 One of the characteristics of deltas is that they prograde or advance into the standing body of water through time. The rivers are bringing in sediment and there's enough sediment for the delta to build to build outward. And so that creates a characteristic distribution of facies. So I've defined four facies here. One is a delta plane facies which will include a lot of the meandering river type facies, plus lakes or bays, typical of the very flat top of the delta. Right, where the river meets the standing water I've defined a mouth bar facies which would be characteristic of river dominated deltas. If you have waves that would include beaches and shoreline features and if you have tides that would include some of the tidal flow type features. This part of the delta is the one that's most variable because it has high energy and it's influenced by the various transport processes. Further down into deeper water there's the delta slope facies which would contain things like turbidites, storm deposits, and occasionally some tidal flows can bring sediment out there as well. As you go further into the basin there's less and less influence from the river and that sediment and you go into the pro delta facies which are mostly mudstones with a little bit of sediment from the river coming in at certain times. So if we keep the water level the same what happens through time is that the delta plane extends out and it doesn't extend out into the water itself. It's deposited on something and so basically the mouth bar shoreline facies extend out and the slope facies extend out like this and the pro delta facies just advance further into the shore and in general the whole thing advances towards the basin through time. So if we look at any so overall you have this just shifted environments towards the basin. If we look at any one spot in place this is what we would see in a stratigraphic column. So what we would see through time at any given location for example for measuring a stratigraphic column would be the pro delta facies overlaid by the delta slope facies overlaid by the shoreline mouth bar facies and then at the top the delta plane facies. Thanks for watching.