Synsedimentary submarine slope failure and tectonic deformation in deep-water carbonates, Cow Head Group, western Newfoundland

1986 ◽  
Vol 23 (4) ◽  
pp. 476-490 ◽  
Author(s):  
Mario Coniglio
Keyword(s):  
Large Scale ◽  
Slope Failure ◽  
Shear Zones ◽  
Small Scale ◽  
Tectonic Deformation ◽  
Head Group ◽  
Shallow Subsurface ◽  
Deformation Structures ◽  
Lenticular Bedding ◽  
Basin Morphology

The Cow Head Group, interpreted as a southeast-dipping base-of-slope carbonate apron, contains intraformational truncation surfaces and slide masses. Synsedimentary shear zones are formed (1) below intraformational truncation surfaces; (2) in the basal parts of slide masses; and (3) in the shallow subsurface because of downslope creep. Shear zones are characterized by a variety of synsedimentary deformation structures. Limestones are subject to folding, brecciation, rotation of fragmented beds, and the development of fitted-lenticular bedding. In the interbedded shales, there is both disruption of fine laminations and small-scale isoclinal folding and faulting. Outcrops characterized by these features and the lack of truncation surfaces or slide masses may reflect minor downslope creep. The presence of truncation surfaces, slide masses, and shear zones indicates deposition on an unstable sloping surface.The recognition of intraformational truncation surfaces and slide masses usually requires extensive strike exposure, which when lacking, (e.g., drill cores), limits the potential of these large-scale features as useful indicators of slope deposition. In the Cow Head Group, the recognition and proper interpretation of the common, small-scale deformation structures of synsedimentary shear zones provides evidence for slope deposition that is independent of other sedimentologic, stratigraphic, and regional data.In some parts of the Cow Head Group, "wrinkled" limestones characterized by a prominent dome-and-basin morphology reflect layer-parallel shortening related to tectonic deformation. The deformation of these limestones was previously considered to be synsedimentary, but their association with late-diagenetic precipitates and tectonic stylolites, in conjunction with their continuity and regularity, distinguishes these folds from those produced during synsedimentary deformation.

Effective rheology of a two-phase subduction shear zone: insights from numerical simple shear experiments and implications for subduction zone interfaces

2021 ◽  
Author(s):  
Paraskevi Io Ioannidi ◽  
Laetitia Le Pourhiet ◽  
Philippe Agard ◽  
Samuel Angiboust ◽  
Onno Oncken
Keyword(s):  
Simple Shear ◽  
Large Scale ◽  
Confining Pressure ◽  
Shear Zones ◽  
Dislocation Creep ◽  
Small Scale ◽  
Two Phase ◽  
Weak Phase ◽  
Pure Phases ◽  
Geodynamic Models

<p>Exhumed subduction shear zones often exhibit block-in-matrix structures comprising strong clasts within a weak matrix (mélanges). Inspired by such observations, we create synthetic models with different proportions of strong clasts and compare them to natural mélange outcrops. We use 2D Finite Element visco-plastic numerical simulations in simple shear kinematic conditions and we determine the effective rheology of a mélange with basaltic blocks embedded within a wet quartzitic matrix. Our models and their structures are scale-independent; this allows for upscaling published field geometries to km-scale models, compatible with large-scale far-field observations. By varying confining pressure, temperature and strain rate we evaluate effective rheological estimates for a natural subduction interface. Deformation and strain localization are affected by the block-in-matrix ratio. In models where both materials deform viscously, the effective dislocation creep parameters (A, n, and Q) vary between the values of the strong and the weak phase. Approaching the frictional-viscous transition, the mélange bulk rheology is effectively viscous creep but in the small scale parts of the blocks are frictional, leading to higher stresses. This results in an effective value of the stress exponent, n, greater than that of both pure phases, as well as an effective viscosity lower than the weak phase. Our effective rheology parameters may be used in large scale geodynamic models, as a proxy for a heterogeneous subduction interface, if an appropriate evolution law for the block concentration of a mélange is given.</p>

Gravitational sliding or tectonic thrusting?: Examples and field recognition in the Miura-Boso subduction zone prism

2021 ◽  
Author(s):  
Yujiro Ogawa ◽  
Shin’ichi Mori
Keyword(s):  
Large Scale ◽  
Accretionary Prism ◽  
Small Scale ◽  
Tectonic Deformation ◽  
Detachment Faults ◽  
Thrust Belts ◽  
Fold And Thrust Belt ◽  
Fold Belts ◽  
Geologic Record ◽  
Accretionary Prisms

