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Author Topic: Laurentide Ice Sheet/forensic analysis of deglaciation using varves, etc.  (Read 7294 times)

budmantis

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I'm fairly new at this, so bear with me please. Not sure if I've placed this new thread in the right spot, but here goes. Having spent most of my life in New Hampshire and having done a great deal of hiking, I'm fascinated with the history of glaciation during the last ice age. Having seen plenty of glacial erratics, eskers, drumlins, moraine and kettle ponds, I wondered if there was forensic evidence mapping the deglaciation period to the point where the last vestiges of the Laurentide Ice Sheet are now found on Baffin Island.

Here I was in the summer of 2012, shortly after being diagnosed with pulmonary fibrosis, I found I had some time on my hands. That's when I discovered a form of soil deposition in fresh water lakes and ponds called "varves".

What interested me the most was this question; is there any reliable record of how the Laurentide Ice Sheet receded and what over the course of millennia did it look like? Putting it another way, when did the ice recede to Canada and when did it recede to northern Quebec? After that, when did it recede further north onto Baffin Island? One other thing that caught my eye when I started following the decline of Arctic sea ice, was the Modis imagery of northern North America, showing a very odd looking lake called Great Slave Lake. The eastern arm of this lake looks a lot like an outwash plain.

Perhaps this subject doesn't fit in as part of the theme of this forum, but if anyone is interested,  I would appreciate any insight and comments the members of this esteemed forum would have to share.

budmantis

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Re: Laurentide Ice Sheet/forensic analysis of deglaciation using varves, etc.
« Reply #1 on: September 05, 2016, 08:10:59 AM »
Here's a website explaining varves, etc.

Tealight

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Re: Laurentide Ice Sheet/forensic analysis of deglaciation using varves, etc.
« Reply #2 on: September 05, 2016, 10:38:18 AM »
It's always good to start at Wikipedia and check External Links ,Further reading and References.

There you find a link to the Illinois State Museum, which made a gif animation of the retreat:
http://www.museum.state.il.us/exhibits/ice_ages/

budmantis

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Re: Laurentide Ice Sheet/forensic analysis of deglaciation using varves, etc.
« Reply #3 on: September 05, 2016, 10:59:20 AM »
Thanks Tealight.

budmantis

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Re: Laurentide Ice Sheet/forensic analysis of deglaciation using varves, etc.
« Reply #4 on: September 06, 2016, 09:19:43 AM »
I've attached descriptions and illustrations from Wikipedia for glacial landforms that dot the landscapes of previously glaciated lands. I'd like to invite lurkers interested in this subject to de-lurk and post your comments, no matter how insignificant. I realize that this subject might not interest a vast cross-section of the Forum, but please comment if this subject interests you. Thanks!

budmantis

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Re: Laurentide Ice Sheet/forensic analysis of deglaciation using varves, etc.
« Reply #5 on: September 06, 2016, 09:22:26 AM »
Additional descriptions of glacial landforms.

budmantis

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Re: Laurentide Ice Sheet/forensic analysis of deglaciation using varves, etc.
« Reply #6 on: September 09, 2016, 07:19:17 AM »
I've been searching the web for articles discussing the Laurentide Ice Sheet. I've briefly looked over a lot of them, most had a tendency to make my eyes glaze over. The attached article is from Ohio State University and it has some animated graphics.

http://polarmet.osu.edu/PolarMet/paleonwp.html
« Last Edit: September 09, 2016, 03:59:27 PM by budmantis »

oren

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Re: Laurentide Ice Sheet/forensic analysis of deglaciation using varves, etc.
« Reply #7 on: September 09, 2016, 08:57:10 AM »
I've been searching the web for articles discussing the Laurentide Ice Sheet. I've briefly looked over a lot of them, most had a tendency to make my eyes glaze over. The attached article is from Ohio State University and it has some animated graphics.

Note: Downloading the article from here you will not be able to utilize the animated graphics. Sorry, I'm not very good at setting up links. The article will provide plenty of info on how to access it yourself on the internet.

Just copy the URL, when posting click "insert URL", looks like this , paste the URL between the tags "url" and "url", and you're all set.

sidd

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Re: Laurentide Ice Sheet/forensic analysis of deglaciation using varves, etc.
« Reply #8 on: September 09, 2016, 09:17:42 AM »
You may wish to read

https://forum.arctic-sea-ice.net/index.php/topic,804.msg23021.html#msg23021

which refers to a nice paper by Gregoire et al.  doi:10.1038/nature11257

Gray-Wolf

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Re: Laurentide Ice Sheet/forensic analysis of deglaciation using varves, etc.
« Reply #9 on: September 09, 2016, 11:54:53 AM »
I'm also curious as to the loss of the last glacial Ice.

I live in the UK 'Pennines' and our region is a deeply dissected upland plateau. The Valleys are not glaciated but the rivers they carry are far too small to have created the depth ,and steepness, of the landscape nor some of the landscape features (like the massive rotational slip on the hill facing a point where a tributary stream flows into the river Calder?).

