@Filbert,
Filbert wrote:
That's true, there doesn't appear to be any layer of broken down plants and trees though, whihc might turn into some kind of dirt as they break down, this image here:
http://imgur.com/9e3C7hn
Red chalk I think, topped by white chalk. One material stops another starts, no sign of anything in between. This one is on a beach, so maybe not too many trees there although you can see the grass on top. In any case this seems to be the norm, one layer of one type of material, then an instant stop, with no dirt or anything before the next layer of is laid down, which will usually be one type of material as well, like the chalk layers above.
I've been watching people try to explain this to layman like me in you-tube videos, They'll do a demonstration of how layers are made and take a bucket or a bag of one kind of material and pour it out, then take another bag of a different material, pour it out and say: "Over time a new layer appears"
But no one is pouring out these layers in nature. I would of thought there might be a gradual change of material instead of this instant switch we see.
The difficulty in explaining this process is the underline details take a lot of time to explain and how everything relates. So they skip over the details.
Okay lets take your two layer example. Red layer, white layer with nothing between.
The red layer is probably mostly clay. This layer was probably laid down by a good amount of water which changed its course. See here is where I would have to skip the details. Why? Because how does water change its course? It depends on what kind of water, ie. River, lake, ocean inlet, seaside, ect. Each type have slightly different reasons why they change over time.
So red layer was distributing a clay deposit for many years, then the water source changed. Happens a lot with rivers, they tend to "cut" new paths over time.
This new layer of white is caused by the water source tearing into a different rock deposit. When the water returns it sets this new layer down because the material being broken down by the water is different. The clay deposit is no longer supplying material due to water course change.
However; the water course could shift back to the clay deposit. Causing a flip flop effect in the layers, ie. Red, white, red, white, red.
Okay now why no in between material? The rock was not exposed long enough for plants to grow on it until "now" when the layer was obviously pushed up from plate buckling. The grass grew on top is recent, no plant material deeper because it was not exposed long enough to allow it.