This is a follow up posting to Younger Dryas -The Rest of the Story!
Guest post by Don J. Easterbrook
Dept. of Geology, Western Washington University.
The Younger Dryas was a period of rapid cooling in the late Pleistocene 12,800 to 11,500 calendar years ago. It followed closely on the heels of a dramatically abrupt warming that brought the last Ice Age to a close (17,500 calendar years ago), lasted for about 1,300 years, then ended as abruptly as it started. The cause of these remarkably sudden climate changes has puzzled geologists and climatologists for decades and despite much effort to find the answer, can still only be considered enigmatic.
The Younger Dryas interruption of the global warming that resulted in the abrupt, wholesale melting of the huge late Pleistocene ice sheets was first discovered in European pollen studies about 75 years ago. Terrestrial plants and pollen indicate that arboreal forests were replaced by tundra vegetation during a cool climate. This cool period was named after the pale yellow flower Dryas octopetella, an arctic wildflower typical of cold, open, Arctic environments. The Younger Dryas return to a cold, glacial climate was first considered to be a regional event restricted to Europe, but later studies have shown that it was a world-wide event. The problem became even more complicated when oxygen isotope data from ice cores in Antarctica and Greenland showed not only the Younger Dryas cooling, but several other shorter cooling/warming events, now known as Dansgaard-Oerscher events.
The Younger Dryas is the longest and coldest of several very abrupt climatic changes that took place near the end of the late Pleistocene. Among these abrupt changes in climate were: (1) sudden global warming 14,500 years ago (Fig. 1) that sent the immense Pleistocene ice sheets into rapid retreat, (2) several episodes of climatic warming and cooling between ~14,400 and 12,800 years ago, (3) sudden cooling 12,800 years ago at the beginning of the Younger Dryas, and (4) ~11,500 years ago, abrupt climatic warming of up to 10º C in just a few decades. Perhaps the most precise record of late Pleistocene climate changes is found in the ice core stratigraphy of the Greenland Ice Sheet Project (GISP) and the Greenland Ice Core Project (GRIP). The GRIP ice core is especially important because the ages of the ice at various levels in the core has been determined by the counting down of annual layers in the ice, giving a very accurate chronolgoy, and climatic fluctuations have been determined by measurement of oxygen isotope ratios. Isotope data from the GISP2 Greenland ice core suggests that Greenland was more than~10°C colder during the Younger Dryas and that the sudden warming of 10° ±4°C that ended the Younger Dryas occurred in only about 40 to 50. years.
Figure 1. Temperature fluctuations over the past 17,000 years showing the abrupt cooling during the Younger Dryas. The late Pleistocene cold glacial climate that built immense ice sheets terminated suddenly about 14,500 years ago (1), causing glaciers to melt dramatically. About 12,800 years ago, after about 2000 years of fluctuating climate (2-4), temperatures plunged suddenly (5) and remained cool for 1300 years (6). About 11,500 years ago, the climate again warmed suddenly and the Younger Dryas ended (7).
Radiocarbon and cosmogenic dating of glacial moraines in regions all over the world and abrupt changes in oxygen isotope ratios in ice cores indicate that the Younger Dryas cooling was globally synchronous. Evidence of Younger Dryas advance of continental ice sheets is reported from the Scandinavian ice sheet, the Laurentide ice sheet in eastern North America, the Cordilleran ice sheet in western North America, and the Siberian ice sheet in Russia. Alpine and ice cap glaciers also responded to the abrupt Younger Dryas cooling in both the Northern and Southern hemispheres, e.g., many places in the Rocky Mts. of the U.S. and Canada, the Cascade Mts. of Washington, the European Alps, the Southern Alps of New Zealand, and the Andes Mts. in Patagonia of South America.
Figure 2. Temperature fluctuations over the past 15,000 years showing the abrupt cooling during the Younger Dryas and other warming and cooling periods, the Oldest Dryas (cool), Bölllng (warm), Older Dryas (cool), Allerød (warm), InterAllerød (cool), and Younger Dryas (cool).
Figure 3. Oxygen isotope record from the Greenland ice core showing an abrupt temperature drop 12,800 years ago, 1300 years of cool climate, and sudden warming 11,500 years ago.
The Younger Dryas had multiple glacial advances and retreats
The Younger Dryas was not just a single climatic event. Late Pleistocene climatic warming and cooling not only occurred before and after the YD, but also within it. All three major Pleistocene ice sheets, the Scandinavian, Laurentide, and Cordilleran, experienced double moraine-building episodes, as did a large number of alpine glaciers. Multiple YD moraines of the Scandinavian Ice Sheet have long been documented and a vast literature exists. The Scandinavian Ice Sheet readvanced during the YD and built two extensive end moraines across southern Finland, the central Swedish moraines, and the Ra moraines of southwestern Norway(Fig. 4). 14C dates indicate they were separated by about 500 years.
Figure 4. Double Younger Dryas moraines of the Scandinavian Ice Sheet.
Among the first multiple YD moraines to be recognized were the Loch Lomond moraines of the Scotish Highlands. Alpine glaciers and icefields in Britain readvanced or re-formed during the YD and built extensive moraines at the glacier margins. The largest YD icefield at this time was the Scotish Highland glacier complex, but smaller alpine glaciers occurred in the Hebrides and Cairngorms of Scotland, in the English Lake District, and in Ireland. The Loch Lomond moraines consist of multiple moraines. Radiocarbon dates constrain the age of the Loch Lomond moraines between 12.9 and 11.5 calendar years ago.
Multiple Younger Dryas moraines of alpine glaciers also occur throughout the world, e.g., the European Alps, the Rocky Mts., Alaska, the Cascade Range, the Andes, the New Zealand Alps, and elsewhere.
Figure 5. Double Younger Dryas moraines at Titcomb Lakes in the Wind River Range of Wyoming.
Implications
The multiple nature of YD moraines in widely separated areas of the world and in both hemispheres indicates that the YD consisted of more than a single climatic event and these occurred virtually simultaneously worldwide. Both ice sheets and alpine glaciers were sensitive to the multiple YD phases. The GISP2 ice core shows two peaks within the YD that match the glacial record. The absence of a time lag between the N and S Hemispheres glacial fluctuations precludes an ocean cause and is not consistent with the North Atlantic Deep Ocean Water hypothesis for the cause of the Younger Dryas, nor with a cosmic impact or volcanic origin.
