Geology ‘far from the madding crowd’, along the northern border of Vietnam     

Mark Williams  Toshifumi Komatsu  Phong Nguyen Duc  Tom Harvey  Thijs Vandenbroucke 《Geology Today》2019,35(6):217-220

To the north of Hanoi, about a day's drive by car, lies Ha Giang Province, the northernmost region of Vietnam. Ha Giang is remote from the hustle and bustle of daily life, and beyond its eponymous provincial capital towards the border with China, mountains rise quickly to Quan Ba, ‘Heaven's Gate’. The mountains form an uneven landscape of steep‐sided karst rising from deep river‐cut gorges and form a formidable barrier on the northern frontier of Vietnam. Beyond ‘Heaven's Gate’ lies the little travelled region of Dong Van, with its majestic mountains of Palaeozoic strata rising precipitously to the sky. Here, a century ago, the French geologists Henri Mansuy and Jacques Deprat documented early finds of fossils from lower Palaeozoic strata on the border with China.  相似文献   

Evaluating soil water routing approaches in watershed-scale,ecohydrologic modelling     

Garett Pignotti  Indrajeet Chaubey  Keith Cherkauer  Mark Williams  Melba Crawford 《水文研究》2021,35(3):e14034

Soil water dynamics are central in linking and regulating natural cycles in ecohydrology, however, mathematical representation of soil water processes in models is challenging given the complexity of these interactions. To assess the impacts of soil water simulation approaches on various model outputs, the Soil and Water Assessment Tool was modified to accommodate an alternative soil water percolation method and tested at two geographically and climatically distinct, instrumented watersheds in the United States. Soil water was evaluated at the site scale via measured observations, and hydrologic and biophysical outputs were analysed at the watershed scale. Results demonstrated an improved Kling–Gupta Efficiency of up to 0.3 and a reduction in percent bias from 5 to 25% at the site scale, when soil water percolation was changed from a threshold, bucket-based approach to an alternative approach based on variable hydraulic conductivity. The primary difference between the approaches was attributed to the ability to simulate soil water content above field capacity for successive days; however, regardless of the approach, a lack of site-specific characterization of soil properties by the soils database at the site scale was found to severely limit the analysis. Differences in approach led to a regime shift in percolation from a few, high magnitude events to frequent, low magnitude events. At the watershed scale, the variable hydraulic conductivity-based approach reduced average annual percolation by 20–50 mm, directly impacting the water balance and subsequently biophysical predictions. For instance, annual denitrification increased by 14–24 kg/ha for the new approach. Overall, the study demonstrates the need for continued efforts to enhance soil water model representation for improving biophysical process simulations.  相似文献   

Cognitive and Affective Predictors of Illinois Residents’ Perceived Risks from Gray Wolves     

Adam C. Landon  Maarten H. Jacobs  Craig A. Miller  Jerry J. Vaske  Brent D. Williams 《社会与自然资源》2020,33(5):574-593

Abstract

Increasing wolf populations are a concern for wildlife managers in the Midwestern U.S. Understanding the psychological mechanisms that contribute to public perceptions of risk will enable development of strategies that seek to mitigate these risks, and suggest where outreach efforts may facilitate acceptance of wolves. We examined the psychological factors that influence Illinois residents’ perceived risks from wolves. We hypothesized that individuals’ perceived risks from wolves were a function of their attitudes toward wolves, negative affect toward wolves, and basic beliefs about wildlife. Data were obtained from a survey of the Illinois public (n?=?784). Negative affect and attitudes toward wolves were direct predictors of perceived risks. Basic beliefs predicted attitudes and negative affect toward wolves. Negative affect predicted attitudes. Basic beliefs had direct and indirect effects on perceived risks.  相似文献   

From Grain to Floodplain: Evaluating heterogeneity of floodplain hydrostatigraphy using sedimentology,geophysics, and remote sensing     

H.F. Malenda  N.A. Sutfin  G. Guryan  S. Stauffer  J.C. Rowland  K.H. Williams  K. Singha 《地球表面变化过程与地形》2019,44(9):1799-1815

