Geologic Mapping C Question Marathon

[Pupitre]

That second question is solvable, and I just solved it

Here's how (Click to Show Hidden Text)

First, note that the bluntness=1. This means that it is a circular fold. Because it is concentric, the layers all have the same thickness. The borehole at the inflection points cuts along the diameter of the circle. Because there are 3 layers on each side of the axial plane, there are 6 layers cut overall. Thus, the thickness of each layer is 1000/6. Now, we need to find the chord formed by the intersection of the surface with the circle. To do this, use the formula for a chord 2*(r^2-d^2)^.5, where r is the radius of the circle and d is the perpendicular distance from the chord to the center. D is 2*1000/6=1000/3, and r is 1000/2=500. Then, to find the distance of the road, we use the formula sec(a)*c, where a is the angle between the line perpendicular to the exposed surface and the road, and c is the chord length. The answer is 1763.66 meters.

Your questions:

... (Click to Show Hidden Text)

1. Klippes and fensters? Low ridges? I'm not sure.
2. Awesome question: If the hinge is N then the slip is NE on the right side and NW on the left side of the axis.

Yep but you didn't explain what a nappe is A nappe is essentially when the hangingwall of a thrust fault moves more than 2 km from its original position. When a nappe moves, sometimes erosion loosens connecting portions in the sheet, creating a hole where a portion kind of falls out of the nappe. That is a klippen. A fenster any hole in a nappe where other rock crops or just nothing exists. For question 2, I was just looking for perpendicular but that's according to my source so I'm curious to hear where you learned that.

[elephantower]

Perpendicular? That sounds realllly suspect--what would that even mean when the layers are clearly not perpendicular to the hinge? The only exception is at the hinge point, but there is also no slip at the hinge-point. Basically, flexural slip is like folding a phone-book--look at the slip of the pages ( it isn't horizontal). To quote wikipedia "flexural slip allows folding by creating layer-parallel slip between the layers of the folded strata". Nowhere except the hinge zone are layers perpendicular to the hinge, thus layer parallel slip is not slip perpendicular to the hinge.
A helpful image:


Bonus Q:

What is a schuppen structure?

[elephantower]

So you seem to like domes and basins:

Eons ago, in a land far, far away, undeformed strata underwent folding in a small area. A few eons later, the whole region underwent folding again (but no faulting has occured in the area). The strata in the small area originally deformed now form dome-and-basin structures. What is the angle between the axial planes of the first set of folds and the second set of folds (outside of the originally deformed region)?

[Pupitre]

Perpendicular? That sounds realllly suspect--what would that even mean when the layers are clearly not perpendicular to the hinge? The only exception is at the hinge point, but there is also no slip at the hinge-point. Basically, flexural slip is like folding a phone-book--look at the slip of the pages ( it isn't horizontal). To quote wikipedia "flexural slip allows folding by creating layer-parallel slip between the layers of the folded strata". Nowhere except the hinge zone are layers perpendicular to the hinge, thus layer parallel slip is not slip perpendicular to the hinge.
A helpful image:


Bonus Q:

What is a schuppen structure?

Hm well that lecture power point I was looking at must have been wrong then. A schuppen structure is the same as an imbricate structure/fan right? It's when a series of branching reverse faults terminate at the same point.

[elephantower]

Yup! Can you link the source about slip? I'd definitely be inclined to trust a university lecture over my rambling...

[elephantower]

Why are slickenside fibers better indicators of fault history than slickenlines?

PS When did you start studying? Because I only started seriously studying around 1.5 months ago...

[Pupitre]

Yup! Can you link the source about slip? I'd definitely be inclined to trust a university lecture over my rambling...

https://www.google.com/url?sa=t&rct=j&q ... 0100,d.cGU

Idk if that will work. Otherwise, search the following and it should be the first thing you see (or the first ppt you see)

introduction to folds (pg 372-413) powerpoint

EDIT: Well I did this trial last year so I knew the bare basics, but seriously studying for maybe two to three weeks. Before that just like idk an hour a day or so.

[elephantower]

Weird: look at the diagrams they have: the arrows are not perpendicular to the hinge! There's something here I don't understand....

[Pupitre]

Weird: look at the diagrams they have: the arrows are not perpendicular to the hinge! There's something here I don't understand....

I have a feeling it was referring to something slightly different or at least from a different vantage point than what we were thinking. I'd be more inclined to believe that over the powerpoint being inherently incorrect.

[elephantower]

I agree...what is the vantage point though?