Both 14C and 10Be production rates in the upper atmosphere changed during the YD. 14C and 10Be are isotopes produced by collision of incoming radiation with atoms in the upper atmosphere. The change in their production rates means that the Younger Dryas was associated with changes in the amount of radiation entering the Earth’s atmosphere, leading to the intriguing possibility that the YD was caused by solar fluctuations.
Why the Younger Dryas is important
What can we learn from all this? The ice core isotope data were hugely significant because they showed that the Younger Dryas, as well as the other late Pleistocene warming and cooling events could not possibly have been caused by slow, Croll-Milankovitch orbital forcing, which occurs over many tens of thousands of years. The ice core isotope data thus essentially killed the Croll-Milankovitch theory as the cause of the Ice Ages.
In an attempt to save the Croll-Milankovitch theory, Broecker and Dention (1990) published a paper postulating that large amounts of fresh water discharged into the north Atlantic about 12,800 years ago when retreat of the Laurentide ice sheet allowed drainage of glacial Lake Agassiz to spill eastward into the Atlantic Ocean. They proposed that this large influx of fresh water might have stopped the formation of descending, higher-density water in the North Atlantic, thereby interrupting deep-water currents that distribute large amounts of heat globally and initiating a short-term return to glacial conditions. If indeed that was the case, then the Younger Dryas would have been initiated in the North Atlantic and propagated from there to the Southern Hemisphere and the rest of the world. Since that would take time, it means that the YD should be 400-1000 years younger in the Southern Hemisphere and Pacific areas than in the Northern Hemisphere. However, numerous radiocarbon and cosmogenic dates of the Younger Dryas all over the world indicate the cooling was globally synchronous. Thus, the North Atlantic deep current theory is not consistent with the chronology of the Younger Dryas.
The climatic fluctuations before and after the Younger Dryas, as well as the fluctuations within it, and the duration of these changes are not consistent with a single event cause of the YD. Neither cosmic impact or volcanic eruptions could produce the abrupt, multiple climatic changes that occurred during the late Pleistocene.
###
Related articles
- Younger Dryas -The Rest of the Story! (wattsupwiththat.com)
- New evidence of Younger Dryas extraterrestrial impact (wattsupwiththat.com)
- Catching up with the Younger Dryas: do mass-extinctions always need impacts? (skepticalscience.com)
- Study Finds New Evidence Supporting Theory of Extraterrestrial Impact (sott.net)
- The Great Ice Meltdown and Rising Seas: Lessons for Tomorrow (giss.nasa.gov)
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Some of the denials of the YD impact event are getting ludicrous.
There can no longer be any argument that the YDB layer is in fact a global impact layer. There is only one other global stratigraphic horizon with the same assemblage of impact markers; the Cretaceous/Tertiary Boundary layer.
The amount of data from many different papers, and research teams, at numerous locations around the world have shown conclusively that the YDB has the most comprehensive set of high energy impact markers of any stratigraphic horizon in 65 million years. And the only thing anyone is “Invoking” an impact to explain is the ET chemistry, and high energy blast-effected materials in that 12,900 year old global stratigraphic horizon.
Exploring possibilities, and speculating on what else the event may have caused should not be seen as ‘invoking’ it.
To say that the authors and proponents of the YDIH are invoking an impact to explain anything else comes under the heading of invoking a straw man argument to side-step the point.
But to pretend that an impact event of such magnitude had no effect on the climate, or biosphere of this world is absurd. And to leave the old Uniformitarian/Gradualist assumptive theories in the box in the light of this new knowledge doesn’t make a lot of sense either.
One can explain the extermination of the giant animals by recognizing what effect the event must have had on the food supply.
Much of the edible biomass of North America would have been burned away down to the last blade of grass.
The bigger you are, the more you need to eat every day. The animals that survived the impact event and didn’t face extinction were simply those that didn’t need to eat so much.
Most of the Mega fauna that went extinct after the event probably just starved. And with them went any specialist predators that depended on them for food.
higley7 says:
June 19, 2012 at 1:05 pm
OK, I’ll bite.
If the Younger Dryas warming ended 11,500 years ago, how did it end the Ice Age 17,500 years ago?
Just asking.
It didn’t. The Wisconsinan Glacial ended about 17,000 BP. Conditions were generally warming for about 3,000 years. That warming trend was interrupted by the YD. Effectively, the YD delayed the onset of the modern climatic regime (the Holocene) by about 1,400 years. The YD was global in scale, was correlated with some very odd phenomena, occasionally suggested as causal agents for the YD, and ended just as abruptly as it started. There were lots of profoundly dramatic events taking place and there is no way to gauge their influence. Look up the Missoula or Spokane floods and wonder what effects they had on circulation in the Pacific.
As rule we like “simple explanations” where ever we can apply them and even where we can’t – viz the team’s insistence on CO2 as the cause of global warming, even though empirical evidence is against them. Like the YD is an event that was plainly more complex than any explanation offered for it can fully explain. It is possible for instance that what ever extraterrestrial event marked the initiation of the YD, may have simply imposed a signature effect on an already begun trend. We do not have data of adequate resolution to say. Similarly the freshening of the North Atlantic is proposed as a single event, but possibly a series of large melt events occurred rather than a single really large one. The Spokane Floods were like this. If these were coincident with the ET event, then the combined effect is not something any theorist has taken on.
There is also a consistently unsung correlation that is persistently ignored by anyone who doesn’t use upper Pleistocene radiocarbon dates. The YD is also marked by a whopping C-14 anomaly. It is an anomaly so large that C-14 dates for the YD initially were thought to place the beginning around 12,500 BP – about 1,000 years too young. That anomaly makes all dates from the YD span far too young and also collapses around 1,500 years into an apparent 500 year span. That means that unless the ET event was a nuclear war, the sun’s and or the planet’s magnetic field(s) was significantly depressed for a fairly long time span, OR there was a supernova near enough to seriously irradiate the planet. So we have probably two unrelated ET events, one of which may have resulted in creased cloud cover, possible freshwater floods in two ocean basins on scales no modern human has ever experienced, possibly also a Daansgard-Oerschger event as well. Arguing about what “caused” the YD is very likely pointless, There was simply too much going on – “mammoth bad luck” one might say.
agfosterjr says:
June 20, 2012 at 10:03 am
The scenario fits hunting extermination to a tee.
You’ve dealt your own argument a serious blow by noting that bison and deer survived. Are we to understand that humans would rather hunt (and eat) big, tough Wooly Mammoths, when there are plenty of much tastier, substantially less formidable prey about?