ABSTRACT Discrimination between gravity slides and tectonic fold-and-thrust belts in the geologic record has long been a challenge, as both have similar layer shortening structures resulting from single bed duplication by thrust faults of outcrop to map scales. Outcrops on uplifted benches within the Miocene to Pliocene Misaki accretionary unit of Miura-Boso accretionary prism, Miura Peninsula, central Japan, preserve good examples of various types of bedding duplication and duplex structures with multiple styles of folds. These provide a foundation for discussion of the processes, mechanisms, and tectonic implications of structure formation in shallow parts of accretionary prisms. Careful observation of 2-D or 3-D and time dimensions of attitudes allows discrimination between formative processes. The structures of gravitational slide origin develop under semi-lithified conditions existing before the sediments are incorporated into the prism at the shallow surfaces of the outward, or on the inward slopes of the trench. They are constrained within the intraformational horizons above bedding-parallel detachment faults and are unconformably covered with the superjacent beds, or are intruded by diapiric, sedimentary sill or dike intrusions associated with liquefaction or fluidization under ductile conditions. The directions of vergence are variable. On the other hand, layer shortening structure formed by tectonic deformation within the accretionary prism are characterized by more constant styles and attitudes, and by strong shear features with cataclastic textures. In these structures, the fault surfaces are oblique to the bedding, and the beds are systematically duplicated (i.e., lacking random styles of slump folds), and they are commonly associated with fault-propagation folds. Gravitational slide bodies may be further deformed at deeper levels in the prism by tectonism. Such deformed rocks with both processes constitute the whole accretionary prism at depth, and later may be deformed, exhumed to shallow levels, and exposed at the surface of the trench slope, where they may experience further deformation. These observations are not only applicable in time and space to large-scale thrust-and-fold belts of accretionary prism orogens, but to small-scale examples. If we know the total 3-D geometry of geologic bodies, including the time and scale of deformational stages, we can discriminate between gravitational slide and tectonic formation of each fold-and-thrust belt at the various scales of occurrence.

Subprovince accretion tectonics in the south-central Superior Province

1990 ◽  
Vol 27 (4) ◽  
pp. 570-581 ◽  
Author(s):  
Howard R. Williams
Keyword(s):  
Large Scale ◽  
Accretionary Prism ◽  
Shear Zones ◽  
Small Scale ◽  
Calc Alkaline ◽  
Volcanic Arcs ◽  
Late Archaean ◽  
South Central ◽  
Type Granite ◽  
Planar Fabric

Development of tectonic subprovinces as shear-bounded granite–greenstone and sediment-dominated terranes during the late Archaean is reviewed and interpreted from relationships between portions of the Wabigoon, Wawa, and Quetico subprovinces.Greenstone-dominated subprovinces (Wabigoon and Wawa) are complex successions of tholeiites, 2.76–2.70 Ga calc-alkaline volcanic centres, and derived sediments. Supracrustal rocks aggregated on a scale of tens of kilometres, forming homoclines, locally upright folded, intruded by granitoids, exhibiting variable fabric trends and strains, and cut by transcurrent shear zones. Small-scale (10–100 km) accretion juxtaposed these varied supracrustal sequences, which were engulfed granitoid magmas, to form greenstone belts.Sediment-dominated subprovinces (Quetico) are metamorphosed wacke sequences deposited during and after the volcanic climax in the period 2.70–2.69 Ga. Overthrust imbrication at both the Wabigoon–Quetico and the Quetico–Wawa contacts occurred along north-dipping shears, now vertical. Continued right-lateral convergence at subprovince margins induced progressive shortening within the Quetico Subprovince, producing a regional planar fabric. Abukuma–style metamorphism, migmatite formation, and S-type granite intrusions occurred during the period 2.67–2.65 Ga.Greenstone-belt developments, terminated during large-scale (100–1000 km) late neo-Archæan accretion, are preserved within elongate, batholith-dominated terranes separated by metasedimentary migmatite belts. Geochronological, lithotectonic, and metamorphic patterns on a scale of hundreds of kilometres are permissive of an accretionary model of greenstone terrane coalescence in which formation of long-lived, complex volcanic arcs and a complementary fore-arc accretionary prism culminated in large-scale accretion and the formation of stable continental crust.

scholarly journals Strain localisation in mechanically Layered Rocks, insights from numerical modelling

