Burrowing in the Rock

There’s plenty of reasons to love Newfoundland and Labrador. For Liam, it’s because the province is an ichnological paradise…

When I tell people I’m a palaeontologist, I usually get one of three responses:

  1. Oh, you’re an archaeologist!
  2. Oh, like Ross from Friends!
  3. Oh, you study dinosaurs!

To debunk the first I point out that archaeology and palaeontology are different words. The second I reject on the grounds that I’ve never lived in a New York penthouse with Jennifer Aniston and never owned a pet monkey.

You’re an ichy…ichy…what?

The third misapprehension is a bit fiddlier. All dinosaur experts are palaeontologists, but not all palaeontologists are dinosaur experts. I’m one of the latter: my research looks at life in the oceans, mostly from periods when fearsome lizards weren’t even a twinkle in evolution’s eye.

Strictly speaking, though, I’m not just a palaeontologist. I’m an ichnologist. And if I tell people I’m one of those, the response is much more straightforward:

“You’re a what?”

I’m an ichnologist. It was ichnology that brought me to the Rock. Newfoundland is an ichnological Mecca, and in the summer of 2012 hosted the 3rd International Congress on the topic.

I don’t expect you to know this, so, for the rest of this piece, I will try to explain what ichnology is and why it matters.

As far as anyone knows, the word was coined in 1851, by a Scottish naturalist and baronet, Sir William Jardine. Ichnos is the Greek word for footprint, and Jardine had discovered an amazing array of fossilized footprints in a sandstone quarry on his estate near Lockerbie.
So enraptured by the fossil tracks was Jardine that he described them, analysed them, and painted enormous colour images of them. He then compiled everything into a giant book, and needing a scientific term to encapsulate his work, called it ichnology. The Ichnology of Annandale, or Illustrations of Footmarks Impressed on the New Red Sandstone of Corncockle Muir, to be precise.

Over the subsequent century and a half, ichnology has come to include research on all forms of fossilized tracks, trails and burrows. Ichnologists work at a multitude of scales, from microscopic borings in ancient reefs to giant tunnel networks in Ice Age soils, but they all study the same thing: trace fossils.

As opposed to body fossils, which are the petrified remains of dead organisms, trace fossils preserve structures made by a creature whilst it was alive.

A body can be transported a long way from where the animal originally lived. A burrow or a footprint cannot: it will only be preserved in situ. Trace fossils therefore tell you what living things were doing in a particular place at a particular moment in time. When trying to figure out the behaviour of long-gone critters, they are absolutely vital.

Using the present to get at the past

As most Earth scientists will tell you, though, the present is the key to the past. If you want to understand what happened at a particular moment in geological time, you need to look at equivalent modern-day environments. Nowhere is this truer than in ichnology.

Oxford University geologist William Buckland famously applied this maxim to Sir William Jardine’s fossil footprints. Wondering what kind of creature might have made them, Buckland persuaded some tortoises to walk across a table covered in pie dough. This took a while, but eventually the recalcitrant reptiles did his bidding and produced tracks remarkably similar to the fossils.

I’m not trying to tell you that Buckland thought that the ancient world was made of pie dough. He was simply demonstrating that tortoise-like animals must have walked across soft sediments to produce Jardine’s trackways. He proved that you need to apply a modern, experimental approach to understanding the past.

Here in Newfoundland, under the leadership of another geologist with an Oxford background – Duncan McIlroy – the MUN Ichnology Group tries to follow Buckland’s lead. For various reasons, though, its research doesn’t involve tortoises and pie dough. It features sand and mud and worms and shrimp instead.

These beasties can be found digging up the seabed in vast numbers at the present day, producing huge areas of churned-up, or bioturbated sediment. They and their relatives have been doing this for millions of years: Jurassic rocks, for example, are full of burrow structures very similar to those we see in today’s seas.

This is important: marine sandstones comprise some of the world’s major petroleum reservoirs, including those of offshore Newfoundland & Labrador. Understanding which intervals are bioturbated, where the fossil burrows go, and what they do to the rock properties is very important to the efficient recovery of oil and gas.

To be really useful, then, ichnological information needs to be in 3D, which is why some members of the MUN team spend much of their time destroying rocks.  This is very precise destruction, though: tiny increments of burrowed rock are ground away, the newly revealed surface is photographed, and its permeability measured.

This process is repeated over and over again, until a huge stack of digital images is produced.  By combining the pictures with the permeability data, complete reconstructions can be made, showing exactly what the burrows do to the rock.

The research doesn’t just help petroleum geology, though.  It also tells us a great deal about what the trace-makers were up to. Long-lived groups of burrowing animals can become ecosystem engineers, producing habitat and food sources for other creatures. They’ve probably been doing it for more than 500 million years.

Maybe in a future piece I’ll venture back to that dim and distant past, and explain Newfoundland’s key role in our understanding of the Cambrian Explosion.

In the meantime, though, if you do bump into a palaeontologist, why not turn the tables of understanding?  I’d be interested to know how startled they are if you say, “yes, that sounds very interesting, but do you know anything about ichnology?”

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