Native Americans had been killing and eating deer and bison for thousands of years before the arrival of the Europeans, apparently without making much of a dent in the vast herds of those animals.
–sorry Mods; left off blockquote tags….
agfosterjr says:
June 20, 2012 at 10:03 am
You’ve dealt your own argument a serious blow by noting that bison and deer survived. Are we to understand that humans would rather hunt (and eat) big, tough Wooly Mammoths, when there are plenty of much tastier, substantially less formidable prey about?
Native Americans had been killing and eating deer and bison for thousands of years before the arrival of the Europeans, apparently without making much of a dent in the vast herds of those animals.
The reason for the YD cold period and the 8200 years ago cool period and all other cool periods and warming periods is due to VARIATIONS in solar activity. The sun drives the earth’s climatic /oceanic systems, therefore any change it may undergo will have an impact on those systems.
I will follow with a more detail explanation of how this may all come about. All the other theories in my opinion are garbage when it comes to the initial cause of climate change ranging from Co2 increases, to changes in the Thermohalline Circulation,to geomagnetic jerks, to comet/asteroid impacts, ETC ETC. Ridiculous ,to say the least.
It is the initial changes on the sun, followed by the secondary effects those initial changes on the sun have , that changes the climatic /oceanic systems of the earth, in all sorts of varying degrees ,due to the fact that the changes the sun undergoes varies in duration of time, and in degree of magnitude , on a constant basis.
Since Oct .2005 solar activity went from a very active phase, to a phase of very little activity. Solar Cycle 24, is probably peaking, if it has not already done so in late 2011, and if this level of intensity turns out to be the peak for this cycle, it will make it as weak, if not weaker then very weak sunspot cycle 5, which brought on the DALTON MINIMUM. The DALTON MINIMUM , being a time of lower temperatures, more weather extremes and an increase in volcanic activity.
Here we are in year 2012 ,and all the items which I feel control the climate are now set up to put us into a new climate regime,which will feature colder temperatures, and more extreme weather events. I expect the transition to take place between now and year 2014, and to be completed by no later then year 2017.
I expect the above to take place because I expect the peak of solar cycle 24 to be ending in the very near future ,and that the next solar sunspot cycle, solar cycle 25,to be the weakest ever on record, way weaker then even solar cycle 24.
WHAT IS IN PLACE TO CAUSE THIS CLIMATIC SHIFT?
1. WEAK SOLAR ACTIVITY SINCE 2005 ,AND BECOMING EXTREMELY WEAK AFTER THE PEAK OF SOLAR CYCLE 24 PASSES BY. SOLAR FLUX READING WILL FAIL TO TOP 100 ,ONCE THIS PEAK PASSES,ALTHOUGH SOME SPURTS OF ACTIVITY WILL BE PRESENT FROM TIME TO TIME.
2. VOLCANIC ACTIVITY WILL BE ON THE RISE,AS A RESULT OF THE MOSTLY WEAK SOLAR ACTIVITY,BUT WITH THE SPURTS OF ACTIVITY NEEDED TO MAKE AN INCREASE IN VOLCANIC ACTIVITY MORE LIKELY.
3. THE PACIFIC OCEAN IS NOW AND WILL REMAIN IN IT’S COLD PHASE FOR AT LEAST ANOTHER 30 YEARS .ATLANTIC WILL BE IN THE SAME PHASE BY YEAR 2015.
4. EARTH’S WEAKENED MAGNETIC FIELD WILL MAGNIFY CHANGES IN SOLAR ACTIVITY, CAUSING THOSE CHANGES TO HAVE A BIGGER IMPACT THEN IF THE MAGNETIC FIELD WAS STRONGER.
5. LA NINA WILL BE THE RULE GOING FORWARD, RATHER THEN EL NINO.
6. ARCTIC WILL EXHIBIT ABOVE NORMAL TEMPERATURES ,YES ABOVE NOT BELOW NORMAL TEMPERATURES.
7. A WEAKER SOLAR WIND WILL ALLOW MORE COSMIC RAYS IN, WHICH WILL ENHANCE CLOUD COVERAGE. LOW CLOUDS.
HOW DOES THE ABOVE MAKE IT COLDER?
The weakened state of the sun will serve to cause a lesser amount of UV light to enter into our atmosphere ,which in turn will cause a change in the OZONE distribution and concentrations, in such a way that it will cause the atmosphere in the upper troposphere and lower stratosphere, to warm in the polar regions relative to the lower latitudes, which will in turn create a more MERIDIONAL atmospheric pattern (-AO).
Also any spurts of activity will create more NO2 which also destroys OZONE.
The other item, the increase in volcanic activity (especially if it is in the higher latitudes) will increase the amounts of SO2 particles in the atmosphere which will cause the stratosphere to warm , while the surface temperatures will fall. That is in general, which on balance should reinforce a more -AO atmospheric pattern. A key to having a climatic shift.
The -AO ATMOSPHERIC CIRCULATION will enhance snow cover,cloud cover and precipitation for the N.H. This in turn will increase earth’s ALBEDO.
The PDO in it’s cold phase alone, is enough to lower the temperatures on a global scale ,never mind the above ,I have just mentioned. The PDO being in it’s cold phase will likely aid to an increase in low cloud coverage,and will bring about an increase in cool LA NINAS ,as opposed to the warm EL NINOS. An increase in cosmic rays might enhance even more low cloud coverage.
Most of the above happens in the NORTHERN HEMISPHERE, while the S.H. will show less dramatic effects due to the geography there, as opposed to the N.H.
The S.H. is almost all water, which has a much higher specific heat ,then does land ,hence it is slow to heat up or cool down , in contrast to land. In addition a change in the atmospheric circulation in the S.H. would not change the snow cover as much in the S.H. since most of the snow would fall into water, and where it is already present, that being ANTARCTICA.
Those climatic events in my opinion are much more pronounced in the N.H ,then the S.H, and when they happen, they happen very very fast. This is not a slow process, which is what the thinking was in the recent past.
You need a set up to bring this about, I believe we have the set up ,it is in place. Once the set up is in place THRESHOLDS can be reached if duration and degree of magnitude of the items causing the set up are extreme enough. Again I think that will be the case, once the peak of solar cycle 24 comes to a close.
Many people think and I say wrongly that it is a change in the ocean currents that bring about climatic change, such as a shift in the GULF STREAM, OR THE DEEP WATER THERMOHALINE CIRCULATION. My thinking is those don’t change, unless the atmospheric circulation changes. They follow ,they don’t lead. They of course will have a big impact on the climate ,if and when they change, but I think they are after the fact.
