scholarly journals Syn-thrusting, near-surface flexural-slipping and stress deflection along folded sedimentary layers of the Sant Corneli-Bóixols anticline (Pyrenees, Spain)

Solid Earth ◽  
2017 ◽  
Vol 8 (2) ◽  
pp. 405-419 ◽  
Author(s):  
Stefano Tavani ◽  
Pablo Granado ◽  
Pau Arbués ◽  
Amerigo Corradetti ◽  
J. Anton Muñoz
Keyword(s):  
Stress Tensor ◽  
Central Portion ◽  
Near Surface ◽  
Growth Strata ◽  
Folding Process ◽  
Angular Unconformity ◽  
Shear Structures ◽  
Spanish Pyrenees ◽  
Unconformity Surface

Abstract. In the Spanish Pyrenees, the Sant Corneli-Bóixols thrust-related anticline displays an outstandingly preserved growth strata sequence. These strata lie on top of a major unconformity exposed at the anticline's forelimb that divides and decouples a lower pre-folding unit from an upper syn-folding one. The former consists of steeply dipping to overturned strata with widespread bedding-parallel slip indicative of folding by flexural slip, whereas the syn-folding strata above define a 200 m amplitude fold. In the inner and outer sectors of the forelimb, both pre- and syn-folding strata are near vertical to overturned and the unconformity angle ranges from 10 to 30°. In the central portion of the forelimb, syn-folding layers are gently dipping, whereas the angular unconformity is about 90° and the unconformity surface displays strong S–C shear structures, which provide a top-to-foreland slip sense. This sheared unconformity is offset by steeply dipping faults, which are at low angles to the underlying layers of the pre-folding unit. Strong shearing along the unconformity surface also occurred in the inner sector of the forelimb, with S–C structures providing an opposite, top-to-hinterland slip sense. Cross-cutting relationships and slip senses along the pre-folding bedding surfaces and the unconformity indicate that regardless of its orientation, layering in the pre- and syn-folding sequences of the Sant Corneli-Bóixols anticline were continuously slipped. This slipping promoted an intense stress deflection, with the maximum component of the stress tensor remaining at low angles to bedding during most of the folding process.

scholarly journals Syn-thrusting, near-surface flexural-slipping and stress deflection along folded sedimentary layers of the Sant Corneli-Bóixols Anticline (Pyrenees, Spain)

2017 ◽  
Author(s):  
Stefano Tavani ◽  
Pablo Granado ◽  
Pau Arbués ◽  
Amerigo Corradetti ◽  
Josep A. Muñoz
Keyword(s):  
Stress Tensor ◽  
Central Portion ◽  
Near Surface ◽  
Growth Strata ◽  
Folding Process ◽  
Angular Unconformity ◽  
Shear Structures ◽  
Shear Sense ◽  
Spanish Pyrenees ◽  
Unconformity Surface

Abstract. In the Spanish Pyrenees the Sant Corneli-Bóixols thrust-related anticline displays an outstandingly preserved growth strata sequence. These strata lie on top of a major unconformity exposed at the anticline’s forelimb that divides and decouples a lower pre-folding unit from an upper syn-folding one. The former consists of steeply-dipping to overturned strata with widespread bedding-parallel shears indicative of folding by flexural-slip, whereas the syn-folding strata above define a 200-m amplitude S-shaped fold. In the inner and outer sectors of the forelimb, both pre- and syn-folding strata are near-vertical to overturned and the unconformity angle ranges from 10° to 30º. In the central portion of the forelimb, syn-folding layers are shallowly-dipping, whereas the angular unconformity is about 90° and the unconformity surface displays strong S-C shear structures, which provide a top-to-the foreland shear sense. This sheared unconformity is offset by steeply-dipping faults which are at low angles to the underlying layers of the pre-folding unit. Strong shearing along the unconformity surface also occurred in the inner sector of the forelimb with S-C structures providing an opposite, top-to-the hinterland, shear sense. Cross-cutting relationships and shear senses along the pre-folding bedding surfaces and the unconformity indicate that regardless of its orientation, layering in the pre- and syn-folding sequences of the Sant Corneli-Bóixols anticline was continuously sheared. This shearing promoted an intense stress deflection, with the maximum component of the stress tensor remaining at low angles to beds during most of the folding process.

scholarly journals Analysis of the Snow Water Equivalent at the AEMet-Formigal Field Laboratory (Spanish Pyrenees) During the 2019/2020 Winter Season Using a Stepped-Frequency Continuous Wave Radar (SFCW)

