Pennsylvanian Paradox Formation - The Rocks of Utah | Discovery Geology

Buried deeply in the red rock country of Utah lays a slumbering giant. The fractured landscape of desert red rock hides this concealed monster from view. Only the intrepid geologist is aware of its existence. This is the story of the Pennsylvanian Paradox Formation, Utah's most elusive and bizarre layer of rocks. Our story begins about 315 million years ago, during the Pennsylvanian Period, which is the second half of the Carboniferous, when the majority of Utah was submerged under a broad, shallow tropical sea that deepened into the largest ocean of Earth's history, the Panathus Ocean. Utah was located along the western coastline of a small island chain that arose from the rise of a group of mountains called the Ancestral Rocky Mountains, located further to the east in Colorado. This broad, low shallow ocean was home to a wide diversity of Paleozoic life, as Utah was much closer to the equator than it is now, and much of it was below sea level, except for two broad peninsulas that projected westward into Utah, forming this Mediterranean like seaway. Marine deposition resulted in the accumulation and eventual lithification of shales, siltstones, and limestones, typical of marine sedimentation. However, the sedimentation within this Mediterranean like seaway differed in the fact that the surrounding land would occasionally get cut off the seaway from the open ocean. The warm equatorial climate led to the evaporation of trapped warm ocean waters. This evaporation left behind deposits of ocean salts and anhydrite buried within typical marine sediments. It is estimated that the Paradox Formation represents about 30 cycles of evaporation, each cycle representing the Mediterranean like sea being cut off from the open ocean, leaving behind evaporated salt deposits, and then re-flooding by the ocean, which buries the salt and mud and sands under the floodwaters, and then another event of evaporation of the ocean waters, and the cycle repeats about 30 times. Over millions of years, this cycle of flooding and evaporation left an upward thickness of about a mile over 5,000 feet thick layers of salt and anhydrite behind, buried under the deserts of eastern Utah. These deposits formed the Paradox Formation. Now these salts behave strangely in the subsurface. Salt is ductile, rather than your typical brittle rocks that you find in the lithosphere. These salt layers will twist and squish in the subsurface like dough, sometimes moving upward in cracks and fissures, pushing the rocks above apart. This accelerates when there is ground water entering into the salt layers, which then dissolves the salt, especially under intense pressure. This again pushes up these layers that have an abundance of salt in them. These salts form what are called dipores. These are domes or anaclinal folds of buried rock that are being pushed up by this big blob of salt moving upward through the crust. These large bulges form unique geological features, some as thick as 10,000 feet deep, pushing up from the pressure of the overlying rock layers. These dipores are eventually expressed on the surface as rising topography in these folds and domes. Two areas of bulging salt in the subsurface are found along the Colorado River just southwest of Moab. These two bulges are called the Cane Creek Anacline to the north and the Schaefer Dome to the south. Despite not eroding out on the surface, the deep thick layers of salt beneath this region hold vast quantities of potash, potassium rich salts. Potash is mined by flushing the subsurface with injected water, and pumping the slurry or solution to the surface where the brine is evaporated in ponds and processed into potassium rich salts which are used to produce fertilizers. These lakes that are down here, these kind of real bluish lakes, are evaporation ponds that are where they've taken the water that's dissolved the salts and they bring them up to the surface and then they basically put them in these evaporation ponds to evaporate the salts out and then they collect the salts. You can see one of these anaclinal folds from up here near Dead Horse Point and if you look out like above where the evaporation pits you can see that the beds have this gentle sort of fold in them folding up and that's the Cane Creek Anacline that's down there. The old time uranium miners out here would often look for these anaclinal folds to look for uranium deposits in the overlying Chinle Formation. While the Paradox Formation did not push through to the surface of this area, the rock layer just above it did. The fossil rich limestone layer of the late Pennsylvanian Hanukkah Trail Formation can be found along the axis of these underground bulges. We're going to look for exposures along the Colorado River and see if we can find some fossils in this marine shallow ocean. So I'm standing basically on the apex of this anaclinal feature that sits above one of these big salt domes and we are low enough in the stratigraphic column to pick up these Pennsylvanian Hanukkah Trail Formation outcrops along the Colorado River and what's really interesting about this rock is that it is kind of a grayish color and it really stands out from all the surrounding red rocks along the Colorado River. Above this you have the Cutler Group, the Moenkopi, the Chinle, and the Windgate Formations which are all these really bright red colors that are really characteristic of the region around Moab. But the Hanukkah Trail is a limestone and it tends to be a more grayish color than what you see typically around the Moab area so it kind of stands out when you do encounter an outcrop of it. This is going to be a little hard to see this but you can see some crinoid stems in here. So all this kind of white stuff are crinoid stems. All right you can see this like little branch thing here and that right there is a piece of coral of a bryozoan and if you look very closely there are lots of little holes in the surface so that's a little piece of coral. So here's a really nice bryozoan coral. This rock is just super fossiliferous. Brachiopod, crinoid there, all sorts of interesting things. I'm heading to a famous place where the Paradox Formation may have burst upward into the surface from a deep salt diapore forming a spectacular geological feature in Canyonlands National Park. This geological feature is perhaps one of the most contentious geological features in Utah. This is Upheaval Dome. Early geologists thought that this crater was formed either from volcanic activity or a meteorite impact. One of the strongest