Also ocean changes could not explain the many many temperature fluctuations the earth has and has had, with some changes being very abrupt. Example, the YOUNGA DRYAS, a deep cold period,that came on so fast and ended equally fast.
In closing we know form looking at past history, that the earth’s climate is not really stable. Let me phrase that differently. It is fairly stable once it is in a particular regime , but the problem is from time to time it flips from one climatic regime to another climatic regime, that being glacial to interglacial. That is a fact,and I think the other fact is this is a quick process ,not a long drawn out process, due to the fact, set up’s get in place and they in turn eventually make it possible for thresholds to be crossed, which in turn ,results in the abrupt climatic changes that have taken place on earth in the past, and which will happen again in the future.
If the earth’s climate were truly stable , we would never have has ice advances, and ice retreats.
The other last point I want to make is, it is not easy to change the temperature of the earth, and yet at the same time it only takes a small change to make a big impact.
There you have it, my thinking on what could happen this decade. Time will tell if this is right or not ,providing solar behavior does as is forecasted.
Mainstream has their heads in the sand, and the SETUP is in place and has been in place for at least 3 years to cause this climate regime we are currently in, to finally change into another climate regime. Now when I say change into another climate regime ,that does not necessarily mean a drastic drop in temperatures, but what it means is the temperatures will decline ,and it won’t be gradual, it will be in quick jerks and these jerks could be as small as .2C to as much as 2.0 C, but the jerks themselves will be fast,although the magnitude of jerks in temp. will depend on how the items that control the climate phase in with one another, with solar activity leading the way.
I expect all this to take place soon, as soon as the peak in solar cycle 24 passes on. Once we get rid of this peak we should have a very very subdued sun for years and years, and the impact this time will be greater, due to the fact this solar setup started way back in Oct. of 2005. The atmosphere today is much more susceptible to a subdued sun then it was back in 2005, due to the seven odd years of solar activity much below average.
The climate system is nonlinear which means a very small change in some parameters(the sun) can cause great qualitative differences in the resulting behavior (chaos)of the climatic system.
Much of the time the net climate feedback is NEGATIVE,which will neutralize amplifying POSITIVE FEEDBACKS, unless the forcing grows to a point from the POSITIVE FEEDBACK,that it takes over, at which point it gets to EXERT its explosive amplifying effects on the climate system, until something puts it in check, but it is in that in BETWEEN TIME, when the abrupt changes in the climatic system take place.
I say that the SUN will be the source of the POSITIVE FEEDBACK, which will allow the force of that POSITIVE FEEDBACK ,to take over to one degree or another,the net NEGATIVE FEEDBACK in earth’s climatic system, that will cause the climate to go into some varying degree of a climate regime change, for some defined time.
The sun will cause this to take place, due to a slight drop off in solar irradiance, UV light intensity drastically reduced, a much weaker solar wind allowing more cosmic rays to enter into earth’s atmosphere etc etc., which will then create the secondary effects, such as atmospheric circulation changes,more clouds ,more geological activity etc etc.
When I read other explanations for the climate to change , such as changes in the THERMOHALINE CIRCULATION, or GEOMAGNETIC JERKS, they to me can’t explain the many temperature changes that have occurred throughout earth’s climatic history, let alone the recent MAUNDER MINIMUM and DALTON MINIMUM. They may be a consequence of the changes earth undergoes due to solar activity changes,(or solar activity changes itself). They may follow ,but they do not lead the climate into another regime change in my opinion, they are the result and not the cause . Again geomagetc jerks being a consequence of solar changes,,just to emphasize my point..
In the above is what I have to say about our present situation, and this also can be applied to PAST
cold periods such as the YD.
There are to many past changes in temperature to have the source of this change be nothing other
then the sun. The sun is the only source that exhibits enough change often enough, that can be tied
into all the past temperature changes on earth. There is no other source.
Steve P says:
June 20, 2012 at 11:52 am
In general the game species that survived were smaller and faster than the others, and tended to be of Eurasian origin. Why bison survived and horses didn’t, I don’t know, and neither do you. I challenge you to come up with any detail this species discrimination through catastrophe. I repeat, the K/T event did discriminate by size as much as behavior. Most of the little critters were wiped out too.
Dennis Cox says:
June 20, 2012 at 11:22 am
Some of the denials of the YD impact event are getting ludicrous.
==============================================================
Same goes for you. No food for horses? What did the buffalo eat? Why did island animals survive better than continental dwellers? The meteors avoided islands? Nothing about your nebulously defined theory makes any sense. How big was it? Why didn’t it affect Africa? Or Antarctica? Or did it? Let me remind you that the K/T even was as devastating to marine as to terrestrial species. Use your head now and tell us, does the fact that insular species fared better than continental species favor meteoric or human causes? Why were South American species decimated and New Zealand species unaffacted–until humans arrived?
This silly nonsense can only thrive in vastly ignorant minds. –AGF
timetochooseagain says: @ur momisugly June 19, 2012 at 9:42 pm
…………..
The Milankovitch theory is too successful to justify throwing it out completely.
________________________________________
Yes especially since Gerald Roe got the kinks out of the theory by using the rate of change in the Ice.
Luboš Motl discusses the paper HERE.
agfosterjr says:
Hmmm…
Those “vastly ignorant minds” have sure been producing, and publishing a lot of work.
In Europe: Tian et al, 2010 went searching for diamonds in the YDB (In Europe it is also referred to as the Usselo Horizon) in Belgium. They wrote that “our findings confirm, and in fact reveal more direct proof than the earlier studies, the existence of diamond nanoparticles also in this European YDB layer No such particles are found in the overlying silt and clay or in the underlying fine sands.”
Van Hoesel A, Hoek W, Braadbaart F, van der Plicht H, Drury MR. (2011) Nanodiamonds and the Usselo layer. Paper #1556, XVIII INQUA-Congress, 21-27 July 2011 in Bern, Switzerland, reported finding “carbon aggregates [consistent with] nanodiamond” in YD-aged sediments In the Netherlands.
