Late Quaternary distal tephra-fall deposits in lacustrine sediments, Kenai Peninsula, Alaska   总被引：1，自引：0，他引：1  

Christian S. de Fontaine  R. Scott Anderson  Christopher F. Waythomas 《Quaternary Research》2007,68(1):64-78

Tephra-fall deposits from Cook Inlet volcanoes were detected in sediment cores from Tustumena and Paradox Lakes, Kenai Peninsula, Alaska, using magnetic susceptibility and petrography. The ages of tephra layers were estimated using 21 ¹⁴C ages on macrofossils. Tephras layers are typically fine, gray ash, 1-5 mm thick, and composed of varying proportions of glass shards, pumice, and glass-coated phenocrysts. Of the two lakes, Paradox Lake contained a higher frequency of tephra (0.8 tephra/100 yr; 109 over the 13,200-yr record). The unusually large number of tephra in this lake relative to others previously studied in the area is attributed to the lake's physiography, sedimentology, and limnology. The frequency of ash fall was not constant through the Holocene. In Paradox Lake, tephra layers are absent between ca. 800-2200, 3800-4800, and 9000-10,300 cal yr BP, despite continuously layered lacustrine sediment. In contrast, between 5000 and 9000 cal yr BP, an average of 1.7 tephra layers are present per 100 yr. The peak period of tephra fall (7000-9000 cal yr BP; 2.6 tephra/100 yr) in Paradox Lake is consistent with the increase in volcanism between 7000 and 9000 yr ago recorded in the Greenland ice cores.  相似文献   

Probabilistic clustering of extratropical cyclones using regression mixture models   总被引：4，自引：2，他引：4  

Scott J. Gaffney  Andrew W. Robertson  Padhraic Smyth  Suzana J. Camargo  Michael Ghil 《Climate Dynamics》2007,29(4):423-440

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Gendered access to customary land in East Timor     

Pyone Myat Thu  Steffanie Scott  Kimberly P. Van Niel 《GeoJournal》2007,69(4):239-255

Land tenure rights reflect the deeper structures of society, particularly gender distinctions in relation to land. Considering the structural differences between patrilineal and matrilineal customary tenure systems in East Timor are understudied, this paper explores men and women’s experiences in accessing land under such arrangements. The comparative analysis of two patrilineal with one matrilineal land tenure systems in Ainaro and Manufahi districts suggests a significant degree of flexibility within both systems with respect to the norms of gendered inheritance. Therefore, the binary constructs of ‘patrilineal’ and ‘matrilineal’ societies are limiting. Both men and women in these communities may acquire land rights under different circumstances, mainly through negotiations with their parents or hamlet chief. Daughters in the patrilineal communities could inherit family land upon their parents’ death and sons in the matrilineal community could gain land by cultivating and maintaining unclaimed customary land. Empirical evidence show that inheritance principally determines usufruct rights to land, but marriage exchange practices complicates a deeper understanding of traditional East Timorese land rights.

Pyone Myat ThuEmail:

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Factors Controlling the Fractionation and Seasonal Mobility Variations of Ga and In in Systems Impacted by Acidic Thermal Waters: Effects of Thermodynamics and Bacterial Activity     

Yasumasa Ogawa  Daizo Ishiyama  Naotatsu Shikazono  Koichi Suto  Chihiro Inoue  Noriyoshi Tsuchiya  Bernhardt Saini-Eidukat  Scott A. Wood 《Aquatic Geochemistry》2018,24(1):5-25

