Figure 1b shows the lineation plotted on the stereonet. Stereographic projection the basics geological digressions. Stereographic projection and rose diagram plotting. Form due to the intersection of two planar fabric elements e. Project a slickenline lineation to that plane having a plunge of 43 e. Jun 15, 2017 the bedding cleavage intersection lineation will lie parallel to the hinge lines of the fold which means these lineations will plot in a cluster close to the fold axes on the stereonet figure 15. Draw a line representing the strike line of the plane. Plane dip and strike, lineation plunge and trend, structural.
Fabric is used to describe the spatial and geometric relationships that make up the rock. Moreover, the great circles and poles of each bedding plane and platform are plotted in stereonet and as a rose diagram in fig. Exe can be used and will be demonstrated in lab to plot a net of this size. Relationship between axial planar cleavage and fold data on a. These long lines are parallel to the true north line on the side of the map. Small circles angles are slightly distorted and make the circles appear as ellipses. Other common uses for stereonets calculating rake we use rake to describe the angle between a plane and lineations on that plane. The plunge and trend of three of these are 46 s86e, 29 n62e, and 32 s2w. There are different methods by which the points of intersection with the lower hemisphere are projected onto the stereonet. Trace lineations are formed by intersecting foliations. If the map surface is horizontal the trace is also the strike line of the plane. Contents school of earth and environment 2 contents introduction to stereonets 4 stereonet terminology 6 setting up a stereonet 7 1.
Each quadrangle on the stereonet is equal in size or area, whereas shape of quadrangles varies from almost square near the center to narrow, curved rectangles near the edge. Orientations of lines and planes in space a definitions of. Notice how the bedding cleavage lineation and the jointcleavage lineation lie on the cleavage plane. Intersection lineations are measured in relation to the two structures which intersect to form them. The bedding cleavage intersection lineation will lie parallel to the hinge lines of the fold which means these lineations will plot in a cluster close to the fold axes on the stereonet figure 15. Ppt foliation and lineation powerpoint presentation free. Trying to interpret such data plotted as raw orientations scatter plots on a stereonet, without further data treatment is difficult and susceptible to. Linear structures appear as points in the stereonet. Crains petrophysical handbook structural analysis stereonets. How to plot a moment tensor solution on a stereonet youtube how to plot a moment tensor solution on a stereonet. The trace of bedding on an intersecting foliation plane commonly appears as color stripes generally parallel to local fold axes hence it is sometimes called strip ing lineation.
The line of intersection between the plane and the sphere will then represent a circle, and this circle is formally known as a. Plot all the fabric data on the stereonet, and conduct a careful study of the orientation data. Gy403 structural geology lab university of south alabama. Steeply dipping planes will run close to the center of the stereonet and shallow dipping planes will be closer to the outer circle. Here a lineation is measured at the point the strike and dip measurements are taken. The plane z 0 runs through the center of the sphere. Strike of plane, apparent dip direction, apparent dip angle 2 draw straigtht line representing the strike of the plane depict azimuth through center of stereonet. The line of intersection dips about 19 34 degrees in a direction 31 degrees east of north. Sl slip lineation, fa fold axis 4 planes and 2 lineation are recorded above.
Equalarea stereonet i schmidt stereonet the equalarea or schmidt stereonet is a different stereographic projection on which size is preserved, but angles and shape are distortedsee fig. The intersection line between two planes passes throught the points 1,0,2 and 1,2,3 we also know that the point 2,4,5is located on the plane,find the equation of the given plan and the equation of another plane with a tilted by 60 degree to the given plane and has the same intersection line given for the first plane. Cleavage planes can be difficult to measure in the field, but measuring beddingcleavage intersection lineation. A similarly accurate result can be obtained by plotting the bedding orientation data on a stereographic projection. The tail of the lineation arrow is at the point the measurement is taken.
Usually the diameter of the primitive is some convenient length, such as 10 cm. On the stereonet the lineation is where the two great circles intersect. Evaluating magnetic lineations ams in deformed rocks. Lineation return to linear structures can be sedimentary e. Two nonparallel foliations can also produce an i ntersection lineation. Data is entered either by pasting from the clipboard from other applications, or from ascii text files, in a wide range of file formats, and using a range of orientation. How to interpret fold data on a stereonet by dr jacqui houghton. Magnetic lineation in rocks is given by a cluster of the principal axes of maximum susceptibility k max of the anisotropy of magnetic susceptibility ams tensor. Lay a piece of tracing paper over your stereonet, draw in the outer circle and mark and label the four corners. We will practice with a line it could be a fold axis or a mineral lineation or the dip of a bed that has a bearing of 060 and a plunge of 60.