Abstract from Marshall W, Head K, Clough R, Fisher A. (2011) Exceptional iridium concentrations found at the Allerød-Younger Dryas transition in sediments from Bodmin Moor in southwest England. Paper #2641, XVIII INQUA-Congress, 21-27 July 2011 in Bern, Switzerland. Elevated iridium values, dated to start of the Younger Dryas cooling event, have been found in sediments deposited at a number of Late Glacial sites in North America and one in Europe. It has been proposed (e.g., Firestone et al., 2007, PNAS 104: 16016-16021) that this widespread iridium enrichment signal is the result of an explosive disintegration of a large extraterrestrial object over North America around 12,900 cal. yr BP, and it is contended that it was this event which instigated the Younger Dryas cooling. This scenario is controversial, and the ‘ET’ explanation of these geochemical signals is not universally accepted. This notwithstanding, we report here the finding of an iridium anomaly in the Allerød-Younger Dryas boundary sediments at Hawks Tor in the southwest of England. The concentration of iridium and other elements is determined in peat monoliths using ICP-MS, operated in collision-cell mode, and ICP-OES instruments. We find an increase of over 300 % in the iridium concentration measured in the bulk sediment immediately above the Younger Dryas boundary compared with the values found below the transition. The iridium-titanium ratio is used to confirm a lag between the start of the iridium enrichment and the timing of abrupt environmental disruption at the site signalled by decreases in the organic carbon content, and changes the concentrations of potassium, iron and manganese. These geochemical changes coincide with a shift from a humified peat to a minerogenic lithology. By using a new calibration of existing 14C ages, integrated with new AMS dates and optically stimulated luminescence ages, we show that the timing of this iridium enrichment found in southwest England is in agreement with the dates proposed for the iridium enrichment signals previously found in North America and Belgium.
In Germany: Wolfgang Roesler et al., Carbon Spherules With Diamonds In Soils
In South America: Mahaney WC, et al. (2010a) Evidence from the northwestern Venezuelan Andes for extraterrestrial impact: The black mat enigma. Geomorphology, v. 116, iss. 1-2, p. 48-57.
Mahaney WC, Krinsley D, Kalm V (2010b) Evidence for a cosmogenic origin of fired glaciofluvial beds in the northwestern Andes: Correlation with experimentally heated quartz and feldspar. Sedimentary Geology, v. 231, iss. 1-2, p. 31-40.
Mahaney WC, David Krinsley, Kurt Langworthy, Kris Hart, Volli Kalm, Pierre Tricart and Stephane Schwartz. (2011a)Fired glaciofluvial sediment in the northwestern Andes: Biotic aspects of the Black Mat. Sedimentary Geology. 237, (1-2), pp73-83
Mahaney, WC, Dave Krinsley, James Dohm, Volli Kalm, Kurt Langworthy and J. Ditto. (2011b) Notes on the black mat sediment, Mucunuque Catchment, northern Mérida Andes, Venezuela.. Journal of Advanced Microscopic Research, vol. 6, no. 3.
And on the North American Continent Firestone RB, et al. (2007) Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling. Proc Natl Acad Sci USA 104:16016–16021.
Baker DW, Miranda PJ, Gibbs KE. (2008) Montana Evidence for Extra-Terrestrial Impact Event That Caused Ice-Age Mammal Die-Off. American Geophysical Union, Spring Meeting 2008, abstract #P41A-05.
Fayek, M.; Hull, S.; Anovitz, L.; Haynes, V.; Bergen, L. (2008) Evidence of impact material and the extinction of the mega-fauna 12,900 years ago. American Geophysical Union, Fall Meeting 2008, abstract #PP13C-1469.
Tankersley K. (2009) “Evidence of the Clovis Age Comet at Sheriden Cave, Ohio.” Midwest Chapter of the Friends of Mineralogy Symposium and Field Conference (Geology Department of Miami University, Oxford, Ohio, USA), 5 September 2009.
Firestone RB. (2009) The Case for the Younger Dryas Extraterrestrial Impact Event: Mammoth, Megafauna, and Clovis Extinction, 12,900 years Ago. Journal of Cosmology (journalofcosmology.com) Kennett DJ, et al. (2009a)
Shock-synthesized hexagonal diamonds in Younger Dryas boundary Sediments, Proc Natl. Acad. Sci. USA, 106 (31): 12623-12628. Kennett DJ, et al. (2009b)
Nanodiamonds in the Younger Dryas boundary sediment layer. Science 323:94.
Sharma M, Chen C, Jackson BP, Abouchami W. (2009) High resolution Osmium isotopes in deep-sea ferromanganese crusts reveal a large meteorite impact in the Central Pacific at 12 ± 4 ka. American Geophysical Union, Fall Meeting 2009, abstract #PP33B-06.
LeCompte MA, Goodyear AC, Demitroff M, Batchelor D, Mooney C. (2010) An Independent Review of the Younger Dryas Extraterrestrial Impact Hypothesis and its Recent Re-Evaluation by Surovell et al. 21st Biennial Meeting of the American Quaternary Association (AMQUA). Laramie, Wyoming. (this was the rebuttal of Surovell et al that is cited in the Lake Cuitzeo paper)
Andrei V. Kurbatov et al. (Journal of Glaciology, Vol. 56, No. 199, 2010) reported the ‘Discovery of a nanodiamond-rich layer in the Greenland ice sheet’
Scruggs, MA, Raab LM, Murowchick JS, Stone MW, Niemi TM. (2010) Investigation of Sediment Containing Evidence of the Younger Dryas Boundary (YPB) Impact Event, El Carrizal, Baja California Sur, Mexico. Geological Society of America Abstracts with Programs, Vol. 42, No. 2, p. 101.
Wu Y. (2011) Origin and Provenance of Magnetic Spherules at the Younger Dryas Boundary. Thesis, Dartmouth College.
Isabel Israde-Alcántara et al. (2012) Evidence from central Mexico supporting the Younger Dryas extraterrestrial impact hypothesis
T.E. Bunch et al. (2012) Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago by
Bottom line: It has been conclusively demonstrated in publications in major scientific journals that the Younger Dryas Boundary layer is in fact a global impact layer the rivals the Cretaceous/Tertiary layer.
agfosterjr says that “This silly nonsense can only thrive in vastly ignorant minds.”
The thing is, every name on that list is a multiple PhD scientist who’s published their data in refereed ligature; and in very well respected journals at that. And the only thing we read from agfosterjr in response to that data is the kind of off topic straw man arguments, and vulgar, insulting ad hominems that can only originate from a vastly ignorant mind.
agfosterjr says:
Hmmm…
Those “vastly ignorant minds” have sure been producing, and publishing a lot of work.
