the where of it

bridging the great unconformity

• Posted by Summer Wood on July 27th, 2010 filed in craft of writing, flora and fauna, geology
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photo by James G. Gehling for the NY Times

Looks kinda like a gang sign, no? A tribal tattoo? Something from The Matrix?

Actually, it’s a fossil from a time we know very little about, in terms of biology.  The Precambrian era was a very long hunk of time — about 4 billion years, to be imprecise — that predated the explosion of life characterizing the Cambrian period, 542 to 490 million years ago.  An article in yesterday’s NY Times by Sean B. Carroll describes recent work by geologists and paleontologists to access fossils prior to that period of intense proliferation.  In places like the Namibian Desert and the evocatively named Mistaken Point on the Avalon Peninsula of Newfoundland, they’ve discovered fossils that provide interesting, if puzzling, clues to the evolution of life from simple single-celled creatures to the more complex animals with bilateral body symmetry that showed up during the Cambrian.

This is news? Rock lays on rock, right?  Shouldn’t they just be able to look lower to find fossils from an older period?  After all, we know life dates as far back as three and a half billion years.

The trouble is,  there’s a lengthy period of the earth’s history — roughly 1.2 billion years — that’s gone AWOL.  Lost and unaccounted-for.  And disappeared with it are the trace evidence of life — the fossils — that might clarify the transition from billions of years of unicellular simplicity to the startling development of structural and functional complexity.

Geologists call this (writers, you will love this) The Great Unconformity.  To me that conjures pictures of a turn-of-the-century magician, a man out of step with his time in a mysterious and possibly lucrative and alluringly shady way, who must perpetually dodge efforts by the more boring conformities to toss him in jail and throw away the key.

No, no.  The Great Unconformity for geologists is a gap in the rock record.  You can actually lay your hand on it.  Go to the outcrop on highway 337 near the Doc Long Picnic Area in the Sandia Mountains east of Albuquerque.  Lay your hand so your thumb points down and you can touch granite 1.4 billion years old with your lower digit; your pinkie will rest on sandstone from the Mississippian Period, roughly a billion years younger.

The significant distinguishing factor?  Precambrian rock almost everywhere is devoid of fossils.  No evidence of life.  While the massive sediments that accrued while this neck of the wood lay under vast inland seas are teeming with fossils of creatures who roamed the murky depths and crawled up onto the shores.

The Great Unconformity.  No-life to rampant life.  Ever remind you of your writing?

Whoa, now.  I know.  Hell of a leap.  But, still:  though the analogy is far from watertight, I think there’s something interesting in thinking about how those sometimes dull and awkward first drafts can morph into writing that’s possessed of a life of its own; something bigger, somehow, than the me what made it.

It feels like that to me, sometimes.  A quickening.  The quicksilver leap from raw material to a thing of beauty and intelligence and for which I can take only some of the credit.

And maybe not so quick, really.  Because the only way I know to get from A to B is through tuned-in exploration, patient excavation, and a really good dose of luck.

Not unlike the paleontologists who have hunted down the mystery fossils in the land lost to time.