do05.makkie.com/zur-lust-verfuehrt-german-edition.php Primary data sets for structural geology are collected in the field. Structural geologists measure a variety of planar features bedding planes , foliation planes , fold axial planes, fault planes , and joints , and linear features stretching lineations, in which minerals are ductily extended; fold axes; and intersection lineations, the trace of a planar feature on another planar surface. The inclination of a planar structure in geology is measured by strike and dip.
The strike is the line of intersection between the planar feature and a horizontal plane, taken according to the right hand convention, and the dip is the magnitude of the inclination, below horizontal, at right angles to strike. Alternatively, dip and dip direction may be used as this is absolute.
Dip direction is measured in degrees, generally clockwise from North. Note that this is the same as above. The term hade is occasionally used and is the deviation of a plane from vertical i. Fold axis plunge is measured in dip and dip direction strictly, plunge and azimuth of plunge. The orientation of a fold axial plane is measured in strike and dip or dip and dip direction. Lineations are measured in terms of dip and dip direction, if possible. Often lineations occur expressed on a planar surface and can be difficult to measure directly.
In this case, the lineation may be measured from the horizontal as a rake or pitch upon the surface. Rake is measured by placing a protractor flat on the planar surface, with the flat edge horizontal and measuring the angle of the lineation clockwise from horizontal. The orientation of the lineation can then be calculated from the rake and strike-dip information of the plane it was measured from, using a stereographic projection. If a fault has lineations formed by movement on the plane, e. The convention for analysing structural geology is to identify the planar structures , often called planar fabrics because this implies a textural formation, the linear structures and, from analysis of these, unravel deformations.
Planar structures are named according to their order of formation, with original sedimentary layering the lowest at S0. Often it is impossible to identify S0 in highly deformed rocks, so numbering may be started at an arbitrary number or given a letter S A , for instance. In cases where there is a bedding-plane foliation caused by burial metamorphism or diagenesis this may be enumerated as S0a.
If there are folds, these are numbered as F 1 , F 2 , etc.
Generally the axial plane foliation or cleavage of a fold is created during folding, and the number convention should match. For example, an F 2 fold should have an S 2 axial foliation.
Deformations are numbered according to their order of formation with the letter D denoting a deformation event. Folds and foliations, because they are formed by deformation events, should correlate with these events. For example, an F 2 fold, with an S 2 axial plane foliation would be the result of a D 2 deformation. Metamorphic events may span multiple deformations. Sometimes it is useful to identify them similarly to the structural features for which they are responsible, e.
This may be possible by observing porphyroblast formation in cleavages of known deformation age, by identifying metamorphic mineral assemblages created by different events, or via geochronology. Intersection lineations in rocks, as they are the product of the intersection of two planar structures, are named according to the two planar structures from which they are formed.
For instance, the intersection lineation of a S 1 cleavage and bedding is the L intersection lineation also known as the cleavage-bedding lineation.
Stretching lineations may be difficult to quantify, especially in highly stretched ductile rocks where minimal foliation information is preserved. Where possible, when correlated with deformations as few are formed in folds, and many are not strictly associated with planar foliations , they may be identified similar to planar surfaces and folds, e.
For convenience some geologists prefer to annotate them with a subscript S, for example L s 1 to differentiate them from intersection lineations, though this is generally redundant. Stereographic projection is a method for analyzing the nature and orientation of deformation stresses, lithological units and penetrative fabrics wherein linear and planar features structural strike and dip readings, typically taken using a compass clinometer passing through an imagined sphere are plotted on a two-dimensional grid projection, facilitating more holistic analysis of a set of measurements.
On a large scale, structural geology is the study of the three-dimensional interaction and relationships of stratigraphic units within terranes of rock or geological regions.
This branch of structural geology deals mainly with the orientation, deformation and relationships of stratigraphy bedding , which may have been faulted, folded or given a foliation by some tectonic event. This is mainly a geometric science, from which cross sections and three-dimensional block models of rocks, regions, terranes and parts of the Earth's crust can be generated. Study of regional structure is important in understanding orogeny , plate tectonics and more specifically in the oil, gas and mineral exploration industries as structures such as faults, folds and unconformities are primary controls on ore mineralisation and oil traps.
Modern regional structure is being investigated using seismic tomography and seismic reflection in three dimensions, providing unrivaled images of the Earth's interior, its faults and the deep crust. Further information from geophysics such as gravity and airborne magnetics can provide information on the nature of rocks imaged to be in the deep crust.
Rock microstructure or texture of rocks is studied by structural geologists on a small scale to provide detailed information mainly about metamorphic rocks and some features of sedimentary rocks , most often if they have been folded. Textural study involves measurement and characterisation of foliations , crenulations , metamorphic minerals, and timing relationships between these structural features and mineralogical features.
Usually this involves collection of hand specimens, which may be cut to provide petrographic thin sections which are analysed under a petrographic microscope. Microstructural analysis finds application also in multi-scale statistical analysis, aimed to analyze some rock features showing scale invariance see e. Guerriero et al. Geologists use rock geometry measurements to understand the history of strain in rocks. Strain can take the form of brittle faulting and ductile folding and shearing.
Brittle deformation takes place in the shallow crust, and ductile deformation takes place in the deeper crust, where temperatures and pressures are higher. By understanding the constitutive relationships between stress and strain in rocks, geologists can translate the observed patterns of rock deformation into a stress field during the geologic past. The following list of features are typically used to determine stress fields from deformational structures.
The mechanical properties of rock play a vital role in the structures that form during deformation deep below the earth's crust.
The conditions in which a rock is present will result in different structures that geologists observe above ground in the field. You can view this on the NLA website. Login Register. Advanced search Search history. Browse titles authors subjects uniform titles series callnumbers dewey numbers starting from optional. See what's been added to the collection in the current 1 2 3 4 5 6 weeks months years.
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To learn more about Copies Direct watch this short online video. Support will be available when practical classes run: 1. Hands-on teaching in computer workstations by experienced staff and demonstrators. Independent learning using GIS software. A wide range of support can be provided for those students who have further or specific learning and teaching needs.
Undergraduate Postgraduate taught Postgraduate research Foundation Years Pre-sessional English language courses How to apply Clearing Free online learning Continuing professional development Prospectuses. Aims and Objectives Learning Outcomes Transferable and Generic Skills Having successfully completed this module you will be able to: Development of 3D perception Manipulation of data using spread sheets Assessment of data quality Time management of project Presentation of scientific results View and edit data using GIS.
Subject Specific Practical Skills Having successfully completed this module you will be able to: Be able to present and manipulate data, e. Learning Outcomes Having successfully completed this module you will be able to: Appreciate the effect of variables e. Understand brittle and ductile deformation processes Be able to classify and understand fractures, fault rocks, rock fabrics, folds and associated processes.