that's silly! Do you get flat material from rock tumblers?!
Not as far as I know, so how do you get flat rocks in the river, if tumbling is the process that supposedly produced the roundish river rock? Walking the pebble beds, and seeing lots of flat rocks, my first thought was that the rocks don't tumble, but lay on the river bed with water/sand flowing over the top, gradually flattening them. But they are flat on both sides, what are the odds of that? Flat on one side, roundish on the other maybe.
Anyway, further investigation throws that idea out the window, though you might find this idea even sillier! And as far as I am aware, it would indeed be a New Insight.
The flat rocks in the pebble beds have the edges worn just enough that you can see they consist of very thin layers, not at all the composition of the roundish pebbles, so different sources it would seem.
However, in some narrow channels in the bedrock upriver there are rocks of various size, shape and colour wedged in the crack, so tight that they can not be moved at all or pulled out. This is one example:
https://picasaweb.google.com/1133457513 ... 5907406514
Just a random example of rocks and coarse sand getting wedged in there, you'd say, and maybe so.
I'm not going to try and dig out those pebbles incase I need that location one day for independent analysis.
Yesterday I found another very similar situation, but had my hammer and chisel along with me, and as I had suspected, one pebble was not complete, the bottom is joined to the bedrock.
In this enlargement you see the gray pebble that seems like it is joined with another almost pebble, the separation is not complete.
I hammered the top off, and there is no bottom, rounded portion, I am down to bedrock.
I think it safe to say now that all the pebbles, regardless of shape, composition, colour, are formed, probably in an instant, by electrical and resonant forces in these locations, and that they were flung far and wide and came down even at much higher elevations in a rain of rocks. There has been very little or even no modification of these pebbles by tumbling or water and sand erosion.
I have been gobsmacked the last few days by what I have seen in the Sooke River valley, and would challenge any geologist to explain the forces involved in the creation of this area by accepted geological processes. You really have to experience it to appreciate it, it is absolutely otherworldly in places.