On the Rocks Again — in which a pair of intrepid palaeontologists head for the hinterland.

Posted: November 7, 2011 - 11:59 , by David Rudkin

Ah, the romance of fieldwork. There’s nothing quite like waiting for the morning sun to rise high enough to illuminate a cold, wet outcrop, so that one can spend the next 8 or 9 hours kneeling in mud and splitting razor-sharp rock slabs. But we have hot coffee in the thermos, dry gloves in the pack, and — hopefully — there are some new fossils to be found!

Heading north across the Grand Rapids Uplands on a fine September morning, with the "road icing" warning flashing on the instrument panel of our 4x4. Conversation during the 100 kilometre post-breakfast journey is dominated by such phrases as, "oh, I'm sure we'll drive out of it" and "well, it can't do this ALL day long".

Yes, it’s autumn on the Grand River Uplands – 500 kilometres north of Winnipeg and smack in the middle of nowhere! For Graham Young (Curator of Geology and Paleontology at The Manitoba Museum) and me, this has become an annual pilgrimage of sorts.  Some years, we make the trek during the summer months and with a larger crew – on those occasions, dust, dehydration, and haematophagous flies are the more usual concerns. Graham has also been here in May, and in 2009 we did a mid-October run … both times pushing the weather envelope with sub-zero temperatures and snow.

What brings us back to this remote part of central Manitoba, time and again, is an intriguing sequence of Upper Ordovician (445 million-year-old) sedimentary rocks. At first (even second, third or fourth) glance, the thinly layered dolostone deposits do not seem to hold great palaeontological promise, but their barren appearance belies an extraordinary fossil content. Graham has a number of excellent posts about this locality and related topics [see his blog at http://ancientshore.com/], so I won’t go into too much detail here. Suffice to say that these amazing fossils are the remains of organisms (animals and simple algal “sea weeds”) with little or no hard shelly components to their anatomy. In many cases, they are directly comparable to the rare fossils we have been uncovering from rocks of the same age near Churchill, nearly 1000 kilometres to the northeast on Hudson Bay [check my previous ROM blogs for more Churchill background]. Together, these two occurrences are revealing exciting and very important new information about life in shallow seas at a crucial time in the history of the biosphere.

In the foreground, tools of the trade: gad pry bar, hand sledge, chisels, and wet, muddy gloves. In the background, Graham concentrates on splitting a small slab.

So, our tasks on this short 3-day foray are to re-collect from a few key layers in our previous excavations and extend the search down to slightly lower levels. Much of the work is mechanical and repetitive, prying recalcitrant rock slabs from carefully measured and demarcated horizons, splitting slabs into thinner sheets (while avoiding self-inflicted chisel wounds), cleaning sticky mud from rock surfaces (and from spattered eyeglasses), and scanning the wet, grimy rocks for frustratingly subtle hints of fossils. All this is interspersed with expletive-deleted comments on the weather and on those parts of the aging body that insist on seizing up or shutting down.

It would be dreary work if it wasn’t for those wonderful, but all too infrequent “eureka!” moments, when one of us (on this trip, mostly Graham) hits paydirt.

One of Graham’s September “eurekas” – a rock split exposing a superb example of Lunataspis aurora, an early horseshoe “crab” – on the right is the positive part, and on the left the negative counterpart. We described and named this species in 2008, based on fossils we found near Churchill and here on the Grand Rapids Uplands, but new specimens are providing additional insights on anatomy and growth. 

After the rain and cloud, our last full day at the site this Fall proves to be ideal, weather-wise: cool, clear, and with enough of a breeze to keep the few surviving black flies at bay. We continue to peel back new slabs from the section, but also spend time carefully re-examining pieces of rock set aside in our previous excavation seasons … on more than one occasion these “spoil heaps” have produced fossils that we missed the first time around. By the time we’re ready to pack up and head south again, the day’s haul includes a couple of small partial eurypterids (“sea scorpions”), several beautiful jellyfish (exceptionally rare in the fossil record elsewhere), and a number of enigmatic fragments that will require careful study in the lab.

Late in the day, Graham scours one of the “spoil heaps” along side our main excavation. Low-angle rays of the setting sun can accentuate the very subtle relief of some fossils, making them just a little easier to spot, but lingering on the chilly outcrop long enough to take advantage of this splendid illumination takes a serious toll on knees and back. The discovery that our vehicle has heated seats makes the long drive back a less daunting prospect!

 

With the last of the field notes recorded, equipment loaded, and samples securely wrapped and stowed, it’s time to make our way carefully along the deteriorating gravel track to the all-but-deserted highway … just a couple of long-haul tractor trailers and the occasional pick-up truck on this lonely stretch tonight. Another hour on the road — it will be dark by the time we reach our temporary home and a hot meal at the “lodge”. About halfway back we pull over on the shoulder. The sun has just dropped behind a skeletal army of burned-out conifers, throwing charred reminders of a 2008 forest fire into sharp relief against the cobalt sky. It’s an eerie, but strangely beautiful sight — well worth delaying our return to for a few more minutes (yes, even a stony-hearted palaeontologist will admit there is more to this part of the world than just fossils).

The setting sun smolders like an unextinguished ember, silhouetting scorched victims of a 2008 blaze that engulfed 29,000 hectares on the Grand Rapids Uplands. Natural fires are powerful agents of regeneration in the boreal biome, and we have been watching the slow re-greening of this charred landscape on our annual treks.

Early next morning we’re on the road again, southbound to Winnipeg and a few days of puzzled head-scratching at The Manitoba Museum. Ah, the romance of lab work…

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