I've been saying from the point I entered this thread that the upper and lower segments of the Siccar unconformity look about equally weathered. The appearance of weathering (or erosion or whatever is the cause of the obvious breakdown of the rocks into their splintery form) is the only comparison I've commented on. The point has been from the beginning that I see no evidence of the usual interpretation of angular unconformities, that there is a difference of millions of years between the tilted lower portion and the upper horizontal portion of such formations.
I'm not sure how to explain it any more simply.
As the rocks are weathered, the weathered parts are carried away by mechanical erosion. This exposes more fresh rock to weathering. That way, the rock always looks fresher than one might expect. The exposed surface is being constantly renewed.
If that were the case, I argued, the lower section should be utterly reduced to a small pile of splintery rock at a location like Siccar Point with the constant battering of the elements. MILLIONS of years. I don't think such a huge time span can be encompassed by anybody's mental set, it's beyond comprehension. But sedimentary rock should disintegrate under the conditions at Siccar Point in far far less time.
And they do. The question is, how long has that particular part of the rock been exposed to weathering.
Why do you think that geologists carry hammers? It's to break through the part of a rock that is weathered to see the original rock characteristics.
The upper segment is identified as Devonian, the lower as Silurian, the usual difference in age between these time periods being in the millions. This is all I've been referring to from the beginning. I thought you answered earlier in terms that reduced the difference in age. Now you are answering in terms of the appearance of age. On the appearance of age I argue that the differences couldn't possibly reflect millions of years.
They don't.
You understand that the Silurian rocks were being weathered in the Devonian, right up until they were being covered by the sand.
We can't even tell when the weathering started. That's one of the tricky things about unconformities. They seem like a fairly simple concept, but when you really get into it, there's a lot of complications and implications.
How long does it take? How long has the upper section been there?
The upper section started forming in the Devonian. The lower section was eroded sometime after it was deformed. All we really know is that erosion ended in the Devonian.
Even that section should have been reduced to rubble by now according to the usual time spans proposed by standard geology. That any of the formation is still standing at all is testimony to a much shorter span of time than that.
Not really. Erosion is a process, it starts when the rock is exposed to the elements and it ends when deposition begins anew.
The topic is still pretty confused it seems to me.
Well, frankly, it is confusing to most people. But most people will try to understand the processes acting over time.