scholarly journals Characteristics of Striae and Clast Shape in Glacial and Non-Glacial Environments

2021 ◽  
Author(s):  
◽  
Clifford Barrie Atkins
Keyword(s):  
Mass Movement ◽  
Coarse Grained ◽  
Significant Advance ◽  
Tectonic Deformation ◽  
Glacial Origin ◽  
Wide Range ◽  
Glacial Environments ◽  
Glacial Processes ◽  
Characteristic Features ◽  
Different Origins

<p>Linear abrasion features on rock surfaces are produced by interacting rock particles in relative motion. The most common examples are striae produced by temperate glaciers, and as a consequence, striae have long been used as a means of identifying the passage of past glaciers. However, there are many non-glacial processes that can produce striae. These have been sporadically documented in the geological literature but have failed to make a lasting impression on the wider Earth Sciences community. These non-glacial processes include tectonic deformation, meltwater flow, non-glacial ice, wind action, volcanic blasting, mass movements of rock debris, among many others. Many produce coarse-grained deposits similar in character to glacial tills and there are several instances where non-glacial deposits and striae have been misinterpreted as glacial in origin. This thesis examines linear abrasion features (mostly striae) from five different environments, three glacial (temperate, polythermal and cold) and two non-glacial environments (mass movement and tectonic) to characterise the striae from different origins. The aim was to assess if there are readily observable and measurable differences in striae character between environments and to develop field-based criteria that allow a sound judgement of their origin in the geological record. Over 760 measurements of individual striae were made (orientation and size) on around 20 representative clasts and characteristic features of about 50 striated clasts from the various environments are illustrated in an "Atlas of linear abrasion features". In addition clast shape and striae occurrence were measured on 1260 clasts from deposits and about 100 bedrock linear abrasions from a cold-based glacier were recorded. The results show that some striae are diagnostic of certain environments but a combination of clast shape and striae characteristics is the most reliable method of correctly interpreting coarse-grained deposits with striated clasts. Results also highlight the wide range of striae characteristics within each environment and the importance of lithology in striae generation. This is evident even within the well-known temperate glacial environment where there is a marked contrast between striae formed within a thick debris layer and those formed in thin debris-rich basal ice. There appears to be little difference in striae formed by temperate and polyhermal glaciers, but glacial striae are readily distinguishable from striae found in various mass movement deposits or tectonically deformed conglomerates. Glacial striae tend to be sub-parallel to the clast long axes and show a high density on individual surfaces, whereas those in non-glacial origin typically show a lower density of slightly shorter, wider striae and show either no preferred orientation or weak grouping. The survivability of glacial abrasion features of clasts once they have entered a fluvial system has been assessed in a small South Island glacier fed river. This has provided a basis for estimating the proximity of a glaciofluvial deposit to the glacier front. Striae are found to survive only 1 to 2 km and glacial facets are mostly removed within 6 km. The study has also documented previously undescribed linear abrasion features from a cold-based glacier in Antarctica. This discovery is a significant advance in understanding cold glacial processes, and has provided new criteria for recognising the passage of cold-based glaciers in polar areas or regions where cold-based ice may have existed in the past.</p>

scholarly journals Characteristics of Striae and Clast Shape in Glacial and Non-Glacial Environments

2021 ◽  
Author(s):  
◽  
Clifford Barrie Atkins
Keyword(s):  
Mass Movement ◽  
Coarse Grained ◽  
Significant Advance ◽  
Tectonic Deformation ◽  
Glacial Origin ◽  
Wide Range ◽  
Glacial Environments ◽  
Glacial Processes ◽  
Characteristic Features ◽  
Different Origins

