We have spent two days at the Badlands. Before we arrived, my sister, a geophysicist, told us about an interesting combination of sedimentary layers found within it. It turns out that in one layer there are lots of fossils, and in the one above it, there are almost none. In other words, it documents a massive die-off in species millions of years—the same one, in fact, that took away the dinosaurs.
But I would like to protest. I am in South Dakota, and John Thune is the senator in these parts. A staunch evangelical Christian, he doesn't believe any of this hogwash about sedimentary layers. To him, the paleontological record at the Badlands shows nothing more than the inventiveness of the Evil One, who is always thinking of new ways to tempt us with the folly of evolution. He's a senator, mind you. My sister is merely a geophysicist. What would she know?
The Badlands are, of course, one of the weirdest landscapes you'll ever find. They rise abruptly out of a grass green prairie like an upside down version of the Grand Canyon. Bands of red and gray sandstone alternate in spired hills, intricate and numerous. One day, we saw a mountain goat framed against the sky as he peered off the edge of a high ridge. What's better than that?
I've included my sister's letter in the comments.
3 comments:
my sister wrote...
So I spent a good part of the morning perusing a 65 page report on the geology of the Badlands. Initially, I was completely bored…pages and pages of marine sediments (the underlying Pierre Shale) studied by paleontologists who traced how baculites evolved over time (it's a rod-shaped organism). I can't think of anything more mind-numbing than studying marine sediments (my disdain for marine sediments is documented in my previous post regarding three hellish days in Nevada). Well ok, maybe some of the limestone concretions were slightly interesting.
I was very impatient with the paper, which, while thorough, took 35 pages to get to the good part – where were all the awesome colors coming from? Where are all the good fossils I read about? Finally I got to the Fox Hills Formation. The formation itself isn't all that spectacular, but the story it tells is fantastic. The formation consists of marine sediments, however at one point in the unit, there is a "Disturbed Zone" (DZ). These sediments were deposited after a catastrophic event that obliterated nearly all life on the planet; in geoscience this is referred to as the Cretaceous-Tertiary (K-T) boundary (yes it's the event that killed the dinosaurs).
The evidence for claiming the DZ represents the K-T boundary is compelling. Marine organisms below the DZ were teeming with life, evidenced by prolific bioturbation (worm/critter traces in the beds). Marine sediments above the DZ have little to no bioturbation, indicating a huge change in fauna, yet still marine sediments were being deposited (this post-DZ rock is called the Unnamed marine facies – creative geologists were hard at work naming things in this area). Later deposition in the Fox Hills Formation saw steadily increasing bioturbation as the years went on & a population restored itself, however they were not directly related to any of the critters below the DZ.
Although beautiful, the rest of the rock history isn't that spectacular. Above the DZ, the Fox Hills Formation chronicles the expanding and shrinking of the Western Interior Seaway. Different sediments were deposited in various stages – marine sediments were green, orange could be a meandering stream, blue could be from an inland freshwater lake, then another layer of green could be tidal flats.
About 50 million years ago, the last remnants for the Western Interior Seaway were gone for good and the area became a subtropical forest. The clastic sediments of the White River group are from the Black Hills and other areas; they began to fill in the area and mammals began their reign. These rocks contain fossils of relatives of the animals we are familiar with today – deer, pigs, horses, big cats were all present.
Today the formation is undergoing a process it began about 23 million years ago – erosion. Every drop of rain contributes to the ongoing disintegration of these fascinating rocks. The water and air mix with the minerals in the sands & shales to generate the beautiful palette of rocks you see today.
I remember the first day in a History of Geology class - the very first thing the teacher said was "There will be no debate on the Theory of Evolution in this class. If you want to debate that topic, you're in the wrong room."
It hadn't really occurred to me how easily the class could veer off track with someone claiming the earth was 2000 years old. Upon reflection, I am somewhat bummed he took away that opportunity for some excellent bible-thumping entertainment.
I had that debate with someone at work the other day. She told me there is no way she evolved from monkeys - she was created as is. And it's all plainly in the Bible if I cared to look at it.
I was so stunned to be informed of this I didn't really know what to say.
Post a Comment