Cape Breton's Magazine

> Issue 62 > Page 31 - C.B.'s Geology: A Talk on the Rocks!

Page 31 - C.B.'s Geology: A Talk on the Rocks!

Published by Ronald Caplan on 1993/1/1 (268 reads)

gonish. Unfortvinately • or perhaps interestingly • there's a younger rock which has intruded into it, and it doesn't ever really come to the shore very well. But you can certainly see it in some of the logging roads in the centre of Cape Breton Highlands. And that marks the boundary between the Bras d'Or ter? rane and some this yoimgest terrane • the Aspy terrane. We've moved into the ages of rocks when fossils are pre? served in them. Though these rocks have all been baked and stewed so much that the fos? sils are all now unrecognizable. Their ages are around about 430 to 370 million years old. And they include some very complex schists and gneisses, in the headwaters of the Aspy Rivers in particular. And also in the Jumping Brook area. A remnant of South America is preserved as the Mira terrane of southeastern Cape Breton.... As those two continental fragments approached each other, the continental rocks are lighter than the ocean-floor rocks, and they can't go down the subduction zone. They're too buoyant. They won't sink down into the mantle of the earth. So what happens is that all the ocean floor gets _ , , , , , . • ...-. pushed down, or sucked Rocl's m Louisbourg were left behind down, the subduction zone * r* XI. A - '' these two large frag- as a souvenir of South America s ments of continents come to- , , '' r?? J. I gether. And it's just like two Visit to Cape Breton l cars meeting head on • at the speed of 10 centimeters a year! And they collide. But the forces are so immense and so powerful that the collision perhaps goes on for 20 million years before everjrthing finally comes to a grinding halt. And by the time this has happened, a huge mountain range has been forced up. And later on, these were intruded by granites. The Margar- ee granite on the west side, and the Black Brook granite coming out at Neil's Harbour on the east side, are two ex? amples of that. But what was happening here was that we had another sliv? er of rocks caught between the vices of two continents mov? ing along. You remember I said earher that the ocean plates were moving down a subduction zone. But those ocean plates also carried on them, like a piggyback rider, frag? ments of continent. One of these continental fragments by this time was probably South America. It's preserved to? day • a remnant of South America is preserved as the Mira terrane of southeastern Cape Breton. Another was North America, carried on a difierent plate. And its remnant is the northwestern Highlands, by Pollett's Cove. We know from the kinds of minerals that are preserved in the central Cape Breton Highlands, west of Cheticamp Lake, that that area was covered by mountains which were at least LADIES' ' & MEN'S MADE-TO-MEASURE SUITS • ALTERATIONS AND REPAIRS • Leather Work a' 737 Grand Lake Road ''' (Across from Mayflower Mall) OPEN MONDAY TO SATURDAY • 9:00 a.m. to 6:00 p.m. TELEPHONE 562-4462 You can make it happen. '''X ''''A?" 'l'> '''HVtfartt****' ' 'v Atlantic Canada Aj;enct de Opportunities promotiun eeunumique Agency du Canada atlantique Enterprise Societe jII' Cape Breton d'expansion Corporation du Cap-Breton There are few careers more rewarding than owning your own business. Both for you - and the economy. That's because 80% of new jobs in Canada are created by small business owners. Most of whom never expected to become entrepreneurs. If you're interested in owning your own business, we have a list of organizations in your area ready to help you. Just call 1-800-565-LIST. Canada
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