2021 ◽  
Vol 13 (4) ◽  
pp. 616
Author(s):  
Rafael Alonso ◽  
José María García del Pozo ◽  
Samuel T. Buisán ◽  
José Adolfo Álvarez
Keyword(s):  
Software Defined Radio ◽  
Continuous Wave ◽  
Snow Water Equivalent ◽  
Cosmic Ray ◽  
Relative Dielectric Permittivity ◽  
Near Surface ◽  
Wave Radar ◽  
Spanish Pyrenees ◽  
Snow Water ◽  
Stepped Frequency

Snow makes a great contribution to the hydrological cycle in cold regions. The parameter to characterize available the water from the snow cover is the well-known snow water equivalent (SWE). This paper presents a near-surface-based radar for determining the SWE from the measured complex spectral reflectance of the snowpack. The method is based in a stepped-frequency continuous wave radar (SFCW), implemented in a coherent software defined radio (SDR), in the range from 150 MHz to 6 GHz. An electromagnetic model to solve the electromagnetic reflectance of a snowpack, including the frequency and wetness dependence of the complex relative dielectric permittivity of snow layers, is shown. Using the previous model, an approximated method to calculate the SWE is proposed. The results are presented and compared with those provided by a cosmic-ray neutron SWE gauge over the 2019–2020 winter in the experimental AEMet Formigal-Sarrios test site. This experimental field is located in the Spanish Pyrenees at an elevation of 1800 m a.s.l. The results suggest the viability of the approximate method. Finally, the feasibility of an auxiliary snow height measurement sensor based on a 120 GHz frequency modulated continuous wave (FMCW) radar sensor, is shown.

scholarly journals Integrated evaluation of the geology, aerogammaspectrometry and aeromagnetometry of the Sul-Riograndense Shield, southernmost Brazil

2016 ◽  
Vol 88 (1) ◽  
pp. 75-92 ◽  
Author(s):  
LÉO A. HARTMANN ◽  
WILLIAM R. LOPES ◽  
JAIRO F. SAVIAN
Keyword(s):  
Data Acquisition ◽  
Gamma Rays ◽  
Analytic Signal ◽  
Central Portion ◽  
Advanced Stage ◽  
Magnetic Signal ◽  
Near Surface ◽  
Future Studies ◽  
Crustal Structures ◽  
Field Geology

ABSTRACT An integrated evaluation of geology, aerogammaspectrometry and aeromagnetometry of the Sul-Riograndense Shield is permitted by the advanced stage of understanding of the geology and geochronology of the southern Brazilian Shield and a 2010 airborne geophysical survey. Gamma rays are registered from the rocks near the surface and thus describe the distribution of major units in the shield, such as the Pelotas batholith, the juvenile São Gabriel terrane, the granulite-amphibolite facies Taquarembó terrane and the numerous granite intrusions in the foreland. Major structures are also observed, e.g., the Dorsal de Canguçu shear. Magnetic signals register near surface crustal compositions (analytic signal) and total crust composition (total magnetic signal), so their variation as measured indicates either shallow or whole crustal structures. The Caçapava shear is outstanding on the images as is the magnetic low along the N-S central portion of the shield. These integrated observations lead to the deepening of the understanding of the largest and even detailed structures of the Sul-Riograndense Shield, some to be correlated to field geology in future studies. Most significant is the presence of different provinces and their limits depending on the method used for data acquisition - geology, aerogammaspectrometry or aeromagnetometry.

Analysing landforms, borehole logs, and geophysics, for localization and assessment of active faults in the central Vienna Basin (Austria)

2020 ◽  
Author(s):  
Michael Weissl ◽  
Decker Kurt ◽  
Adrian Flores-Orozco ◽  
Matthias Steiner
Keyword(s):  
Active Faults ◽  
Fault System ◽  
Tectonic Activity ◽  
Fluvial Sediments ◽  
River Channels ◽  
Vienna Basin ◽  
Geothermal Resources ◽  
Near Surface ◽  
Growth Strata ◽  
Fault Scarps

