I notice you're a writer but of course I don't know what your background is. Something occurred to me and as a matter of curiosity I wonder if you've ever looked into the possibility of massive sand blows contributing to the creation of the Sahara? I read a foreign published work within the last day or two that made some compelling arguments re volcanism, massive volcanism, being the culprit responsible for the "green glass" and the abrupt changes to North Africa. Could it be part of the answer?
Having studied the Sahara and Arabian deserts for a number of years now I can say with a good deal of confidence that no matter what you read on the internet the provenance of the quartz grains that form the deserts in unknown (the same would apply to the deserts, beaches, sandstone deposits, etc. worldwide). Pretty amazing given they both contain vast oceans of sand. Some say the underlying Nubian sandstone (almost pure quartz sand) may be the source but then they cannot say where this originated. Volcanism largely produces basalt which is mainly devoid of quartz altogether, so this cannot be the source.
I’m in the middle of writing my third book “Extraterrestrial Desert Sands” in which I proposed the deserts (& quartz sand globally) were formed VERY recently. In short: Cosmic chaos involving mainly Mars (once home to humans the same as you and I) created unfathomable quantities of vaporised rock - this condensed as it fell to earth, precipitating out of the atmosphere to form quartz crystals. In other words it rained sand! Vast swaths of it - this is the origin of the deserts (beaches, dune sand, etc.) of the world! All this occurred in the last few thousand years. Prior to this the Sahara was a green savanna, as too were vast regions of the Arabia peninsular.
I’m in favour of the ‘green glass’ the result of a bolide event... as follows.
“The latest research almost proves that Libyan desert glass is the terrestrial by-product of a massive bolide impacting in desert sands. Analysis shows rapidly quenched molten silica with signs of molecularly altered zircon crystals, shocked quartz and metals such as nickel and iron. The only force that can produce this material is really a cosmic impact. Nuclear blasts come close, but the material is very low quality and frothy. Fulgerites from lightning impact is even more frothy and grainy, and looks more like cemented sand.”
http://www.abovetopsecret.com/forum/thread960470/pg2
But I would ignore any “gazillion years old” dates. Everything we see today in geological terms occurred mainly in the last few thousand years (catastrophist not creationist!). Earth is still simmering down as a result of recent planetary encounters.
Loads more on my web.
Apologies if I appear illusive, it’s all eyes down in trying to get book completed!