2012 ◽  
Vol 4 (2) ◽  
pp. 1165-1204 ◽  
Author(s):  
L. Le Pourhiet ◽  
B. Huet ◽  
P. Agard ◽  
L. Labrousse ◽  
L. Jolivet ◽  
...  
Keyword(s):  
Large Scale ◽  
Shear Bands ◽  
Structural Diversity ◽  
Shear Zones ◽  
Small Scale ◽  
Lithostatic Pressure ◽  
Shear Direction ◽  
Strain Localisation ◽  
Initial Anisotropy ◽  
Micro Structures

Abstract. Small scale deformation in stratified rocks displays a large diversity of micro-structures, from the microscopic scale to the scale of orogens. We have designed a series of fully dynamic numerical simulations aimed at assessing which parameters control this structural diversity and which underlying mechanisms lead to strain localisation. The influence of stratification orientation on the occurrence and mode of strain localisation is tested by varying the initial dip of inherited layering versus the large scale imposed simple shear. The detailed study of the models indicates that (1) the results are length-scale independent, (2) the new shear zones are always compatible with the kinematics imposed at the boundary (3) micro-structures formed encompass the full diversity of micro-structures observed in the field and chiefly depend on the direction of the initial anisotropy versus shear direction, (4) depending on the orientation of the anisotropy, the layers may deform along subtractive or additive shear bands, (5) the deformation in anisotropic media results in non-lithostatic pressure values that are on the order of the deviatoric stress in the strong layers and (6) the introduction of brittle rheology is necessary to form localised shear bands in the ductile regime.

Multi-scale spatial distribution of K, Th and U in an Archaean potassic granite: a case study from the Heerenveen batholith, Barberton Granite-Greenstone Terrain, South Africa

2021 ◽  
Author(s):  
J-F. Moyen ◽  
M. Cuney ◽  
D. Baratoux ◽  
P. Sardini ◽  
S. Carrouée
Keyword(s):  
Large Scale ◽  
Gamma Ray ◽  
Shear Zones ◽  
Small Scale ◽  
Multi Scale ◽  
Gamma Ray Spectrometer ◽  
Rock Types ◽  
Large Scale Integration ◽  
Scale Integration

Abstract We describe the multi-scale distribution of K, Th and U in the ca. 3.1 Ga Heerenveen batholith of the Barberton Granite-Greenstone Terrain. Data were obtained with a combination of tools, including a portable gamma-ray spectrometer from the scale of the whole batholith to the scale of outcrops, and autoradiography for the thin section scale. U is concentrated preferentially in minor phases in the border shear zones of the batholith and, within these shear zones, in late pegmatites as well as fractures. The processes responsible for the concentration of U in the Heerenveen batholith is discussed in terms of magmatism, hydrothermalism (redistribution of U in fissures associated with magmato-hydrothermal fluids), and supergene alteration. The statistical properties of K, Th and U concentrations are different. K shows spatial correlation over large distance, largely mirroring mappable rock types, with increased variability at larger scales. In contrast, U is dominated by small-scale variations (“nugget effect”) and its variability is, averaged and smoothed by large-scale integration. Spatial and statistical features thus offer useful and complementary insights on petrogenetic and metallogenic processes in granitoids in addition to standard approaches (petrography, geochemistry).

scholarly journals Suggestion of Measurement Management Criteria for Soil Slope Failure Based on Displacement

2021 ◽  
Vol 21 (1) ◽  
pp. 251-260
Author(s):  
Sun-Gyu Choi ◽  
Jae-Wook Suk ◽  
Hyang-Seon Jeong
Keyword(s):  
Literature Review ◽  
Field Data ◽  
Large Scale ◽  
Slope Failure ◽  
Small Scale ◽  
Soil Slope ◽  
Short Term ◽  
Literature Reviews ◽  
Under Construction

This paper describes the Measurement Management Criteria (MMC) of a soil slope failure based on displacement using literature reviews, small-scale experiments, large-scale experiments, and field data. Two types of measurement management criteria were developed, i.e., short-term criteria for slopes under construction or requiring urgent measurements, and long-term criteria for slopes under continuous management. First, the measurement criteria for the short term were determined based on small- and-large scale experiments, and were determined to be “1 mm/min for the watch level,” “4 mm/min for the caution level,” and “21 mm/min for the alert level.” Next, the criteria for the long term were determined through a literature review and field data, and were “2 mm/day for the watch level,” “8 mm/day for the caution level,” and “56 mm/day for the alert level”.