True dip from strike and apparent dip 1 given data. For instance, according to the measurement conventions of structural geology, original bedding, s 0 intersected by a folds axial plane foliation, forms an intersection lineation l. Jan 24, 2011 how to interpret fold data on a stereonet by dr jacqui houghton. Let n 0, 0, 1 be the north pole, and let m be the rest of the sphere. State intersection safety implementation plans fhwa recognized that while a number of states had intersection safety as an emphasis area in their strategic highway safety plans shsp, they lacked an action plan to guide their intersection safety implementation activities on state and local roads. The rake angle is measured from a specific end of the strike line so that end must be recorded with the rake angle ex. We will start with a definition of the intersection of two sets. To plot the great circle, the dip di rection and dip must be known. Folds are completely defined by the attitude of their. Common linears are polepoints of planes, foldaxes, stretchinglineations, intersectionlineation, but also things like crystallographic orientation of mineral grains or magnetic fabric orientation for a more detailed discussion see for example. Elements of the stereonet a the outer perimeter of the stereonet is termed the primitive. In some cases, you will need to read off the trend and plunge of a line from a stereonet. This is a printable 2 degree equal angle wulff stereonet in pdf format. The orientations of lines and planes can be plotted relative to the center of a sphere, called the projection sphere, as shown at the top of fig.
If a plane projects onto the stereonet as a great circle, then a line or lineation on the plane will plot as a point on the same great circle. Notice how the planes have a threedigittwodigit format and the lineation have a twodigitthreedigit format. B by looking for all the elements a and b have in common. The orientation of a plane is represented by imagining the plane to pass through the centre of a sphere fig. Make a tick mark at the planes strike and then rotate your stereonet so that this mark is aligned with north. Contents scoo o t n nvironent 4 introduction to stereonets a stereonet is a lower hemisphere graph on to which a variety of geological data can be plotted. Given two sets a and b, the intersection is the set that contains elements or objects that belong to a and to b at the same time. Structural geology final exam questions 22nd may 2006. Georient plots orientation diagrams equal area, or equal angle stereographic projections, and rose diagrams as shown in the composite image above or this screenshot. For instance, according to the measurement conventions of structural geology, original bedding, s 0 intersected by a folds axial plane foliation, forms an intersection lineation l 01, with an azimuth and. Cleavage planes can be difficult to measure in the field, but measuring the lineations on two different. Background information on the use of stereonets in structural analysis. A line is drawn from that projection point to the lower hemisphere intersection point light green dashed lines.
Axial plane strike, dip hingeline trend, plunge most folds are noncylindrical. Dipmeter calculations with stereonets the stereonet is an old, traditional tool for dipmeter analysis that has become unconventional by the passage of time. Stereographic projection is about representing planar and linear features in a twodimensional diagram. This is part five of a series of videos used on the first year structural geology course at the university of leeds. Explain the following rems with the help of diagrams.
Spherical projections with osxstereonet request pdf. This lesson will explain how to find the intersection of sets. A crenulation lineation is a special type of intersection lineation. Map overlay problem outputsensitive algorithms some attempts map overlay to solve map overlay questions, we need at the least intersection. Structural geology laboratory university of south alabama. In trying to document the character of structural elements it is not uncommon to have hundreds of orientation readings.
Orientations of the planes are not specific to this problem. Preferred alignment of tabular or acicular mineral grains. A users manual for stereonet 9 is available within the lab materials folder at the geol305 sakai site. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext.
To illustrate, we will find the true dip and strike of a plane for which we have measured two apparent dips. Also, planes have the alphabet modifier whereas a lineation doesnt. Not always a true elongation lineation 19 elongated clasts pebbles cobbles breccia clasts etc. In this example a projection point exists one sphere radius directly above the center.
A fateful phone call leads naz to a stranger holding dangerous information. Data is entered either by pasting from the clipboard from other applications, or from ascii text files, in a wide range of file formats, and using a range of orientation conventions. Ppt foliation and lineation powerpoint presentation. It is useful to remember that in areas of cylindrical folding the trend of the hinge line is. Structural geology exercises with glaciotectonic examples part iii james s. The schmidt stereonet is a different projection on which size is preserved, but angles and shape are distorted fig. Each quadrangle on the stereonet is equal in size or area, whereas shape of quadrangles. Stereographic projection an overview sciencedirect topics. This will be a straight line across the center of the stereonet intersecting the outer circle at the strike bearing. Plot the great circle representing the plane of bedding. Stereographic plot showing requirements for a wedge failure hoek and bray, 1981, watts if the intersection of two great circles. The dip line and strike line intersect at the point the measurement is taken.
Six months later, a mysterious phone call results in a tragic loss, a wrongful arrest and the revelation of a longheld secret in the karasu family. Schematic of the intersection lineation l between a planar unconformity and a planar dyke. Course organization introduction line segment intersection plane sweep motivation. Setting up your stereonet stereonet plotting by hand is usually done using a piece of tracing paper over a stereonet from a book. A piece of tracing paper for every stereonet problem. Stereonet analysis of data from arbuckle mountains near. For example the axial trace is the intersection of the axial plane with the map surface. A stereographic projection, or more simply a stereonet, is a powerful method for displaying and manipulating the 3dimensional geometry of lines and planes davis and reynolds 1996.