Problem 3 The following data represent attitudes of bedding planes you have meas

Question

Problem 3 The following data represent attitudes of bedding planes you have measured in a slate unit 311, 87 NE 310, 90 (vertical) 128, 86 sw- overturned 132, 88 sw- overturned 316, 68* NE 321, 59 NE 315, 48 NE 111, 20 Sw 113, 26 sW 114, 34" sW 84, 12 S 80, 17 S n the field you observed several outcrop-scale folds with an axial planar slaty clcavage, Being a field geologist, you have also measured the attitudes of this cleavage (listed below) 125, 63 Sw 128, 60" Sw 124, 59 Sw 121, 62 SW Plot poles to these planes. Use a different symbol for bedding planes and cleavage planes. Answer the following questions a) What is the orientation of the fold axis? b) Is the cleavage folded? Why or why not? c) What is the average orientation of the fold axial plane? d) Draw a sketch of this fold (in cross-sectional view with directions indicated) illustrating the fold geometry and style.

Explanation / Answer

a) orientation of fold axis is( fold axis is always perpendicular to the cleavage and slickensides and straitions

153°SW or 25° NW

150°SW or 22° NW

149°SW or 21° NW

152°SW or 23° NW

b) slaty cleavage is a pervasive, parallel foliation of fine-grained, platy minerals (mainly chlorite and sericite) in a direction perpendicular to the direction of maximum finite shortening, developed in slate or other homogeneous sedimentary rocck by deformation and low-grade metamorphism.

c) average orientation of fold axis is 22.75° NW which could be easily calculated from general formula of arithmetic mean

Further all these questions can also be solved easily by using concepts of stereonet where we plot 2D figure for every 3D figure, it's a kind of projection plots which reduces field roblems of geology to very extent

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