Archaeologica.org

http://www.nature.com/news/2009/091012/ ... 9.997.html

No evidence of an extraterrestrial impact 13,000 years ago, studies say.

Rex Dalton

An independent study has cast more doubt on a controversial theory that a comet exploded over icy North America nearly 13,000 years ago, wiping out the Clovis people and many of the continent's large animals.

I like Adam Smith's comment; "It's always a relief when you can conclude that every study but yours is 'flawed'. . . ." The "firsters" will stick together, won't they.

Denial is a natural human reaction.

Comets (and some asteroids) hit at hypervelocities - thus it does not take too much mass to have a large effect. The energies released are beyond the simply physical, but molecular and nuclear as well.

Thus not much remains of the impactor, which was not all that massive to start out with, and finding those remains is detailed work. It is easy to slip up, and that goes for stratigraphic levels as well.

You need to remember that the impactor that extincted the dinosaurs was fairly large, and while the KT layer is easily visible, so little has been recovered that there is still an open question as to whether it was a comet or an asteroid that hit. (By the way, I am strongly of the first school). So you can imagine how small the mammoth killer was; after all, we're here now.

For your reading pleasure, some of the First Peoples' accounts of events:
http://forum.palanth.com/index.php/topic,1093.0.html

If there was not a comet impact, then one is left looking for a reason for them to have made these up.

Let's end this one fast:

2009 FALL AGU San Francisco, CA
Field-Analytical approach of land-sea records for elucidating the Younger Dryas Boundary syndrome
SECTION/FOCUS GROUP: Paleoceanography and Paleoclimatology (PP)
SESSION: Younger Dryas Boundary: Extraterrestrial Impact or Not? (PP15)
AUTHORS (FIRST NAME, LAST NAME): Thierry Ge1, MARIE-AGNES MICHELE COURTY2, Francois Guichard3
INSTITUTIONS (ALL):
1. Geoarcheology, INRAP, Pessac, France.
2. Prehistory -IPHES-ICREA, CNRS-MNHN, Tarragona, Spain.
3. Paleoocenography, CNRS-CEA UVSQ, Gif-sur-Yvette, France.

Linking lonsdaleite crystals, carbon spherules and diamond polymorphs from the North American dark layers at 12.9 cal yr B.P. to a cosmic event has questioned the nature and timing of the related impact processes. A global signal should trace the invoked airshocks and/or surface impacts from a swarm of comets or carbonaceous chondrites.

Here we report on the contextual analytical study of debris fall events from three reference sequences of the Younger Dyras period (11-13 ka cal BP):

(1) sand dune fields along the French Atlantic coast at the Audenge site;
(2) A 10 m record of detrital/bioorganic accumulation in the southern basin of the Caspian Sea with regular sedimentation rate (0.1 to 3 mm per year) from 14 to 2-ka BP cal;
(3) the Paijan sequence (Peruvian coastal desert) offering fossiliferous fluvial layers with the last large mammals and aquatic fauna at 13 ka BP sealed by abiotic sand dunes.

The three sequences display one remarkable layer of exogenous air-transported microdebris that is part of a complex time series of recurrent fine dust/wildfire events. The sharp debris-rich microfacies and its association to ashes derived from calcination of the local vegetation suggest instantaneous deposition synchronous to a high intensity wildfire. The debris assemblage comprises microtektite-like glassy spherules, partly devitrified glass shards, unmelted to partly melted sedimentary and igneous clasts, terrestrial native metals, and carbonaceous components. The later occur as grape-clustered polymers, vitrified graphitic carbon, amorphous carbon spherules with a honeycomb pattern, and green carbon fibres with recrystallized quartz and metal blebs. Evidence for high temperature formation from a heterogeneous melt with solid debris and volatile components derived from carbonaceous precursors supports an impact origin from an ejecta plume. The association of debris deposition to total firing would trace a high energy airburst with surface effects of the fireball. In contrast, microfacies and debris composition of the recurrent fine dust/wildfire events would trace a series of a low energy airburst. Their record is expressed in the Audenge sequence by a series of water-laid laminae of charred pine residues formed of carbonaceous spherules wrapped by carbonaceous polymers that includes lonsdaleite crystals as detected by high resolution in situ micro-Raman analysis. This association suggests recurrent flash forest wildfires ignited by hot spray of carbon-rich debris, followed by heavy snow falls. The record from the Peruvian desert suggests a possible linkage between the repeated debris fall/wildfires during the Younger Dryas and the following irreversible aridity along the Peruvian cost. In contrast the Caspian record of the Younger Dryas period indicates more gradual changes, possibly buffered by the hydrological functioning of the Caspian sea in a complex region. The Audenge context offers the amplified signal needed to understand at local to global scales the spatio-temporal pattern of impact-airburst events.