This work assessed both the fractionation and the seasonal mobility variations of Ga and In in systems impacted by acidic thermal waters. This was accomplished by performing thermodynamic calculations using the PHREEQC algorithm and by assessing the activity of acidophilic iron-oxidizing bacteria. The pH of the Kusatsu thermal waters in Gunma Prefecture, central Japan, is rapidly increased following the addition of a lime suspension. After an abrupt pH increase, under which conditions free ions of Ga and In and their complexes with Cl^? and SO₄^2? exist only in negligible quantities, the majority of dissolved Ga and In is removed by sorption onto suspended hydrous ferric oxides (HFOs). These HFOs are then transported to an artificial lake without significant sedimentation along the river. Subsequently, the suspended HFOs settle out and are added to sediments without significant fractionation between Ga and In. The Tamagawa thermal waters in Akita Prefecture, northeast Japan, are also treated with lime. However, complete neutralization requires mixing with some tributary streams, leading to a gradual downstream increase in pH. Dissolved Ga is, in general, sorbed by HFOs in upstream areas, leading to wide dispersal of Ga across the entire watershed. In comparison, In is transported to the lake inlet predominantly as a Cl^? complex species without significant removal along the river, with the majority being precipitated in an artificial lake, where Cl^? concentrations are too low to form stable complex species with In, and thus, dissolved In is sorbed by HFOs. As a result, In is effectively concentrated within downstream lakebed sediments, whereas Ga is dispersed along the river. Seasonal variations in Ga mobility within the Tamagawa field between snowmelt and low-flow seasons are primarily controlled by pH, because hydrolysis reactions of these metals, which are related to sorption reactions, tend to occur in the upstream regions in the snowmelt season. However, under warmer conditions, HFO formation preferably occurs due to the activity of acidophilic iron-oxidizing bacteria. Thus, under similar pH variations, dissolved Ga is more effectively removed by HFOs during warmer seasons. On the contrary, because HFOs are abundantly formed in low-flow season, even under colder conditions, before In hydrolysis reaction starts to occur, In mobility is less affected by water temperature and then bacterial activity.  相似文献   

Karrat Fjord (Greenland) tsunamigenic landslide of 17 June 2017: initial 3D observations     

Dave Gauthier  Scott A. Anderson  Hermann M. Fritz  Thomas Giachetti 《Landslides》2018,15(2):327-332

On 17 June 2017, a landslide-generated tsunami reached the village of Nuugaatsiaq, Greenland, leaving four persons missing and presumed dead. Here, we present a preliminary high-resolution analysis of the tsunamigenic landslide scar based on three-dimensional (3D) reconstructions of oblique aerial photographs taken during a post-failure reconnaissance helicopter overflight. Through a 3D quantitative comparison with pre-failure topography, we estimate that approximately 58 million m³ of rock and colluvium (talus) was mobilized during the landslide, 45 million m³ of which reached the fjord, resulting in a destructive tsunami. We classify this event as a “tsunamigenic extremely rapid rock avalanche,” which likely released along a pre-existing metamorphic fabric, bounded laterally by slope-scale faults. Further analysis is required to properly characterize this landslide and adjacent unstable slopes, and to better understand the tsunami generation.  相似文献   

Late Triassic sauropodomorph and Middle Jurassic theropod tracks from the Xichang Basin,Sichuan Province,southwestern China:First report of the ichnogenus Carmelopodus     

Li-Da Xing  Jin Ba  Martin G.Lockley  Hendrik Klein  Sheng-Wu Yan  Anthony Romilio  Chun-Yong Chou  W.Scott Persons IV 《古地理学报》2018,(1)

Upper Triassic and Middle Jurassic strata of the Xichang Basin in Sichuan Province, southwestern China, yielded important dinosaur ichnofossils. From the Xujiahe Formation of the Yiguojiao tracksite, we report a Late Triassic footprint assemblage in China and the first discovery of diagnostic Triassic sauropodomorph tracks in this region. The tracks share a number of features in common with the ichnogenera Eosauropus(Late Triassic) and Liujianpus(Early Jurassic). The neighboring Bingtu tracksite is stratigraphically younger(Shaximiao Formation, Middle Jurassic) and preserves small tridactyl theropod tracks that represent the first occurrence of the ichnotaxon Carmelopodus in China and Asia. While these tracks are morphologically comparable to those from the Middle Jurassic type locality in North America, the specimens from China show the proximal margin of the digit IV impression in a more cranial position, which may indicate a trackmaker with a relatively short metatarsal IV. In addition to the skeletal record, the Carmelopodus footprints document the presence of small theropods in the dinosaur fauna of the Middle Jurassic Shaximiao Formation.  相似文献   

