2012-03-10 04:03:40Younger Dryas - the blog-post
John Mason

johntherock@btopenworld...
81.129.232.193

Hi folks,

Nasty wet afternoon here in Wales so decided to finish-off the post I started a couple of weeks ago:

http://www.skepticalscience.com/younger-dryas-recent-research.html

Conclusions are not what I thought they might be when I started reading the literature and the final take-home is actually pretty chilling. Although the impact theory is once again gaining ground, if it happened it wasn't what finished off the megafauna. It was subtle ecological change occurring over centuries - just as is occurring right now.

Have a read and say if you agree or disagree with me :)

 

Cheers - John

 

2012-03-10 16:18:18
Chris Colose

colose@wisc...
72.226.121.32

Here is another view on the YD that I wrote about at RealClimate.  I think the comet stuff has been pretty well discredited at this point, but also note different views on the source of the freshwater input and likely similar events during previous deglaciations.

http://www.realclimate.org/index.php/archives/2010/07/revisiting-the-younger-dryas/

2012-03-10 19:23:51
John Mason

johntherock@btopenworld...
81.129.232.193

Just re-read that, Chris.

What I find fascinating is the way this tale is developing. As I point out in the text, the YD impact theory is strictly juvenile in age, but it is interesting to note that although apparently debunked in 2010, since that time the literature has recorded further evidence regarded by the authors who report it as strongly in favour of an impact, as referenced in the piece. TBH I don't think my piece is much at odds with yours with the exception of that new research that has been published since: it is important to acknowledge as we both have that the YD presents us with several 'known unknowns', so that statements like 'mammoths wiped out by comet' or 'mammoths not wiped out by comet' are sweeping and inaccurate - the stuff of tabloid journalism. My reading suggests that whether there was a bolide of whatever type, or not, the megafauna lived on for another 1400 years - and of course in the case of Wrangel Island for a lot longer again.

It's worth having a read of Israde-Alcatara et al 2012 in PNAS: their concluding remark is a bold one and will doubtless lead to further work:

"Although the origin of these YDB markers remains speculative, any viable hypothesis must account for coeval abundance peaks in NDs, magnetic impact spherules, CSps, and charcoal in Lake Cuitzeo, along with apparently synchronous peaks at other sites, spanning a wide area of Earth’s surface. Multiple hypotheses have been proposed to explain these YDB peaks inmarkers, and all but one can be rejected. For example, the magnetic impact spherules and NDs cannot result from the influx of cosmic material or from any known regular terrestrial mechanism, including wildfires, volcanism, anthropogenesis, or alternatively, misidentification of proxies. Currently, only one known event, a cosmic impact, can explain the diverse, widely distributed assemblage of proxies. In the entire geologic record, there are only two known continent-wide layers with abundance peaks in NDs, impact spherules, CSps, and aciniform soot, and those are the KPg impact boundary at 65 Ma and the YDB boundary at 12.9 ka."

Cheers - John

2012-03-10 20:59:42
John Mason

johntherock@btopenworld...
81.129.232.193

Digging a bit deeper, there's a blooper in Israde-Alcatara et al 2012.

They say: At Murray Springs, Arizona,
Haynes et al. (13) observed highly elevated concentrations of
YDB MSp and iridium. Abundances of MSp were 340 × higher
than reported by Firestone et al. (1) and iridium was 34 × higher,
an extraordinary enrichment of 3,000 × crustal abundance. Those
authors stated that their findings are “consistent with their (Fire-
stone et al.’s) data.”

 

The reference,

13. Haynes CV, Jr, Lauretta DS, Ballenger JAM (2010) Reply to Firestone et al: No confir-
mation of impact at the lower Younger Dryas boundary at Murray Springs AZ. Proc
Natl Acad Sci USA 107:E106–E106.

can be read in full at http://www.pnas.org/content/107/26/E106.full

 

It makes no such claim. More alarm-bells ringing here!

