Textural characteristics of sediments along the southern Red Sea coastal areas,Saudi Arabia     

Omar A. Alharbi  Allan T. Williams  Michael R. Phillips  Tony Thomas 《Arabian Journal of Geosciences》2016,9(19):735

A lack of understanding exists of the origin and textural characteristics of Saudi Arabian Red Sea coastal sediments. This paper concerns the southern coastline of Jizan on the Saudi Red Sea. It is some 160 km long characterised by either narrow rocky headlands with intermittent pocket beaches or wide low-lying beaches dissected by wadis. Granulometric testing of samples from 135 locations showed that beach sand size was mainly very fine to medium grained (M _z = 3.93 Ø), sorting ranged from 1.65 to 0.41 and skewness values from ?051 to 0.39, being mainly negative; dune sands were medium to fine grained (M _z = 1.13 Ø; average sorting 2.8), while skewness variations within dune samples indicated symmetrical to fine skewed values (б _Ι = 0.55 to 0.89). Most foreshore samples were derived from wadis. Wadi mud levels can be high, e.g. Baysh (84%), and wadi Samrah (90%) with mean grain size ranging from very fine to medium sand (M _z = 3.9 Ø), sorting being well to poor (0.45 to 1.52) due to sediment influxes. Sabkha had a wide range of sand/mud and significantly higher carbonate percentages than other environments. Sediment source differences and littoral reworking contributed to grain size variation. The carbonate content varied between 1.5 and 31.5% due to hinterland contributions, and spatial analysis showed increasing quantities of carbonate minerals towards the south. On the wider geographical front, findings from Jizan are similar to those of the Northern United Arab Emirates (UAE), including sabkhas, being composed of sand, skeletal carbonate, fine fluvial material and wind-blown silt and clay components of wadi origin. Further work on the northeastern Red Sea edge can hopefully confirm these findings.  相似文献   

The development of the subduction channel and “turning on” of slab-to-mantle material exchanges at the start of subduction: insights from eruptive serpentinites (IODP Exp 366) from the forearc of the Mariana subduction system     

Jeffrey G. Ryan  Raymond Johnston  P. Fryer  C.G. Wheat  T. Williams 《《地质学报》英文版》2018,92(Z1):167-167

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SPH approach for simulating hydro-mechanical processes with large deformations and variable permeabilities     

M. Gholami Korzani  S. A. Galindo-Torres  A. Scheuermann  D. J. Williams 《Acta Geotechnica》2018,13(2):303-316

A simulation framework based on Smoothed Particle Hydrodynamics (SPH) is introduced to model problems involving the interaction between flowing water and soil deformation. Changes in soil porosity and associated permeability are automatically adjusted within this framework. The framework’s capabilities are presented and discussed for three geotechnical problems caused by flowing water. The comparison between simulation results and experiments shows that SPH with the proposed concept is capable of quantitatively simulating the hydro-mechanical processes beyond limit state with satisfactory agreement. To improve the computational stability, a correction procedure and a new algorithm for the selection of the optimal time step are introduced.  相似文献   

Stability study on the northern batter of MBC Open Pit using Plaxis 3D     

Lei Zhao  Greg You 《Arabian Journal of Geosciences》2018,11(6):119

Cracks appeared on the northern batter at Maddingley Brown Coal Open Pit Mine, Victoria, Australia, on 8 November 2013 and a 2-day rainfall event happened 5 days later. This study models the stability of the northern batter considering the effect of the rainfall event and an emergency buttress using finite element method (FEM) encoded in Plaxis 3D. It is found that the batter tended to lead to block sliding after overburden removal. The observed vertical crack would be a combined action of the overburden removal and groundwater flow. The simulated location of cracks agrees well with the actual location, and the simulated heave of the coal seam is in good agreement with the experience in Victoria brown coal open pit mining. The rainfall accelerated the development of the cracks. With the construction of the emergency buttress, the batter became stable that is in good agreement with the monitored data.  相似文献   

The stratigraphical signature of the Anthropocene in England and its wider context     

Jan Zalasiewicz  Colin Waters  Mark Williams  David C. Aldridge  Ian P. Wilkinson 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(3):482-491

The Anthropocene deposits of England, here regarded as those formed after ～1950 CE, are now extensive, take various forms, and may be characterized and recognized by a number of stratigraphic signals, such as artificial radionuclides, pesticide residues, microplastics, enhanced fly ash levels, concrete fragments and a novel variety of ‘technofossils’ and neobiotic species. They include the uppermost parts of both ‘natural’ deposits such as the sediment layers formed in lakes and estuaries, and more directly human-made or human-influenced ones such as landfill deposits and the ‘artificial ground’ beneath urban areas and around major constructions. ‘Negative deposits’ include the worked areas of quarries and regions such as the English Fenland, where thick peat deposits have ablated to leave a strongly modified underlying landscape, and extend beneath into the subterranean realm as mine workings, metro systems and boreholes. The production of these is still rapidly increasing and evolving in character, while the early signs of global change, such as warming, sea level rise, and modifications to biotic assemblages, are beginning to further modify the emerging geology of this new phase of Earth history.  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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On the estimation of ice thickness from scattering observations     

