What are these basal rip up clasts in North Dakota?

North Dakota’s Stone Story: What Those Rip-Up Clasts Are Really Telling Us

North Dakota. You might picture endless fields, but beneath that prairie lies a wild geological story, etched in stone over millions of years. And trust me, it’s way more interesting than it sounds. One of the coolest clues to this history? Basal rip-up clasts. Sounds like something out of a sci-fi movie, right? But they’re actually rock fragments, and they’re whispering secrets about North Dakota’s past.

So, what are these things? Basically, imagine a riverbank. As the river flows, it erodes bits of mud and clay, right? Those bits get swept downstream and eventually get stuck in a new layer of sediment. Boom – you’ve got rip-up clasts. “Basal” just means they’re hanging out at the bottom of a rock layer, marking a change in the geological weather. Think of it like the foundation of a new chapter in Earth’s storybook.

Now, North Dakota’s Hell Creek Formation is where things get really interesting. This rock layer is like a time capsule from the Late Cretaceous period. Dinosaurs roamed here – the big names, like Tyrannosaurus and Triceratops. But the Hell Creek Formation also has something else: it includes the famous K-Pg boundary. Remember the asteroid that supposedly wiped out the dinosaurs? This boundary marks that moment, roughly 66 million years ago.

We’re talking about the Chicxulub impact, down in Mexico’s Yucatán Peninsula. Scientists found a thin layer of sediment all over the world with a ton of iridium in it – an element rare on Earth but common in asteroids. That’s the smoking gun.

And then there’s the Tanis site, a spot in southwestern North Dakota that’s basically a geological goldmine. This place is wild. Right under that iridium layer, there’s this crazy mix of stuff: marine creatures, freshwater critters, all jumbled together. It’s like a geological Jackson Pollock painting.

Here’s where those rip-up clasts come back into the picture. At Tanis, they’re jagged chunks of the Hell Creek Formation. The theory? When that asteroid hit, it sent seismic waves rippling across the planet. These waves triggered massive surges of water that came crashing inland, tearing up the landscape and dumping everything – including those rip-up clasts – in a chaotic mess. So, those clasts aren’t just rocks; they’re witnesses to one of the most dramatic events in Earth’s history. Imagine holding a piece of evidence from the day the dinosaurs met their doom!

But hey, it’s not just about the dinosaurs. You can find similar rip-up clasts in other rock formations across North Dakota. The Spearfish Formation has them, indicating different environments. The Three Forks-Bakken Unconformity also contains them. Even the Jurassic Swift Formation has its share of rip-up clasts. Each occurrence tells a slightly different story about erosion and deposition in North Dakota’s past.

So, next time you’re driving through North Dakota, remember there’s more than meets the eye. Those seemingly ordinary rocks hold clues to a past filled with ancient seas, giant reptiles, and earth-shattering events. And those basal rip-up clasts? They’re like little time travelers, giving us a glimpse into the raw power of our planet. Pretty cool, huh?