[at-l] Appalachian Mountains' Geologic History

[camojack at comcast.net]

As it so happens, I'll be there next week...
-El Señor "Camo" 

-------------- Original message -------------- 
From: "David Addleton" <dfaddleton at gmail.com> 

> Looks like if you want to finish hiking ALL the appalachians, you'll have to 
> go down to Mexico!! 
> 
> New theories and evidence: 
> http://us.lrd.yahoo.com/SIG=124i3jufc;_ylc=X3oDMTNrajk1NDh2BFJfYWlkAwRSX2QDaHR0c 
> DovL3d3dy5ldXJla2FsZXJ0Lm9yZwRSX2Rpc3QDTmV3cwRSX2RtbgNldXJla2FsZXJ0Lm9yZwRSX2ZpZ 
> AM0MzMxNTA3MzRiNDJjYzY5YmZhNzdjZWMzYzc2MTc5MwRSX2x0cAMx/**http%3A//www.eurekaler 
> t.org/pub_releases/2006-11/ou-gfn111606.php 
> 
> Geologists find new origins of Appalachian Mountains Study redraws ancient 
> map of continents 
> 
> Athens, Ohio (November 16, 2006) -- Geologists have developed a new theory 
> to explain how and when the Appalachian Mountain range was created. Their 
> research redraws the map of the planet from 420 million years ago. 
> 
> The scientists recently discovered a piece of the Appalachian Mountains in 
> southern Mexico, a location geologists long had assumed was part of the 
> North American Cordillera. The Cordillera is a continuous sequence of 
> mountain ranges that includes the Rocky Mountains. It stretches from Alaska 
> to Mexico and continues into South America. 
> 
> For the past decade, geologists have collected information from Mexico's 
> Acatlán Complex, a rock outcropping the size of Massachusetts. As they 
> uncovered each new piece of data from the complex, evidence contradicting 
> earlier assumptions about the origins of that part of Mexico emerged. 
> 
> "It was a story that had the Appalachians written all over it," said Damian 
> Nance, Ohio University professor of geological sciences and lead author of 
> an article detailing the findings, which was published in the October issue 
> of Geology. "This will change the way geologists look at Mexico." 
> 
> It also changes existing theory regarding the creation of the Appalachians, 
> which has radically altered scientists' understanding of the planet's 
> geography, said Nance. Age data, newly unearthed fossils and chemical 
> analysis of the rocks show that the complex is much younger than previously 
> thought. It records a pivotal part of the Appalachian story not preserved 
> elsewhere. 
> 
> According to the conventional map of 420 million years ago, two main land 
> masses were separated by the Rheic Ocean. In the south sat Gondwana, a 
> supercontinent consisting of South America, Africa, India, Australia and 
> Antarctica. To the north was Laurussia, made up of North America, Greenland, 
> Europe and part of Asia. The old map showed the Acátlan Complex attached to 
> Laurussia. The complex broke off Gondwana about 80 million years earlier, 
> drifted toward North America along with the other land masses, closing an 
> older ocean, known as the Iapetus Ocean, as it did so. The collision created 
> the Appalachian Mountains. 
> 
> The new map looks rather different. 
> 
> Evidence collected by Nance and his colleagues from rocks in the Acatlán 
> Complex shows that its collision with Laurussia actually occurred about 120 
> million years later. The rocks once existed on an ancient ocean floor, but 
> this ocean has proven to be the Rheic, not Iapetus as previously thought. 
> 
> The explanation, Nance and his fellow authors say, is that the Acatlán 
> Complex was originally attached to Gondwana. Gondwana and the complex 
> eventually slammed into North America, closing the Rheic Ocean in the 
> process. This cataclysmic crunch of continental plates formed the goliath 
> land mass known as Pangea, Nance said, and created the Appalachian 
> Mountains. 
> 
> "We believe we have found the missing piece of the Rheic suture where 
> Gondwana and North America converged," said Nance. "All the evidence point 
> to that and, as far as we know, it is the best preserved piece of this 
> puzzle in North America." 
> 
> Now geologists from around the world, funded by the United Nations 
> Educational, Scientific and Cultural Organization (UNESCO), are expanding 
> the search for evidence of the Rheic Ocean in order to unravel its history 
> from initial opening to final closure. 
> 
> "We want to see if the ocean opened and closed everywhere at the same time 
> or at different times like a jaw opening and closing. We want to understand 
> the mechanics of these processes," said Nance. 
> 
> ### 
> 
> The Acatlán Complex study was funded by the National Science Foundation, the 
> Natural Sciences and Engineering Council of Canada, the Spanish Ministry of 
> Education and Science and a Mexican Papiit Grant. 
> 
> Brent V. Miller of Texas A&M University, J. Duncan Keppie of Universidad 
> Nacional Autonoma de Mexico, J. Brendan Murphy of St. Francis Xavier 
> University in Nova Scotia and Jaroslav Dostal of St. Mary's University in 
> Nova Scotia co-authored the paper appearing in Geology. 
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