<p>The formation of pull apart basins and normal faulting at splays along the Vienna Basin strike-slip fault system resulted in the dissection of the Pleistocene river terraces of the Danube. Displacements of terrace segments are visible on the surface as fault scarps or dells what allows mapping the system of active faults. Furthermore displacement rates can be estimated from the elevation of the basis and the thickness of Quaternary fluvial sediments.</p><p>With regard to the prospective utilization of geothermal resources in the area of Vienna a research group was built (Geotief Explore 3D, funded by Wien Energie and FFG) with the objective to identify, map, and assess, Quaternary faults, because such rupture zones are not suitable for the reinjection of thermal water in view of the hazard of triggered earthquakes.</p><p>Normal splay faults define the eastern and western margins of Pleistocene Danube terraces north of Vienna. The bodies of these terraces are built up of coarse sandy gravel and sand whereas their surfaces are covered with aeolian and alluvial sediments of the last glacial. Tectonic displacements during the Pleistocene left distinct marks in the late glacial landform configuration of the terraces. Therefore many fault scarps and fault related valleys are clearly cognizable in high resolution LiDAR and satellite images.</p><p>During the last decade three distinct fault scarps of the Vienna Basin Transform Fault situated at the terrace edges could be investigated by trenching and transect analysis. Actual research has the objective to model the 3D geometry of the base of the Quaternary strata (horizon Base Quaternary) from a compilation of shallow drillings and the construction of a regional isopach map showing the thickness of Quaternary (growth-) strata.</p><p>In the course of research it becomes apparent that within the tectonically subsided areas evidence of neotectonics is overprinted by fluvial sediments and alluvium what hinders accurate localization of faults. However, the sinuosity of palaeochannels in the Danube floodplain seems to be related to tectonics and therefore the pattern of former river channels can be used as sign for tectonic activity during the Pleistocene. In places where signs for active faulting are completely overprinted by fluvial sedimentation and cryoturbation the approved methods for the localization and the assessment of active faults are electrical resistivity tomography and near-surface seismics.</p>

scholarly journals Growth of triangle zone fold-thrusts within the NW Borneo deep-water fold belt, offshore Sabah, southern South China Sea

Geosphere ◽  
2019 ◽  
Vol 16 (1) ◽  
pp. 329-356
Author(s):  
Jonny Wu ◽  
Ken McClay ◽  
Jose de Vera
Keyword(s):  
South China Sea ◽  
South China ◽  
Deep Water ◽  
Three Dimensional ◽  
Petroleum Industry ◽  
Fold Belt ◽  
Southern South China Sea ◽  
Near Surface ◽  
Growth Strata ◽  
Triangle Zone

Abstract The NW Borneo deep-water fold-and-thrust belt, offshore Sabah, southern South China Sea, contains a structurally complex region of three to four seafloor ridges outboard of the shelf-slope break. Previous studies have suggested the seafloor ridges formed either above shale diapirs produced by mass movement of overpressured shales (i.e., mobile shale) or above an imbricate fold-and-thrust array. Here, we performed tectonostratigraphic analyses on a petroleum industry three-dimensional (3-D) seismic volume that imaged the full growth stratal record. We show fold growth history, deformation styles, along-strike structural variabilities, and synkinematic sedimentation during triangle zone–style fold growth. Nine seismic horizons within growth strata were mapped and correlated to petroleum industry seismostratigraphy. Synkinematic sedimentation interactions with growing folds and near-surface strains were analyzed from seismic attribute maps. We interpret that the seafloor structures were formed by imbricate thrusts above multiple detachments. We estimate ∼8 km minimum shortening since the late Miocene ca. 10 Ma. The folds show oversteepened fold forelimbs, back-rotated backlimbs, and forward-vergent (NW to NNW) “blind” thrust ramps that terminate within the growth strata. Fold cores show evidence of internal shear. Immature folds show detachment fold geometries, whereas mature folds show forelimb break thrusts, type I triangle zones, and rotated forward-vergent roof thrusts. Thrust linkages spaced ∼10 km apart were exploited as thrust top synkinematic sedimentation pathways; the linkages also partition near-surface strains. Our comprehensive, three-dimensional documentation of triangle zone fold growth and sedimentation in a deep-water fold belt highlights internal shear, multiple detachments, and opposite thrust vergence; mobile shales are not required to explain the deformation.

SBGBBG: A computer program for strain/stress tensor calculation from X-ray diffraction data

1993 ◽  
Vol 8 (4) ◽  
pp. 214-215 ◽  
Author(s):  
T. Wieder
Keyword(s):  
Computer Program ◽  
Stress Tensor ◽  
Diffraction Data ◽  
Grazing Incidence ◽  
X Ray Diffraction ◽  
Near Surface ◽  
X Ray ◽  
Strain Stress ◽  
Stress States ◽  
Depth Dependency

Near-surface triaxial strain/stress states in polycrystalline solids are required for a full tensorial treatment including all elements of the strain/stress tensor. A possible depth dependency of the strain/stress is at best observed by grazing incidence diffraction in Seemann–Bohlin geometry (SBG). The computer program SBGBBG calculates the full strain/stress tensor from X-ray diffraction data measured either in SBG or in Bragg–Brentano geometry (BBG). At present SBGBBG is applicable only on texture-free materials.

