Talk:Midcontinent Rift System

Sources

• Need a source for the hotspot under Lake Superior bit and extension of the rift system into/with Quebec basalts ca 900 mya. Vsmith 02:20, 8 June 2007 (UTC)
  • Here is the source for most of it Vsmith [1]. Black Tusk 11:27, 8 June 2007 (UTC)
    • Rewritten to conform to this source; volcanism actually stopped ~1084 mya, no ref given for effects in Quebec. Kablammo 03:37, 9 June 2007 (UTC)
      • Well, I found the information about the Quebec basalts in a book, so it can't be wrong. Black Tusk 12:14, 9 June 2007 (UTC)

What book? The Quebec basalts are likely related to the later Grenville orogeny, rather than directly related to the mid-continent rifting. I've rewritten based on a better ref (not just a field trip guide) and used the Afar triple junction as an analogous example. The Yellowstone hotspot example seemed less fitting (is it a rift?) Vsmith 04:29, 9 June 2007 (UTC)

I don't really know anything about the Yellowstone hotspot. But in one of my books where I got the information from, it says this in the exact same paragraph, "Some of the most ancient geological remnants of basaltic plains lie in Canada's Precambrian Shield. The Keweenawan basalts in Michigan, Ontario and Quebec are some 900 to 1100 million years old. Eruption of plateau lavas near the Coppermine River southwest of Coronation Gulf in the Arctic, built an exclusive plateau about 1200 million years ago with an area of about 170 000 km² (65 000 sq mi) representing a volume of lavas of at least 500 000 km³ (120 000 cu mi)." Black Tusk 12:42, 9 June 2007 (UTC) —Preceding unsigned comment added by 209.105.206.84 (talk • contribs) 04:45, 9 June 2007

Again, what book - the quote above seems far too general for direct application here. And please log in and sign correctly to avoid confusion w/ regard to user id and timezone diffs. Vsmith 04:57, 9 June 2007 (UTC)

Sorry, I thought I was loged in. What do you mean what book? how am I supposed to prove it on the internet? Black Tusk 04:59, 9 June 2007 (UTC)

Maybe it's not possible to prove it directly over the internet, but if you tell the rest of us what the book is called, it would give us a chance to confirm it. Not just to confirm it, really, but to get a better understanding of the original author's meaning than an isolated quote can provide. -- Avenue 08:20, 9 June 2007 (UTC)

The book is called "M.B. Lambert VOLCANOES" and its cover photograph is the eruption of Eldfell in 1973. The page where I got the imformation from was at the bottom on page 38. Black Tusk 09:34, 9 June 2007 (UTC)

Perhaps Lambert's phrase "Keweenawan basalts" is just a shorthand and perhaps imprecise term for similar volcanic basalts, and not intended to describe a common origin for similar formations. As other sources neither extend the rift into Quebec nor state it continued beyond c. 1084 mya, the present text seems more precise. Kablammo 17:11, 9 June 2007 (UTC)

Agreed, I spent quite a bit of time looking through print and online pubs and can find no indication of an extension of the rift, nor, strictly speaking, of Keweenawan age basalts into Quebec. There are some that are older and younger, but I can't find any evidence of the Mid-Continent Rift or an extension of it in Quebec. Cheers Geologyguy 20:12, 9 June 2007 (UTC)

I think your right, if you look up "Quebec rift basalts 900 Ma" on google, you will find all different ages that are similar to the Keweenawan age basalts. Black Tusk 21:23, 9 June 2007 (UTC)

Well, the Quebec basalts might be related to the Saint Lawrence Rift System, but I'm not really sure if the rift is volcanic though. Black Tusk 08:01, 20 June 2007 (UTC)

Given that the Quebec basalts are about 900 Ma, and the age indicated in the article of the St Lawrence Rift is probably no older than post-Upper Ordovician (500 million years younger than the Quebec basalts), more likely post-Upper Devonian, and possibly as young as Mesozoic, it is difficult to imagine them being related. The article has no mention of any basalts; the Cretaceous magmatism that they suggest could be related to activity on the St Lawrence Rift structures is alkaline. Cheers Geologyguy 20:23, 20 June 2007 (UTC)

I do remember reading something about rift basins streching from Quebec to Virginia which has basaltic rocks, but I don't think this would be the St. Lawrence Rift though. Black Tusk 05:01, 21 June 2007 (UTC)

You're probably thinking of the Triassic graben system that developed as the Atlantic Ocean began to form. Things like the Connecticut Graben, Newark (NJ) Graben, and so on at least as far south as a graben in SW South Carolina (subsurface). Many but not all of those grabens contain basalt flows, dike, sills, and red beds associated with the early extensional phase of North Atlantic opening. The article you cited seemed to suggest the possibility that the St Lawrence Rift was at least somewhat rejuvenated at that time, though not with basaltic igneous activity. Cheers Geologyguy 17:32, 21 June 2007 (UTC)

That's probably what I'm thinking about then, but what would the 900 Ma basalts in Quebec be? Black Tusk 04:23, 22 June 2007 (UTC)

Perhaps a Canadian geologist can help; I don't know - refs to the 900 Ma basalts are pretty sparse and casual. The most often-cited rift-related basalts I can find info about are in the Cape Smith Fold Belt (Ungava Peninsula), related to 2.04 Ga extension. Cheers Geologyguy 17:47, 22 June 2007 (UTC)

Lake Winnepeg

• question: is lake Winnepeg part of this rift system?

—Preceding unsigned comment added by 64.216.155.121 (talk) 12:25, 31 January 2008 (UTC)

Nope. Cheers Geologyguy (talk) 15:35, 31 January 2008 (UTC)

Similarities

There's an interesting similarity with the Midcontinent Rift System and the Mackenzie dike swarm. The Mackenzie dike swarm extends in a northwesterly direction across the whole of Canada from the Arctic to the Great Lakes where it meets the Midcontinent Rift System. Both have similar ages and produced basaltic lava by hotspot volcanism. Therefore there's a potential link with these formations and would probably be appropriate to add this in the article. Black Tusk (talk) 18:49, 11 July 2008 (UTC)

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