My Sediments Exactly

Outing the Real Age of the Colorado River: An Interview with Dr. Shannon Dulin, University of Oklahoma

• Medha Chaturvedi • Episode 5

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Summary
The Colorado River, one of the oldest rivers in the world, has been the subject of a joint study by the US Geological Survey and several universities. The study reveals that the river is younger than previously thought, with its grand debut occurring between 4.8 and 4.63 million years ago. The research used paleomagnetics and magnetostratigraphy to analyze sedimentary rocks and map out the river's history. This new understanding of the river's age has implications for the tectonics of the southern US and the management of water resources in the region. In this episode, we speak to Dr. Shannon Dulin from the University of Oklahoma who is a co-author of the study to discuss these findings. 

Keywords
Colorado River, US Geological Survey, joint study, river's age, paleomagnetics, magnetostratigraphy, sedimentary rocks, tectonics, water resources

Takeaways


  • The Colorado River is younger than previously thought, with its grand debut occurring between 4.8 and 4.63 million years ago.
  • The study used paleomagnetics and magnetostratigraphy to analyze sedimentary rocks and map out the river's history.
  • The research has implications for the tectonics of the southern US and the management of water resources in the region.
  • Understanding the history of the Colorado River can help in disaster preparedness and managing water scarcity.

You can find Shannon Dulin's podcast, Don't Panic Geocast Here. 


My Sediments Exactly. Follow us at @SpringerGeo and Springer Environmental Sciences at @SpringerEnviro on X , formerly known as Twitter. We would love to hear from you. If you have questions, comments or would like to be featured on this podcast, please send your feedback to medha.chaturvedi@springernature.com

Medha Chaturvedi (00:00.46)
If you were to write a book about the history of the Colorado River, I bet it'll be a flowing narrative.

Medha Chaturvedi (00:28.174)
to my sediments exactly where we take nothing for granite. I'm your host Medha Chaturvedi and do I have a fluvial and sentimental episode for you today. We are about to paddle down the ebbs and flows of the Colorado River in the USA. The Colorado River is one of the oldest rivers in the world and flows for a whopping 2330 kilometers or for our US listeners 1450 miles.

through seven US states. It's a vital source of water for about 40 million people. This river likes to go with the flow, and perhaps that is the secret of its longevity. Now it turns out the Colorado River has been keeping a secret. You might say it's been a bit of a river riddle. Previous research models suggested that the river started its journey around 5 .3 million years ago.

But hold on to your horseshoe, because this new research is about to change the course of what we know. A joint study by the US Geological Survey and the universities of Oklahoma, New Mexico, Arizona, and Utah have spilled the sediments on what the Colorado River really started flowing from the Colorado Plateau to the Gulf of California. And folks, it's not what you thought.

This study pinpoints the river's grand debut between 4 .8 and 4 .6 three million years ago. Looks like the Colorado River is a bit younger than we thought. Talk about a river -juvenation. I have with me today one of the co -authors of the study, Dr. Shannon Doolin from the University of Oklahoma. She's an assistant professor in the School of Geosciences.

Shannon works extensively on paleomagnetics and magnetostratigraphy to analyze the late Miocene, early Pliocene, Baus formation in the lower Colorado River corridor in Arizona. She's also the co -host of a hugely popular weekly geoscience podcast, Don't Panic Geocast. Now I must admit, I have been following this podcast for years myself, and it was one of the inspirations behind starting this

Medha Chaturvedi (02:51.532)
So I'm frankly a little starstruck. Welcome Shannon and thank you for joining us today. my goodness. 

Shannon Dulin
That was such an impressive introduction to some of my work, man. I'm so excited to be here with you today. 

I'm so excited to have you here. I must confess, Shannon, last year in April, I visited the Grand Canyon for the first time. Now, I'm not saying I'm a mermaid, but when I hiked down the canyon to the Colorado River, I did feel like I had no legs and really felt a strong urge to swim. 

Shannon Dulin
I can 100 % get behind that. That is quite the hike, I will say. What did what did you think of it? Isn't it impressive? 

