Friday, May 13, 2011

Angular Unconformities: An Alternative Interpretation Part 2: Charles Lyell Proves My Point

Now I want to go into more detail in the attempt to demonstrate that angular unconformities are created after the whole stack of layers is laid down, which contradicts the current interpretation of angular unconformities as gradually developing and requiring a very long time to form.

Since the Grand Canyon - Grand Staircase area has the advantage of showing pretty much the entire Geologic Column from "Precambrian" to "Quaternary" or "Recent" rock, it makes the best display of undisturbed horizontality of ALL the strata up through the entire stack. The whole area was clearly completely undisturbed until the canyons and cliffs were cut into the strata and the area was raised and tilted and mounded, all probably brought about by the volcanic activity in the area. Even this activity didn't disturb the strata for thousands of miles, it merely slightly tilted and cut into them.

The Great Unconformity at the base of the Grand Canyon I've already explained as most likely caused by the same volcanic force AFTER all the strata were in place. It's an educated conjecture in that case (just as the build-tilt-erode-build interpretation is conjecture), but there is another angular unconformity in the region that I think clearly shows that it had to have been created in that order. Here are some diagrams:

Click to see enlarged. This is an official government drawing showing the whole area from the Grand Canyon through the Grand Staircase.

Below is the north end of the Staircase from this same diagram showing the angular unconformity to the north of the Hurricane Fault. This unconformity was apparently created by the slipping of the fault line. The land dropped about 4000 feet and tilted the strata both against the nearly-vertical fault line and against the layer above marked “V” which remains horizontal.

Perhaps this section fell simultaneously with the raising of the main body of the strata. Probably the volcanic eruption indicated in the magma dike which exits in a lava flow at the very top of the Staircase was the cause of the whole displacement.

Since we see the same stack of strata on both sides of the Hurricane Fault, in the same order, but one side is tilted except for the horizontal Clarion layer “V” and the other is continuous, all parallel, this ought to suggest that the unconformity was created in one event. This should bring into question Hutton’s interpretation of angular unconformities as requiring a great deal of time for tilting and erosion before the laying down of new horizontal strata. In this case the horizontal layer was almost certainly already there as it is continuous with the one to the right above, and the whole structure appears to have been formed in one event.

I've been trying for some time to come up with a good model for how I think this happens -- that is, how lower strata could be folded or tilted beneath higher strata without disturbing the higher strata -- and although I can describe it I can't think of practical examples that demonstrate it.

The example comes to mind of the trick of pulling a tablecloth out from under a full table setting of dishes and cups and so on without disturbing them and that does demonstrate that force can be applied to an object beneath other objects without disturbing them. The conditions required for this to work would be heavier solid upper objects and more flexible lower objects, which is exactly what I have in mind, but of course this example doesn't exactly DO what an angular unconformity does. There must be many other examples but I keep drawing a blank.

I've also imagined an experiment with modeling-clay strata but that's really beyond my means to set up and it would be much too hard to recreate anything like the circumstances of the actual strata on such a small scale. But then I found a description of exactly that sort of experiment having already been done, in Chapter 5 of Elements of Geology by Charles Lyell, friend of Darwin and popularizer of Hutton's theory of a very old earth and the principle of uniformitarianism. He was trying to explain how folded strata form, such as in this sketch on the same page:

Folding by Lateral Movement.—An experiment was made by Sir James Hall, with a view of illustrating the manner in which such strata, assuming them to have been originally horizontal, may have been forced into their present position. A set of layers of clay were placed under a weight, and their opposite ends pressed towards each other with such force as to cause them to approach more nearly together. On the removal of the weight, the layers of clay were found to be curved and folded, so as to bear a miniature resemblance to the strata in the cliffs. Chap 5, p. 76
I've been looking for a way to illustrate the upright tilting of strata but this experiment demonstrated how they are folded or buckled. It's very important for my purposes that he placed the clay layers under a weight before applying lateral pressure. Lyell doesn't explain this but it seems intuitively necessary to do this. What I've been claiming is that the weight of strata above is a necessary resistance to the tilting of the strata beneath in the creation of angular unconformities; that is, the strata above would have to have already been in place before the tilting occurred, as opposed to the accepted theory which puts the tilting first, then erosion, then the laying down of strata above. The heavy and horizontal weight overhead would force the tilting or folding strata to form a horizontal upper surface, probably the result of violent erosion from friction between them and the upper layer as the force was applied.

