Determining axes, axial planes, and sections of macroscopic folds using computer-based methods

1976 ◽  
Vol 13 (1) ◽  
pp. 54-65 ◽  
Author(s):  
H. A. K. Charlesworth ◽  
C. W. Langenberg ◽  
J. Ramsden
Keyword(s):  
Rocky Mountains ◽  
Axial Plane ◽  
Fold Axis ◽  
F Test ◽  
Smallest Eigenvalue ◽  
Computer Based ◽  
Direction Cosines

The fold-axis is the eigenvector associated with the smallest eigenvalue of a symmetrical 3 × 3 matrix of direction cosines of poles to the folded surface, only if the fold is cylindrical. Cylindricity can be tested using either a χ2 or an F test. Sections showing the traces of macroscopic surfaces and of the axial plane may be constructed with the aid of computer plots that show the projection of each outcrop as well as the trace of the folded surface. The orientation of the axial plane can be calculated from the orientations of the fold-axis and the trace of the axial plane on a section normal to the fold-axis. These numerical procedures are illustrated by an analysis of four folds from the Rocky Mountains.

A textbook example of triply-folded Ediacaran carbonates – insights into geodynamics and geomorphology (Hat Plateau, Jabal Akhdar Dome, Oman Mountains)

2021 ◽  
Author(s):  
Andreas Scharf ◽  
Ivan Callegari ◽  
Frank Mattern ◽  
Katharina Scharf ◽  
Eugenio Carminati
Keyword(s):  
Abrupt Change ◽  
Block Diagram ◽  
Satellite Image ◽  
Sudden Change ◽  
Axial Plane ◽  
Fold Axis ◽  
Oman Mountains ◽  
Arid Conditions ◽  
Oriented Parallel ◽  
Natural Laboratory

<p>The Jabal Akhdar Dome (JAD) of the Oman Mountains contains superbly exposed sedimentary Neoproterozoic formations in its core. Carbonates of the Hajir Formation are resistant against erosion in the prevailing semi-arid conditions unlike the subjacent and overlying siliciclastic formations. Structural fieldwork and satellite image analyses reveals that the central-western JAD (Hat Plateau) was affected by three folding events. Each event produced its own fascinating fold style with associated structures. The widely exposed Hajir carbonates displays these folds spectacularly. The geomorphology of these carbonates reflects the folds with differently oriented rides and troughs as anti- and synclines, respectively. Thus, the JAD acted as a natural laboratory where the 3D fold styles can be directly linked to the geomorphology and vice versa.</p><p>A previously unrecognized folding event (F1) produced overturned NNE-verging tight folds. The fold amplitude ranges between tens and hundreds of meters, and the overall non-plunging fold axes trend ESE. The F1 folds are associated with a gently to moderately SSW-ward dipping penetrative axial plane cleavage. Open to tight upright kilometric F2 folds refolded the F1 structures. The F2 folds are overall non-plunging and NE/NNE-trending, and contain a penetrative sub-vertical axial plane schistosity, parallelly oriented to the F2 axes. The youngest folding event (F3) produces one open and broad anticline. The F3 fold axis trends WNW through the Hat Plateau and the anticline contains a WNW-striking sub-vertical spaced axial plane schistosity.</p><p>The deformation style of the F2 folds and related structures changes abruptly along a NNE-oriented zone at the western end of the Hat Plateau. West of this, the F2 structures are ENE-oriented while east of it the orientation is NE to NNE. Furthermore, the amplitude of the F2 folds decreases from ~3 km in the west to <1 km in the east. We relate this sudden change of the F2 style to the western flank of a pre-existing subsurface basement horst. We suggest that this NNE-striking horst is the northern continuation of the Makarem-Mabrouk High/Horst below the JAD. The eastern horst shoulder would be at the eastern margin of the JAD and parallel to the Semail Gap. A buttressing effect along the western horst’s shoulder during NW/SE to WNW/ESE-directed F2 shortening would explain the dramatic change in the F2 style.</p><p>In summary and in 3D terms, the F1 folds were originally oriented parallel to the present F1 anticline, i.e. before the F2 deformation, while the F2 folds strike almost perpendicularly to this direction. The F1 and F2 folding episodes associated with the abrupt change in F2 style are depicted in a steric block diagram, which visualizes the complex findings, allowing for a 3D understanding of the structures.</p>

A Study of Quartz Orientation and its Relation to Movement in Shear Folds

1962 ◽  
Vol 99 (1) ◽  
pp. 69-84 ◽  
Author(s):  
P. K. Gangopadhyay ◽  
M. R. W. Johnson
Keyword(s):  
Laminar Flow ◽  
Axial Plane ◽  
Orthorhombic Symmetry ◽  
Fold Axis ◽  
Kinematic Axis ◽  
Quartz Grains ◽  
Small Shear

AbstractThe orientation of quartz in small shear folds, which belong to two movement episodes, is considered to result from laminar flow along the axial plane surfaces. The locations of fabric maxima and girdles are controlled by the orientation of thea–kinematic axis, which in shear folds may not be normal to the fold axis, and the shear surfaces. The earlier fabric consists, essentially, of paired maxima arranged systematically about the axial plane;ac–girdles are absent. The explanation of the near-orthorhombic symmetry of the first fabric in terms of a late “flattening” overprinted upon the previously-formed fold is not favoured: quartz orientation developed during the first folding. The later fabric results from the recrystallization of quartz grains with their largest dimensions andc–axes parallel to the calculateda–kinematic axis of second folding.