T.D. Williams  V.A. Squire 《Dynamics of Atmospheres and Oceans》2010,49(2-3):215-233

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Response of detrital zircon and monazite,and their U–Pb isotopic systems,to regional metamorphism and host‐rock partial melting,Cooma Complex,southeastern Australia     

I. S. Williams 《Australian Journal of Earth Sciences》2013,60(4):557-580

Progressive Early Silurian low‐pressure greenschist to granulite facies regional metamorphism of Ordovician flysch at Cooma, southeastern Australia, had different effects on detrital zircon and monazite and their U–Pb isotopic systems. Monazite began to dissolve at lower amphibolite facies, virtually disappearing by upper amphibolite facies, above which it began to regrow, becoming most coarsely grained in migmatite leucosome and the anatectic Cooma Granodiorite. Detrital monazite U–Pb ages survived through mid‐amphibolite facies, but not to higher grade. Monazite in the migmatite and granodiorite records only metamorphism and granite genesis at 432.8 ± 3.5 Ma. Detrital zircon was unaffected by metamorphism until the inception of partial melting, when platelets of new zircon precipitated in preferred orientations on the surface of the grains. These amalgamated to wholly enclose the grains in new growth, characterised by the development of {211} crystal faces, in the migmatite and granodiorite. New growth, although maximum in the leucosome, was best dated in the granodiorite at 435.2 ± 6.3 Ma. The combined best estimate for the age of metamorphism and granite genesis is 433.4 ± 3.1 Ma. Detrital zircon U–Pb ages were preserved unmodified throughout metamorphism and magma genesis and indicate derivation of the Cooma Granodiorite from Lower Palaeozoic source rocks with the same protolith as the Ordovician sediments, not Precambrian basement. Cooling of the metamorphic complex was relatively slow (average ～12°C/10⁶y from ～730 to ～170°C), more consistent with the unroofing of a regional thermal high than cooling of an igneous intrusion. The ages of detrital zircon and monazite from the Ordovician flysch (dominantly composite populations 600–500 Ma and 1.2–0.9 Ga old) indicate its derivation from a source remote from the Australian craton.  相似文献   

Cone-penetrometer exploration of Sinkholes: Stratigraphy and soil properties     

D. Bloomberg  S. B. Upchurch  M. L. Hayden  R. C. Williams 《Environmental Geology》1988,12(2):99-105

Four sinkholes with varying surficial expressions were subjected to detailed stratigraphic and soil analysis by means of Standard Penetration Tests (SPT) and Electric Friction Cone Penetration Tests (CPT) in order to evaluate applications of CPT to sinkhole investigations. Although widely used, SPT data are of limited value and difficult to apply to sinkhole mapping. CPT is sensitive to minor lithologic variability and is superior to SPT as a cost-effective technique for determining geotechnical properties of sinkholes. The effectiveness of CPT data results from the force measurements made along the sleeve of the cone. The friction ratio (ratio of sleeve to tip resistance) is a good indicator of soil stratigraphy and properties. By smoothing the friction-ratio data, general stratigraphy and changes in soil properties are easily identified. Stratigraphy of the sinks has been complicated by intense weathering, karstification and marine, transgressions. The resulting deposits include five stratigraphic units. I and II represent Plio-Pleistocene marine sediments with Unit II being the zone of soil clay accumulation. III and IV are horizons residual from Miocene strata and indicate an episode of karstification prior to deposition of Units I and II. Conduit fill is a mixture of materials with low cohesion. The fill materials indicate centripetal and downward movement of insoluble sediments derived from the surrounding strata. Loss of cohesion results in near-zero friction ratios. Very low friction ratios, coupled with materials with little cohesion, indicate potentially-liquefiable soils in the immediate vicinity of zones where piping failure may be imminent. SPT does not provide sufficient data to predict these zones of potential, failure. CPT provides sufficient information for recognition of sinkhole stratigraphy and geotechnical properties. When coupled with laboratory soil analysis, CPT provides unique information about sinkhole geometry and dynamics. In contrast, SPT data fail to produce consistent indicators of sinkhole stratigraphy or properties. With laboratory soil data, SPT indicates general, inconclusive trends.  相似文献   

An in-situ integrated suspended sediment stream sampler (IS3)     

Ronald J. Scrudato  Greg Yogis  Grady Hocutt 《Environmental Geology》1988,12(3):177-179

An inexpensive, lightweight stream sampler is described which provides a method for continuous collection of suspended stream sediments. The IS^3* sampler collects integrated suspended stream samples, and because the sampler relies on basic sedimentation principles, it can be deployed to collect suspended sediment stream samples for environmental studies or geochemical exploration in remote areas. The sampler trapped from 0.45 to 1.2 g of dry sediment during 7- to 8-d field tests conducted during 1985.  相似文献