Equal Area Equal AngleGRAPHICAL PRESENTATION AND STATISTICAL ORIENTATION OF STRUCTURAL DATA PRESENTED WITHSTEREOGRAPHICPROJECTIONS FOR 3-D ANALYSES. COMMONLY USED PLOTTING ANDCONTOURING TOOLS CAN BE DOWNLOADED FOR VARIOUSOPERATING SYSTEMS FROM THE WEB.Commonly used in structural geology Commonly used in min/crystalEqual Area Equal AngleGRAPHICAL PRESENTATION AND STATISTICAL ORIENTATION OF STRUCTURAL DATA PRESENTED WITHSTEREOGRAPHICPROJECTIONS FOR 3-D ANALYSES. COMMONLY USED PLOTTING ANDCONTOURING TOOLS CAN BE DOWNLOADED FOR VARIOUSOPERATING SYSTEMS FROM THE WEB.Commonly used in structural geology Commonly used in min/crystalROSE DIAGRAM, only 2-d Statistics VganecracksN = 30Class Interval = 5 degreesMaximum Percentage = 16.7Mean Percentage = 5.88 Standard Deviation = 4.11Vector Mean = 353.3Conf. Angle = 31.23R Magnitude = 0.439Rayleigh = 0.0031From 3 dimensions to stereogramFrom great circle to poleEqual area projectionsEqual AreaPLOT PLANE 143/56(data recorded as right-hand-rule)143Great circles andpolesEqual AreaPLOT PLANE 143/56(data recorded as right-hand-rule)143POLEGreat circles andpolesEqual AreaPLOT PLANE 143/56(data recorded as right-hand-rule)143POLEGreat circles andpolesEqual Area90 56Equal AreaPLOT PLANE 143/56(data recorded as right-hand-rule)143POLEGreat circles andpolesPole to best-fit great circle to foliations FoliationsStretching lineationShear planesTYPICAL STRUCTURAL DATA PLOT FROM A LOCALITY/AREA. Crowded plots may be clearer with contouring of the data. Common method, % = n(100)/N (N- total number of points)1% ofareaThere are various forms of contouring, NB! notice what method you choose in the plotting program.Kamb contouring statistical significance of point concentration on equal area stereograms: binominal distribution with mean - = (NA)and standard deviation - ! = NA[(1-A)/NA]1/2or!/NA = [(1-A)/NA]1/2N - number of points, A area of counting circle, if uniform distribution (NA) - expectednumber of points inside counting circle and [N x (1-A)] points outside the circleA is chosen so that if the population has nopreferred orientation, the number of points(NA) expected to fall within the counting circle is3! of the number of points (n) that actually fall within the counting circle under random sampling of the population Equal AreaN = 70 C.I. = 2.0%/1% areaEqual AreaN = 70 C.I. = 2.0%/1% area N = 70 C.I. = 2.0 sigmaScatterPlot: N =70 ;Symbol =1%AreaContour:N =70;Contour Interval = 2.0 %/1% areaKambContour: N =70 ;first line =1 ;last line =70ContourInt.=2.0sigma;CountingArea= 11.4%ExpectedNum.=7.97Signif.Level=3.0sigmaNB! the contouring is differentwith different methods!Poles to bedding S-domain, Kvamshesten basin.Equal AreaN = 70 C.I. = 2.0%/1% areaEqual AreaN = 70 C.I. = 2.0%/1% area N = 70 C.I. = 2.0 sigmaScatterPlot: N =70 ;Symbol =1%AreaContour:N =70;Contour Interval = 2.0 %/1% areaKambContour: N =70 ;first line =1 ;last line =70ContourInt.=2.0sigma;CountingArea= 11.4%ExpectedNum.=7.97Signif.Level=3.0sigmaEqual AreaN = 70 C.I. = 2.0 sigmaNB! the contouring is differentwith different methods!Poles to bedding S-domain, Kvamshesten basin.STEREOGRAM, STRUCTURAL NORDFJORD.A)Eclogite facies pyroxene lineationB)Contoured amphibolite facies foliations(Kamb contour, n=380)C)Amphibolite facies lineationsEqual AreaRotation of data. We often want to findthe orientation of predeformation structures1) Determine the rotations axis2) Make the axis horizontal, (remember that all points mustundergoes the same rotationas the axis along small circles)3) Rotate the desired angle (all pointsfollow the same rotation along small circles)4)Oppositeorder back to present-day Equal Area Equal AreaRotation of data. We often want to findthe orientation of predeformation structures1) Determine