[jysk (OP)]

The west coast of the continent of South America looks like it is smashing into a gigantic telephone pole.

The landmass to the North of the Peruvian/Chilean border is rotating counterclockwise many degrees, and to the South of that same Peruvian/Chilean border, is rotating clockwise.

That point isn't strictly standing still. Bolivia, due east of the Andes at that point is riding up onto something and has had 4.6 Kms of up-lift!

Paleomagnetic data suggest that the Andean range was once a straight line of mountains.






I don't see the "giant telephone pole".

Any ideas as to what could be hanging up the tectonics at this point?

Mike

[jysk (OP)]

I'm really puzzled by this geology. I know there are good geoscience people on this forum.

I'd hate to suggest folks living at the Peruvian/Chilean border are guilty of product testing on animals, but I will if it spurs some discussion.  []



Mike

[JimBob]

Well, I have been gone for some time getting my abdominal vascular plumbing attended to so I have not been posting for several months.

But I am somewhat in a quandry about this perceived rotation. Could you please tell me the source of the paleomag data you refer to. I have not seen it in any of the literature or periodicals I read.

As for the "kink" in the line of the Andies, there are three things right off the top of my head. 1.) geology rarely happens in straight lines; 2.) The Nazca Plate underides all of the Western Coast of South America and 3.) Bolivia is being raised by the Nazca Plate, a much more accurate description than Bolivia overiden, as Bolivia is the passive element.

The only significant geological feature at the place where the northward trend (from the south to the north) is the southern edge of the Amazon Basin aprox. coincident with a line E-W through the inflection point. The basin extends much deeper into the mantel than the crust under Bolivia (I think).

I need to do some reading and will check this out the next time I am at the university library. My health has kept me away but that is changing. Should be able to do it after the holidays.

[jysk (OP)]

Hi Jimbob,

I hope your plumbing is acting right, and in just the one direction. Doesn't sound like you underwent a pleasant procedure.

The paleomagnetic data is new to me too, but it's been often referred too. Myrl Beck Jr. of U of C, Riverside was trying to make sense of it as recently as 2004.

http://www.ingentaconnect.com/content/bsc/gji/2004/00000157/00000003/art00029;jsessionid=edshh5nomnl8.alice

The Nazca Plate is approaching that point of S/America with seemingly uniform forces to the North and South. The deformation of the entire S/American continent is astounding.

As you suggest, a deep root system under the Amazon Basin is a possibility, but I'm skeptical if that root system alone could resist movement so staunchly without actually being anchored down.

I don't subscribe to Bolivia being a passive element. I think that the whole continent must suffer westward movement with origins at the Atlantic Rift Spreading Zone. Having said that, I don't think that any perceived movement of Bolivia complicates of simplifies the model anyway.

Please do check this out the next time your at the university library. You'll see it's not so simple. I'm interested on your take of the problem.

Mike