On the present theory it's hard to see how tilted strata without a weight overhead could be anything but very irregular and jagged. And this is also where I question the idea that erosion at this point would level such a formation. I also question the idea of a hiatus or time gap during which the strata are no longer forming. What could cause that cessation? And if the strata did keep on forming after such a tilting of strata the new sediments would be forced to settle in the crevises between the jagged or folded uprights, they wouldn't just neatly arrange themselves in a new horizontal layer lying flat across the top of them.

Lyell even explains the absence of upper horizontal strata in some such formations this way:

the ... upper portion, being supposed to have been carried away by denudation, or that action of water which will be explained in the next chapter.
He next discusses an experiment which comes even closer to what I've been envisioning:

We may still more easily illustrate the effects which a lateral thrust might produce on flexible strata, by placing several pieces of differently coloured cloths upon a table, and when they are spread out horizontally, cover them with a book. Then apply other books to each end, and force them towards each other. The folding of the cloths (see Fig. 58) will imitate those of the bent strata; the incumbent book being slightly lifted up, and no longer touching the two volumes on which it rested before, because it is supported by the tops of the anticlinal ridges formed by the curved cloths. In like manner there can be no doubt that the squeezed strata, although laterally condensed and more closely packed, are yet elongated and made to rise upward, in a direction perpendicular to the pressure.
I would never have thought of using CLOTH, but it makes the point beautifully. Again a weight is placed above and the "strata" are shown to buckle just as real strata do under the weight with pressure applied from the side.

Lyell has accepted Hutton's view of an old earth and his principle of uniformitarianism, so throughout this book he assumes extremely slow processes for all the formations, but what's interesting is that he pictures a weight over the folding and tilting strata as essential to the explanation, and that contradicts Hutton's idea that the strata were FIRST tilted and THEN the upper strata were laid down over them. In fact that was essential to Hutton's idea of an old earth and now Lyell has shown that it's not necessary at all, apparently without grasping the implication that an old earth is not needed to explain these formations.

As you read on in this chapter of his book you find him showing how upright strata were probably originally folded, giving some good examples, including one of Siccar Point as part of a larger formation that includes such folded strata. He then describes the unconformity at Siccar Point in Hutton's terms: is evident that a period had elapsed between the production of the two sets of strata, and that, during this interval, the older series had been tilted and disturbed. Afterwards the upper series was thrown down in horizontal strata upon it.
The model of the cloth strata between the books shows that this is most likely not the real order of events, that the weight of already-existing upper horizontal strata would have been necessary to the formation of the tilted strata.

I've also been imagining a tilting following a breaking of lower strata, but Lyell brings up the very likely possibility that the lower strata were originally folded and the bent or folded section was lost. He discusses only the case of their being lost through water denudation, but in the examples I have in mind they'd have been sheared off in the process of being forced under a resistant horizontal weight of strata above them. After the shearing what is left is simply tilted strata without evidence of the prior folding. I still think it possible that in some cases there was first a breaking and then a tilting and shearing off without folding. In fact I think that's most likely what happened in the angular unconformity illustrated above at the far north of the Grand Staircase. Maybe Lyell even considers that somewhere. His book is quite a tome but I expect to keep reading it.

So, the explanation for the unconformity at Siccar point is that there was originally a great depth of horizontal strata there just as there was everywhere else around the world after the Flood of Noah. Then tectonic or volcanic forces tilted or folded a block of the LOWER strata, which were sheared off at the top under the weight of higher strata that remained horizontal though they may have been raised by the force. Then it was probably the rush of receding Flood waters that scoured off the layers above those that remain. And the same thing occurred in the formation of the Great Unconformity at the base of the Grand Canyon except that a huge depth of strata remained in place above it, as only the very highest strata, those above the Kaibab layer that continue in the Grand Staircase to the north, were scoured off by the receding Flood waters.

I really think we could put QED to this here. Lyell himself in the very act of supporting Hutton's idea of extremely slow geological formation ignores Hutton's own inciting example in favor of an example that demonstrates that lower strata can be deformed under strata that remain horizontal, which does not require millions of years, but could easily have occurred in the time frame of the Flood of Noah and subsequent tectonic and volcanic pressures afterward.

***Blog Post Powered by Prayer***

This one was definitely powered by prayer more than others I've done as I was struggling to find the best models for what I've been envisioning and the Lord answered prayer for those models by leading me to Lyell's book, the most striking example being the cloth strata, but I credit the Lord for all the other ideas as well. I couldn't think a useful thought without his guidance. Of course, all errors are my own.

1 comment:

PLEASE just register somewhere, there seem to be many options. A Google account is easy. And give SOME kind of pseudonym at least. THANKS!