Medha Chaturvedi
It's absolutely breathtaking. And I mean that literally my breath was taken. I had no breath left by the time I reached the river.

Shannon Dulin
Yeah, it's quite a hike. We're out here doing our field camp right now. So we've been hiking for six weeks and yeah, I'm surprised I have breath left to do this podcast too. 

Medha Chaturvedi
A field camp? What is that about? Tell me more. 

Shannon Dulin
Right. So really all around the world, the culmination of an undergraduate geology degree generally ends in field camp, which is almost always a six week course and it's where you go out to a place or you're camping all around and you wind up doing a lot of hiking and geologic mapping and just learning all the things like putting all the things into practice that you learned as an undergraduate in geology. 

Medha Chaturvedi
That's awesome. Does this field camping also require you to be a good hiker or is it just for everyone? 

Shannon Dulin
Well, in general, it is. And definitely back in the day, I will say it was 100 % focused on being able to prove yourself as a hiker. But honestly now and precipitated by COVID, we actually have online field camp. So the University of Oklahoma plus a few other large universities also offer an online sort of a digital mapping that goes along with that for those who can't get outside for any reason at all, really. And so we offer an alternative just because geology is for everybody now. So. 

Medha Chaturvedi
You know, what would be the greatest alternative in my mind would be a jet pack. If we could just jet pack down to all of these places, that would be amazing. 

Shannon Dulin
It's unbelievable. So we saw a guy on the trail that was riding one of those little mono scooters and just had a single wheel and he was out where we were walking and he was just riding along and we were all very, very jealous. 

Medha Chaturvedi
That is rocking.
 
Shannon Dulin
Indeed. 

Medha Chaturvedi
Anyway, mermaid or not, breathtaking or not, let's get back to the science of it all. So Shannon, before anything else, for the uninitiated like me, could you give us a brief introduction on what exactly paleomagnetics and magnetostratigraphy. And how did you find yourself attracted to these? 

Shannon Dulin
I'm going to up my game here on these. I do have a magnetic personality, as you may have noticed from the podcast. so how it happened was how a lot of these things happen is it was pure serendipity. I started to work in the University of Oklahoma's Paleomagnetics Laboratory as an undergraduate because there's a lot work that has to be done that's not research, it's just actually prepping samples and running samples. And I started that and it wound up turning into a master's and then later my PhD. And so what we're doing is we take rock samples and we take all kinds. We do igneous, but mostly we do sedimentary rocks. My advisor, Dr. Doug Elmore is really one of the founders of paleomagnetics and sedimentary rocks. And we're looking at the tiny little magnetic minerals in there that wind up recording something about what happened to the rock. Sometimes it's when the rock formed, sometimes it's an event that happened after the rock formed. So something like mountain building events or any sort of fluid flow events can change the way those magnets are arranged. And then we can get back out and say, oh, well, this rock had to have formed 90 million years ago because that's what the magnetic mineral alignment tells us. That's just absolutely fascinating.

Medha Chaturvedi (07:29.196)
A day when I can learn something new is a good day. And this seems to be a really, really good day. 

Shannon Dulin
that's fantastic. So it doesn't seem like it is different. But just like you said, paleomagnetics and magnetostratigraphy are kind of two different things. so paleomagnetics looks at all of those events that have happened. But magnetostratigraphy is really something where we want to capture the magnetic orientation of those minerals when the rocks were either made, if you're talking about an igneous rock, so when they were extruded, or if you're talking about a sedimentary rock, when they were deposited. And so, as you know, the Earth's magnetic field flips back and forth over geologic time, and you're essentially just mapping out those flips as you look at this pile of sediment. And hopefully, it's the oldest at the bottom, right, and the youngest at the top, and you can read that those magnetic orientations just like a map and you can say, this map matches to 4 .3 to 5 .2 billion or million years. There you go. 

Medha Chaturvedi
My sentiments are all over the place right now. 

