First Harvard, now Dartmouth: More independent evidence for Younger Dryas impact

Cevin and Trent –

It sounds like we are all on more or less the same page on hunter-gatherers. It would be odd if the development toward ag and domestication of animals didn’t happen gradually, so it seems there would have been a (possibly long) transition away from being nomadic hunter-gatherers.

And by long, I mean as short of a time as 1,000-5,000 years. I see people compressing such time periods as if they were overnight changes, and that isn’t the case at all. After all, we are less than 5,000 years from Stonehenge to iPhones and 3D printers – if you accept their dates for Stonehenge of ~2500BCE.

Is changing to settled communities that big of a deal? I would think all nomadic h-gs had preferred regions, ones where they had found nice caves or stream beds, and that they would have tended to stay in those locations somewhat longer. If life was hard on the move, it is fairly human to linger in the places in which life was nominally easier.

A possible example:

The Dordogne valley in southern France, with its cliff caves would have afforded increased security, due to the natural lookout capabilities all over the cliffs.

Not all locations were equal, and it would seem that locations would – for the women especially – be preferred to life “on the road.” IMHO, women are – and I assume always have been – the settlers. Also IMHO, it is almost certain that the women were also the weavers of the cloth that those twisted fibers came from.

Hmmm…

Actually there is only one “trapdoor volcano” on this world. It’s at a place called Manuel Benavedes. And it’s just south of the Mexican border, and right across from Big Bend Ranch State Park in southwest Texas. And it was an American geologist named F. W. McDowell who proclaimed that we are looking at a giant 17 mile “trapdoor”, not a Mexican. And he makes this assumption without any consideration whatsoever for the crazy mantle physics required to produce a 17 mile wide, perfectly semi-circular trapdoor vent; much less any consideration of the structural integrity that would have to exist in the rock of that “trapdoor” in order for the thing to have opened, and closed repeatedly without breaking.

See:

McDowell, F. W., 2010, Geologic Map of Manuel Benavides area, Chihuahua, Mexico. Map and Chart no. 99. Geological Society of America, Boulder, Colorado.

Abstract:

This map and text cover an area of eastern Chihuahua state adjacent to the Rio Grande and the Big Bend of Texas. The area contains an 1100-m-thick volcanic section very similar in lithology and age (by Ar-Ar dating) to that exposed in both Big Bend National and State Parks. This includes, from older to younger, a heterogeneous sequence very much like to the Chisos Formation, a thick locally derived rhyolitic flow complex comparable to the Tule Mountain trachyandesite, distal thin ignimbrites similar in age to the Mitchell Mesa ash-flow tuff (the largest unit in the Trans-Pecos volcanic field), and a caldera source for both the 31 Ma San Carlos tuff and the 28 Ma Santana tuff. The caldera is an unusual trap-door type with a hinge zone on the southwest and two separate collapse and eruption margins around the north and east. Its outer diameter is approximately 25 km, which is unusually large for the tuffs that erupted from it, suggestive of a shallow collapse. Inflation or tumescence prior to the eruptions modified a preexisting Laramide fold by bowing it outward toward the north and east; a 31.5 Ma granitoid was intruded into the fold axis, resulting in the formation of skarn deposits in the surrounding limestones of the fold.

The map itself consists of two crude hand drawn maps with all the data resolution of a comic book page, and done by a couple of graduate students back in the eighties. In 2010 Mr McDowell simply kludged the two together into a single map. That map has almost no correlation whatsoever to actual geologic features clearly visible in modern hi resolution satellite imagery, and verifiable from the ground. And McDowell completely disregards that modern satellite data because it just isn’t supportive of his too many unsupported assumptions, and suppositions to count.

There is no question that something different, and inconceivably violent happened there. But as for me, I prefer to think of it as a “pseudo explosion” structure not a volcano; leaving the door open for further study to determine what really happened there without all the unquestioned, gradualist-assumptive reasoning.

Hi Steve,

That thing is behind a GSA paywall anyway so even if that old link worked all you’d get without paying is the abstract. But I have a copy that I can share. I’ll send you an email telling you how.

If it is a crpto explosive structure, Dennis, then it dates from millions of years ago.
You probably want to check both the magentic maps and gravity maps as well.