advocates for Upheaval Dome to have been formed by a meteorite impact was a well-known planetary geologist Gene Shoemaker who advocated for this process when seismic surveys revealed little to no salt beneath the dome. Salt has a unique opaque seismic profile. With this lack of evidence Shoemaker advocated for a violent and sudden meteorite impact in the deserts of Utah. However a number of more recent studies have suggested that salt from the underlying Paradox Formation may have resulted in the structure after all. Salt may have formed into a diapore and as it pushed upward through the underlying Chinle, Wingate, Kayenta, and Navajo Sandstone the salt diapore was pinched off at its base by these hard sandstone layers, forming a blob which slowly eroded as it approached the surface. The evidence for this scenario is in the fracture patterns that you see along the canyon walls, suggesting long term growth of the structure over a long period of time, rather than an instantaneous impact from a meteor impacting into the Earth. So it's a bit like a large pimple on Earth's surface erupting from depth. Gene Shoemaker was part of the team of geologists to map this part of Utah, and he got really excited about this possible meteorite impact in the deserts of Utah, so much so they dedicated his life to studying the geology of meteorite impacts. Sadly in the late 1990s he died while doing field work in Australia, but many folks thought they should have a nice memorial to Gene Shoemaker, and many planetary geologists, the folks at NASA decided to memorialize him by sending his ashes up to the moon on a rocket. So to this date he is the only person to have had their remains sent to another celestial body on the moon. So they sent a rocket to the moon, crashed into the moon, which carried his ashes. So kind of a weird piece of trivia, but this is just a really cool place to to definitely visit and check out. So there's actually a really easy test that someone could do to differentiate whether this is a meteorite impact or a salt dome, and that is to sample some of these sediments in here and look for platinum group elements, which be indicative of extraterrestrial material, and just do a geochemical workup on on these rocks particularly in here. So I know a place that we can go and get an actual sample of the paradox formation from an outcrop that's actually exposed at the surface. It's a little bit of a bumpy and kind of a scary drive, but it's worth it to get some actual samples of this bizarre rock in our hands. So I'm here at one of the few places where the paradox formation actually is exposed at the surface, and this is actually an exceptional exposure. And one of the things that you'll notice about these rocks that make them look so strange is that they don't really have sort of recognizable beds. You'll see that everything is like jumbled. It almost looks a bit volcanic in the way in which the rocks have basically risen through the earth. You can kind of see some beds in there that are all twisted and deformed, just sort of squished. So you can see some beds up in there. You can see some patterns, but you contrast that to the cutler group, which is these red beds up here, and you can see that they're all nicely bedded. You can see the layers of rock, but the paradox base, the paradox formation is just just a jumble of rocks. And so let's go and take a look at it and see if we can get some some samples in our hands. So this rock, you can just see all of this salt. So it's just covered in salt. Just such a jumble of rocks. And you know, you see you see limestone in here in some of these beds. But what's what's kind of amazing about this exposure is just how there's very little bedding. And you can see that there's like these zones in here that are just like powdery salts. A lot of this is migrating out with the groundwater too. So this is a huge chunk of salt right here. I've heard geologists describe it as sort of lithified toothpaste, because it's all like it's all ductilely deformed. And but it's just just actually really incredible to see all of this salt in here. Now, how do we know it's salt? Well, you taste it. Yeah, it's salty. That's for sure. So I think this is a structural geologist, a structural geologist, crazy, almost impossible way to figure out what's going on. These beds are so deformed. It's crazy. It's just crazy. I mean, just look at this. Yeah, I don't know if you could actually tell what the bedding was originally on some of these salt layers. It's really incredible. The very cool outcrop. Wow, it's amazing. It's so cool. So when I was a kid, I remember doing a trip with my family and we stopped and saw some of the paradox formation. And I remember, you know, my dad pulled over and I ran out and was like, Oh, I'm gonna collect some really cool crystals out of that rock. And we looked for a little bit. It was a really hot day like today, so we didn't stay very long. But I came away and said, it's so weird how those rocks are not laid down in like layers like most sedimentary rocks or something strange going on with those rocks. And it wasn't until I went off to college that I learned about salt dipores and salt deformation in the subsurface. And I went, Oh, that's what I saw. And it's just amazing when you connect something as a kid that you see, and you're like, something's weird about those rocks. And then later on, when you actually learn about these rocks, you realize what that strange thing is. And, you know, these are really weird, weird features. They are really important in terms of exploration for oil and gas, particularly in places like the Gulf of Mexico, where oftentimes these salt dipores will lead to traps, stratigraphic traps, for the accumulation of oil. And so many of the oil, big oil reserves are found in salt dipores like these. So it's really special. You get to come to an actual outcrop to actually see what these things look like. Oh, it's hot. My camera started sending out messages that it was getting too hot. So I had to come back in. That's crazy. So yesterday when I was out and about hiking, I ran into a couple from the Netherlands. And I remarked how different this landscape of Utah is to the flat lowlands of the Netherlands. And one of the things that really struck me, I think, during the Pennsylvanian period, when a lot of these rocks were being deposited, this area kind of a bit looked like it was fairly low, marine, the equator. Maybe something that looked a little bit more like so that landscapes change over time. Some driving footage. Pick my nose. Gotta pick my nose. But I'm on camera.