Significance of AMS analysis in evaluating superposed folds in quartzites

2010 ◽  
Vol 147 (6) ◽  
pp. 910-918 ◽  
Author(s):  
MANISH A. MAMTANI ◽  
POULOMI SENGUPTA
Keyword(s):  
Magnetic Susceptibility ◽  
Large Scale ◽  
Regional Scale ◽  
Axial Plane ◽  
Magnetic Fabric ◽  
Fold Axis ◽  
Eastern India ◽  
Mesoscopic Scale ◽  
Ductile Shearing ◽  
Magnetic Foliation

AbstractQuartzites tend to be compositionally homogeneous, and because of this, deformation related fabric elements (foliations and lineations) are poorly developed in them. This makes structural analysis of deformed quartzites challenging. The measurement of anisotropy of magnetic susceptibility (AMS) is useful for recognizing structural imprints in rocks that lack mesoscopic fabrics and the present study is carried out with an aim to demonstrate the robustness of AMS in analysing such deformation imprints in quartzites. AMS data of samples from folded quartzites located in an approximately 10 km2 area around Galudih (eastern India) are presented. Although on a regional scale, superposed deformation and ductile shearing are known from the area, the investigated quartzites do not preserve mesoscopic evidence of these large-scale features and have developed folds that plunge gently towards the SE with a vertical NW–SE-striking axial plane. The magnetic foliation recorded from AMS analysis is parallel to the axial plane, while the orientation of the magnetic lineation varies from SE through vertical to NW. This is similar to the large-scale fold axis variations recorded in various regional domains mapped over an area of about 200 km2. It is concluded that although the imprint of regional superposed deformation is not obvious on the mesoscopic scale in the quartzites around Galudih, this imprint can be detected from the magnetic fabric. The present study thus highlights the usefulness of AMS in analysing superposed folds in quartzites.

Microfabrics of a recumbent fold in cross-bedded sandstones

1979 ◽  
Vol 116 (2) ◽  
pp. 105-116 ◽  
Author(s):  
K. Yagishita ◽  
R. C. Morris
Keyword(s):  
Thin Section ◽  
Similar Type ◽  
Axial Plane ◽  
The Other ◽  
Small Scale ◽  
Fold Axis ◽  
High Angle ◽  
Plane Normal ◽  
Quartz Grains ◽  
Shear Planes

SummaryA thin-section study of the orientation of long-axes of quartz grains was conducted for a similar type fold of overturned cross-bedding in Carboniferous sandstones. Preferred orientation of detrital grains of the fold shows that (a) apparent long-axes of grains are parallel to the axial plane in a plane normal to the fold axis, (b) long-axes of grains in the axial plane are oriented in a high angle to the fold axis, and (c) grains are aligned parallel to the fold axis in a plane perpendicular to the other two directions. From the dimensional orientation of quartz grains in this sample, it is concluded that the overturned fold was made by a shear mechanism immediately following sedimentation in which the original quartz grains were reorientated by small-scale slippage along the shear planes.

Cell morphology, volume, and surface area determinations from multilevel contouring within HVEM micrographs of serial sections and whole-cell mounts

1987 ◽  
Vol 45 ◽  
pp. 588-589
Author(s):  
M. Marko ◽  
A. Leith ◽  
D. Parsons
Keyword(s):  
Surface Area ◽  
Electron Micrographs ◽  
Cell Morphology ◽  
Individual Variation ◽  
Serial Section ◽  
Stereo Pair ◽  
Complex Structures ◽  
Serial Sections ◽  
Surface Areas ◽  
Computer Based

The use of serial sections and computer-based 3-D reconstruction techniques affords an opportunity not only to visualize the shape and distribution of the structures being studied, but also to determine their volumes and surface areas. Up until now, this has been done using serial ultrathin sections.The serial-section approach differs from the stereo logical methods of Weibel in that it is based on the Information from a set of single, complete cells (or organelles) rather than on a random 2-dimensional sampling of a population of cells. Because of this, it can more easily provide absolute values of volume and surface area, especially for highly-complex structures. It also allows study of individual variation among the cells, and study of structures which occur only infrequently.We have developed a system for 3-D reconstruction of objects from stereo-pair electron micrographs of thick specimens.

