Permian seasonality
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16-06-2015, 02:13 PM
RE: Permian seasonality
That's badass.
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16-06-2015, 03:28 PM
RE: Permian seasonality
Hmm. So what was your independent constraint? Dropstones and glendonites if I read your abstract aright? What's a dropstone? Hah. OK wikipedia knows. So this area you studied was a place where glaciers were found in winter...

So you use the winter temp constraint to calculate the water composition and then use the water composition to calculate the summer temp? Something like that?

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(06-02-2014 03:47 PM)Momsurroundedbyboys Wrote:  And I'm giving myself a conclusion again from all the facepalming.
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16-06-2015, 03:40 PM
RE: Permian seasonality
(16-06-2015 03:28 PM)morondog Wrote:  Hmm. So what was your independent constraint? Dropstones and glendonites if I read your abstract aright? What's a dropstone? Hah. OK wikipedia knows. So this area you studied was a place where glaciers were found in winter...

So you use the winter temp constraint to calculate the water composition and then use the water composition to calculate the summer temp? Something like that?

Right. Dropstones themselves don't give me any indication of temperature (except that it is cold and that there is sea ice), but the glendonites do, as well as the bivalves themselves in a way.

Glendonites are a pseudomorph of calcite after the mineral ikaite (CaCO3*2H2O) and ikaite only forms in sediments today that are 4°C or less. And bivalves (with few exceptions) don't grow at temperatures beneath 0°C. So knowing that winters must have been at least as cold as 0-4°C when the bivalves would have stopped growing (the existence of the dark growth bands), this allows for me to turn the calcite temperature equation on its head to calculate water composition instead of temperature for the winter shell values [ T( °C) = 16.9 - 4.0 *( δ18O{calcite] - 18O{water}) ].

I then use that calculated water composition for the rest of the seasonal calcite values to calculate temperature.

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16-06-2015, 03:51 PM
RE: Permian seasonality
I'm intrigued enough that I'm gonna try read this thing properly...

You can get an average temp for summer and winter right? How fine-grained is this technique? I guess year on year? So you can get a sequence of temperatures... How long does a bivalve live? Not that super long I would guess... Argh. Not gonna be getting a nice weather chart from 270 million years ago then... But you know for some years around that period roughly the sequence of temps for say... a decade?... Holy shit. Awesome stuff. Grats on getting published Smile

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(06-02-2014 03:47 PM)Momsurroundedbyboys Wrote:  And I'm giving myself a conclusion again from all the facepalming.
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16-06-2015, 03:56 PM
RE: Permian seasonality
(16-06-2015 03:51 PM)morondog Wrote:  I'm intrigued enough that I'm gonna try read this thing properly...

You can get an average temp for summer and winter right? How fine-grained is this technique? I guess year on year? So you can get a sequence of temperatures... How long does a bivalve live? Not that super long I would guess... Argh. Not gonna be getting a nice weather chart from 270 million years ago then... But you know for some years around that period roughly the sequence of temps for say... a decade?... Holy shit. Awesome stuff. Grats on getting published Smile

It is pretty neat. My resolution is only limited by the size of the bivalve and the size the sampling instrument I use. For instance, I sampled at a fairly coarse resolution and only did 6 samples per year (so better than quarterly). I could sample at a finer resolution but I have to combat the curvature of the shell which would causing the mixing of signals as I sample into the shell. There are techniques for in situ analysis with a ion microbeam, but I only know of one lab with that instrument, so it isn't feasible yet to sample at the super high resolutions.

Also, for bivalves and how long they live, the oldest known living animal was a bivalve.
http://sciencenordic.com/new-record-worl...-years-old

Some bivalves can consistently live to be over a 100 (usually the arctic bivalves). The ones I sampled lived at least a couple of decades.

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