scholarly journals Deformation structures resulting from anisotropy during high-strain deformation of ice 1h with initial CPO

2021 ◽  
Author(s):  
Tamara de Riese ◽  
Paul D. Bons ◽  
Enrique Gomez-Rivas ◽  
Albert Griera ◽  
Maria-Gema Llorens ◽  
...  
Keyword(s):  
Steady State ◽  
Structural Geology ◽  
Shear Bands ◽  
Shear Zones ◽  
Small Scale ◽  
Strain Localisation ◽  
Full Field ◽  
Dislocation Glide ◽  
Deformation Structures ◽  
Very High

<p>Ice 1h shows a strong viscoplastic anisotropy, as the resistance to activate dislocation glide on basal planes is at least one order of magnitude smaller than on the other slip planes. During flow the viscoplastic anisotropy leads to the development of a crystallographic preferred orientation (CPO). The anisotropic behaviour of flowing ice can lead to strain localisation. Only when the ice is layered (e.g. due to cloudy bands) it may be possible to identify localisation structures, as ice otherwise has no readily recognisable strain markers.</p><p>We use the Viscoplastic Full-Field Transform (VPFFT; Lebensohn and Rollett, 2020) crystal plasticity code coupled with the modelling platform ELLE (http://www.elle.ws; Piazolo et al., 2019) to simulate the deformation of intrinsically anisotropic ice 1h with an initial single maximum CPO in dextral simple shear up to very high strains. The VPFFT-approach simulates deformation by dislocation glide, taking into account the different available slip systems and their critical resolved shear stresses. We use an anisotropy similar to that of ice 1h, systematically vary the orientation of the initial CPO, and use passive markers/layers to visualise deformation structures.</p><p>The localisation behaviour strongly depends on the initial CPO, but reaches a consistent steady state after very high shear strains of about 30. The fabric and stress evolution reach a steady-state situation as well. The orientation of the CPO controls the style of deformation, which varies from (1) synthetic shear zones with a stable shear-direction parallel orientation and that widen with ongoing strain to unstable, (2) rotating antithetic shear bands, (3) initial formation of antithetic shear bands and subsequent development of synthetic shear bands and (4) distributed localisation. Furthermore, evolving visual structures depend on the presence and orientation of a visual layering in the material. However, at very high strains, the material is almost always strongly mixed and any original layering would be destroyed.</p><p>Our results highlight the challenge to identify strain localisation in ice, yet they can help the ice community to identify and interpret deformation structures in large ice masses (e.g. the Greenland ice sheet). As strain localisation in anisotropic materials behaves scale independent (de Riese et al., 2019), large-scale equivalents may occur of the observed small-scale structures (Jansen et al., 2016).</p><p>References:</p><p>de Riese, T., Evans, L., Gomez-Rivas, E., Griera, A., Lebensohn, R.A., Llorens, M.G., Ran, H., Sachau, T., Weikusat, I., Bons, P.D. 2019. Shear localisation in anisotropic, non-linear viscous materials that develop a CPO: A numerical study. Journal of Structural Geology, 124, 81-90.</p><p>Jansen, D., Llorens, M.-G, Westhoff, J., Steinbach, F., Kipfstuhl, S., Bons, P.D., Griera, A., Weikusat, I. 2016. Small-scale disturbances in the stratigraphy of the NEEM ice core: observations and numerical model simulations. The Cryosphere 10, 359-370.</p><p>Lebensohn, R.A., Rollett, A.D. 2020. Spectral methods for full-field micromechanical modelling of polycrystalline materials. Computational Materials Science, 173, 109336.</p><p>Piazolo, S., Bons, P.D., Griera, A., Llorens, M.G., Gomez-Rivas, E., Koehn, D., ... Jessell, M.W. 2019. A review of numerical modelling of the dynamics of microstructural development in rocks and ice: Past, present and future. Journal of Structural Geology, 125, 111-123.</p>

scholarly journals Morphology of small-scale submarine mass movement events across the northwest United Kingdom

2021 ◽  
Author(s):  
Gareth Carter ◽  
Rhys Cooper ◽  
Joana Gafeira ◽  
John Howe ◽  
David Long
Keyword(s):  
United Kingdom ◽  
Large Scale ◽  
Slope Failure ◽  
Mass Movement ◽  
Morphometric Parameters ◽  
Single Type ◽  
Small Scale ◽  
Mass Movements ◽  
Submarine Landslides ◽  
Coastal Inlets

