The the swamp model for the origin of coal fails to explain the features
of banded coals of the eastern US. The alternate model, which more
readily fits the data, is that coal seams are the result of floating mats
of organic debris which settled out of water. The swamp model prevails
only because it fits with the uniformitarian model of earth history.
Last year I read Geological Society of America Special Paper 286:
"Modern and Ancient Coal-Forming Environments." About 20 authors
contributed 12 articles, most of which presented the vast peat swamps of
Indonesia as being modern analogues for Pennsylvanian coal swamps. Not
one of the authors mentioned or probably even recognized a glaring
inconsistency in that comparison.
Coal seams of the eastern US generally exhibit very sharp contacts
between the coal and the underlying clay, shale or sandstone, and also
make sharp contacts with thin interbeds of impurities, called partings.
By contrast, the peat swamps of Indonesia have gradational contacts with
the mineral substrate. The contact between the organic layer and the
mineral substrate is *by definition* the depth where the ash content of
the organic material (when it is burned) exceeds 25%. In other words,
the contact between organics and substrate is completely gradational.
The contact between coal and its substrate is generally very sharp. The
two should not be considered analogous.
Furthermore, had the coal bed come from an organic bed accumulating in a
swamp, then the thin bedding evident in banded coals would have been
destroyed by the bioturbation of rooting by the trees in the swamp.
"Trees in the mixed peat-swamp forest and pole forest have spreading,
buttressed, and prop roots, which are generally confined to a root mat
50-80 cm thick at the top of the peat and do not penetrate to the deeper
peat or mineral sediments below the thick peat. If the peat beds of
Indonesia were to become coal, they would not look like the banded coals
of the eastern US. The 50 to 80 cm thick root mat would have destroyed
all thin-bedded structure that we observe in banded coal seams.
From SP 286, cross-sections on pages 30-31and 36-39 show "mineral
substrate >25% ash". Graphs on pages 34-35 plot % ash against depth, and
show ash gradually increasing with depth from about 1% to 25%+ over depth
intervals of about 1 to about 4 feet.
Increment columns of the Middle Pennsylvanian Stockton and Fire Clay
coals of West Virginia and Kentucky graph % ash from the underclay up
through the coal seams and into the roof rock in about 6-inch intervals,
except for a ~1-inch parting in the middle of the Stockton which is
analyzed by itself.
In both the Stockton and Fire Clay coals, there is no apparent gradation
in ash content going from coal to the parting in the middle of each seam,
nor is there any apparent gradation going from the base of the coal seams
to the underclays.
This lack of gradation going from coal to underclays or from coal to
partings is consistent with field observations, which will normally show
a razor-sharp contact of coal/underclay and coal/partings.
Coals also typically show banded structure, which is primary, not
developed during diagenesis. On page 8 of SP 286: "An immature soil,
developed atop the thin veneer of quartzose silt of the levee, is
darkened by organic material; primary sedimentary structures have been
destroyed by roots and soil-forming processes. The rooted soil profile
grades downward into undisturbed planar and ripple-bedded quartzose silt
in the cutbank." Roots destroy primary sedimentary structures. Coals
have primary sedimentary structures, therefore they were not rooted, but
sedimentary.
I understand that coal seams do commonly show a widespread progression of
plant types up through the section, and this is said to be evidence for
in situ growth. I maintain that the evidence for the organics having
settled from floating mats outweighs the evidence for in situ growth, and
therefore the progression observed in plant types has been
misinterpreted.
By analogy, I maintain that the observed "progression" of organisms in
the geologic record may have also been misinterpreted as being the result
of evolution. To present evolution as fact is to overstep the boundaries
of our knowledge, IMHO.
I would appreciate any comments from those who might take issue with my
understanding of the origin of coal.
Bill
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