Fold analysis using Rick Allmendinger's Stereonet 11

[@ryanoughtibridge2676]

Hey mate, can you use the axial plane finder to determine the strike of the axial surface? is this also any information on using this for refolded folds?

[@edwardbeck4182]

Hi, I was just wondering would this technique work for recumbent folds

[@SalihAmarir]

Thank you for this video, and please if you can add a video that shows how we can flip and rotate layers

[@spacecadet9636]

Hi, when plotting the great circle to the bedding poles, it generates many different great circles rather than 1 do you know why

[@Geology_clips]

The surface of limbs of natural folds is always uneven and therefore compass readings show some variation for each limb. This results in some scattering of great circles or poles to planes. Average orientations of the limbs are therefore used to construct representative hinge line orientations and axial surfaces.

[@Merlijntrades]

Can you plot shear senses of lineation measurement, and if so how?

[@amv553]

Hello, just wondering how you got the number 304 for the strike of the actual surface at 14:44?

[@Geology_clips]

The strike of the axial surface must be obtained from field observation or from geological maps. It cannot be determined graphically using the stereonet.

[@nils6097]

​@@Geology_clipsHello, can you please provide some guidance how to do that? Did you maybe refer to it in another video?

[@Geology_clips]

On a geological map you might see the typical lobes of fold closures where layers bend around the hinge and curve into the direction of the opposite limb. A line perpendicular to the folded layer in the hinge, and parallel to the limbs, is the best guess for the strike direction of the axial surface. If you are in the field try and find a view point in which you can see onto the pi-plane of the fold 9view direction parallel to the hinge and the axial surface). Then you can take a compass bearing and obtain a reasonably accurate estimate of the AS strike. In such situations you also can align your compass with the orientation of the AS and get a good estimate of its orientation. If you are lucky and the there is an axial plane cleavage developed, you can measure the AS directly, but take care to do this always in the centre of the fold hinge. @@nils6097

[@nils6097]

@@Geology_clips First of all, many thanks for the quick and comprehensive reply. I finally got what you meant. I hope you have a nice day.

[@phuthegomoloto672]

Hi there, Where or how did you get the strike of the Axial Surface?

[@Geology_clips]

From field observation or from geological maps.

[@karlcarmody9935]

@@Geology_clips What is meant by the strike of the axial surface? I have lots of strike and dip data of the ascending limbs of an anticline, which i'm plotting on stereonet, how do I get the strike of the axial surface?

[@Geology_clips]

@@karlcarmody9935 For the geometric analysis you need data from both limbs . The axial surface ideally can be measured or estimated in the hinge zone. Otherwise fold closures of the fold itself or other folds nearby should be visible on geological maps. The best estimate for the strike of the axial surface one can get in such cases is by connecting the hinges of different layers on the map.

[@Geology_clips]

To my knowledge Stereonet 11 doesn't allow this. What I normally do is exporting the stereonet as a PDF, import that PDF into Adobe Illustrator (or any other graphics software) and add my annotations as needed.

[@ignaciofuentestoro1414]

Which is the company that created this software?

[@Geology_clips]

This is from Rick Allmendinger's software collection : www.rickallmendinger.net/

[@austinwaugh9869]

How is your pi plane 307, 71? 307, 71 will dip in the NE direction.

[@Geology_clips]

All orientations are given as dip azimuth and dip angles (Clar readings).

[@austinwaugh9869]

I understand this. However, even after adding 90 to the great circle strike value on my stereonet then it plotting it as a separate line, it still does not match the best cylindrical fit. Why could this be the case?

[@Nanu-km9vj]

How do you ploy pi-plane on stereonet?

[@Geology_clips]

That's explained at 10 min 30 sec to 12 min in the video.

[@turnupforturnips3807]

Thank you

[@asaimani4796]

i have one doubt sir can you explain