Shannon Dulin
It's kind of a lot. It's a lot to wrap your head around. I feel like I still don't even know a fifth of what is out there to know this magnetostratigraphy but this is certainly something I'm just now getting into. I did more paleomagnetics work for my PhD and my previous research before this Colorado River stuff came along and so magnetostratigraphy is a little bit new for me but obviously the physics is all the same. 

Medha Chaturvedi
That's fantastic. So now coming back to this research related to the Colorado River. Now, I think we all would like to know how your team got interested in this topic of ascertaining the age of Colorado River. I mean, you've really outed it this time. has the Colorado River always been on your radar or was it something which happened by chance? What's the story behind this research? 

Shannon Dulin
So, not at all. It was definitely not on my radar. Just like you, I was just breathtaking the first time I saw the Grand Canyon. It wasn't until I was in college and it was unbelievable. And so it's something I've always thought about and also the headwaters of the Colorado River are just north of our field camp. And so we see this tiny little trickle, like it's in a field with cows everywhere and it's a foot wide. And to just think as soon as it gets down to Arizona, it's made this huge canyon. So just as a geologist, it's a very inspiring thing. I never thought I'd work on it, but as is so frequently happens and is hard to explain, it was serendipitous.

I had a student that wound up getting an internship with the USGS and he worked with Ryan Crowe and Kyle House who are authors on this paper. And it wound up that I also sort of knew them tangentially and we said this would be a great master's thesis. And so the second author in this paper, John Schwinn, was my second master's thesis student. And that's how it came about. It's really interesting that a river which in one place it looks so small and it just moves along and suddenly just widened so much that it just seems like an ocean at some point. So this study suggests that the Colorado rivers integration happened later than previously thought. 

Medha Chaturvedi
Now, can you walk us through how your team uncovered this aspect and how does it impact the communities who lived and also live along the river since it is one of the oldest rivers? 

Shannon Dulin
Right. Exactly. That is exactly right. I came into this research, like said, much later. The USGS and the Arizona Geological Survey have been working on this for a long time. But that's one of the things in geology. It's expensive to get exact dates. It's cheap to get relative dates, right? And so it's easy to say something's older or younger. But now you got to get down to the brass tacks of what are the exact ages. And magnetostratigraphy is one of those things that it's actually not very expensive. And you can get pretty good dates as long as you something else to like hang your map on, right? So you've got these reversals, right? So if Earth's magnetic field today, if it were to flip, that would be called a reversal and you're tracking these reversals. So what we have been doing is looking at these deposits that are not only from the Colorado River, but that have preceded the Colorado River and trying to get those maps of reversals and tried to date them because most of where we work so far is you went to the Grand Canyon, right? And then the Grand Canyon turned south or the Colorado River turned south along the Arizona California border right there. And that turn is where we started to work at these different basins. As the river turned, what it did was it filled up these lakes that were dammed either by like landslides or lava flows. And then as soon as you fill it up, it spills over and fills up the next basin spills over and fills up the next basin. And that leaves behind these sediments. And those are the ones that we're looking at to try to figure out what is the timing of when the Colorado River got there, filled it up, and what did it leave behind? 

Medha Chaturvedi
That sounds like excruciating work. But just on a a side note, I must say for all of those who are on dating websites, you heard it first here, the best dates are on magnetostratigraphy. So just remember that.

Shannon Dulin
Exactly right. No relative dating. 

Medha Chaturvedi
That's perfect. All right. now just coming back again, what kind of methods did you use and how was it working with a team of scientists from so many different institutions? Because I can imagine that having a team of people that you know already well can be a bit difficult at times. So with so many different institutions involved, how was it and what kind of methods did you use?

