July 25: Do We Really Want To Sample This? Well… Maybe Just A Little Bit.

Camp on the Maymecha River

Camp on the Maymecha River

As we raft down the Maymecha through these immense layers of igneous rock, it has been impossible not to marvel at how much is still unknown about the Siberian Traps. Even aside from the dramatic questions surrounding a potential connection between the Siberian Traps and the end-Permian extinction, there are countless other unknowns at an absolutely fundamental level.

The timing of eruption onset, the total duration of the eruption, and the rate of eruption are still not known to the maximum possible level of precision. The structure and functioning of the magmatic plumbing system remain more or less a mystery. The exact reasons that tuffs erupt during certain intervals–also the subject of debate.

Just to the north of our camp tonight, a reddish weathered fringe of dunite forms cliffs at the edge of the Maymecha River. Beyond that, reddish mountains rise against the horizon. This dunite is the outer layer of a huge layered ultramafic intrusion, the Guli Complex. Its history and relationship to the Siberian Traps are still pretty darned hazy.

Even the original cause of the Siberian Traps–why they erupted when and where they did, and why and how the volume of lava was so huge (an estimated 4,000,000 cubic kilometers or more, according to Fedorenko et al., 2000)–is far from well understood.

With every sample we collect, there is the hope that it could lead us towards an answer to one of these questions. But as we sit on the outcrop and look at the rocks and talk about what they might mean, it often seems like we are generating more questions than we could possibly answer. Sometimes the most pressing question we are trying to answer is simple: what the hell is this rock?

Some days we hike a few miles and come across superb, surprising, super exciting outcrop. Like the thirty meters of tuff we found in a cliff just upriver from Kayak. This tuff (in a totally unexpected place, though Ben’s advisor, Lindy Elkins-Tanton, had a hunch there might be something cool in those cliffs) had huge clasts, up to half a meter across, that had been thrown into the air and then incorporated into the tuff by the power of the eruption. And to cap it all off, many of these clasts were coal, an intriguing potential source for volatiles.

Other days (like, for example, today) we hike up a series of ever higher peaks, clambering up precarious slopes of talus and battling through mosquitoey swamps, only to reach some of the most god-awful outcrop you could ever imagine. But if you’d like to try imagining it, think of little tiny bits of rock buried in piles of dirt. Even those little tiny bits of rock, however, could still yield crucial information about the eruption.

That’s the thing–that’s why the past month has been so exciting (aside from rafting down rapids and stuff like that). The questions themselves are just cool, exciting questions. And you can’t help looking at every single rock you see out here–every single junky piece of float and every single layer of tuff–you can’t help looking at them and thinking to yourself: Well, maybe that rock could help us find some of the answers. So we label it and add it to our (ahem) slightly large pile of samples. And then we sit around the campfire and try to plot and plan exactly how we are going to get all our rocks home past Russian customs.


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