Stratigraphy is a fundamental component of floodplain heterogeneity and hydraulic conductivity and connectivity of alluvial aquifers, which affect hydrologic processes such as groundwater flow and hyporheic exchange. Watershed-scale hydrological models commonly simplify the sedimentology and stratigraphy of floodplains, neglecting natural floodplain heterogeneity and anisotropy. This study, conducted in the upper reach of the East River in the East River Basin, Colorado, USA, combines point-, meander-, and floodplain-scale data to determine key features of alluvial aquifers important for estimating hydrologic processes. We compare stratigraphy of two meanders with disparate geometries to explore floodplain heterogeneity and connectivity controls on flow and transport. Meander shape, orientation, and internal stratigraphy affected residence time estimates of laterally exchanged hyporheic water. Although the two meanders share a sediment source, vegetation, and climate, their divergent river migration histories resulted in contrasting meander hydrofacies. In turn, the extent and orientation of these elements controlled the effective hydraulic conductivity and, ultimately, estimates of groundwater transport and hyporheic residence times. Additionally, the meanders’ orientation relative to the valley gradient impacted the hydraulic gradient across the meanders—a key control of groundwater velocity. Lastly, we combine our field data with remotely sensed data and introduce a potential approach to estimate key hydrostratigraphic packages across floodplains. Prospective applications include contaminant transport studies, hyporheic models, and watershed models. © 2019 John Wiley & Sons, Ltd.  相似文献   

Iceland as a therapeutic landscape: white wilderness spaces for well-being     

Brooke  Kaelan  Williams  Allison 《GeoJournal》2021,86(3):1275-1285

Therapeutic landscapes are reputed to have a lasting repute for realizing healing. Traditional therapeutic landscapes have recognized natural environments as often sought after places for well-being. Such places promote wellness via their close encounter with nature, facilitating relaxation and restoration, and enhancing a combination of physical, mental, and spiritual healing. The physical environment of Iceland is explored through a case study approach, primarily employing data from the field notebooks of post-secondary students travelling in Iceland, as well as the authors’ ethnographic field experience in Iceland. Iceland is examined using both a traditional understanding of therapeutic landscapes, as well as the contemporary understanding of the coloured landscape. In addition to the colour white, reflected in the glacial ice, moving water, and geo-thermal steams, black and various other colours in combination are discussed.

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Quantifying the response of cotton production in eastern Australia to climate change   总被引：1，自引：0，他引：1  

Allyson Williams  Neil White  Shahbaz Mushtaq  Geoff Cockfield  Brendan Power  Louis Kouadio 《Climatic change》2015,129(1-2):183-196

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A high-resolution,multi-channel,over-sea-ice seismic reflection survey over the Mackay Sea Valley,Granite Harbor,Antarctica     

B. P. Williams  M. A. Speece  R. D. Powell 《Marine Geophysical Researches》2011,32(3):383-395

In the austral summer of 2007, 20.5 km of high-resolution over-sea-ice seismic reflection data were collected in the Granite Harbor region of southern McMurdo Sound over the Mackay Sea Valley. The goal of the survey was to image thin pelagic sediment deposited in the Mackay Sea Valley after the Last Glacial Maximum. A generator–injector air gun was lowered beneath the sea ice through holes drilled by an auger drill system. The recording system was a 60 channel snow streamer with vertically oriented gimbaled geophones spaced 25 m apart. Unique problems in the over-sea-ice seismic reflection survey—noise from the ice column flexing and timing delays caused by trapped air at previous shot points—were overcome to improve the quality of the seismic data. The Mackay Sea Valley survey produced seismic data with a vertical resolution of 6.3 m. The processed seismic data show pelagic sediment thickness of up to 50 m within the Mackay Sea Valley with some locations showing possible older sediments beneath the pelagic sediment layer.  相似文献   

Using existing scientific capacity to set targets for ecosystem-based management: A Puget Sound case study     

Jameal F. Samhouri  Phillip S. Levin  C. Andrew James  Jessi Kershner  Greg Williams 《Marine Policy》2011