Shannon Dulin
It was really great. The people on not only this paper that we have together, but the pretty robust research group is just the best group of scientists I've ever worked with. They're so welcoming. They're so knowledgeable. And they just love being outside. A lot of these researchers are like big time river runners. Like they get in the rafts and do all this stuff. And I'm like, no, that's fine. I'll just carry my little drill over here on this side because I'm actually super scared of that. So I just do a lot of the stuff up on the land and they're much more adventurous. It works really well. They have a really good rapport together and to bring other people in, it's really already set out fairly well about like, this is what this group of people is doing. So like, I will bring my students out and they'll be like, this is your, you know, goal in area that we're going to be at. We were actually just out right before I came to field camp. So in May, we went out and looked at some of the basins before the Colorado River gets to the Grand Canyon. And so I brought my students. People were out there to do some mapping, but they were also there to help us gather samples for my current students master's thesis. Same thing looking at

And I'm impressed at how well it works. The sampling itself is just what you said. It's kind of grueling. It's very hot, as you can imagine. So this area, especially when we're down south, we have to be there in the wintertime and it's still 90 degrees. And it actually snowed on us two months ago when we were out there. So it was the complete opposite when we were on the eastern side of the Grand Canyon. And it's hard because it's not hard.

And what I mean by that is the rocks are pretty young, as you said before, right? We're talking about four million year old rocks and they actually crumble fairly easily. And so we literally have to saw them out with non -magnetic tools, saw them out of where they're at. And we wind up with these little cubes and we can take those cubes back to the lab and then figure out the magnetic mineral orientation.

Medha Chaturvedi
All right, so with these new revelations, now, how does this new understanding shift our perspective on the geological history of this area? 

Shannon Dulin
I mean, it lengthens it, honestly. it instead of being an older incision rate here, the Colorado River is probably much younger. And as you saw, because you walked all the way down, right, the bottom of the Grand Canyon is the Vishnu Schist, which is over a billion years almost two billion years old, right? And so it kind of lengthens the history that you can see actually in the Grand Canyon. And it just pushes this date back, which has a lot of implications on the tectonics of the southern part of the U .S. And so while that's not my realm of study, that's for other authors on this study, I'm just here to give some dates. It's important because this is, you know, right along the salt and trough. It's a large right along the San Andreas Rift. So figuring out the history of that tectonic basin is important because obviously there's a lot of people that live there that you indicated before. So knowing the history helps us model what could happen in the future there. And the Colorado River is just one part of that, figuring out those ages of the geologic past. 

Medha Chaturvedi
You're absolutely right. Standing by the end of that hike, I must confess that I don't feel like I'm the youngest person in most situations these days. But over there, I was like, well, I'm not a billion years old, so I am young here now. Exactly. I drove some solace in that. 

Shannon Dulin
Yeah, even after that hike, you didn't look as messed up as that schist does down there. No, no, that's true. 

Medha Chaturvedi
I mean, I did look a bit rocky, but that's just who I am.

Shannon Dulin
I'll polish you right up as soon as you get up there. That's right. And then get some dates on the magnetostratigraphy. That's right. Yeah, if you could grab some rocks and then hike them back out for me next time, that'd be great. 

Medha Chaturvedi 
That's absolutely right. This research has opened up these new avenues for future studies, which also determine, as you mentioned, that the history, and this is just one part of that history, can determine how our future looks as. So what are some of the exciting directions you see this research heading in and how might it help us understand other fluvial systems under changing climatic conditions? 

Shannon Dulin
So I think that this is one piece of what you can do when you're trying to understand these huge fluvial systems, right? So you can do, as you know, doing this sedimentary podcast. There are a lot of pieces to put together.

And doing sedimentary provenance is one thing and you have to kind of add all that together. So you can do these provenance studies on the sediments to figure out where these rivers are coming from. And this is around the world, right? And then because it's expensive, you could get a few absolute age dates by doing stuff like we do down here is we look at different ash flows because these ashes have minerals that we can get exact age dates on and because they're lakes, they capture these ash flows very well. And you can do that. And then to fill in the gaps, like we're also doing in each of these basins, you can do this magnetostratigraphy. It's kind of a really cool recipe that you could take to basically any hole that has water in it and then try to figure out these histories anywhere around the

Medha Chaturvedi
Yeah, this is a very exciting time to follow geology research at this point, I feel, because every new research coming out of different parts of the world is aimed towards solving a real world problem and is one piece of the puzzle, I would say. So now, based on that, I will also ask you one question that I think is very important here is

With these historical dynamics becoming a little bit clearer and our understanding of freshwater systems becoming a little bit clearer, how does this contribute towards managing water resources sustainably given that this is a really big concern in our world at the moment? 