In Europe: Tian et al, 2010 went searching for diamonds in the YDB (In Europe it is also referred to as the Usselo Horizon) in Belgium. They wrote that “our findings confirm, and in fact reveal more direct proof than the earlier studies, the existence of diamond nanoparticles also in this European YDB layer No such particles are found in the overlying silt and clay or in the underlying fine sands.”
Van Hoesel A, Hoek W, Braadbaart F, van der Plicht H, Drury MR. (2011) Nanodiamonds and the Usselo layer. Paper #1556, XVIII INQUA-Congress, 21-27 July 2011 in Bern, Switzerland, reported finding “carbon aggregates [consistent with] nanodiamond” in YD-aged sediments In the Netherlands.
Abstract from Marshall W, Head K, Clough R, Fisher A. (2011) Exceptional iridium concentrations found at the Allerød-Younger Dryas transition in sediments from Bodmin Moor in southwest England. Paper #2641, XVIII INQUA-Congress, 21-27 July 2011 in Bern, Switzerland. Elevated iridium values, dated to start of the Younger Dryas cooling event, have been found in sediments deposited at a number of Late Glacial sites in North America and one in Europe. It has been proposed (e.g., Firestone et al., 2007, PNAS 104: 16016-16021) that this widespread iridium enrichment signal is the result of an explosive disintegration of a large extraterrestrial object over North America around 12,900 cal. yr BP, and it is contended that it was this event which instigated the Younger Dryas cooling. This scenario is controversial, and the ‘ET’ explanation of these geochemical signals is not universally accepted. This notwithstanding, we report here the finding of an iridium anomaly in the Allerød-Younger Dryas boundary sediments at Hawks Tor in the southwest of England. The concentration of iridium and other elements is determined in peat monoliths using ICP-MS, operated in collision-cell mode, and ICP-OES instruments. We find an increase of over 300 % in the iridium concentration measured in the bulk sediment immediately above the Younger Dryas boundary compared with the values found below the transition. The iridium-titanium ratio is used to confirm a lag between the start of the iridium enrichment and the timing of abrupt environmental disruption at the site signalled by decreases in the organic carbon content, and changes the concentrations of potassium, iron and manganese. These geochemical changes coincide with a shift from a humified peat to a minerogenic lithology. By using a new calibration of existing 14C ages, integrated with new AMS dates and optically stimulated luminescence ages, we show that the timing of this iridium enrichment found in southwest England is in agreement with the dates proposed for the iridium enrichment signals previously found in North America and Belgium.
In Germany: Wolfgang Roesler et al., Carbon Spherules With Diamonds In Soils
In South America: Mahaney WC, et al. (2010a) Evidence from the northwestern Venezuelan Andes for extraterrestrial impact: The black mat enigma. Geomorphology, v. 116, iss. 1-2, p. 48-57.
Mahaney WC, Krinsley D, Kalm V (2010b) Evidence for a cosmogenic origin of fired glaciofluvial beds in the northwestern Andes: Correlation with experimentally heated quartz and feldspar. Sedimentary Geology, v. 231, iss. 1-2, p. 31-40.
Mahaney WC, David Krinsley, Kurt Langworthy, Kris Hart, Volli Kalm, Pierre Tricart and Stephane Schwartz. (2011a)Fired glaciofluvial sediment in the northwestern Andes: Biotic aspects of the Black Mat. Sedimentary Geology. 237, (1-2), pp73-83
Mahaney, WC, Dave Krinsley, James Dohm, Volli Kalm, Kurt Langworthy and J. Ditto. (2011b) Notes on the black mat sediment, Mucunuque Catchment, northern Mérida Andes, Venezuela.. Journal of Advanced Microscopic Research, vol. 6, no. 3.
And on the North American Continent Firestone RB, et al. (2007) Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling. Proc Natl Acad Sci USA 104:16016–16021.
Baker DW, Miranda PJ, Gibbs KE. (2008) Montana Evidence for Extra-Terrestrial Impact Event That Caused Ice-Age Mammal Die-Off. American Geophysical Union, Spring Meeting 2008, abstract #P41A-05.
Fayek, M.; Hull, S.; Anovitz, L.; Haynes, V.; Bergen, L. (2008) Evidence of impact material and the extinction of the mega-fauna 12,900 years ago. American Geophysical Union, Fall Meeting 2008, abstract #PP13C-1469.
Tankersley K. (2009) “Evidence of the Clovis Age Comet at Sheriden Cave, Ohio.” Midwest Chapter of the Friends of Mineralogy Symposium and Field Conference (Geology Department of Miami University, Oxford, Ohio, USA), 5 September 2009.
Firestone RB. (2009) The Case for the Younger Dryas Extraterrestrial Impact Event: Mammoth, Megafauna, and Clovis Extinction, 12,900 years Ago. Journal of Cosmology (journalofcosmology.com) Kennett DJ, et al. (2009a)
Shock-synthesized hexagonal diamonds in Younger Dryas boundary Sediments, Proc Natl. Acad. Sci. USA, 106 (31): 12623-12628. Kennett DJ, et al. (2009b)
Nanodiamonds in the Younger Dryas boundary sediment layer. Science 323:94.
Sharma M, Chen C, Jackson BP, Abouchami W. (2009) High resolution Osmium isotopes in deep-sea ferromanganese crusts reveal a large meteorite impact in the Central Pacific at 12 ± 4 ka. American Geophysical Union, Fall Meeting 2009, abstract #PP33B-06.
LeCompte MA, Goodyear AC, Demitroff M, Batchelor D, Mooney C. (2010) An Independent Review of the Younger Dryas Extraterrestrial Impact Hypothesis and its Recent Re-Evaluation by Surovell et al. 21st Biennial Meeting of the American Quaternary Association (AMQUA). Laramie, Wyoming. (this was the rebuttal of Surovell et al that is cited in the Lake Cuitzeo paper)
Andrei V. Kurbatov et al. (Journal of Glaciology, Vol. 56, No. 199, 2010) reported the ‘Discovery of a nanodiamond-rich layer in the Greenland ice sheet’
Scruggs, MA, Raab LM, Murowchick JS, Stone MW, Niemi TM. (2010) Investigation of Sediment Containing Evidence of the Younger Dryas Boundary (YPB) Impact Event, El Carrizal, Baja California Sur, Mexico. Geological Society of America Abstracts with Programs, Vol. 42, No. 2, p. 101.
