Hope this clears it up, et
Mike Baillie was among the first to ascribe the collapse of 536 CE to planet Earth intersecting the dust stream of Comet Enkce. This was contested by David Keys, who ascribed the climatic and cultural collapse to volcanic dust from SE Asian eruptions.
My review, including documentation of the destruction of the Bazas region of France in 580 CE, may be found at:
http://abob.libs.uga.edu/bobk/ccc/ce082202.html
Recently, Ducan Steel and an Italian team have been working at Sirente.
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