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  Introduction to Carbonate Mounds and the Orogrande Basin

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- [Ali] This video series, from here onwards, covers carbonate mounds. Now, it's very important to know what a carbonate mound is. The definition given on this particular slide is the original definition, but basically a mound is a feature that actually looks like a mound, and the one thing that most mounds have in common is that they are created by microbes, okay, so these are basically bacteria, microscopic organisms that tend to live together in communities, and they can make rods, they can make filaments, but they're essentially bacteria, but you'll often hear about phylloid algal mound. When you hear that, yes, phylloid algae are not microbes, these are actual algae, they used to look like lettuce fronds, but it's not just phylloid algae. The phylloid algae, as they were growing, were being bound together by these microbes. Same thing, people talk about Waulsortian mounds, well, what is a Waulsortian mound? It's essentially a bryozoan mound, but it's not just bryozoans, there's a microbial community associated with the bryozoans. Now, a rock that's essentially composed of microbes is known as a microbilite. It has a very distinct texture to it, and you'll get to see that in this video series. On the screen right now you can see a thin section, and that shows that microbial texture. Some people like to call this clotted micrite, just because it has that clotted texture to it. And then a lot of people are confused about, well, what's micrite? I mean, but there's really no confusion here, there shouldn't be any confusion. Micrite is just carbonate matrix. You split carbonate matrix up into micrite, microspar, and calcium sultite based on what the individual grain sizes are within the matrix, and if they happen to be between one and four microns, you call it micrite, so it's simple enough. Now, these mounds tend to be associated with micrite, and a lot of this is what's called organomicrite, so this is micrite that was bound together by these microbes, and that's common to almost all microbial carbonates. When you're thinking about carbonate mounds, and like well, what's the motivation, why would you even wanna go check these things out? Well, it's because carbonate mounds can be prolific reservoirs and they produce, they host large amounts of hydrocarbons in quite a few basins. The slide you're currently looking at is an overview of the carbonates in the Barents Sea, the Barents Sea is located between Norway and Russia, and lately there's been a lot of interest in the carbonates of the Barents Sea, there have been certain discoveries up there, and the discoveries have all been made from carbonate mounds. So in here, you've got basically three different intervals where you have productive carbonates. The first one are phylloid algal mounds, later on, as climate in that area changed, water temperature decreased, and you move from more of a photozoan, light-dependent to a heterozoan, light-independent community, and then you start getting bryozoan mounds, and then the final episode right before the permi-criassic extinction was with sponge mounds. The Permian Basin makes an excellent analog for the Norwegian Barents Sea because we get all three kinds of carbonate mounds present, and you can actually go up to them and see what facies are producing, or what facies can be productive, and the cool thing about the Norwegian Petroleum Directorate is everything's published on their website in the sense that all the core photos are there, so you can print out your core photos, you can take them up right to the outcrop, and you can compare the textures. So fantastic analog for the Norwegian Barents Sea. Another area that's extremely popular right now, there's a lot of research going on, are the pre-salt carbonates of Brazil. And the pre-salt carbonates of Brazil can be roughly split up into two categories. There's the coquinas and then there's the microbialites. And the Permian Basin, again, happens to be an excellent analog for those microbialites at a seismic scale. Now this is important, it's very important to figure out exactly how the Permian Basin happens to be an analog, because most of the analogs that people are using are from modern lakes in Australia, people are using the Green River formation, which is Eocene in age in Colorado, Wyoming, and Utah, there's modern lakes in Brazil, Lago Alsegada in Brazil that people are using for the Macae and qui-si-ma members, or formations, and the problem with all of those is they're great analogs on a microscopic scale, they're also suitable analogs at a core scale, but they're certainly not analogs at a seismic scale. The largest of these buildups happens to be some very large-size stromatolites from the Green River formation up in Colorado, and even those are just maybe a few meters high, you definitely couldn't resolve them in seismic. So to get around this, these mounds in the Orogrande Basin in New Mexico, they're fantastic analogs at a seismic scale, and that's the best place for it if you really want to understand their seismic stratigraphy. Now the caveat is, all the mounds that you're gonna see during this field trip in the Orogrande Basin, they're all marine, and we know for a fact that the pre-salt carbonates of Brazil are lacustrine. But again, I want you to keep an open mind, and know there are no one to one analogs for the Brazilian stuff, and certainly there are no seismic analogs that have