Measurements of the Temperature Structure-Function Parameters with a Small Unmanned Aerial System Compared with a Sodar     

Timothy A. Bonin  David C. Goines  Aaron K. Scott  Charlotte E. Wainwright  Jeremy A. Gibbs  Phillip B. Chilson 《Boundary-Layer Meteorology》2015,155(3):417-434

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Downscaling near-surface wind over complex terrain using a physically-based statistical modeling approach   总被引：1，自引：1，他引：0  

Hsin-Yuan Huang  Scott B. Capps  Shao-Ching Huang  Alex Hall 《Climate Dynamics》2015,44(1-2):529-542

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Unusual dinosaur trackway preservation as clues to paleo-landscape and behavior from the Lower Cretaceous Luohe Formation,Shaanxi Province,China     

Lida Xing  Martin G.Lockley  Yongzhong Tang  Hendrik Klein  W.Scott Persons IV  Miaoyan Wang  Xingwen Li  Hao Wu 《地学前缘(英文版)》2021,12(2):737-745

Poorly preserved tracks have limited ichnotaxonomic or biotaxon utility,but may reveal useful information about the paleoenvironment,behavior and track taphonomy.Eight mostly parallel to sub parallel trackway segments(T1–T8)were registered on a truncation surface in the Lower Cretaceous Luohe Formation of Shaanxi Province.These attest to the passage of several bipeds,probably all theropods,in a paleo-contour-parallel,south-north direction in an arid setting.Quality of preservation in these trackways is poor,but notably superior in two additional trackways(T9–T10)on a foreset surface.Trackway T9 indicates a didactyl trackmaker,probably a deinonychosaurian,heading north to south.This is the 13th report of deinonychosaurian tracks from the Lower Cretaceous of China.If any or all the eight south-north oriented trackway segments represent continuations of other segments in the same trackways,the total number of individual trackmakers heading in this direction may have been as lowas three.Although the trackway pattern and sedimentological evidence could indicate a physically controlled pathway influencing the direction taken by these trackmakers,the possibility that the trackways also represented small social or gregarious group cannot be ruled out.  相似文献   

Individual risk evaluation for landslides: key details     

Strouth  Alex  McDougall  Scott 《Landslides》2022,19(4):977-991

Risk-taking is an essential part of life. As individuals, we evaluate risks intuitively and often subconsciously by comparing the perceived risks with expected benefits. We do this so commonly that it passes unnoticed, like when we decide to speed home from work or go for a swim. The comparison changes, however, when one entity (such as a government) imposes a risk evaluation on another person. For example, in a quantitative risk management framework, the estimated risk is compared with a tolerable risk threshold to decide if the person is ‘safe enough’. Landslide risk management methods are well established and there is consensus on tolerable life-loss risk thresholds. However, beneath this consensus lie several key details that are explored by this article, along with suggestions for refinement. Specifically, we suggest using the risk unit, micromort (one micromort equals a life loss risk of 1 in 1 million), in describing risk estimates and thresholds, to improve risk communication. For risk estimation, we provide guidance for defining and combining landslide scenarios and for recognizing where unquantified risk from low-probability/high-consequence scenarios ought to inform risk management decisions. For risk tolerance thresholds, we highlight the pitfalls of selecting unachievably low thresholds and suggest that there is no single universal threshold. Additionally, we argue that gross disproportion between costs and benefits of further risk reduction, which is integral to the As Low As Reasonably Practicable (ALARP) principle, is a commonly unachievable and counter-productive condition for risk tolerance, and other conditions centered on proportionality often apply. Finally, we provide several figures that can be used as risk communication tools, to provide context for risk estimates and risk tolerance thresholds when these values are reported to decision makers and the public.

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