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  Stop 7. Reef Facies in the Guadalupe Mountains: a) Fenestrate Pores and Teepees b) Teepee Details c) Pisoids

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Transcript

- [Ali] We are looking at supratidal facies that are on top of the reef and you can see the beds are fairly horizontal. As I start panning my camera towards the left, you see this structure and that right there is what's called a teepee. I want you to look at this picture that shows a modern teepee from the Dead Sea. Basically what's happening is you're in a supratidal environment. You've got evaporite precipatation that form these sheets from evaporite. As they expand, where one sheet meets another, they buckle up and form these teepees. We're going to move a little closer and have a closer look at what this teepee is like. I've got my trekking pole for scale and what I'm going to do is, I'm going to walk you a little bit closer so you can see what the teepee itself is actually made up of. Now these teepees are very useful in the sense that they're really good indicators of a supratidal setting. That is the only setting where they develop. When you do find a teepee, you know that you're in a supratidal environment. The layers we've got buckled over here, if you get closer into them, you can see fenestrate porosity Because you can also see some cements right there and above that, the cavity you see is a dissolved sponge. Because of course we're still on the reef and the reef of course, here, was made by sponges. Teepees, along with pisoids. Pisoids are a little trickier to see in this particular section. But in the next video we're going to show you some pisoids, which tend to occur with teepees in these supratidal environments. We're looking at some pisoids. These are coated grains, but their genesis and their environment deposition is very different from ooids. The first thing is, you can see my trekking pole so you can see these things are gigantic I like ooids that develop in high energy settings such as tidal channels, ebb and flood deltas, etc. These pisoids actually develop often under conditions that are not very high energy and if you look at some of them, you can see that they're not even very well-rounded They've got irregular shapes. These tend to develop in a modern environment under beach rocks often. Not just in marine settings, but in lacustrine settings as well you get pisoids in some lakes in Australia. But, again, they're highly diagnostic of a supratidal environment. You don't get pisoids in subtidal settings. Here in the Permian Basin, these pisoids occur often at the top of cycles and these cycles are showing oferds so just like the example I'm showing you right now, they often form these supratidal caps two tidals, two cycles that may have a subtidal or intertidal component. You can see them repeating and often times these pisoids occur with teepees that you saw in the last video. The other important thing to understand is their context. We are still on top of the reef So this is the subaerially exposed part of the reef further developing. Even if you got into the platform interior and we got into the supratidal belt in the platform interior you would see pisoids there as well. Again, found with teepes. From an allochem perspective, these are mainly abiotic grains. Coater grains, much like ooids, cortoids, oncoids, rodoids. Except they're extremely useful in telling you what the depositional environment is, which happens to be supratidal.