- [Dr. Jaffri] The purpose of this tutorial is to go over trace fossils, or ichno fossils, and bioturbation. Now, back in the day, when people used to describe core, and they would get into sections that had a lot of bioturbation, they would just completely write those sections off, just put down "bioturbation", but now we know that bioturbation can actually give us a lot of information about environmental deposition, and there's even a proven relationship between the degree and type of bioturbation and reservoir quality. So we don't ignore that stuff anymore. It's very important. So I wanna give you the basics today, going through the core, as to what kind of things we're even looking for, and hopefully we can identify some common trace fossils. Before we do that though, I want you to take a look at this. We've got a coal right there, and you can see these streaks, these black streaks, coming down from the coal. Now, a lot of times, people will confuse bioturbation with root leads, and that's what you've got right here. We've got root traces that are coming in. This was a paleo surface, probably plants were growing there. That's why you have organics, which are not coal, and then their roots were coming down. How do you know something is roots and not bioturbation? It's often fairly crinkly, disorganized, and roots often tend to fork downwards. There are certain trace fossils that do that, but it's extremely rare. So those are roots, but now we are getting into a marine succession right here. You can see some burrowing right there. There's another burrow right there. Now, what we have here is what we call a Glossifungites surface, okay? Basically what happened was, this stuff was semi-consolidated, then it was subaerially exposed. After that, we hit organisms that started burrowing into it after the sand was deposited. So the sand is in-filling these burrows right here. We're gonna talk about that more in the sequence stratigraphy tutorial, but you can see there's a line burrowed right there. That is Paleophycus. Going through this, you will get to see the most common shallow marine fossil, which is this guy, okay? And it's fairly easy to identify because it has this ring around, and the ring has these undulations. So basically what that is, is it's Ophiomorpha, which are basically shrimp. And as the shrimp are burrowing, they take their poop, and they use their poop almost like bricks, and they line their burrows with it to stabilize the burrow. And once you lithify it, it has this niceedging, so you can't mistake Ophiomorpha for anything else. We've got some Ophiomorpha burrows in here. The next thing you will see quite a bit of are these little rings, they look like little doughnuts. Here's a good example of one right there. Here's another little guy. And what those are, it used to be called Terabellina, now it's called Schaubcylindrichnus. Now, I know it's hard for you to write these names down with me just saying them, so in the slides I will have these names for you. So that's another example right there. You can see it's a nice, it looks like a little doughnut. Besides that, you can see this burrow going across. That is Zoophycos. Now, when you're going through these, you are trying to identify as many individual trace fossils as you can. For example, this one happens to be Asterosoma. That's Planolites. There's some large Planolites right there. They're missing that ring. There's no ring around it like you saw in Phycosiphon. So, this section is, it's fairly burrowed. So what do you do with this information? We identified some common trace fossils right there, but what do you do with it? Well what you do is, you come up with Ichnofacies. Just like you have Lithofacies, you have Ichnofacies, and then the Ichnofacies give you information. There's some common Ichnofacies that you should be familiar with. Skolithos, or actually let's start with line-wards, we're going to base-wards. We go from Psilonichnus, Skolithos, Cruziana, and then Zoophycos. And then, in the deeper marine, we have the Nereites Ichnofacies, but let's just focus on the shallow marine for now. Once you have the Ichnofacies, the Ichnofacies are just yet another tool in your interpretation for environmental deposition. For example, Cruziana, which you generally were finding here, those are mainly deposit feeders. So these are organisms that tend to make horizontal burrows. So let's look at a different core. Let's see what else we can find. This stuff is tricky. It's bioturbated, but you hardly see the bioturbation, and because of that, we call it cryptic bioturbation. So what I'm gonna do, is I'm gonna spray it, and hopefully by spraying it, you should be able to see the burrows clearly. Now you can see what looks like, almost like rice grains right there. Those are Macaronichnus. Macaronichnus is what we find in what's called the toe of the beach, which means it's right where the beach is ending, waves are crashing in. The pore spaces between the grains are fairly aerated, and that's where these blood worms are swimming around, and they will create Macaronichnus. There's another burrow right there. So the idea is, when you are going through, you are noting the burrows. You identify what you can. What you cannot identify, you take a picture of, and then you can compare it with some sort of ichnology atlas. There's quite a few of them out there right now. So you could find one that you like and that's what you use. So we're gonna go to a different core. See if you can find some trace fossils in here. And, what you see is how churned up this thing is, and that's the next thing we wanna note. We wanna note... How much of the original sedimentary structure is preserved. Now, let's compare this guy over here where you see it's completely churned up, you can't tell where the original sedimentary fabric was, and then you compare it with this guy where you can see some faint traces of the original sedimentary structure, to this guy, where you actually see most of the sedimentary structure preserved and you can see a few burrows. So this would be a bioturbation index of one. This stuff on top is, you can still see sedimentary structures, but it's fairly bioturbated. That would be like a three. You come down here, there's completely churned up, and you can't really see anything, that'll be like a five. So it goes from, some people use a scale that goes from one to five. Others use one that goes from one to six. But whatever you use, just be consistent. So, you can see some sedimentary structure in here, individual burrow right there. Again, almost a bioturbation index of one. How we use this, is when you are creating your core description and you've got your grain size plotted, you also wanna plot that bioturbation index on there. What that's gonna do, is it's gonna give you some more information. Here, in this case, we've got these little black grains, and those are Chondrites. Again, a very common marine trace fossil. So the general sense is, you should be able to identify some basic, common trace fossils, especially things like these giant Schaubcylindrichnus, which used to be called Terabellina. So, at least the top five to 10 trace fossils you should be familiar with, that Ophiomorpha, things like that, and make sure you don't ignore them. They should definitely be part of your core description.