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  #1  
Old 07-03-2004, 06:55 PM
Reeder Reeder is offline
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Geologists..the oldest mountain range in the US.

The Uwharries? The Arbuckles? What is the oldest range in the US?
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  #2  
Old 07-03-2004, 08:06 PM
Ringo Ringo is offline
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The Appalachians might be a good candidate. They date from possibly the late Proterozoic (700+ MMYA), and certainly were underway by the Ordovician Taconic Orogeny (435-485 MMYA) and have not yet become cratonic flatlands yet.

I don't know if that's the answer or not, and I'm not up to research tonight. They are certainly older than the products of the Laramide Orogeny (Rockies, Sierra Madres, etc.).
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  #3  
Old 07-03-2004, 08:08 PM
MsRobyn MsRobyn is offline
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Quote:
Originally Posted by Ringo
The Appalachians might be a good candidate. They date from possibly the late Proterozoic (700+ MMYA), and certainly were underway by the Ordovician Taconic Orogeny (435-485 MMYA) and have not yet become cratonic flatlands yet.

I don't know if that's the answer or not, and I'm not up to research tonight. They are certainly older than the products of the Laramide Orogeny (Rockies, Sierra Madres, etc.).
I love it when you talk Orogeny. :swoon:

Robin
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  #4  
Old 07-03-2004, 08:13 PM
Squink Squink is offline
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Youngsters. The Penokean mountains of Minnesota, Wisconsin and Michigan date back to ~1.8 billion ybp.
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Old 07-03-2004, 08:21 PM
David Simmons David Simmons is offline
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Quote:
Originally Posted by Ringo
The Appalachians might be a good candidate. They date from possibly the late Proterozoic (700+ MMYA), and certainly were underway by the Ordovician Taconic Orogeny (435-485 MMYA) and have not yet become cratonic flatlands yet.

I don't know if that's the answer or not, and I'm not up to research tonight. They are certainly older than the products of the Laramide Orogeny (Rockies, Sierra Madres, etc.).
[hijack] I actually saw what looked like the spreading of the Atlantic ocean floor pushing back the North American continent one time. I was on a flight from LA to DC and we descended over the mountains of VA/WVA (the Blue Ridge?) in the evening when there were long shadows. The primary structure of the mountains were three parallel ridges that looked very much like a throw rug that has been pushed from one edge.[/hijack]
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  #6  
Old 07-03-2004, 08:22 PM
Polycarp Polycarp is offline
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"Oldest mountains" is one of those terms that seems simple but is not. If I wrote a letter yesterday on a piece of papyrus recovered from an ancient tomb, how old is that letter?

There's three possible ways to answer this question:
1. What mountains are composed of the oldest rocks?
2. What still-extant mountains are the product of the oldest orogeny?
3. What still-extant mountains were upthrust the longest time ago?

2 and 3 sound synonymous -- but remember that orogenies and continued upthrust in their aftermath may continue for millions of years, so not all mountains that are part of the Laramide Revolution will be of the same age -- some may be significantly younger than others.

Having said that, I don't have a concrete answer to any of the three questions -- but at least I've distinguished between them. Squink's Penokeans probably are the right answer to question #1 -- but they may be quite a bit younger, as mountains, than ranges with much younger rocks.

I recall reading that the Laurentian Mountains of Quebec date back to the early Paleozoic (Silurian, IIRC) in terms of orogeny creating them, though I doubt any single mountain now present in the range was there to challenge the dinosaurs to climb it.
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Old 07-03-2004, 08:37 PM
Squink Squink is offline
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Polycarp, I think the Penokeans are also the right answers to your questions 2 and 3. The meagre sources I was able to find give ~1.8 billion ybp as the date of their orogeny.
It's not clear to me, but rib mountain Wisconsin may be a remnant.
The Laurentions only formed about a billion years ago.
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  #8  
Old 07-03-2004, 08:49 PM
Reeder Reeder is offline
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The Uwharries are part of the Appalachians. I live right in among them.
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  #9  
Old 07-03-2004, 08:52 PM
Abbie Carmichael Abbie Carmichael is offline
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Last year in Geology my professor said it was the Appalachians.


At least we're ranked first in SOMETHING ...
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  #10  
Old 07-03-2004, 11:51 PM
AHunter3 AHunter3 is offline
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I'm pretty sure the Ouachita range, which runs east-west through the US (and from which Wichita KS got its name) is the bony stub of a range that in its youth was as formidable as the Rockies, and it's much much older than the Appalachians (which in turn are much much older than the Rocky Mountains).
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  #11  
Old 07-04-2004, 12:21 AM
Squink Squink is offline
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Quote:
The Pennsylvanian (from 323-290 million years ago) rocks are well represented in Oklahoma, and cover nearly 25% of the surface area of our state. Two events were occurring simultaneously that give the Pennsylvanian rocks of Oklahoma a unique character.
First, the Pennsylvanian Period was a time of extensive mountain building activity, also called orogenesis. Uplift and erosion of the Ancestral Rocky Mountains contributed large volumes of sediment from the west, while the Wichita orogeny in southwest Oklahoma uplifted older (Precambrian through Mississippian) rocks, exposing them to erosion during the Early Pennsylvanian. This event was followed by the Ouachita orogeny during the Middle Pennsylvanian, which caused strong deformation of the sediments in the Ouachita Basin, and formed the Ouachita Mountains.
OK Geological Survey

Found details on the Penokean orogeny:
Quote:
major early Proterozoic mountain building episode that began soon after the rifting episode 2.4 bya. We see the roots of this ancient line of mountains today as a zone of deformed Archean and early Proterozoic rocks along the southern edge of the Superior Province from Minnesota eastward through the north shore of Superior. The orogeny began with the passive margin sedimentation after a rifting event along the southern edge of the Superior province. These sediments include the Iron Formations, that were subsequently deformed by the collision of an island arc around 1.85 bya. A second crustal body collided into the island arc around 1.84 bya. The Penokean orogeny closed with some post tectonic magmatism.
The Penokean Collisions
There are definitely still remnants of these mountains around:
Quote:
Eventually mountains were produced in this area, possibly as high as the Rocky Mountains. What you see as hills in the area today are the remnants of these mountians. They are called the Penokean Hills.
Geology of the Mississagi Valley
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  #12  
Old 07-07-2012, 11:38 PM
JohnnyJ JohnnyJ is offline
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Before the Penokean Mountains, there were the Algoman Mountains which stretched across what is now northern Minnesota. They were eroded between 2,700 and 2,000 million years ago. They may have once looked like the Alps or the Himalayas. Some of the granites that formed deep within the mountains are now exposed at the surface. From p. 10--Roadside Geology of Minnesota by Richard Ojakangas.
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  #13  
Old 07-08-2012, 12:33 AM
GreasyJack GreasyJack is online now
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Note that all the mountain ranges are now 8 years older than the dates given when this thread started.
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  #14  
Old 07-08-2012, 09:48 AM
Exapno Mapcase Exapno Mapcase is offline
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Very simple. The oldest mountains are the shortest.

That makes Death Valley the oldest of them all.
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  #15  
Old 07-08-2012, 11:39 AM
DrCube DrCube is offline
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The Ozarks?
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