You have gotten way off the thread of the Praclaux Crater which Joel started
dealing with vegetation change in France during the Quaternary. I am still
waiting for a credible YEC account dealing with the pollen record presented.
There is no bioturbation discussed in the original articles and as a
Quaternary scientist who has worked with Holocene terrestrial sediments I
wouldn't expect significant bioturbation in the French sediments described.
For those that have been following the Praclaux Crater discussion who are
not geologists familiar with the terminology, the craters under discussion
are maars, which result from subsurface magma coming into contact with
significant ground water. The steam pressure that builds up above the magma
eventually blows off the overlying material. In the French case there was
no lava or volcanic tephra produced by these explosions. The tephra
discussed in the original articles was identified as coming from another
volcanic province about 100 km to the northwest, the pollen studies help
date those volcanic eruptions as well as the maars themselves. The phreatic
eruptions which formed the craters near Le Puy (where the pollen profiles
under discussion were collected) do not appear to be related to the
eruptions from volcanoes near the center of Auvergne which produced the
tephra. If there are any geologist on line who are familiar with French
volcanic history please correct me if I am wrong here ( information on
French geology is tough if you cannot read French).
As an interesting aside one tephra discussed contained pollen also. The
pollen assemblage present in it was one which suggests that the distant
volcano erupted in Spring. Those palynologists of us who were living in the
Pacific NW in 1980 also found the pollen spectrum of Mount St. Helens, at
the time of the May eruption, in samples of ash along with very minor
amounts of the local pollen spectra. All pollen was of plants flowering in
either of the two regions at the time of the eruption. Some of the pollen
from Mount St. Helens which I collected in Moscow, Idaho was even chard.
Yes, there was some charcoal from trees on St. Helens also in the ash.
I wish a knowledgeable YEC would deal with the issue of pollen profiles,
such as those discussed, which show the vegetational changes that have
occurred world wide over the past150,000 years (we do not need to discuss
the record further back than that for now). If I am wasting my time
researching these changes, I want to know so I can stop and get on with my
Thank you Joel for alerting me to these long core records; my palynological,
library research lately has been confined to Last Glacial and Holocene
articles and I overlooked these.