<p>Linear abrasion features on rock surfaces are produced by interacting rock particles in relative motion. The most common examples are striae produced by temperate glaciers, and as a consequence, striae have long been used as a means of identifying the passage of past glaciers. However, there are many non-glacial processes that can produce striae. These have been sporadically documented in the geological literature but have failed to make a lasting impression on the wider Earth Sciences community. These non-glacial processes include tectonic deformation, meltwater flow, non-glacial ice, wind action, volcanic blasting, mass movements of rock debris, among many others. Many produce coarse-grained deposits similar in character to glacial tills and there are several instances where non-glacial deposits and striae have been misinterpreted as glacial in origin. This thesis examines linear abrasion features (mostly striae) from five different environments, three glacial (temperate, polythermal and cold) and two non-glacial environments (mass movement and tectonic) to characterise the striae from different origins. The aim was to assess if there are readily observable and measurable differences in striae character between environments and to develop field-based criteria that allow a sound judgement of their origin in the geological record. Over 760 measurements of individual striae were made (orientation and size) on around 20 representative clasts and characteristic features of about 50 striated clasts from the various environments are illustrated in an "Atlas of linear abrasion features". In addition clast shape and striae occurrence were measured on 1260 clasts from deposits and about 100 bedrock linear abrasions from a cold-based glacier were recorded. The results show that some striae are diagnostic of certain environments but a combination of clast shape and striae characteristics is the most reliable method of correctly interpreting coarse-grained deposits with striated clasts. Results also highlight the wide range of striae characteristics within each environment and the importance of lithology in striae generation. This is evident even within the well-known temperate glacial environment where there is a marked contrast between striae formed within a thick debris layer and those formed in thin debris-rich basal ice. There appears to be little difference in striae formed by temperate and polyhermal glaciers, but glacial striae are readily distinguishable from striae found in various mass movement deposits or tectonically deformed conglomerates. Glacial striae tend to be sub-parallel to the clast long axes and show a high density on individual surfaces, whereas those in non-glacial origin typically show a lower density of slightly shorter, wider striae and show either no preferred orientation or weak grouping. The survivability of glacial abrasion features of clasts once they have entered a fluvial system has been assessed in a small South Island glacier fed river. This has provided a basis for estimating the proximity of a glaciofluvial deposit to the glacier front. Striae are found to survive only 1 to 2 km and glacial facets are mostly removed within 6 km. The study has also documented previously undescribed linear abrasion features from a cold-based glacier in Antarctica. This discovery is a significant advance in understanding cold glacial processes, and has provided new criteria for recognising the passage of cold-based glaciers in polar areas or regions where cold-based ice may have existed in the past.</p>

scholarly journals Provenance signals in metaturbidites of the Paleoproterozoic greenstone belt of the Guiana Shield in Suriname

2016 ◽  
Vol 95 (4) ◽  
pp. 467-489 ◽  
Author(s):  
R. Naipal ◽  
S.B. Kroonenberg
Keyword(s):  
Greenstone Belt ◽  
Factor Score ◽  
Coarse Grained ◽  
Turbidity Currents ◽  
Mafic Mineral ◽  
Source Areas ◽  
Fine Grained ◽  
Grain Sizes ◽  
Wide Range ◽  
Characteristic Features

AbstractThe sedimentological, metamorphic, petrographic and geochemical characteristics of the Armina Formation, part of the Paleoproterozoic Greenstone Belt of Suriname in South America, are described, based on field, geochemical and petrographic evidence obtained through fieldwork along the Marowijne River and study of diamond drill cores from Rosebel Gold Mine (RGM). The metagreywackes show characteristic features of deposition by turbidity currents: coarse-grained, poorly sorted graded greywackes, covered by fine-grained, parallel-laminated phyllitic beds, often with convolute structures and climbing ripples. Their immature character and composition suggest deposition in an arc-trench environment. In the Marowijne River three different facies of metagreywackes are distinguished: (1) the greyish Bonnidoro Falls facies, characterised by common red millimetre-sized pseudomorphs after siderite in the finer beds, (2) the green Paroe Tabiki metagreywacke facies, with decimetre-sized calcsilicate nodules, both metamorphosed in the lower greenschist facies with chlorite as the main mafic mineral, and (3) the grey Armina Falls metagreywacke facies, geochemically similar to the Bonnidoro type but of higher metamorphic grade with biotite as the main mafic mineral. The metagreywackes from the Marowijne River show a predominance of quartz, plagioclase and lithic (tonalitic) clasts, suggesting exhumation of tonalite–trondhjemite–granodiorite plutons before deposition of the turbidites. There is a slight increase in maturity from (1) to (3), suggesting increasing weathering in the source areas. The metagreywackes of the RGM (JZone) have a predominantly metavolcanic origin, suggesting that they have a different provenance area than the Marowijne metagreywackes. Geochemically the spread in composition within each facies is larger than between the facies because of the wide range in grain sizes in each turbidite sequence. A large part of the rocks from the RGM, classified by previous authors as arenites, are geochemically and petrographically metagreywackes. Only a few RGM samples are real arenites, and plot as a separate cluster in geochemical factor score plots because of their low Fe and Na contents.