been used for the Brazilian stuff, and if you look in the slide, it shows the Macae and I want you to notice the build phase and then the fill phase right on top of those carbonate mounds, and I want you to compare those with the photo that's taken from the Waco Mountains, and you can see the build and fill pattern really nicely. So we're gonna try to use these as analogs for the Macae of Brazil. Another area where everything you see in this video series is super-applicable, both the first part with the Capitan Reef and the second part focusing on the carbonate mounds is the Pre-Caspian Basin of Kazakhstan. Some of the largest fields like Tengiz, Korolev, Kashagan, Karchaganak, they're all producing from carbonates, and they're all microbial carbonates. The stuff in the Permian Basin and the Orogrande Basin has been used for a while by Mitch Carez, Jerome Cantor, and others as a possible analog. But the cool thing is in this case, the age is very similar of the Permian Basin, and the Orogrande Basin, and the subsurface reservoirs in Kazakhstan. Not only is the age the same, the builders are the same. Archaeolithoporella, tubiphytes are a huge component, so is phylloid algae. So this is, the Permian Basin happens to be an excellent analog for the stuff in the Pre-Caspian Basin as well. This is an overview map, again, for those of you who are not familiar with the location of the Orogrande Basin, Orogrande Basin is specifically in New Mexico, and within New Mexico, we're gonna go visit the Sacramento Mountains, that's where all the outcrops are at that you're gonna see in this video series. The red box highlights the location of the Orogrande Basin with respect to the Delaware and Midland Basins, so technically it's not really the Permian Basin, but it's right next to it. There's the stratigraphic section of the Orogrande Basin, and it shows the arrows are pointing towards formations that do contain carbonate mounds. Now, specifically we will be visiting the Lake Valley and the Holder formation microbialites as part of this video series. This map shows all the typographic features that you should know about. As I mentioned in the previous PowerPoint series, we started from El Paso, Texas, we drove from El Paso towards Carlsbad, driving right along the Guadalupes, and most of our field stops were in the Guads. Then we went behind the Guads and looked at platform interior shoaling upward cycles. What we're gonna do now is, we're gonna go from Carlsbad to Artesia through Cloudcroft, and then descend into Alamogordo. And all our outcrops are around Alamogordo in the Sacramento Mountains. So in this series I'd like to cover as many different kinds of carbonate mounds as we possibly can. We're gonna start with the most famous carbonate mound of all time, which is Muleshoe Mound, and this is what a lot of people like to call Waulsortian. That is because it was discovered in Belgium near the town of the same name, but we're not gonna call them Waulsortian mounds, these are essential bryozoan mounds, and as I mentioned earlier, the bryozoans aren't the only ones living there, there's a microbial community, and then there's crinoids associated with this mound as well. So that's the first type of mound we're visiting. On this slide, which you can see is Teepee Mound, Teepee Mound was constructed by completely different organisms than Mule Shoe Mound that you saw in the previous slide. So Teepee Mound was a phylloid algal mound, but again it's not just phylloid algae, there's microbes living in there as well. It is a photozoan community, they do like to build up towards the photic zone. And phylloid mounds are extremely important, not just for the stuff we've already talked about, like the Norwegian Barents Sea and Kazakhstan, but even within the U.S., the Paradox Basin produces from phylloid algal mounds. If you go up into the Williston Basin, there's phylloid algal mounds in there as well. So definitely important reservoir analog. Another mound type that we're gonna be covering in this virtual geology field trip, there's no specific name for the mound, some people like to call it Leopard Knob, some people like to call it Leopard Rock, it's because of this funky texture that the rock has, and you'll get a better sense of it in the video itself. But these mounds are microbial, again, but this time it's encrusting forams and plumose algae that are constructing these. They're not superlarge but what's interesting about these is that they tend to have a thrombolytic texture, again, somewhat analogous to some of the textures you see in the microbialites off off-shore Brazil. So one of the mounds we're gonna visit on this field trip. This slide focuses on sponge mounds. Now, the sponge mounds are not in Orogrande Basin, these are still in the Permian Basin, Permian in age but very important because again, they provide analogs for the sponge mounds in the Tempelfjorden Group, and more specifically the Roye formation in the Norwegian Barents Sea, and there's no other analogs for it that are this good. And what's really nice again is you can walk up to these, you can see what mound core facies are like versus flying facies, and if you've got core photos from Permian sponge mounds and the subsurface, you could compare them very nicely. So overall we're going to be looking at four different mounds. We've got phylloid algal mounds, we've got bryozoan mounds, we've got leopard rock, and then we've got these sponge mounds. So altogether I think you guys are gonna enjoy this. It's a very wide, diverse suite of carbonate mound types.