Holohan map and stereonet exercises analyzing the geometry of noncylindrical folds. Description, measurement and analysis of glacitectonically. The input consist therefore of the dip direction and dip of planes 1 and 2, and the azimuth and the plunge of lineation 1 and 2 respectively. The orientation is converted automatically to a line with a trend and plunge, but still remains veiwable as a rake. Structuralgeologylabmanual university of south alabama. What is the orientation of the regional fold axis indicated by the beddingcleavage intersection lineation see example in fig. Two lineations are found in that plane, one oriented n90e, the other oriented n30 e. The intersection of the planes of the two joint systems, measured on the stereonet, dips at 45 with a dip direction of 26. An online stereonet application that allows you to create and view all of your geologic stereonet information in 3d.
Geologic map of the grasshopper geochemistry junction 7. Project a slickenline lineation to that plane having a plunge of 43 e. Consider a micarich rock in which layers of mica flakes can be identified as individual fold layers. This is part three of a series of videos used on the first year structural geology course at t. We can now consider how two lines the ones in green plot. Structural geology lines and planes in structural geology definitions terms for lines. 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. Script for the excelbased applet stereogramheijn v2.
Apparent dip the inclination of any line on an inclined plane that is oblique to the planes dip direction. Deformation of the earth fall semester schedule 2008. What is the plunge of the lineation a 67 b 80 c 19 d 23 e. Pdf the mapping of geological structures geological society.
Cleavage planes can be difficult to measure in the field, but measuring the lineations on two different surfaces and plotting them on the stereonet allows cleavage to be defined. Draw a line representing the strike line of the plane. Jun 17, 2002 it is apparent from the stereonet projection that the principal axes of k min parallel the pole to cleavage orientation. Sample stereonet analysis here are the results of the stereonet analysis. Solution for angle of intersection for two planes in dips.
How to plot a lineation on a stereonet by dr jacqui houghton. Problems associated with fold analysis on the stereonet. Where the lower hemisphere intersects the horizontal plane is the outward trace. Insert a check in this box to activate the plotting of the programcomputed bestfit great circle on the stereonet. What is plotted on the stereonet is a projection of where a given line or plane intersects the lower hemisphere surface. Stereonet analysis of data from arbuckle mountains near. Crains petrophysical handbook structural analysis stereonets. 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. As noted above, in areas devoid of f 2 folds, the rake of the l 1 lineation is generally 7090 indicating dominantly dipslip motion for d 1. In this situation, magnetic lineation will track the intersection axes of the planar grains.
Domainal trace lineation example of domainal trace lineation. Pdf stereographic projection basic formulations and matlab. Hydrogeology and water quality at bent creek research station. Structural geology is the study of the threedimensional distribution of rock units with respect to their deformational histories. Intersection of lines, and planes, angles, apparent dip p. Intersection lineations are formed by the intersection of two planar fabrics. Usually the diameter of the primitive is some convenient length, such as 10 cm. Stereonet h n 9, with average lineation nearly vertical green square 1 in figure 3h and p and t axes disposed symmetrically about the lineation pole, suggests dip slip on steeply southeastdipping, northeaststriking shear zones nw side up, whereas stereonet i n. 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.
A fault plane displays two different sets of slip lineation. True dip from strike and apparent dip 1 given data. In some cases, you will need to read off the trend and plunge of a line from a stereonet. Also, planes have the alphabet modifier whereas a lineation doesnt. Figure 1b shows the lineation plotted on the stereonet.
The output consists of the projection of the lineation 1 and 2 and both the pole and the great. A piece of tracing paper for every stereonet problem. Intersection of two planes form a line, its bearing will be defined by the slope of the line connecting points 0, 0 and x, y with y axis assumes as north, as bearing usually measured from north in horizontal plane. Schematic of the intersection lineation l between a planar unconformity and a planar dyke. To activate the plotting of the mean lineation vector, insert a check in this box. How to use a paper stereonet to find the line of intersection between two planes. The interpretation of stretching lineations in multiply.
Two nonparallel foliations can also produce an i ntersection lineation. Rakes the stereonet program supports rakes through the input of a plane and an orientation rake in that plane. Sl slip lineation, fa fold axis 4 planes and 2 lineation are recorded above. Stereonet options at this point, lets examine the stereonet options dialog, which configures the basic stereonet parameters for the contour plot and all other stereonet plots in dips. Lineation return to linear structures can be sedimentary e. The rake angle is measured from a specific end of the strike line so that end must be recorded with the rake angle ex. Nov 18, 2019 generally, a lineation is a term used to describe linear elements in a rock, this can occur in deformed or undeformed rocks fossen 2016. An online stereonet program that allows you to create and view all of your geologic stereonet information in 3d. Sep 01, 2003 thus, analysis of fabric element orientations on the stereonet would not necessarily reveal the presence of folded lineations that are clearly present in the field, but only in a very small area.