Human actions have altered the structure and function of coastal ecosystems worldwide. In many locations, the overall portfolio of goods, cultural amenities, and supporting services provided by the marine environment has deteriorated. Ecosystem-based management (EBM) offers significant promise for addressing these issues because it is a comprehensive and integrated approach designed to reconcile conflicts and trade-offs among users of marine resources. A key step in the implementation of EBM is the establishment of target reference levels, or desired states, for indicators that reflect the status of the ecosystem. This paper reviews five approaches, borrowed from a variety of disciplines, to establish target reference levels for EBM. The approaches include the use of existing reference levels, reference directions, and reference levels based on nonlinear functional relationships, baselines, or social norms. Each approach is particularly suitable for EBM because it can be used alone or in combination with others to contextualize status for a diverse suite of ecosystem goals influenced by a wide variety of human activities. Perhaps most importantly, these approaches offer a prospectus for moving forward with EBM by using readily available information, motivating existing scientific capacity, and addressing trade-offs implicit to the setting of targets. This last point is articulated via examples of how each type of reference level might be applied in Puget Sound, WA, USA, where the efforts of scientists, managers, and policy makers have aligned recently in the interest of EBM implementation.  相似文献   

Mathematical modeling of thermomechanical erosion beneath Proterozoic komatiitic basaltic sinuous rilles in the Cape Smith Belt,New Québec,Canada     

David A. Williams  Ross C. Kerr  C. Michael Lesher 《Mineralium Deposita》2011,46(8):943-958

Virtually all of the economic Ni–Cu–(platinum group element (PGE)) mineralization in the central part of the Cape Smith Belt of New Québec is hosted by thick olivine cumulate units in the Katinniq Member of the Raglan Formation at the base of the 1.9 Ga Chukotat Group. These units transgress underlying gabbros and pelitic metasediments, forming 50–200-m deep and 300–1,000-m wide V-shaped embayments and have been interpreted on the basis of surface geology, deep diamond core drilling, and magnetic inversion models to represent the remnants of one or more large, long (at least 20 km, possibly ≥50 km), sinuous, komatiitic basalt lava channels that formed by thermomechanical erosion of their substrates. We have used a mathematical model to test these hypotheses regarding komatiitic lava emplacement and erosion by lava. Our modeling predicts that an initially 10-m thick komatiitic basalt flow should have flowed turbulently near the vent and should have thermomechanically eroded unconsolidated pelitic sediment during emplacement to reach the observed degree of contamination of ≤10% at distances of ~30–60 km downstream from the source. Furthermore, our models predict that, at these distances downstream, a fully inflated 100-m thick komatiitic basalt flow would have had thermal erosion rates over consolidated gabbroic substrate of ~0.7–1.5 m/day, requiring ~70–140 days to incise a 100-m deep channel, depending on the initial temperature of the lava, the paleoslope, and the initial temperature and solidus temperature of the gabbro. These erosion rates would have been associated with volumetric flow rates of >10⁵–10⁶ m³/s and eruption volumes of >10³–10⁴ km³. Although these flow rates are orders of magnitude larger than those of most modern terrestrial basaltic flows, they are of the same order as those estimated for the largest terrestrial flood basalt flows and with those inferred for some of the largest extraterrestrial flows. Our predicted flow volumes are also of the same order as those of the largest terrestrial flood basalt units, consistent with the great thickness and widespread distribution of the Chukotat Group. Our modeling of thermomechanical erosion of gabbro by komatiitic basalt results in negligible contamination (<1%), and geochemical studies show that the spatially and petrogenetically related Chukotat basalts are uncontaminated, suggesting that the observed enrichments in U–Th–Light Rare Earth Elements (REE) > Middle REE–Heavy REE > Nb–Ta–Ti represent contamination by underlying Povungnituk semipelites. This result is consistent with present models for the genesis of the Ni–Cu–(PGE) mineralization in the Raglan Formation that involve thermomechanical erosion of unconsolidated, sulfidic semipelitic sediments, and decoupling of the miscible silicate and immiscible sulfide components.  相似文献   

Provenance of chalk tesserae from Brading Roman Villa, Isle of Wight, UK     

Alison Tasker  Ian P. Wilkinson  Mark Williams 《Proceedings of the Geologists' Association. Geologists' Association》2011,122(5):933-937

Thin section petrographical analysis of chalk tesserae at Brading Roman Villa, Isle of Wight, England, identifies a range of planktonic foraminifera and the calcareous algal cyst Pithonella that identify the Late Cenomanian Rotalipora cushmani Biozone (BGS Foraminiferal Biozones 4iii to 7). The local chalk crop to the north of the villa includes rocks of R. cushmani Biozone age, and indicates a likely local, rather than long distance, source for the tesserae. Microfossils provide a powerful tool for identifying the provenance of artefacts in Roman Britain.  相似文献