Patterns in diversity and composition of the microbenthos of subarctic intertidal beaches with different morphodynamics

2020 ◽  
Vol 648 ◽  
pp. 19-38
Author(s):  
AI Azovsky ◽  
YA Mazei ◽  
MA Saburova ◽  
PV Sapozhnikov
Keyword(s):  
Species Abundance ◽  
Abundance Ratio ◽  
Wave Action ◽  
Coarse Grained ◽  
Sediment Properties ◽  
Β Diversity ◽  
Α Diversity ◽  
Wide Range ◽  
Similar Mode ◽  
Abundance And Diversity

Diversity and composition of benthic diatom algae and ciliates were studied at several beaches along the White and Barents seas: from highly exposed, reflective beaches with coarse-grained sands to sheltered, dissipative silty-sandy flats. For diatoms, the epipelic to epipsammic species abundance ratio was significantly correlated with the beach index and mean particle size, while neither α-diversity measures nor mean cell length were related to beach properties. In contrast, most of the characteristics of ciliate assemblages (diversity, total abundance and biomass, mean individual weight and percentage of karyorelictids) demonstrated a strong correlation to beach properties, remaining low at exposed beaches but increasing sharply in more sheltered conditions. β-diversity did not correlate with beach properties for either diatoms or ciliates. We suggest that wave action and sediment properties are the main drivers controlling the diversity and composition of the intertidal microbenthos. Diatoms and ciliates, however, demonstrated divergent response to these factors. Epipelic and epipsammic diatoms exhibited 2 different strategies to adapt to their environments and therefore were complementarily distributed along the environmental gradient and compensated for each other in diversity. Most ciliates demonstrated a similar mode of habitat selection but differed in their degree of tolerance. Euryporal (including mesoporal) species were relatively tolerant to wave action and therefore occurred under a wide range of beach conditions, though their abundance and diversity were highest in fine, relatively stable sediments on sheltered beaches, whereas the specific interstitial (i.e. genuine microporal) species were mostly restricted to only these habitats.

scholarly journals Predictive modelling of soils’ hydraulic conductivity using artificial neural network and multiple linear regression

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Charles Gbenga Williams ◽  
Oluwapelumi O. Ojuri
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Hydraulic Conductivity ◽  
Linear Regression ◽  
Multiple Linear Regression ◽  
Coarse Grained ◽  
Soil Types ◽  
Wide Range ◽  
Artificial Neural ◽  
Input Variables

AbstractAs a result of heterogeneity nature of soils and variation in its hydraulic conductivity over several orders of magnitude for various soil types from fine-grained to coarse-grained soils, predictive methods to estimate hydraulic conductivity of soils from properties considered more easily obtainable have now been given an appropriate consideration. This study evaluates the performance of artificial neural network (ANN) being one of the popular computational intelligence techniques in predicting hydraulic conductivity of wide range of soil types and compared with the traditional multiple linear regression (MLR). ANN and MLR models were developed using six input variables. Results revealed that only three input variables were statistically significant in MLR model development. Performance evaluations of the developed models using determination coefficient and mean square error show that the prediction capability of ANN is far better than MLR. In addition, comparative study with available existing models shows that the developed ANN and MLR in this study performed relatively better.

scholarly journals Quantum information probes of charge fractionalization in large-N gauge theories

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Brandon S. DiNunno ◽  
Niko Jokela ◽  
Juan F. Pedraza ◽  
Arttu Pönni
Keyword(s):  
Degrees Of Freedom ◽  
Gauge Theories ◽  
Entanglement Entropy ◽  
Coarse Grained ◽  
Strongly Coupled ◽  
Information Theoretic ◽  
Large N ◽  
Wide Range ◽  
Charge Fractionalization ◽  
Electric Flux

