Ancient mountain eroded across entire continent, say UA geologists
by Sean McLachlan
UA professors and students have discovered the largest deposit of sediment ever studied by geologists.
The Caledonian mountain range in Greenland and the Appalachians in North America eroded and spread sediment as far away as western Canada and Texas.
The debris from the two ranges, which were once connected, formed into sedimentary rock called shale. A continuous layer of this shale was found across North America.
"It (the research) is important because it shows that once mountains exist, even if they are very far away, they will dominate all the sedimentary detritus on an entire continental region for a very long time," said P. Jonathan Patchett, a UA geosciences professor.
Patchett, along with UA Lunar and Planetary Laboratory research associate James Gleason, and Gerald Ross of the Geological Survey of Canada published the results of their sediment study in the Jan. 29 issue of Science.
Working from earlier data collected by UA geosciences researcher George Gehrels, the team looked at rock layers deposited 450 to 150 million years ago.
They found the sediment from the mountains "spread rapidly" during the Paleozoic period, according to geosciences graduate student Carmela Garzione, who participated in the Canadian fieldwork.
At that time, Europe, Africa, North and South America, which had been separate continents, all moved together to form a single, giant landmass.
"The (Atlantic Ocean) started to close, plates converged, and mountains started to form." Patchett said.
When the continental plates collided, the mountain range was thrust up at the point of impact. The Highlands of Scotland were once part of this range, but were separated when the continents pulled apart 200 million years ago.
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