I'm kind of of the opinion that the only means to produce such a landscape would be a period of high flow in the rivers/tributaries and this would be generated by the wasting of the great ice sheets from the last ice age? maybe even occasionally accentuated with 'flood' episodes when glacial lakes rapidly drained into the landscape? To find out if such a period existed I'd need sight of the way our local ice sheet retreated at the end of the last glaciation to see if we did indeed spend a significant period close to the decaying ice?
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budmantis

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Re: Laurentide Ice Sheet/forensic analysis of deglaciation using varves, etc.
« Reply #10 on: September 09, 2016, 03:50:12 PM »
http://phys.org/news/2011-02-ice-sheets-age.html

Gray Wolf, here's a link regarding the BIIS (British Isles Ice Sheet). Thanks for your post.
« Last Edit: September 09, 2016, 04:04:25 PM by budmantis »

budmantis

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Re: Laurentide Ice Sheet/forensic analysis of deglaciation using varves, etc.
« Reply #11 on: September 09, 2016, 04:02:37 PM »
I've been searching the web for articles discussing the Laurentide Ice Sheet. I've briefly looked over a lot of them, most had a tendency to make my eyes glaze over. The attached article is from Ohio State University and it has some animated graphics.

Note: Downloading the article from here you will not be able to utilize the animated graphics. Sorry, I'm not very good at setting up links. The article will provide plenty of info on how to access it yourself on the internet.

Just copy the URL, when posting click "insert URL", looks like this , paste the URL between the tags "url" and "url", and you're all set.

Thanks for the tip Oren!

Iceismylife

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Re: Laurentide Ice Sheet/forensic analysis of deglaciation using varves, etc.
« Reply #12 on: September 09, 2016, 05:21:07 PM »
I'm also curious as to the loss of the last glacial Ice.

I live in the UK 'Pennines' and our region is a deeply dissected upland plateau. The Valleys are not glaciated but the rivers they carry are far too small to have created the depth ,and steepness, of the landscape nor some of the landscape features (like the massive rotational slip on the hill facing a point where a tributary stream flows into the river Calder?).

I'm kind of of the opinion that the only means to produce such a landscape would be a period of high flow in the rivers/tributaries and this would be generated by the wasting of the great ice sheets from the last ice age? maybe even occasionally accentuated with 'flood' episodes when glacial lakes rapidly drained into the landscape? To find out if such a period existed I'd need sight of the way our local ice sheet retreated at the end of the last glaciation to see if we did indeed spend a significant period close to the decaying ice?
https://goo.gl/maps/CDbjqtcBSi92
Time vs water.  You've got plenty of water to cut those valleys.  The mountain in the link I posted use to be twice as tall as it is now. It was eroded by the amount of water visible in the pictures.  Not very much.

If you look around you can see the damage left by the flood water draining when large lakes drained at the end on the last glacial period.

mati

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Re: Laurentide Ice Sheet/forensic analysis of deglaciation using varves, etc.
« Reply #13 on: September 09, 2016, 07:03:16 PM »
https://goo.gl/maps/CDbjqtcBSi92
Time vs water.  You've got plenty of water to cut those valleys.  The mountain in the link I posted use to be twice as tall as it is now. It was eroded by the amount of water visible in the pictures.  Not very much.

If you look around you can see the damage left by the flood water draining when large lakes drained at the end on the last glacial period.

A great example is the Barron River Canyon (which i have hiked and canoed back in the day) when the outflow from the Lake Agassi passed through...
100m deep and 300m? wide  cut through solid granite..

https://en.wikipedia.org/wiki/Barron_River_(Ontario)

http://www.doe.carleton.ca/~ngt/algonquin/barron/barron_text.html

and so it goes

budmantis

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budmantis

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Re: Laurentide Ice Sheet/forensic analysis of deglaciation using varves, etc.
« Reply #15 on: September 10, 2016, 06:53:57 AM »
Another link regarding varves from the Geology Society of America.

https://gsa.confex.com/gsa/2013NE/webprogram/Paper214343.html

budmantis

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Re: Laurentide Ice Sheet/forensic analysis of deglaciation using varves, etc.
« Reply #16 on: September 11, 2016, 07:32:59 AM »

budmantis

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budmantis

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Re: Laurentide Ice Sheet/forensic analysis of deglaciation using varves, etc.
« Reply #18 on: September 22, 2016, 07:12:23 AM »
This paper has more to do with isostatic rebound in southern New England, particularly dealing with lake Hitchcock in Connecticut. However, there is a great map of New England and parts of southern Quebec and New Brunswick, giving us an idea of where the ice sheet was located as it retreated northward. Also shows the meltwater lakes that formed, as well as major terminal moraine locations. The amount of information provided is staggering, I barely scratched the surface.

https://www.researchgate.net/publication/301281001_Glacial_lake_deltas_in_New_England_record_continuous_not_delayed_postglacial_rebound