 

Cheers - John

2012-03-10 23:56:47
John Mason

johntherock@btopenworld...
81.129.232.193

OK I've revised this big-time to include so far as I know all key contributions and the back-and-forth that went on prior to the 'requiem' paper. The blooper mentioned above is a misattribution: Haynes et al DID find those Ir anomalies but the 34x higher quote came from Firestone's response and the 3000x crustal abundance has somehow morphed from their 1000 times terrestrial abundance. The 1ppb crustal abundance figure I used comes from a British Geological Survey publication on PGMs.

What remains unexplained is the widespread "black mat", impact or not. Nice shot of it at Lommel in Belgium from the Tian et al 2011 PNAS paper:

 

Cheers - John

2012-03-11 18:09:36
John Mason

johntherock@btopenworld...
81.129.232.193

One of the problems anybody with a non-scientific background has with the YD is that, in a situation with some striking parallels to the modern climate dingdong, there is an awful lot of crap out there. For example, Google the Usselo Horizon - the term that refers to the dark band in the image above.

The first result takes one to PNAS and the supporting info for Firestone et al 2007, fair play.

The second takes one to a catastrophist website article. Tightening my head-vice I read down through a hotch-potch of science and fantasy, arriving upon this:

"Let us urgently adopt the working hypothesis that they were synchronous and had one and the same cause, and let us then see if everything starts fitting together. The extinction of the Pleistocene megafauna, the sudden ice melting, the catastrophic floods, the rise in sea-level, the sudden demise of the Magdalenian culture after an uninterrupted development of some 30.000 years and the backfall to Mesolithic primitivism. "

This is pure unadulterated bollocks. Point by point:

The extinction of the Pleistocene megafauna, NO this began 50,000 years ago in Australia and the last mammoths died out 3,000 years ago.

the sudden ice melting, NO, there was a sudden cooling that interrupted a steady melting over several thousand years

the catastrophic floods, WELL if Murton et al are right there may have been ONE such flood across NW Canada

the rise in sea-level, NO, sea-level rise rate slowed for the duration of the YD

the sudden demise of the Magdalenian culture after an uninterrupted development of some 30.000 years and the backfall to Mesolithic primitivism. NO, the Magdalenian culture ended 10,000 years ago or some 1,200 years after the end of the YD and the Mesolithic saw a transition from the hunter-gatherers of the Palaeolithic to the farming of the Neolithic

Dear, dear me! I think a sentence or two warning about confirmation-bias outbreaks could usefully be included in the piece!

Cheers - John

2012-03-11 22:27:06
John Mason

johntherock@btopenworld...
81.129.232.193

OK it's done for now, complete with extensive revisions, graphics, images, links etc. Might need to accredit the black mat photo.....

http://www.skepticalscience.com/younger-dryas-recent-research.html

Cheers - John

2012-03-12 04:14:01don't know much about geology
jyyh
Otto Lehikoinen
otanle@hotmail...
193.64.21.48

Can I link to the image at the end? Pretty good read, so there might indeed have been an impact back then! I may have to do yet a third story besides <a href="http://erimaassa.blogspot.com/2008/10/neljs-viesti.html"> note #4</a> and <a href="http://erimaassa.blogspot.com/2008/11/jonkun-verran-pelkotilaa.html"> this</a> to have all bases covered. :-). But really I do not know enough of geology to give a thumb.

2012-03-12 04:46:28
John Mason

johntherock@btopenworld...
81.129.232.193

jyhh - sure!

I'm certainly not saying there was an impact, but that equally it cannot yet be 100% dismissed, which is perhaps where Chris and I differ. My take is that the evidence so far is largely inconclusive, but that this deposit APPEARS to be a marker-horizon over increasing parts of the world is a curious thing that cannot simply be dismissed. This is difficult stuff to work on especially due to the grainsize of a lot of the so-called markers. One of the biggest problems I think is that Firestone et al overstepped the mark to begin with: the fact that the megafauna were already well on the way to die-out YET survived this time in many parts of the world tells me that any severe direct effects - IF there was a bolide - were of a localised nature. I think climate change in this case was a more likely indirect cause of final extinction: indeed on the timescales involved of less than ten thousand years the same might well apply to the K-T away from the zone where the impact for which there is much better evidence occurred.

