Evidence that the Great Unconformity did not Form Before the Strata above it

herebedragons writes: quote: (From Message 204) The maximum height of these monadnocks in the Shinumo quadrangle he gives as 600 feet. Schuchert,” after visiting an area farther east, refers to hills up to 700 feet, and Wheeler and Kerr “’ describe one north of Grand Canyon Village which rises approximately 800 feet above the base of the Tapeats sandstone. These monadnocks are in the same general area as that photograph. Not flat.

An image of the monadnocks would be helpful.

In Message 205, I showed an image with 4 unconformities. How would any of those unconformities form during continuous sedimentation WITHOUT erosion?

Just to clarify, Faith doesn't believe the Great Unconformity was produced through sedimentation or erosion. She believes that tectonic forces caused it to rotate. Regarding non-angular unconformities, I believe Faith's denies that they are unconformities, denies evidence of erosion, and claims continuous sedimentation.

Faith writes: IT SHOULDN"T BE FLAT ANYWHERE! NOT ANYWHERE! IT'S A LUMPY BUMPY POKY SPIKY IRREGULAR SURFACE. IT SHOULD NOT ERODE FLAT ANYWHERE, LET ALONE AS FLAT AS YOU CAN SEE IT IS IN THE PHOTOS I POSTED.

I think more discussion about what erosion does to a landscape would be worthwhile.

herebedragons writes: It has monadnock structures just like the ones I have been describing in the Great Unconformity.

This is a good example of how erosion, which tends to abrade landscapes flat, can produce a lumpy surface due to differential hardness. In this case what you're calling monadnocks have not been eroded because they're composed of harder material that perhaps goes all the way through or perhaps just caps the top.

Might it be helpful to explain how a landscape came to be underlain by both harder and softer materials?

Faith writes: Sure seems like an argument going on here to me. But now you are nitpicking. "FOLLOW THE TRAIN OF THOUGHT" then. Good grief.

I'm finding your train of thought difficult to follow. Clearly you think that people haven't followed your arguments properly and that the rebuttals therefore aren't relevant, but this just as clearly indicates that your arguments require clarification.

Faith writes: Never mind. I know what you'll say and I don't want to get into that right now.

This is the total content of your post, which wasn't addressed to anyone.

I'd like to hope that all participants will continue to make a big effort in keeping this thread focused and constructive.

Faith writes: I'm trying to follow your argument, but it doesn't make sense. You say that the unconformity is 'flat', even though it isn't. Look at the pictures for a definition of "flat."

Many different images have been presented, so it's not possible to tell which you're referring to. Perhaps you could clarify the point you're trying to make here, using images if necessary.

Admin writes: In this case what you're calling monadnocks have not been eroded because they're composed of harder material that perhaps goes all the way through or perhaps just caps the top.

I think it is important to point out that what he was calling monadnocks have not been eroded away yet because they're composed of harder material that perhaps goes all the way through or perhaps just caps the top.

They are in the process of being eroded away and the evidence to support that is all the rubble at the base of each monolith.

Geology is not speculation or what-ifs but rather conclusions based on verifiable evidence.

edge writes: Several lines of evidence have been shown to you that the Great Unconformity is not flat. Even by your pictorial definition.

I think the full argument has to be repeated at intervals. I'm trying to avoid becoming part of the discussion, but I'll briefly summarize my own understanding here and say that the Great Unconformity is not flat because on a large scale the different layers of the supergroup have different hardnesses and will therefore erode at different rates, and on a small scale that local conditions vary such as having ponds and rivers, or being more arid or more wet, or degree of elevation and exposure.

Faith writes: I can't continue this discussion. This is nonsense. Just TRY to get what I'm saying. Somebody shoot me.

If you've been reading my comments, I've been encouraging everyone to clarify and even repeat their arguments as often as necessary.

Faith writes: YOU DON'T HAVE EVIDENCE EITHER. YOU THINK IT COULD AND THAT'S THAT. HOW DO YOU KNOW EROSION COULD DO THIS?

Maybe this is something the discussion needs to focus on. Jar has repeatedly made the point that erosion wears material from high places and carries it to low places, thereby flattening a landscape. If you don't accept this then I think you need to make that clear so it can be discussed.

THERE ARE LUMPY ROCKS WITH FLAT SURFACES.

An image of "lumpy rocks with flat surfaces" might be a helpful clarification.

Faith writes: If you had bothered to read what I wrote you'd know that I was talking about the impossibility of eroding down to flatness tilted surfaces like the angular strata of an angular unconformity and lumpy surfaces like schist and granite, and specifically said I was NOT talking about naturally FLAT surfaces like the Kaibab which is the upper surface of a limestone layer. I SAID THAT IN SO MANY WORDS. Sheesh.

Though I searched, I couldn't find where you said this in so many words, at least not recently.

I continue to urge everyone to clarify or repeat arguments as often as necessary.

Nobody here reads carefully, nobody thinks.

Please, no accusations aimed at the other side.

After I finish catching up today I'm going to object to all claims in any way similar to, "I already told you." There's far too much of this.

Faith writes: No, there is no evidence of how they got that way, it's all fantasy.

It shouldn't be necessary to remind participants that bald declarations like this are inappropriate and unhelpful.

edge writes: That's Siccar Point. It has both upper and lower strata. What I'm saying is that the lower were not eroded flat before the upper were deposited on it. Well, that's pretty obvious from the picture. The point is that this surface is demonstrably caused by erosion.

Presenting the image again:

What evidence in this image indicates that the boundary traced by the yellow line was caused by erosion?

To prove that's possible you need to find uptilted strata somewhere that have been eroded flat but without anything deposited on it. Why would I need to do that? It's your point, not mine.

Faith would like photographic evidence of an angular unconformity at the surface, i.e., one where there's only sky above the unconformity. If I understand her correctly, that's all that's preventing her acceptance that the Grand Unconformity is an erosional surface.

What evidence in this image indicates that the boundary traced by the yellow line was caused by erosion?

The three best pieces of evidence and the ones we have been relying on mostly are:

--sedimentary clasts of the lower rock series within the upper

--stream channels or karst features cut into the lower series, etc.

--the identical appearance of the unconformity surface to the existing surface, along with the lack of any other known process that would form the unconformity surface.

Faith's scenario fails to explain all of these.

In a more general explanation of unconformities, there are other features such as paleosoils or regolith above the surface and weathering effects below it (I'm pretty sure we have seen evidence of this in the GC). Sometimes there are root systems or other fossil features in the lower sequence (which I may call the footwall from time to time), and things like glacial striations. In some places you might find ejecta from hot springs or geysers.

Faith would like photographic evidence of an angular unconformity at the surface, i.e., one where there's only sky above the unconformity. If I understand her correctly, that's all that's preventing her acceptance that the Grand Unconformity is an erosional surface.

As nearly as I can tell I/we have given her several examples. My most recent being only a couple of posts back (that same picture for the third time, by the way); and actually, the image you include with this post of yours shows a modern surface that would be an unconformity were it buried suddenly by a rise in sea level. Remember, my point in showing the Siccar Point picture is to show that the surfaces are not always 'smooth'. And that location is truly an unconformity.

edge writes: This one is especially interesting to me because it has two generations of wave cut terraces: the large one with the lighthouse on it, and several more recent ones down at the wave line; all indicating uplift of the shoreline at this location near Singley Creek in California.

I am, as I said, gradually reading and responding through the thread. Your last three posts contain precisely what I suggested might be helpful a little earlier this morning, thank you. For this particular image, could you clarify what in the image indicates that the layers are tilted?