The stereographic net stereonet is the device used for. Trend the direction of a line on a horizontal plane. A similarly accurate result can be obtained by plotting the bedding orientation data on a stereographic projection. By clicking links on our site, we may earn affiliate commission, but our editorial remains entirely independent and unbiased. G528 introduction to paleocurrent analysis in sedimentary. Make a tick mark at the planes strike and then rotate your stereonet so that this mark is aligned with north. Schematic crosssection showing differential rotation. Wednesday, february 23, 2011 in this lab, you will be introduced to the acquisition of paleocurrent measurements in.
Stereonet procedures for restoring tilted beds class example 7 intuitive example. Pdf stereographic projection basic formulations and. So, lineation as it is defined is a general term to describe any repeated parallelly alignedlinear elements in a rock. Repeat for every intersection until the all the grid intersections within the stereonet have been counted. If a rock has a high enough density of parallel fold axes a lineation can develop. But there are few, a few special type of lineations which are not penetrative. Setting up your stereonet stereonet plotting by hand is usually done using a piece of tracing paper over a stereonet from a book. Draw the great circle of the plane, and plot the two lineation point projections on.
A thesis submitted to the faculty of the department of. Practicing bedding attitude determination 3 geologic maps, cross sections, and apparent dip p. Plane dip and strike, lineation plunge and trend, structural. What is the plunge of the lineation a 67 b 80 c 19 d 23 e 48. Intersection lineations are measured in relation to the two structures which intersect to form them. Aug 12, 2017 lineation the word lineation is used to describe any linear structure that occurs repetitively in a sample of rock.
The apparent dip is always less than the true dip of the. Expand this to select a symbol to represent it on the plot, and the label. Two pieces of information, a trend and a plunge, are necessary to describe the orientation of a line in space. To plot the great circle, the dip di rection and dip must be known. Visible geology runs in the browser so there is no need to download anything, just click to add lines and double click to add planes. Set up a stereonet put a tack through the centre of one piece of your cardboard to make a hole. Lines plot as points of intersection between line and. Plot the great circle representing the plane of bedding. Glue the stereonet paper to the cardboard so that the center of the net lines up with the hole. What is the attitude of the intersection lineation.
It is useful to remember that in areas of cylindrical folding the trend of the hinge line is. Stereonet australia is part of an international network of publications owned wholly by sound media group australia. The plunge and trend of three of these are 46 s86e, 29 n62e, and 32 s2w. Elements of the stereonet a the outer perimeter of the stereonet is termed the primitive. The one line is formed by the intersection of the ns vertical plane and the red plane of interest, and the other by the ew vertical plane and the red plane of. Structural geology laboratory manual university of.
Remember to count the data points on the other side when part of your counting circle falls outside of the stereonet i. Importing text files with stereonet formatting code. Background information on the use of stereonets in structural analysis. Steeply dipping planes will run close to the center of the stereonet and shallow dipping planes will be closer to the outer circle. Stereonet projection of poles to foliations, fold axes, crenulation axes, and mineral. Evaluating magnetic lineations ams in deformed rocks.
The primary goal of structural geology is to use measurements of presentday rock geometries to uncover information about the history of deformation in the rocks, and ultimately, to understand the stress field that resulted in the observed strain and geometries. Rightclick on the contour plot and select stereonet options, or select stereonet options from the setup menu. This will be a straight line across the center of the stereonet intersecting the outer circle at the strike bearing. Lay a piece of tracing paper over your stereonet, draw in the outer circle and mark and label the four corners. Draw the great circle of the plane, and plot the two lineation point projections on that great circle. And as we have defined foliation, lineation is also something that has to occur homogeneouslyin the rock system and at the same time penetratively. Site pyr8 is the only where a stretching lineation was observed, and here the magnetic lineation parallels the stretching direction and not the beddingcleavage intersection. What is the orientation of the regional fold axis indicated by the bedding cleavage intersection lineation see example in fig. Notice how the planes have a threedigittwodigit format and the lineation have a twodigitthreedigit format. Lineations are geometrical arrangement of component features in the rock fabric element in which one dimension is considerably longer than the other two dimensions, as seen in the diagram below fossen 2016. Projection of point x, y, z as per equation 1, 2 and 3 is the stereographic projection of intersection of two planes.
The intersection of the bedding with the spaced cleavage produces a pronounced intersection lineation that is visible on beddingplane surfaces. 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. Orientations of the planes are not specific to this problem. 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.
948 629 174 1357 9 404 1498 658 371 408 468 1188 1108 50 807 235 762 200 70 1335 737 832 226 1276 249 506 1075 1420 455 1466 1036 138 996 1481 1496 467 70 1336