Shannon Dulin
I think that is an excellent question. I'm glad that I work on rocks and not science policy because it almost seems unanswerable sometimes.

I mean, you're exactly right. So if anyone's been following the Colorado River is familiar with it. You know, the last couple of years, there's a huge drought. The manmade lakes. So, yes, there have been geologically made lakes, but there aren't now. These are manmade lakes along the Colorado River. We're going as dry as they've ever been. And then this next year, we had great snowfall this past winter. And it seems like everyone's forgotten about it now. Right. And so it's kind of awful in in that case, but it is good to keep this in the forefront, I think, of everyone's mind. So whether you get really into the Magneto stratigraphy or not, just thinking about what this river has done in the past, what it meant for the people who lived here in the past, right? Because in the desert southwest, there are lots of peoples who have historically relied on the Colorado River. And then currently lots of people that rely on that color. So just keeping it in the forefront and the fact that it's a dynamic system that maybe we need to prepare for. Right. So in some cases things happen that you need to realize this is going to change. Nature is not going to stay the same. This is absolutely going to be different at some point. So you need to pay attention to that. Right.

Medha Chaturvedi
What you're saying then is that this also indicates or gives us some indications towards disaster preparedness, especially related to water scarcity. Is that right? 

Shannon Dulin
I would think so. So like this research doesn't necessarily address that directly. But what it does is make people realize that things change. We sort of get complacent and think, this river has always been here. this lake has always been high. It's always given us water.

But honestly, geologically, it's just a minuscule amount of time. And so we need to know that it's always changing. 

Medha Chaturvedi
Now, I must admit, listening about these significant breakthroughs makes me ever so curious about this topic and how it'll impact our treatment of current sustainability and water -related issues in future. So where can our listeners find more resources to your research and follow your work.

Shannon Dulin
Well, you can find me. I have a faculty website at the University of Oklahoma. You just go to geosciences .ou .edu and I'm right there. I'm working on a lot of other payload magnetic projects too here in Colorado. There are some really enigmatic clastic dikes. So these sandstones that are injected into granite. Christine Siddaway has done a lot of work on that. She's at Colorado College here right nearby. And so we've done a lot of paleomagnetism on that, which is a super fun way to look at the other side of the geologic time scale, because these are maybe a billion years old versus these four million year old sediments in the Colorado River. So that's something. then as always, if you've heard our podcast, Don't Panic Geocast with my co -host, John Lehman, we're very into fieldwork. And so I'm the director of this field camp here for the University of Oklahoma. And so we do a lot field -related research just in terms of field education and getting people not only outside but online. So they also feel like they're getting a good field education, even if it's using products like Google Earth, which are exceptional in order to get everyone looking at geology. 

Medha Chaturvedi
That's so amazing. Thank you, Shannon. It has been such an absolute pleasure speaking to you about your work today.

It's clear that this research is making waves in the geological community and we will continue to dip our toes in further development in the life of the Colorado River. 

Shannon Dulin
thank you so much, Medha. It's been super great and we'll have to have you on our podcast soon too. 

Medha Chaturvedi
I can't wait. 

Shannon Dulin
That sounds wonderful. I can't wait to have you on. Thank you so much, Shannon. 

Medha Chaturvedi
There you have it. The comprehension of the Colorado River's early history may shape future research on river evolution and regional geology, not only in the US, but also in the global context. The significance of understanding the origins of such fluvial systems is in expanding this to the wider understanding of river formation and landscape alteration over time, which is one part of the larger puzzle of what we can learn from history to apply to future proofing our water resources. This conversation doesn't have to end here.

For more latest insights on all things Geo Earth Sciences, follow and subscribe to My Sediments exactly wherever you get your podcasts. This is your host Medha Jaturvedi signing off for now. Stay curious, stay focused, keep your feet dry and your minds open. And until next time, Rock on!