One of the highlights of the summer for me was an evening hike around a series of small lakes on Ragged Island, near the northern tip of Baffin Island, Nunavut.
The rocky heights of the island were grey and rugged, much like the familiar contours of the Canadian Shield. (You might say I took them for granite.) But as we climbed above the scanty tundra, it became clear the rock in question was anything but granite. In fact, we learned, it was limestone, albeit of a kind I’d never seen before: grey and granular, almost like sandstone; swept smooth in places by wind and water, or broken into boulders that were strewn every which way.
But wait, I wondered, how can it be limestone? Isn’t limestone made of organic life forms? Yet we’re so far north, and we’re so high up, and this rock shows no signs of fossils or indeed of any organic origin. What gives? A fellow hiker assured me that the rock was very old, and the planet had shifted monumentally since its creation – but my question remained.
The answer awaited me the next day on the Rock Table, an ad-hoc display collected by a very dynamic Geology Club that formed early on in the trip.
One of those club members, passenger Mark Sleep was a former professor of geology whose passion for his subject was infectious. Mark wrote an amazing letter to explain the mysterious limestone of Ragged Island, and placed it on the Rock Table for all to see.
It says, in part:
This is a sample of one of the oldest limestones IN THE WORLD… There were NO CORALS at this time to produce limestones. There were no CEPHALOPODS (squids, ammonites, nautiloids, etc.) There were NO LAMELLIBRANCS (BI-VALVES) (mussels, razor shells, etc.) There were NO GASTROPODS (coiled shell creatures like snails.) There were no COCCOLITHINA (microscopic creatures that secreted the trillions of exoskeletons that form chalk.)
So where did the waters of this PRE-CAMBRIAN limestone get the carbonates to precipitate out as this sample? The answer is probably the first EVER organisms on Earth — the blue/green algae that go back to about 3,200,000,000 years ago! (give or take a half an hour!!!)
This is a sample of one of the oldest limestones IN THE WORLD! WOW!
I’ll never look at rocks the same way again. In a very tangible way, in the Arctic I came to appreciate the deeper meaning behind the work of the passionate geologist. Rocks may not be living things, but these rocks contain a record of the origins of life itself. WOW is right!