Benthic foraminiferal zonation in deep-water carbonate platform margin environments, northern Little Bahama Bank

1988 ◽  
Vol 62 (01) ◽  
pp. 1-8 ◽  
Author(s):  
Ronald E. Martin
Keyword(s):  
Deep Water ◽  
Benthic Foraminifera ◽  
Carbonate Platform ◽  
Sedimentary Facies ◽  
Depositional Environments ◽  
Near Surface ◽  
Sediment Gravity Flows ◽  
Gravity Flows ◽  
Platform Margin ◽  
Water Carbonate

The utility of benthic foraminifera in bathymetric interpretation of clastic depositional environments is well established. In contrast, bathymetric distribution of benthic foraminifera in deep-water carbonate environments has been largely neglected. Approximately 260 species and morphotypes of benthic foraminifera were identified from 12 piston core tops and grab samples collected along two traverses 25 km apart across the northern windward margin of Little Bahama Bank at depths of 275-1,135 m. Certain species and operational taxonomic groups of benthic foraminifera correspond to major near-surface sedimentary facies of the windward margin of Little Bahama Bank and serve as reliable depth indicators. Globocassidulina subglobosa, Cibicides rugosus, and Cibicides wuellerstorfi are all reliable depth indicators, being most abundant at depths >1,000 m, and are found in lower slope periplatform aprons, which are primarily comprised of sediment gravity flows. Reef-dwelling peneroplids and soritids (suborder Miliolina) and rotaliines (suborder Rotaliina) are most abundant at depths <300 m, reflecting downslope bottom transport in proximity to bank-margin reefs. Small miliolines, rosalinids, and discorbids are abundant in periplatform ooze at depths <300 m and are winnowed from the carbonate platform. Increased variation in assemblage diversity below 900 m reflects mixing of shallow- and deep-water species by sediment gravity flows.

Analysis of 2D and 3D defects associated with precipitation of Cu in silicon

1991 ◽  
Vol 49 ◽  
pp. 870-871
Author(s):  
P.M. Rice ◽  
MJ. Kim ◽  
R.W. Carpenter
Keyword(s):  
Colony Growth ◽  
Dark Field ◽  
Dark Side ◽  
Silicide Phase ◽  
Strain Fields ◽  
Near Surface ◽  
Unknown Composition ◽  
Secondary Precipitates ◽  
20 Nm ◽  
2D And 3D

Extrinsic gettering of Cu on near-surface dislocations in Si has been the topic of recent investigation. It was shown that the Cu precipitated hetergeneously on dislocations as Cu silicide along with voids, and also with a secondary planar precipitate of unknown composition. Here we report the results of investigations of the sense of the strain fields about the large (~100 nm) silicide precipitates, and further analysis of the small (~10-20 nm) planar precipitates.Numerous dark field images were analyzed in accordance with Ashby and Brown's criteria for determining the sense of the strain fields about precipitates. While the situation is complicated by the presence of dislocations and secondary precipitates, micrographs like those shown in Fig. 1(a) and 1(b) tend to show anomalously wide strain fields with the dark side on the side of negative g, indicating the strain fields about the silicide precipitates are vacancy in nature. This is in conflict with information reported on the η'' phase (the Cu silicide phase presumed to precipitate within the bulk) whose interstitial strain field is considered responsible for the interstitial Si atoms which cause the bounding dislocation to expand during star colony growth.

Shock consolidation of Ni-Ti alloy powder

1986 ◽  
Vol 44 ◽  
pp. 430-431
Author(s):  
Naresh N. Thadhani ◽  
Thad Vreeland ◽  
Thomas J. Ahrens
Keyword(s):  
Alloy Powder ◽  
Amorphous Material ◽  
Ti Alloy ◽  
Two Phase ◽  
Near Surface ◽  
Optical Micrograph ◽  
Shock Compaction ◽  
Powder Particles ◽  
Ti Powder ◽  
Rapidly Solidified

A spherically-shaped, microcrystalline Ni-Ti alloy powder having fairly nonhomogeneous particle size distribution and chemical composition was consolidated with shock input energy of 316 kJ/kg. In the process of consolidation, shock energy is preferentially input at particle surfaces, resulting in melting of near-surface material and interparticle welding. The Ni-Ti powder particles were 2-60 μm in diameter (Fig. 1). About 30-40% of the powder particles were Ni-65wt% and balance were Ni-45wt%Ti (estimated by EMPA).Upon shock compaction, the two phase Ni-Ti powder particles were bonded together by the interparticle melt which rapidly solidified, usually to amorphous material. Fig. 2 is an optical micrograph (in plane of shock) of the consolidated Ni-Ti alloy powder, showing the particles with different etching contrast.

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