Wu Y. (2011) Origin and Provenance of Magnetic Spherules at the Younger Dryas Boundary. Thesis, Dartmouth College.
Isabel Israde-Alcántara et al. (2012) Evidence from central Mexico supporting the Younger Dryas extraterrestrial impact hypothesis
T.E. Bunch et al. (2012) Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago by
Bottom line: It has been conclusively demonstrated in publications in major scientific journals that the Younger Dryas Boundary layer is in fact a global impact layer the rivals the Cretaceous/Tertiary layer.
agfosterjr says that “This silly nonsense can only thrive in vastly ignorant minds.”
The thing is, every name on that list is a multiple PhD scientist who’s published their data in refereed ligature; and in very well respected journals at that. And the only thing we read from agfosterjr in response to that data is the kind of straw man arguments, and vulgar, insulting ad hominems that can only originate from a vastly ignorant mind.
agfosterjr says:
June 20, 2012 at 10:03 am and 1:19 pm
No, but you seemed to be arguing that humans hunted the mammoths to extinction. I simply pointed out that it makes no sense for humans to have killed off the biggest beasts, when there were plenty of smaller ones around.
And maybe we should talk about the bone heaps a bit. As you may recall, on Anzhu Islands off the Russian arctic coast near 75°N 141°E, early Russian explorers and traders found not only heaps of mammoth tusks mixed in with rhino and bison bones, but the shattered remains of ancient forests as well.
Do elephants commonly get stuck in the mud and drown in Africa or India? Remains of mammoths were found in the permafrost so commonly by native Siberians that the myth of the giant moles was invented to account for the mystery. It was thought the giant moles died while digging to the surface.
Those vastly ignorant minds will get you every time.
@leftturnandre June 19, 2012 at 2:02 pm:
Always this is the case. Even data and artifact evidence gets interpreted “fundamentally wrong” sometimes, so basically when there is a puzzle it can be from as yet inadequate research or from dead end interpretations that lead down blind alleys.
Good catch on that. I noticed it, too.
This is an assumption most people make, that there were ice sheets extending down roughly equally in both western AND Eastern hemispheres. Not quite so. Notably the mammoths were where the ice sheets were NOT. Yet they ended up UNDER/IN the permafrost. One has to ask, How does that happen? Did sedimentation overcome them suddenly? Obviously not, and therein lies the real question: How did they get under the frozen soil?
Let’s not forget that Darwin himself considered the extinction of the mammoths in northern Siberia to be an unsolvable puzzle.
Steve Garcia
Dennis Cox says:
June 20, 2012 at 2:17 pm
That’s quite a biblography–have you read any of it? Can you answer any of my questions? We know meteors collide and are capable of doing damage–if they land on cities. They haven’t yet; space junk is more likely to. So look; we’ve got different arguments getting mixed up in your head which you need to sort out:
1) The possibility of a good sized meteor some 12 or 12ky. (quite possible)
2) The possibility that it was big enough to affect cliimate. (quite improbable)
3) The possibility that climate change wiped out the megafauna. (improbable)
4) The possibility that meteors wiped out the megafauna. (quite absurd)
You might want to read the literature which applies to the last category and see if you can respond to my challenge. Specify your version of the theory and explain to us the timing and distribution of Pleistocene extinctions. Tell us why mammoths survived on Wrangell Island till 4ky, why buffalo survived, giant ground sloths and horses didn’t, etc. If you can’t answer those simple questions you believe in a silly fairy tale, silly bibliography notwithstanding. –AGF
The solar periodicity seems to be around 500 years as per MWP to LIA to date and the thermohaline circulation is around 1000 years.
H_2’s per cubic centimeter) would be enough to significantly modulate solar luminosity due to the gravitational energy of the infalling materia, and is also dense enough to diffuse downward into the thermosphere and actually invert the Earth’s usual loss of hydrogen while binding up O_3 into OH and H_2O. This could also alter climate in several ways — increase its bond albedo at a very high altitude, for example.
Over time they drift in and out of phase sometimes offsetting and sometimes supplementing one another.
Um, with these periods they would be “drifting in and out of phase” every — 1000 years. As these periods are integer multiples of one another. Also, the transitions observed have timescales as little as 40 to 50 years, which is almost insanely fast as far as climate is concerned. That’s not consistent with “drifting” into resonance.
But then, we don’t really know all of the timescales of solar variability, or the causes of same. Solar dynamics is difficult. I’ve started to study it just a bit (e.g. Landscheit’s paper, a Studies in Geophysics e-book, and other resources as I can find them. A big part of the problem is that a lot of interesting “stuff” happens in the deep core of the sun where dynamics is simultaneously enormously energetic and “fast” and yet constrained by density and hence “slow”. There are some very long term cycles there that we have no easy way to observe — neutrinos are pretty much the only probe that reaches in to where the action is, and beyond that we have models.
So I don’t disagree with the assertion that the short timescale fluctuation out of ice age conditions over a trivially short time might require a solar effect or some other global driver, but I do disagree with the assertion that we can even heuristically peg this to known/observed solar cycles. However, there are some really exotic possibilities out there — the passage of the solar system through a moderately dense tendril of a cloud of interstellar medium (one with a density above an estimated critical threshold on the order of
The difficulty is that many of the exotic possibilities a) violate no known physical laws, that is, they are “plausible”; and b) don’t provide much in the way of a unique paleontological signature. I’d even add c) cannot be either confirmed or rejected on the basis of local observational evidence. We have less than a century of direct measurements from, and of, space. Ruling out astrophysical/solar causes for major climate variations is extremely difficult with so short a baseline and such a crude understanding of the underlying physics and contributory data.
I do really like this article on the YD though. I was not aware of the possible weakness in the sudden dilution/thermohaline argument. Whether or not the moraine data is clear enough to positively refute this, it seems sufficient to make me doubt it more than I was doubting it, which in turn raises the plausibility of alternative explanations including solar variability or the more exotic ones.
rgb
Do elephants commonly get stuck in the mud and drown in Africa or India?
During the monsoon in India, it is far from unknown. The floods the monsoon can cause can be sudden and fearsome. Not so often “in the mud” but in a river bed that was nearly dry that suddenly becomes a deep pool with unclimbable sides.
(I used to live there — stories of elephant death of this sort are recorded in e.g. the writings of Jim Corbett and other naturalists and hunters during the British Raj, although I have no doubt that a more current search would turn them up too.)
rgb
IT IS NOT A METEOR, IT IS NOT A COMET AND IT IS NOT AN ASTEROID THAT CAUSED THE YOUNGA DRYAS. END OF STORY. THAT IS PURE NONSENSE..
