Theo: glaciers and earthquakes had nothing to do with the BRB deposit ...
... and I'll be VERY surprised if << The resident geologist at Black Rock says that the oldest dirt is on top and the youngest on the bottom>>, as you say. If he said this, then he and I need to have a chat. IMO, there's NO WAY this basin is inverted, and I'll bet serious money on that with anyone. 'Upside-down' sedimentary deposits that are unlithified are non-existent in the geological record ...
So that's the first thing I disagree with you on.
Secondly, this area was not glaciated in the recent past, nor was it during the Tertiary (to the best of my knowledge) when the dirts were being deposited - so forget the glaciers ...
Thirdly, the BRB is NOT heavily tectonised - so forget about your <jamming to the left and right>> ...
That leaves us with a relatively simple, 2-dimensional, deposit that has NOT subsequently been inverted, tectonised nor structurally altered. You mention a "45 degree angle" - that does not alter my points in any way, since:
- alluvial fans can deposit rocks on this angle
- regardless, I doubt that the bulk of the BRB was deposited on such a slope: lakes = ZERO degrees slope, rivers = 1 to 5 degrees ...
- even if the BRB was subsequently tilted after deposition, the fact that it is at 45 degrees now (WHICH I SERIOUSLY DOUBT) doesn't change the original depositional process (and it's 2D nature) by one iota ...
I disagree with most of the second half of your post also. I never said understanding what's underground is a piece of cake if it's sedimentary - that's taken out of context!! I said that it's easier to understand (and will require less assaying/sampling) than a typical hardrock deposit would be - please re-read my post 22017 ...
I will not make this post any lengthier - IMO, you have made some very strong generalisations without understanding geological facts.
Paul Nicholson |