Abstract We study in detail various information theoretic quantities with the intent of distinguishing between different charged sectors in fractionalized states of large-N gauge theories. For concreteness, we focus on a simple holographic (2 + 1)-dimensional strongly coupled electron fluid whose charged states organize themselves into fractionalized and coherent patterns at sufficiently low temperatures. However, we expect that our results are quite generic and applicable to a wide range of systems, including non-holographic. The probes we consider include the entanglement entropy, mutual information, entanglement of purification and the butterfly velocity. The latter turns out to be particularly useful, given the universal connection between momentum and charge diffusion in the vicinity of a black hole horizon. The RT surfaces used to compute the above quantities, though, are largely insensitive to the electric flux in the bulk. To address this deficiency, we propose a generalized entanglement functional that is motivated through the Iyer-Wald formalism, applied to a gravity theory coupled to a U(1) gauge field. We argue that this functional gives rise to a coarse grained measure of entanglement in the boundary theory which is obtained by tracing over (part) of the fractionalized and cohesive charge degrees of freedom. Based on the above, we construct a candidate for an entropic c-function that accounts for the existence of bulk charges. We explore some of its general properties and their significance, and discuss how it can be used to efficiently account for charged degrees of freedom across different energy scales.

Groundwater Lowering for Construction of the Kilsby Tunnel – Geological and Geotechnical Interpretation

2021 ◽  
pp. 1-14
Author(s):  
Martin Preene ◽  
Mike Chrimes
Keyword(s):  
Groundwater Flow ◽  
Theoretical Understanding ◽  
Stress Theory ◽  
Glacial Origin ◽  
Buried Channel ◽  
Geological Information ◽  
Ground Conditions ◽  
Glacial Processes ◽  
The Impact ◽  
Groundwater Lowering

The Kilsby Tunnel, constructed in the 1830s, faced severe problems when a section of the tunnel, almost 400 m long, encountered unstable ‘quicksand’ conditions. The engineer for the project, Robert Stephenson, developed an extensive groundwater lowering scheme, unique for the time, using steam engines pumping from multiple shafts, to overcome the quicksand. Modern geological information indicates most of the tunnel was in Middle Lias bedrock, but the ‘quicksand’ section passed through a buried channel of water-bearing sand of glacial origin. In the early 19th century the impact of glacial processes on British geology was not widely accepted and, based on contemporary geological knowledge, Stephenson’s problems appear to be genuine unforeseen ground conditions, not predicted by his experienced advisers. It seems just random chance that trial borings missed the buried channel of sand. The work at Kilsby was two decades before Darcy’s law established the theoretical understanding for groundwater flow, and 90 years before Terzaghi’s effective stress theory described how reducing pore water pressures changed ‘quicksand’ into a stable and workable material. Despite the lack of existing theories, Stephenson used careful observations and interpretation of groundwater flow in the ‘quicksand’ to navigate the tunnel project to a successful conclusion.

scholarly journals Gelation Impairs Phase Separation and Small Molecule Migration in Polymer Mixtures

Polymers ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1576
Author(s):  
Biswaroop Mukherjee ◽  
Buddhapriya Chakrabarti
Keyword(s):  
Phase Separation ◽  
Rational Design ◽  
Surface Segregation ◽  
Multiscale Methods ◽  
Coarse Grained ◽  
Polymer Gel ◽  
Polymer Mixtures ◽  
Separation Processes ◽  
Surface Migration ◽  
Wide Range

Surface segregation of the low molecular weight component of a polymeric mixture is a ubiquitous phenomenon that leads to degradation of industrial formulations. We report a simultaneous phase separation and surface migration phenomena in oligomer–polymer ( O P ) and oligomer–gel ( O G ) systems following a temperature quench that induces demixing of components. We compute equilibrium and time varying migrant (oligomer) density profiles and wetting layer thickness in these systems using coarse grained molecular dynamics (CGMD) and mesoscale hydrodynamics (MH) simulations. Such multiscale methods quantitatively describe the phenomena over a wide range of length and time scales. We show that surface migration in gel–oligomer systems is significantly reduced on account of network elasticity. Furthermore, the phase separation processes are significantly slowed in gels leading to the modification of the well known Lifshitz–Slyozov–Wagner (LSW) law ℓ ( τ ) ∼ τ 1 / 3 . Our work allows for rational design of polymer/gel–oligomer mixtures with predictable surface segregation characteristics that can be compared against experiments.

scholarly journals DISTRIBUTION OF BRYOPHYTES OF AGALYK BASIN (KARATEPA MOUNTAINS OF ZERAVSHAN MOUNTAIN RANGE)

2015 ◽  
Vol 4 (2) ◽  
pp. 80-82
Author(s):  
Holmurod Akimovich Zhalov
Keyword(s):  
Species Composition ◽  
Point Of View ◽  
Mountain Range ◽  
Decayed Wood ◽  
Moss Species ◽  
Comparative Analyses ◽  
Wide Range ◽  
Identification Of Species ◽  
Characteristic Features ◽  
Research Period