the rotations axis2) Make the axis horizontal, (remember that all points mustundergoes the same rotationas the axis along small circles)3) Rotate the desired angle (all pointsfollow the same rotation along small circles)4)Oppositeorder back to present-day Equal Area Equal Area Equal AreaRotation of data. We often want to findthe orientation of predeformation structures1) Determine the rotations axis2) Make the axis horizontal, (remember that all points mustundergoes the same rotationas the axis along small circles)3) Rotate the desired angle (all pointsfollow the same rotation along small circles)4)Oppositeorder back to present-day Equal Area Equal Area Equal AreaRotation of data. We often want to findthe orientation of predeformation structures1) Determine the rotations axis2) Make the axis horizontal, (remember that all points mustundergoes the same rotationas the axis along small circles)3) Rotate the desired angle (all pointsfollow the same rotation along small circles)4)Oppositeorder back to present-day Plunging fold:1) Determine pre-fold sedimentarylineation2) Determine post fold lineationon western limb.Tilt fold axis horizontal(and all other points followsmall-circles)Rotate around the fold axis untilpole to limb P1 is horizontal.All poles rotate along small circlesThe original sedimentary lineation 072/00 must have been horizontal since it was formed on a horizontal bed.The original sedimentary lineation 072/00 or 252/00Rotate P2 back to folded position aroundF and the lineation follows on small circleRotate F back to EW and restore it to originalPlunge, all poles follow on small circles.Restore to original orientation of axis.Lineation on western limb is found 231/09 Plunging fold:1) Determine pre-fold sedimentarylineation2) Determine post fold lineationon western limb.Tilt fold axis horizontal(and all other points followsmall-circles)Rotate around the fold axis untilpole to limb P1 is horizontal.All poles rotate along small circlesThe original sedimentary lineation 072/00 must have been horizontal since it was formed on a horizontal bed.The original sedimentary lineation 072/00 or 252/00Rotate P2 back to folded position aroundF and the lineation follows on small circleRotate F back to EW and restore it to originalPlunge, all poles follow on small circles.Restore to original orientation of axis.Lineation on western limb is found 231/09 252Fold geometries and thestereographic projectionsof the folded surfaceEqual AreaN = 353 C.I. = 2.0 sigmaFOLDED LINEATIONS MAY BE USEFUL HERE TO DETERMINEFOLD MECHANISMSFAULTS AND LINEATIONSSTRESS INVERSION FROMFAULT AND SLICKENSIDE MEASUREMENTSAndersonian faulting, Mohr-Colomb fracture lawOrthorhombicfaults!STRESS AXES LOCATED WITH THE ASSUMPTION OFPERFECT MOHR-COLOMB FRACTURINGSTRESS AXES LOCATED WITH THE ASSUMPTION OFPERFECT MOHR-COLOMB FRACTURINGAngle between fault & !1 is 30Fault contains !2 at 90 to L !1 bisects acute angle between fault 1 and 2Fault 1 and 2 intersect at !2 slip-linear plotSLIP-LINEAR PLOTare particularly usefulfor ananalyses of largefault-slip lineation data sets.Slip-lines points awayfrom !1 towards !3and with low concentration around !2VARIOUS WAYS TO RECORDTHE MEASUREMENTS IN DIFFERENT PROGRAMSFAULTS WITH SLICKENSIDE AND RECORDEDRELATIVE MOVEMENT FROM ONE STATIONSAME DATA AS BEFORE, STRESS-AXES INVERSION,RIGHT HAND SIDE ROTATEDField exercises Tuesday 04/09 Departure from IF w/IF car at 09.00 amStation 1 at Nrsnes(large-scale fault between gneisses and sediments)(ca 2-3 hours)Station 2 a and b at Fornebo(small-scale fractures, veins and faults with lineations)(ca 2-3 hours)Bring food/clothes/notebook/compass/etc.Return to Blindern ca 4 pm.10/09 Report in (presentation of measurements, interpretation and descriptions)