5 mole % Ks have an orthorhombic supercell with parameters equivalent to a, 3a, 3c where a and c are Hahn and Buerger structure cell parameters. Nephelines with 0 to 0.7% Ks consist of two phases with different c axes; one of these phases has the orthorhombic supercell.Pure-Na nephelines (NaAlSiO₄) invert to a hexagonal phase with the Hahn and Buerger structure at 190 °±10 °C; this inversion temperature decreases with increasing Ks and a sample with 0.5% Ks inverts at 170 °±5 °C. The inversion is reversible and is displacive. Another reversible inversion begins at 875 °±10 °C in pure-Na nepheline; this inversion increases in temperature with increasing Ks and a sample with 1.8% Ks begins to invert at 960 °±10 °C.Superstructures with anomalous low-temperature cell parameters in sub-potassic nephelines are attributed to reversible collapse of the framework about the larger cation sites which must be occupied by small Na in subpotassic nephelines. Superstructures in natural nephelines are also related to framework collapse at a displacive inversion.     

The Colorado East River Community Observatory Data Collection

The U.S. Department of Energy's (DOE) Colorado East River Community Observatory (ER) in the Upper Colorado River Basin was established in 2015 as a representative mountainous, snow-dominated watershed to study hydrobiogeochemical responses to hydrological perturbations in headwater systems. The ER is characterized by steep elevation, geologic, hydrologic and vegetation gradients along floodplain, montane, subalpine, and alpine life zones, which makes it an ideal location for researchers to understand how different mountain subsystems contribute to overall watershed behaviour. The ER has both long-term and spatially-extensive observations and experimental campaigns carried out by the Watershed Function Scientific Focus Area (SFA), led by Lawrence Berkeley National Laboratory, and researchers from over 30 organizations who conduct cross-disciplinary process-based investigations and modelling of watershed behaviour. The heterogeneous data generated at the ER include hydrological, genomic, biogeochemical, climate, vegetation, geological, and remote sensing data, which combined with model inputs and outputs comprise a collection of datasets and value-added products within a mountainous watershed that span multiple spatiotemporal scales, compartments, and life zones. Within 5 years of collection, these datasets have revealed insights into numerous aspects of watershed function such as factors influencing snow accumulation and melt timing, water balance partitioning, and impacts of floodplain biogeochemistry and hillslope ecohydrology on riverine geochemical exports. Data generated by the SFA are managed and curated through its Data Management Framework. The SFA has an open data policy, and over 70 ER datasets are publicly available through relevant data repositories. A public interactive map of data collection sites run by the SFA is available to inform the broader community about SFA field activities. Here, we describe the ER and the SFA measurement network, present the public data collection generated by the SFA and partner institutions, and highlight the value of collecting multidisciplinary multiscale measurements in representative catchment observatories.     

Deformation history and timing of granite emplacement in the Butchers Hill — Helenvale region,northern Hodgkinson Province,Queensland

Granite plutons of the Whypalla Supersuite in the Butchers Hill — Helenvale region of north Queensland were intruded into the upper crust of the Hodgkinson Formation during contractional deformation associated with the Permian‐Triassic Hunter‐Bowen Orogeny. A four‐stage structural history has been resolved for the area, with fabric overprinting relationships, porphyroblast‐matrix microstructural geometries and isotopic ages being consistent with granite emplacement during D₄ shortening at ca 274 Ma. Microstructural relationships suggest the possibility of a minor syn‐D₃ phase of granite emplacement. The deformation‐emplacement history of the Butchers Hill — Helenvale area is consistent with that recognised regionally for the Hodgkinson Province, indicating province‐wide synchronous syntectonic granite intrusion during a major phase of contractional deformation. Intense syn‐emplacement deformation partitioning was ongoing in the country rocks during progressive D₄ and was associated with upward translation of country rock from the microscale to the macroscale along D₄ cleavages and shears. Kinematic indicators show that this progressive uplift, at the scale of the area examined, was east‐side‐up.     

Vegetation of Central Transbaikalia in the Late Glacial period and Holocene

Presented are the latest findings from investigating bottom sediments in Lake Arakhlei, containing continuous records of the vegetation evolution in the Beklemishevskaya depression and its mountain surroundings for the last 13 500 years.     