Cheers - John

2012-03-13 08:04:08
John Mason

johntherock@btopenworld...
81.129.232.193

Think BBC R4 are gonna have something on this topic in the next half-hour. Will stay up & listen....

Cheers - John

2012-03-13 11:03:19
Andy S

skucea@telus...
209.121.15.232

John, some comments:

I like the article subject overall (and learned stuff, thanks!) but I think you need to simplify and shorten it for the non-technical, non-geologist reader.

The first figure is good in many ways but I think it would have been better not to have had it as a circle, implying cyclicity which is not there (and with time unfolding anti-clockwise, it's not intuitive). In the caption you say that The later (post-Neolithic) periods refer primarily to the UK. perhaps that would better be "western Eurasia" or "Europe".

I think that you need to stress more clearly  that the YD was pretty much confined to the N Hemisphere.

I'm not sure many punters will understand what the word "bolide" means. Perhaps say "asteroid or comet". Alternatively, link to a page like this.

The whole section between figs 2 and 3 plus a few paragraphs beyond needs to be shortened and simplified. The take-away message is that there are ongoing disputes over the minerals found at the black band. 

the YD impact theory is a baby, that has seesawed in and out of favour Mixed metaphor alert!

You may as well mention that the K/T impact and its role in extinctions is equally contentious, even though the reality of that impact itself is now part of the consensus.

As for this...


...well it made me laugh out loud!

2012-03-14 16:31:15
John Mason

johntherock@btopenworld...
81.129.232.193

Thanks Andy - will work those suggestions in over the next day or three :)

I can easily do a linear graphic.

 

Cheers - John

2012-03-14 21:49:54
John Mason

johntherock@btopenworld...
81.129.232.193

Piece updated......

Cheers - John

2012-03-21 15:48:41
dana1981
Dana Nuccitelli
dana1981@yahoo...
71.137.110.129

Am I correct to assume this is ready to publish, John?

2012-03-21 20:49:09
John Mason

johntherock@btopenworld...
81.158.13.232

Dana,

I've worked-in the uggestions from people, so if they're OK with that then yes. I'd like Chris Colose to have a read of it though as he made some good points and I hope I've struck the right balance with the piece.

Cheers - John

2012-03-22 03:30:26I was always late with my school homework, too...
Same Ordinary Fool

chicagoriverturning@gmail...
68.228.229.4

In the first paragraph you do use the words, "glacial re-advance commenced," which does describe the temperature graph for a more careful and deliberate reader than myself.  For the inattentive among us, a more direct description  (of what is the central take-away about the YD)  would be easier to remember - as a cold spell that briefly interrupted the early warming after the last glacial period.

I thought I'd remembered the Younger Dryas as being associated with a denier myth, so I entered the words  in the SkS Search feature.  There's mention of Monckton and Will Happer from Princeton having so abused it..........Given SkS's debunking focus, it'd satisfy some curiousities like mine, to see a brief description of the denier myths that could be created by misinterpreting it..........Though admittedly, this would interrupt the flow of your narrative...

2012-03-22 05:10:31
Sphaerica

Bob@Lacatena...
72.74.77.39

Great piece.

2012-03-22 10:30:42
dana1981
Dana Nuccitelli
dana1981@yahoo...
71.137.110.129

I tried to email Chris, but it didn't go through.  You sure you want to wait until he reads it?  Because we can't be sure when that will happen.

2012-03-22 19:53:20
John Mason

johntherock@btopenworld...
81.158.13.232

OK Dana - I reckon we can go for it. SOF - I'll look into any myths about the YD and do a post dedicated to them if it looks like they are being bandied-about.

Cheers - John

2012-03-23 03:12:35
dana1981
Dana Nuccitelli
dana1981@yahoo...
64.129.227.4

Okay, I'll give it 1 more day and plan to post this tomorrow.

2012-03-23 03:36:14
jg
John Garrett
garrjohn@gmail...
98.112.44.167

typo in the first paragraph. Extra "I" in this sentence:

my Grandfather grew it I and I did in my time

2012-03-23 04:24:46
John Mason

johntherock@btopenworld...
81.158.13.232

Fixed, thanks! Made me sound like a Rastafarian!

Cheers - John