Friedel'S law breakdown and interpretation of stacking fault images in tetrahedral semiconductors

1987 ◽  
Vol 45 ◽  
pp. 318-319
Author(s):  
Rob. W. Glaisher ◽  
A.E.C. Spargo
Keyword(s):  
Relative Phase ◽  
Point Group ◽  
Binary Compound ◽  
Stacking Fault ◽  
Fold Axis ◽  
Atom Pair ◽  
Tetrahedral Semiconductors ◽  
Group Symmetries ◽  
Thin Crystal ◽  
Phase Differences

Images of <11> oriented crystals with diamond structure (i.e. C,Si,Ge) are dominated by white spot contrast which, depending on thickness and defocus, can correspond to either atom-pair columns or tunnel sites. Olsen and Spence have demonstrated a method for identifying the correspondence which involves the assumed structure of a stacking fault and the preservation of point-group symmetries by correctly aligned and stigmated images. For an intrinsic stacking fault, a two-fold axis lies on a row of atoms (not tunnels) and the contrast (black/white) of the atoms is that of the {111} fringe containing the two-fold axis. The breakdown of Friedel's law renders this technique unsuitable for the related, but non-centrosymmetric binary compound sphalerite materials (e.g. GaAs, InP, CdTe). Under dynamical scattering conditions, Bijvoet related reflections (e.g. (111)/(111)) rapidly acquire relative phase differences deviating markedly from thin-crystal (kinematic) values, which alter the apparent location of the symmetry elements needed to identify the defect.

A hitchhiker’s guide to microscopy and microanalysis using telecommunications, e-mail, and the Internet

1994 ◽  
Vol 52 ◽  
pp. 390-391 ◽  
Author(s):  
Nestor J. Zaluzec
Keyword(s):  
The Internet ◽  
Information Superhighway ◽  
The World ◽  
Exchange Information ◽  
On Line ◽  
Computer Based ◽  
Software And Hardware ◽  
Communication Software ◽  
Basic Ideas ◽  
E Mail

The Information SuperHighway, Email, The Internet, FTP, BBS, Modems, : all buzz words which are becoming more and more routine in our daily life. Confusing terminology? Hopefully it won't be in a few minutes, all you need is to have a handle on a few basic concepts and terms and you will be on-line with the rest of the "telecommunication experts". These terms all refer to some type or aspect of tools associated with a range of computer-based communication software and hardware. They are in fact far less complex than the instruments we use on a day to day basis as microscopist's and microanalyst's. The key is for each of us to know what each is and how to make use of the wealth of information which they can make available to us for the asking. Basically all of these items relate to mechanisms and protocols by which we as scientists can easily exchange information rapidly and efficiently to colleagues in the office down the hall, or half-way around the world using computers and various communications media. The purpose of this tutorial/paper is to outline and demonstrate the basic ideas of some of the major information systems available to all of us today. For the sake of simplicity we will break this presentation down into two distinct (but as we shall see later connected) areas: telecommunications over conventional phone lines, and telecommunications by computer networks. Live tutorial/demonstrations of both procedures will be presented in the Computer Workshop/Software Exchange during the course of the meeting.

Computer based simulated patient for teaching history-taking

1973 ◽  
Vol 37 (8) ◽  
pp. 27-31
Author(s):  
HA Brody ◽  
LF Lucaccini ◽  
M Kamp ◽  
R Rozen
Keyword(s):  
Simulated Patient ◽  
History Taking ◽  
Teaching History ◽  
Computer Based

Auditory Training to Improve Speech Perception and Self-Efficacy in Aging Adults

2020 ◽  
Vol 63 (4) ◽  
pp. 1270-1281
Author(s):  
Leah Fostick ◽  
Riki Taitelbaum-Swead ◽  
Shulamith Kreitler ◽  
Shelly Zokraut ◽  
Miriam Billig
Keyword(s):  
Speech Perception ◽  
Self Efficacy ◽  
Temporal Order Judgment ◽  
Auditory Training ◽  
Intensity Discrimination ◽  
Training Design ◽  
Auditory Temporal Processing ◽  
Temporal Properties ◽  
Computer Based ◽  
Aging Adults

Purpose Difficulty in understanding spoken speech is a common complaint among aging adults, even when hearing impairment is absent. Correlational studies point to a relationship between age, auditory temporal processing (ATP), and speech perception but cannot demonstrate causality unlike training studies. In the current study, we test (a) the causal relationship between a spatial–temporal ATP task (temporal order judgment [TOJ]) and speech perception among aging adults using a training design and (b) whether improvement in aging adult speech perception is accompanied by improved self-efficacy. Method Eighty-two participants aged 60–83 years were randomly assigned to a group receiving (a) ATP training (TOJ) over 14 days, (b) non-ATP training (intensity discrimination) over 14 days, or (c) no training. Results The data showed that TOJ training elicited improvement in all speech perception tests, which was accompanied by increased self-efficacy. Neither improvement in speech perception nor self-efficacy was evident following non-ATP training or no training. Conclusions There was no generalization of the improvement resulting from TOJ training to intensity discrimination or generalization of improvement resulting from intensity discrimination training to speech perception. These findings imply that the effect of TOJ training on speech perception is specific and such improvement is not simply the product of generally improved auditory perception. It provides support for the idea that temporal properties of speech are indeed crucial for speech perception. Clinically, the findings suggest that aging adults can be trained to improve their speech perception, specifically through computer-based auditory training, and this may improve perceived self-efficacy.

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