KEYWORDS: [4901] PALEOCEANOGRAPHY / Abrupt/rapid climate change, [1029] GEOCHEMISTRY / Composition
of aerosols and dust particles, [4924] PALEOCEANOGRAPHY / Geochemical tracers, [5420] PLANETARY
SCIENCES: SOLID SURFACE PLANETS / Impact phenomena, cratering.
Previously Presented Material: Original results, never presented, never published

I am a bit confused.

The article talks about the end of the Clovis people.
Not the start.

How would the impact have anything to do with if there was or was not someone here before them?

If I remember the first round of publication on this correctly, the possibility was floated that the radioactivity the event generated may have re-set the C-14 clock by a large margin -- in the ballpark of 11,000 RYBP equating to perhaps 25,000 actual.

If so (even to a much lesser extent) this would obviously toss a spanner into the chronological gears.

(?)

uniface wrote:If I remember the first round of publication on this correctly, the possibility was floated that the radioactivity the event generated may have re-set the C-14 clock by a large margin -- in the ballpark of 11,000 RYBP equating to perhaps 25,000 actual.

If so (even to a much lesser extent) this would obviously toss a spanner into the chronological gears.(?)

Firestone got his start on this working with C14 calibration curves. He spotted a huge bulge, which he associated with a nearby supernova. Later he came to view this supernova as the injection mechanism for an impactor.

This hypothesis differs from that of Clube, Napier, Shoemaker and others who believe that our solar system passing through the plane of our galaxy (the Milky Way) was the injection mechanism - hence Comet Encke, Comet Shoemaker Lavy 9, and now Comet SW3. However, they do not account for the bulge seen in the Incal98 radiocarbon calibration chart.

I lack the brains to work this out, but it looks like neutrons and protons are released in hypervelocity impacts, as may be seen by the spikes in the Incal98 chart. One spike may be associated with Barringer (Meteor) Crater impact in particular, and there are others.

This question was initially worked in regards to the Tunguska Impact and recent modern RC, but please don't ask me for citations on it. Google away.

O K

So we have R C dating of two different things.
Artifacts and sediments.

And they are trying to correlate the two.

But the possibility of the whole RC dating process being thrown off is mixing things up?

kbs2244 wrote: But the possibility of the whole RC dating process being thrown off is mixing things up?

Possibility? Come on now, which is it? Is this an aberration in the RC dating process, or isn't it? This is something measurable. It ought to be possible to physically (pun intended) analyse it. And if it is an aberration in the RC dating process, it should be possible to quantify it, and then it ought to be possible to factor it into RC dating computing, no? Or is it such a weird unlinear aberration that the whole RC dating methodology is useless in that era? And BTW: what era does this pertain to exactly?

Anyone who doesn't like a particular RC date always claims that SOMETHING interfered with the testing.

I'll put my money on the test.

Rokcet Scientist wrote:

kbs2244 wrote: But the possibility of the whole RC dating process being thrown off is mixing things up?

Possibility? Come on now, which is it? Is this an aberration in the RC dating process, or isn't it? This is something measurable. It ought to be possible to physically (pun intended) analyse it. And if it is an aberration in the RC dating process, it should be possible to quantify it, and then it ought to be possible to factor it into RC dating computing, no? Or is it such a weird unlinear aberration that the whole RC dating methodology is useless in that era? And BTW: what era does this pertain to exactly?

The problem is explaining the patterns seen in the RC calibration curve, Incal 98.

Of course, calibrated dates published earlier than Incal 98, which are often repeated, need recalibration. And conclusions drawn on those earlier calibrations need to be reworked.

The process is similar to what Renfrew did in the 1970's, with the first recalibrations, but extended back 10,000 years.

When I said "possibility" I meant from their point of view.

Personally, I don't put much value on long range RC dating with out it being correlated with another technology.

kbs2244 wrote:When I said "possibility" I meant from their point of view.

Personally, I don't put much value on long range RC dating with out it being correlated with another technology.

Note carefully the construction of the Incal98 calibration.

The big errors in RC dating are due to earlier C14 measuring techniques, before accelerators were used for C14 measurement.

Yeah.

But the dates obtained by those flawed methods are still in the text books and are still being tought.

An eternal problem with text books, kb. They don't self-destruct.