IT IS SOLAR VARIABILITY THAT WAS THE PROBABLE CAUSE OF THE YD. SOLAR VARIABILTY HAS BEEN UNDER ESTIMATED ,UNTIL VERY RECENTLY.
[No need to shout. ~dbs, mod.]
ferd berple says:
“Cut human population from 7 billion back to a more sustainable 7 million. Otherwise, we are all doomed to die within the next 100 years..” [he forgot the /sarc]
_________________________
Dennis Cox says: @ur momisugly June 19, 2012 at 11:38 pm
So what’s your preferred method of mass murder to accomplish the culling of a few billion people without ruining the environment for those who remain? And who decides who get’s taken out?
_______________________
Agenda 21 of course and who gets tthe privilege of breeding? Well the Bureaucrats have that all figured out too.
Why to you think governments such as the UK and the USA are taking DNA samples from all babies and storing those samples indefinitely? Why do you think RFID tags for livestock, drivers licenses, passports are being implemented? Why do you think there is a big push for Universal Health Care?
Want to go to the doctor? Better have your implanted RFID tag or no care, want a job, want to buy food, clothing… Think I am making this up out of whole cloth??
RFID tagging of patients has already been tested. Babies DNA is already taken and stored and the USDA has already funded development of a successful spermicidal corn.
References:
USA: Baby DNA and Newborn Screening
The Citizens’ Council on Health Care has released a report in 2009 that raises concerns about the extension of eugenics into State newborn screening programs.
UK: DNA database created from babies’ blood samples: Millions of newborn babies have had their DNA stored by hospitals without the proper consent of their parents, it has been revealed.
National DNA database ‘worth discussing’: NSW Minister
Hospitals tune in to RFID: Testing gives way to implementation
RFID-based Information System for Patients and Medical Staff Identification and Tracking
.A small California biotech company, Epicyte, in 2001 announced the development of genetically engineered corn which contained a spermicide which made the semen of men who ate it sterile.
The corn has been field tested in tests financed by the US Department of Agriculture along with a small California bio-tech company named Epicyte. Announcing his success at a 2001 press conference, the president of Epicyte, Mitch Hein, pointing to his GMO corn plants, announced, “We have a hothouse filled with corn plants that make anti-sperm antibodies.
Epitcyte was bought out by a privately held company in Pittsboro, North Carolina. A bio tech company. Biolex
And into the “Woo-Woo” or WHO conspiracy type stuff:
Want a connection between the WHO and eugenics? ~ Vaccines
Vaccines: Sterilisation & Abortion
It should be noted that a population study in Africa turned up “strange statistics”
And also noted that the UN was in favor of Eugenics.
And a last couple of studies:
The evolution of racial differences in intelligence Source : Mankind Quarterly, Fall/Winter91, Vol. 32 Issue 1/2, p99, 23p (condensed here) by Richard Lynn, University of Ulster, Coleraine, Northern Ireland
SUNY @ur momisugly Albany press release: Global Warming Could be Reversing a Trend that Led to Bigger Human Brains
It is rather frightening how all this hangs together is it not?
Rivers flowing to the Arctic Sea are always freezing up, creating ice dams and preventing flow to the ocean. Ice periodically forms over enormous stretches of the river basins, the dams break, floods sweep away mammoths and lay sediment over the ice, vegetation grows on the sediment, mammoths graze, ice melts beneath the sediment, mammoths fall through, etc. On islands mountain dust accumulates on snow packed into ice, moss grows, mammoth graze, ice crevasses form, mammoths fall into crevasses, sometimes concentrated like Antarctic meteors. It’s no great mystery.
If you limit your list to the 48 states like Faith and Surovell you miss most of the important data. What F&S show is when temperate Amerinds finished off the big beasts. The Russians have a corner on pertinent evidence, but the big beasts died on the ice primarily in two stages over a period of tens of thousands of years, not all of a sudden. –AGF
“Drop a 60-ton bolide on top of a mile of ice and you won’t find any crater after the ice melts. You’ll get a whale of a lot of water vapor, though…”
Joules
joules/kg, so you’re only talking about vaporizing 
kg of water, around five meters cubed.
joules) and ejected 160 cubic kilometers of pyroclastic ash (pulverized earth) into the air. The sound was heard at least 1600 miles away. And that’s just the largest explosion in recorded history. Given two such events — Krakatoa was comparable, although roughly 4x smaller — in 200 years, it is reasonable to guestimate that 100 Mt volcanic explosions occur on a century timescale, with outliers that can be 10-100 times more violent. These explosions are more violent that the collision of a small asteroid — a 1 km in radius asteroid is has a mass order of Llatex 10^{10}$ kg, making the kinetic energy released quite comparable to Tambora at around a Gt (which failed to cause extinction-level climate change). It takes a big asteroid — one 10 km in radius — to give you the 1000-fold increase in energy released and push you out into extinction territory, at least as far as I can tell with my back of the envelope estimates.
This sort of event is pretty ignorable. Not even a whale of a lot of water vapor — there just isn’t that much energy. Assuming escape velocity for a collision speed, a metric ton of mass (1000kg) has a collision energy of:
(Ignoring factors of 2). Which is really a pretty small amount of energy — the heat of vaporization is
If you want “interesting” events, consider the explosion of Mount Tambora: http://en.wikipedia.org/wiki/1815_eruption_of_Mount_Tambora. It was estimated to be the equivalent of just under a gigaton of TNT (800 Mt,
rgb
Re : agfosterjr – Nobody argues that the extinctions didn’t involve remote outlier populations, while everyone more or less agrees the North American continental megafauna extinctions where synchronous and geologically instantaneous. The species that survived where either smaller, more numerous and much more mobile.
In response to agfosterjr:
Yes, of course I have read them.
My own radical theory of what happened back then is well expressed on my blog. It’s rather lengthy, and off topic to the subject of this thread. Which is the possible climatic effects of the event. My own thrust is the theoretical geomorphology, and planetary scarring it may have produced. If anyone is really interested they’re welcome to take a look.
The only argument I am making here is that the YDB layer is in fact, a global impact layer that rivals the K/T boundary layer. I have made no other assertions, or claims as to the other effects the event that produced it might have caused.
And in light of your previous, and continued small minded, and insulting ad hominems I see nothing whatsoever to gained by dignifying any of your straw man arguments with any further response.