> Most recently, the Younger Dryas Boundary comet strike, that drove 30+ American genera to extinction and wiped out the Clovis culture, has finally been accepted by mainstream geologists.
This statement surprised me because, while I haven't kept any sort of close eye on Younger Dryas research, I had literally never heard of this hypothesis before. A quick search of scholar.google.com for "Younger Dryas impact" focusing on recent papers seems to indicate to me that there is at least an active, ongoing academic dispute between at least two groups over the matter, and I haven't looked at the author lists to figure out if there's only one group on a specific side.
At the very least, I'd be very hesitant to say that it "has finally been accepted by mainstream geologists."
Edit: I should also mention that I did find an r/AskHistorians post on this topic (https://old.reddit.com/r/AskHistorians/comments/du40jl/the_y...) where the archaeologist is clearly not a believer in the hypothesis, linking some articles [including those I found in my aforementioned search] that are critical of the theory. While not gospel truth, it again suggests that "has finally been accepted by mainstream geologists" is not an accurate description of the current status of the hypothesis in the relevant community.
The watershed event was publication of Powell's "Deadly Voyager" this year. Powell is a respected, mainstream geologist. Hancock's most vocal mainstream critics have issued public mea culpas. The book is available on Kindle, free for Prime members, and is a quick and enlightening read.
The opposition for the past 13 years turns out to be a real black eye for geology. One group's failure to discover corroborating evidence was treated as a demonstration of falsehood and possible fraud, rather than what turned out to be a failure to sample the correct stratum. The negative evidence, interpreted correctly, reinforces the Impact Hypothesis by showing that the particles reported occur only in the cited layer, and not in samples straddling the layer.
The most compelling evidence is widespread, very sharp platinum enrichment at the layer, at dozens of sites, and particles that exhibit melting of materials that melt only well over 2000 degrees C, which does not occur in forest fires or volcanic eruptions.
I few trivial searches disqualify your "watershed event":
The "particles" you mention are most probably Highly siderophile elements (HSE) - which indeed only form upwards of 2000°C. That doesn't mean they have to come from outer space, though, as they are also present in earth's upper mantle[0]. Surface HSE presence can therefore also be explained by volcanic activity.
And indeed, a July 2020 publication has shown that the present evidence and thus the Younger Drias Event can also be explained by a series of volcanic eruptions[1].
> The "particles" you mention are most probably Highly siderophile elements (HSE)
From what I saw of some of the articles I was reading, it was nanodiamonds and magnetic microspherules. I'm getting this mostly from [1], which is definitely a strong critical take on the evidence, suggesting that the methodology for identifying these particles is sufficiently subjective that researchers knowing where the samples are to have occurred is biasing their interpretation of the results to find a sharp distinction around the Younger Dryas threshold that isn't corroborated if that context is removed.
You can quibble over this or that equivocal result, but the very sharp platinum concentration results at numerous sites are not so easily dismissed, and are (therefore?) notably not mentioned.
When I first poked at this hypothesis, I came away feeling that the best characterization was that it's an area of academic dispute where both sides have credibility and neither side can be accurately considered fringe or mainstream, in contrast to your initial comment. Nothing you have said has shaken that belief, and I have no relevant scientific expertise to offer in support of one side or the other. I have my personal opinion on which side I feel has the better evidence and prefer on the balance of probabilities, but what that opinion is is ultimately unimportant.
That said, there is one thing that mildly concerned me when I read your first comment and that your later comments have only reinforced my impressions. You seem to be approaching this topic from an evangelical perspective, and not a scientific one: that there is a core belief, this needs to be disseminated to as many people as possible, and that anything that challenges that belief needs to be swiftly eliminated. Your rhetoric--"Neanderthal", "black eye for geology"--does not help your argument. I only bring this up because I saw a video over the weekend [1] discussing Flat Earthers and some of the argumentation style they used, and on reflection, it was striking how similar your comments were, just on an acceptable opinion rather than a loony idea.
That [1] really only examines ratios of osmium to platinum-group elements is telling. At only one place in the paper do they admit that the osmium/osmium isotope ratios found in their samples, from the one cave, do, in fact, match a known bolide. They very carefully avoid addressing the extreme Pt abundances found in the YDB layer at dozens of sites. This is akin to others complaining that iridium abundance at the strata is not especially elevated, without addressing platinum, which lacks other explanation.
"Lack of clear consensus" cited in the paper is revealed to mean that certain individuals, like them, have disagreed, without addressing faulty details. Such individuals have made claims that spherules identified as carbon are spores, without having examined any of them, or that they are not present at all, but which turn out to refer to layers that do not coincide with the YDB.
The European volcanic eruption mentioned is known to have occurred some centuries before the YDB.
You can't refute results from dozens of sites with equivocal results from a single site.
This statement surprised me because, while I haven't kept any sort of close eye on Younger Dryas research, I had literally never heard of this hypothesis before. A quick search of scholar.google.com for "Younger Dryas impact" focusing on recent papers seems to indicate to me that there is at least an active, ongoing academic dispute between at least two groups over the matter, and I haven't looked at the author lists to figure out if there's only one group on a specific side.
At the very least, I'd be very hesitant to say that it "has finally been accepted by mainstream geologists."
Edit: I should also mention that I did find an r/AskHistorians post on this topic (https://old.reddit.com/r/AskHistorians/comments/du40jl/the_y...) where the archaeologist is clearly not a believer in the hypothesis, linking some articles [including those I found in my aforementioned search] that are critical of the theory. While not gospel truth, it again suggests that "has finally been accepted by mainstream geologists" is not an accurate description of the current status of the hypothesis in the relevant community.