<p>Given the potentially devastating consequences of shallow submarine landslides on infrastructure and human lives, it is imperative that we understand potential slope stability issues within marine coastal regions. In Scottish waters, our lack of knowledge regarding the nature of the seabed within the fjords and coastal inlets is concerning given that these sea lochs have similar morphological features and settings to global examples (e.g. Norway) where recent slope failures have had such highly devastating results. Global examples from similar physiographic settings also demonstrate the temporal aspect of these events, highlighting that they are caused by active modern processes and therefore represent contemporary geohazards. In addition, previous studies have highlighted that there tends to be a scale bias towards the mapping and reporting of large-scale events, and there is a requirement for studies that focus on small-scale (≤1 km<sup>3</sup>) mass movements which can still have damaging consequences on seafloor and coastal (both nearshore and onshore) infrastructure.</p><p>In this study, a review of multibeam echo sounder (MBES) survey datasets from five locations around the United Kingdom northwest coast has led to the identification of a total of 14 separate submarine mass movement scars and deposits within the fjords (sea lochs) and coastal inlets of mainland Scotland, and the channels between the islands of the Inner Hebrides. In these areas, Quaternary sediment deposition was dominated by glacial and glaciomarine processes. Analysis of the morphometric parameters of each submarine mass movement has revealed that they fall into four distinct groups of subaqueous landslides; Singular Slumps, Singular Translational, Multiple Single-Type, and Complex (translational & rotational) failures. The Singular Slump Group includes discrete, individual subaqueous slumps that exhibit no evidence of modification through the merging of several scars. The Singular Translational Group comprise a single slide that displays characteristics associated with a single translational (planar) failure with no merging of multiple events. The Multiple Single-Type Group incorporates scars and deposits that displayed morphometric features consistent with the amalgamation of several failure events of the same type (e.g. debris flows or slumps). Finally, the Complex (translational & rotational) Group comprises landslides that exhibited complex styles of failures, including both translational and rotational mechanisms controlling the same slide. The submarine mass movements that comprise this dataset are then discussed in relation to global fjordic and glaciomarine nearshore settings, and slope failure trigger mechanisms associated with these environments are described with tentative links to individual submarine landslides from the database, where appropriate. It is acknowledged that additional MBES data are needed not only to expand this database but also to create a more statistically robust study. However, this initial study provides the basis for a much wider investigation of submarine mass movements and correlations between their morphometric parameters.</p>

Small-Scale Science to Large-Scale Profession

2000 ◽  
Vol 45 (4) ◽  
pp. 396-398
Author(s):  
Roger Smith
Keyword(s):  
Large Scale ◽  
Small Scale

Development of Physics Learning Module Based on Guided Inquiry with Light Wave Material in Class XI of Senior High School

2020 ◽  
Vol 1 (1) ◽  
pp. 1-10
Author(s):  
Evi Rahmawati ◽  
Irnin Agustina Dwi Astuti ◽  
N Nurhayati
Keyword(s):  
Large Scale ◽  
Learning Strategy ◽  
Student Response ◽  
Average Score ◽  
Small Scale ◽  
Design Development ◽  
Teacher Response ◽  
Student Responses ◽  
Analysis Design ◽  
Scientific Skills

IPA Integrated is a place for students to study themselves and the surrounding environment applied in daily life. Integrated IPA Learning provides a direct experience to students through the use and development of scientific skills and attitudes. The importance of integrated IPA requires to pack learning well, integrated IPA integration with the preparation of modules combined with learning strategy can maximize the learning process in school. In SMP 209 Jakarta, the value of the integrated IPA is obtained from 34 students there are 10 students completed and 24 students are not complete because they get the value below the KKM of 68. This research is a development study with the development model of ADDIE (Analysis, Design, Development, Implementation, and Evaluation). The use of KPS-based integrated IPA modules (Science Process sSkills) on the theme of rainbow phenomenon obtained by media expert validation results with an average score of 84.38%, average material expert 82.18%, average linguist 75.37%. So the average of all aspects obtained by 80.55% is worth using and tested to students. The results of the teacher response obtained 88.69% value with excellent criteria. Student responses on a small scale acquired an average score of 85.19% with highly agreed criteria and on the large-scale student response gained a yield of 86.44% with very agreed criteria. So the module can be concluded receiving a good response by the teacher and students.

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