From bryological point of view Zeravshan mountain range remains one of the least studied region. Identification of species composition of true mosses and their ecological-biological peculiarities were not earlier aimed for this region. In the territory of Agalyk basin Karatepa mountains can be divided into four types of substrates where moss species occur: soil, bark of living trees, decayed wood, stones. Characteristics of substrate groups become complicated due to wide range of ecological valency of moss species. Most species select not only one, but several substrates for their settling. During the research period in the soils of Agaliksay basin 20 species were recorded belonging to 13 genera and 10 family. On decayed wood 9 species were recorded belonging to 7 genera and 5 family. On the bark of living trees 15 moss species were recorded belonging to 8 genera and 6 family. Epilyte bryophytes occurred on rocky substrates. On rocky substrates of Agaliksay basin 34 moss species were recorded from 16 genera and 13 family. On the basis of results obtained during the study of substrate groups of mosses in Agaliksay basin, we have conducted comparative analyses of studied substrate groups with the purpose of determining their characteristic features.

scholarly journals A scaled MP-PIC method for bubbling fluidization

2021 ◽  
Author(s):  
Xing Zhao ◽  
Yong Jiang ◽  
Fei Li ◽  
Wei Wang
Keyword(s):  
Fluidized Beds ◽  
Volume Fraction ◽  
Phase Particle ◽  
Scaling Law ◽  
Coarse Graining ◽  
Coarse Grained ◽  
Particle In Cell ◽  
Wide Range ◽  
Pic Method ◽  
Multi Phase

Coarse-grained methods have been widely used in simulations of gas-solid fluidization. However, as a key parameter, the coarse-graining ratio, and its relevant scaling law is still far from reaching a consensus. In this work, a scaling law is developed based on a similarity analysis, and then it is used to scale the multi-phase particle-in-cell (MP-PIC) method, and validated in the simulation of two bubbling fluidized beds. The simulation result shows this scaled MP-PIC can reduce the errors of solids volume fraction and velocity distributions over a wide range of coarse-graining ratios. In future, we expect that a scaling law with consideration of the heterogeneity inside a parcel or numerical particle will further improve the performance of coarse-grained modeling in simulation of fluidized beds.

scholarly journals Dilute Solution Structure of Bottlebrush Polymers

2019 ◽  
Author(s):  
Sarit Dutta ◽  
Matthew A. Wade ◽  
Dylan J. Walsh ◽  
Damien Guironnet ◽  
Simon A. Rogers ◽  
...  
Keyword(s):  
Brownian Dynamics ◽  
Solution Structure ◽  
Coarse Grained ◽  
Poly Lactic Acid ◽  
Linear Polymers ◽  
Molecular Architecture ◽  
Wide Range ◽  
Conformational Properties ◽  
Atomistic Structure ◽  
Insight Into

<div>Bottlebrush polymers are a class of macromolecules that has recently found use</div><div>in a wide variety of materials, ranging from lubricating brushes and</div><div>nanostructured coatings to elastomeric gels that exhibit structural color. These</div><div>polymers are characterized by dense branches extending from a central backbone,</div><div>and thus have properties distinct from linear polymers. It remains a challenge</div><div>to specifically understand conformational properties of these molecules, due to</div><div>the wide range of architectural parameters that can be present in a system, and</div><div>thus there is a need to accurately characterize and model these molecules. In</div><div>this paper, we use a combination of viscometry, light scattering, and computer</div><div>simulations to gain insight into the conformational properties of dilute</div><div>bottlebrush polymers. We focus on a series of model bottlebrushes consisting of</div><div>a poly(norbornene) (PNB) backbone with poly(lactic acid) (PLA) side chains. We</div><div>demonstrate that intrinsic viscosity and hydrodynamic radius are experimental</div><div>observations \emph{sensitive} to molecular architecture, exhibiting distinct</div><div>differences with different choices of branch and backbone lengths. Informed by</div><div>the atomistic structure of this PNB-PLA system, we rationalize a coarse-grained</div><div>simulation model that we evaluate using a combination of Brownian Dynamics and</div><div>Monte Carlo simulations. We show that this exhibits quantitative matching to</div><div>experimental results, enabling us to characterize the overall shape of the</div><div>bottlebrush via a number of metrics that can be extended to more general</div><div>bottlebrush architectures.</div>

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