 Okay, so we're going to cover some example facies and different ways that you can define them. So you want to define your facies based on something that's scientifically interesting in your rock. So one example would be based on grain size. So say I was looking at some sands deposited by a river or sandstones. At the base of the channel where the rental number is highest because the flow is deepest and that's where the flow is fastest, I might have pebbles. So one of my facies might be a pebble, a conglomerate. So conglomerate is the rock made up of particles mostly pebble and it can have sand between the sides of it. As the depth gets lower the rental number decreases and the flow speed also tends to decrease and so you tend to have finer grains sands and so I might have in addition a coarse to medium sandstone. So the way I describe these two, there's a difference in the grain size that would be that would be my facies. Let's say that there's sort of a back eddy at the side of the channel that has a very low flow speed and maybe in that particular case it would have a fine grain sandstone. I describe this in terms of the grain size for the river but I could also do it by sedimentary structure because the sedimentary structure actually changes with the flow speed as well. So it could do grain size and then I could add the sedimentary structures. So the pebble conglomerate at the pebble grain size you can either have upper planar lamination or dune cross stratification or lower planar lamination. A lot of times in rivers that are sort of medium sized rivers you often get the dune cross stratification so I'm going to add with cross stratification. Ripples don't form in pebble size grains so it's implied that it's dune. You could say with dune cross stratification to be more explicit about it. So the coarse to medium sandstone it could either be in the at the flow speed of dunes or ripple cross laminated. So maybe if I was actually doing this the sedimentary structures I would make I might divide this into two. One with dune I'm going to do extract for cross stratification and maybe one with ripple cross lamination. The fine sandstones we talked about those is having a lower flow speed and they don't typically have dune cross stratification. It's usually ripple or upper planar across upper planar lamination so I'm going to say that the flow speeds low so this would be with planar lamination. So we've done sort of two different things with the facies and you could use often it's really nice if you could use both the grain size and the sedimentary structures but if you have say a uniform grain size you might just use the sedimentary structures or if the sedimentary structures are mostly dune and ripple maybe the grain size is more important and you would make that choice based on your scientific question. Then we have the issue of what to call them. How do you name your facies? Often what happens is when a scientist first starts in a field they use a name for them that's very descriptive or is some sort of code. So like I might actually name this one I could name it just like A B C or 1 2 3 that's a little hard for me to remember especially if I have like six or seven different types so I could maybe call this one like P C for pebble conglomerate maybe C E M S S for coarse to medium sandstone fine sandstone that would work if we divided this into two maybe we add another character or indication whether it was dune or cross stratified or ripple cross laminated. So those would be working names when a scientist is making their observations but then often what happens is that we use these facies as a means to interpret the ancient depositional environment that they formed in and in that case sometimes when we do the interpretation we give names that reflect the environment. When we do that sometimes we might say like the facies name would then become the for example the channel base facies or channel bottom and often the coarse to medium sand are on what we call a point bar so we might call that so this would be A 1 or A or P C the point bar facies would be the equivalent of 2 B or the C M S S. So there's this sort of change in the name of the facies a lot of times as a scientist goes from being descriptive about what they see to interpretive about what those groupings of characteristics in the rocks mean. So as we move on to talk about depositional environments we're going to be talking about which facies are typical of those environments and sub environments and giving them names and so this is this is a concept that you can use for a lot of different scientific processes where you're going from observations you're categorizing those observations and you're using the way those categories accumulate to interpret what those observations mean. Thanks for watching.