The subject has been on the tip of my fingers for quite some time and I thought I managed to google up most of the related papers, news articles, and blog posts, but it turns out that I missed one highly relevant discussion: in the January issue of GSA Today, there is a short paper by Nicholas Pinter and Scott E. The first idea is promoted by Dallas Abbott at Lamont Doherty I am looking for szabad nő Observatory and her co-workers, but there is no real peer-reviewed publication yet; the second has been put forward by Richard Firestone of the Lawrence Berkeley National Laboratory et al.
The evidence for the Pinter and Ishman have essentially the same main issue that I have blogged about: landforms that are morphologically identical to the so-called chevron dunes are well-known in the literature and they are called parabolic dunes. This is what they have to say about the chevron dunes: Pinter and Ishman also claim that chevron dunes in Madagascar and on Long Island are aeolian in origin.
We visited both locations and found many features i am looking for szabad nő seem incompatible with an aeolian origin.
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First, parts of the chevrons in both locations contain fist-sized rocks. These rocks are too large to be transported by the wind. Second, the orientations of the chevrons do not match the current prevailing wind direction. In both areas, some of the thicker sand deposits are being reworked into classic windblown dunes.
The direction of movement of these dunes differs 8° to 22° from the long-axis of the chevrons. Third, the degree of roundness of the grains in the chevrons is not characteristic of wind transport over long distances.
In both locations, sand grains on the distal ends of the chevrons are not well sorted or well rounded.
At its distal end, the chevron is 7. It is impossible to transport unabraded marine microfossils to this location via wind-generated saltation. The site is too far above sea level for storm waves, and there is no local agricultural activity. The chevron was deposited by a tsunami.
Well, these seem valid counterarguments at first sight — but it would be nice and it would be time to see actual data: images, measurements, grain size distributions. Which parts of the chevrons are reworked into eolian dunes? What is the difference in the morphology of tsunami dunes and eolian dunes? How does this relate to flow dynamics? Where do they occur exactly?
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And so on. They do this after first admitting that parts of the dunes were indeed reworked into classic wind-blown dunes.
Both stories have played out primarily kislemez rochlitz the popular press, highlighting how successful impact events can be in attracting attention.
The desire for such attention is understandable in an environment where science and scientific funding are increasingly competitive. References Pinter, N. Impacts, mega-tsunami, and other extraordinary claims. GSA Today, 18 1 DOI: GSA Today, 18 6e Firestone, R. Evidence for an extraterrestrial impact 12, years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling.
Proceedings of the National Academy of Sciences, 41