Re: Fossil forest found in So. IL coal mine


"Jo Schaper" <jospamnotschaper34@5socket78dot9net> wrote in message
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George wrote:
<mircea13@xxxxxxxxxxx> wrote in message
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On Tue, 24 Apr 2007 11:45:35 -0400, "George" <george@xxxxxxxxxxxxxxx>
wrote:

The earthquake scenario draws heavily on the sharp contact between
the
coal bed and the overlying shale, as well as the exceptional
preservation of the plant fossils, which both suggest an abrupt
drowning of the mire, and the lateral changes of coals and shale
thicknesses, which favor a fault control interpretation rather than
differential compaction one. The fault was neither directly observed,
nor mapped at a geologic boundary offset; the fault was necessary to
bring together all the other elements of the author's model.

Plus, I think the fact that a lot of the trunks were still standing in
their living positions also argued for a sudden drowning.

You're right, George. That's what I had in mind when I mentioned the
"exceptional preservation." Anyway, only now I notice the subject
header is somehow misleading. The find is in Vermilion County, on the
east side of Illinois, about 50 miles straight east from Urbana and
near the boundary with Indiana. Also, the authors mention the New
Madrid earthquakes and the Reelfoot Lake only as a recent analogue for
their drowned Pennsylvanian forest, but draw no connection between the
New Madrid fault zone and their necessary fault. About the latter,
they'd rather trace it northeastward in Indiana to the Royal Center
fault, which cuts across the Kankakee Arch.

Regards,

Mircea

It would be difficult to say which fault could have done the damage. I
don't know that any known fault has been identified in the immediate
region as being old enough to have caused it. Having said that, The
basement rock along the Wabash is highly deformed, and so any faulting
related to that deformation could be responsible. Also, I wouldn't rule
out the New Madrid area, since it has a very long seismic history.

George

My error on the headline; I was running out the door this a.m. when I
posted it. I suppose it would be more Midstate-- from my vantage, there
are only 2 parts to Illinois: Chicago, Northern Illinois and
Downstate/Southern Illinois. My bro lives in Quincy, and the imaginary
cultural dividing line seems to be the MO/IA border drawn east across the
state, which puts Vermilion in the southern half.

The point which George makes about the long history of the New Madrid
fault(as opposed to the recent hypotheses of short-term, recent activity
only) is the reason this caught my eye. (Twas front page news on the new
Post-Dispatch, too.)

I don't think anyone understands midwestern faulting and its
relationships to adjacent fault zones with enough certainty to rule
anything in or out.

Well, the Fluorspar district, I think, is reasonably well studied that I
think it safe to say that most faults are post-Permian in age to late
Cretaceous. Beyond that in either temperal direction, it's anyone's guess.
But I do agree that there isn't much certainty as to the age of most faults
in the midwest.

Interestingly, I went to my cave grotto meeting after the meeting at a
pizza joint tonight, and a perfect stranger (not with our group)
buttonholed me on the way out, showed me the newspaper, and asked what I
thought about the report. When I finished with the pros and cons of the
article, did a demo of Pangaea with napkins on my fist,and finished with
the young man's questions (about 20 minutes) he wanted to know if he owed
me several hundred dollars for the explanation. I gave him my website
address instead, but that would be the life: getting buttonholed on the
street to explain geology to passersby, and getting paid for it, to boot!

Hehehe. I think that he should have at least offered to pay for the next
round of pizza.

George


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