Impact of mesoscale eddies on particulate organic carbon flux in the western subarctic North Pacific

The mechanism that controls particulate organic carbon (POC) flux in the deep sea differs depending on the season and sea. The POC produced in the western subarctic North Pacific are known to be transported to the deep sea efficiently, but the direct relationship between the POC flux and physical processes is still unclear. In this study, we evaluated the effect of mesoscale eddies on POC flux in the western subarctic North Pacific. The seasonal and interannual variabilities of POC flux were investigated using data from a time-series sediment trap deployed at 4810 m at station K2 (47°N, 160°E) from 2005 to 2018. POC flux was high during May–November, appearing to reflect spring and fall blooms at the ocean surface. POC flux also showed interannual variability, with twelve peaks that were mostly affected by enhanced bloom just before the peak. Nine peaks of the twelve peaks were affected by mesoscale eddies, which enhanced bloom around K2 by extending the area with a high chlorophyll-a concentration along the coastal region into the offshore region, suggesting that mesoscale eddies strongly impact the interannual variability of POC flux at K2.

     

Modelling hydrological connectivity of tropical floodplain wetlands via a combined natural and artificial stream network

The ecological condition and biodiversity values of floodplain wetlands are highly dependent on the hydrological connectivity of wetlands to adjacent rivers. This paper describes a method for quantifying connectivity between floodplain wetlands and the main rivers in a wet tropical catchment of northern Australia. We used a one‐dimensional hydrodynamic model to simulate time‐varying water depths across the stream network (i.e. rivers, streams and man‐made drains). The timing and duration of connectivity of seven wetlands (four natural and three artificial) with the two main rivers in the catchment were then calculated for different hydrological conditions. Location and areal extent of the wetlands and the stream network were identified using high‐resolution laser altimetry, and these data formed key inputs to the hydrodynamic model. The model was calibrated using measured water depths and discharges across the floodplain. An algorithm was developed to identify contiguous water bodies at daily time steps, and this gave the temporal history of connection and disconnection between wetlands and the rivers. Simulation results show that connectivity of individual wetlands to both rivers varies from 26 to 365 days during an average hydrological condition. Location, especially proximity to a main river, and wetland type (natural stream or artificial drain) were identified as key factors influencing these levels of connectivity. Some natural wetlands maintain connection with the river for most or all of the year, whereas the connectivity of some artificial wetlands varies from 26 to 36 days according to their patterns of network connection to adjacent rivers – a result that has important implications for the accessibility of these types of wetland to aquatic biota. Using readily available river gauge data, we also show how connectivity modelling can be used to identify periods when connectivity has fallen below critical thresholds for fish movement. These connectivity patterns within the floodplain network are central to the setting of river flows that will meet environmental requirements for biota that use floodplain wetlands during their life history. Copyright © 2013 John Wiley & Sons, Ltd.     

Mammal remains at Rantis Cave,Israel, and Middle–Late Pleistocene human subsistence and ecology in the Southern Levant

Rantis Cave is a recently discovered filled cave in central Israel, displaying a rich faunal accumulation of micromammals, ungulates and carnivores. U–Th dating assigns the beginning of accumulation to ca. 140 ka. The accumulation is culturally assigned to the late half of the Middle Paleolithic (MP) period. Single‐grain optically stimulated luminescence measurements attest to a complex sedimentological history. We present the cross‐disciplinary results of taphonomic and geomorphological analyses, which point to the cave serving as a natural pitfall trap for the large fauna, with little human or carnivore activity. The fauna is dominated by Dama among the ungulates and by Microtus among the micromammals. These data in conjunction with ungulate tooth mesowear analysis suggest a xeric Mediterranean environment on the eastern margin of the southern Levantine foothills. The relative taxonomic abundance of ungulate taxa shows some differences from anthropogenic MP sites, possibly reflecting the prey choice patterns of MP hunters. Overall, the natural accumulation scenario for Rantis Cave provides a rare paleoenvironmental and paleoeconomic reference to the rich anthropogenic MP faunas of the Southern Levant, enabling the reconstruction of a rich and diverse environmental setting for this important human dispersal route. Copyright © 2011 John Wiley & Sons, Ltd.