Coal /YEC - Gastaldo Critique II

Bill Payne (
Sun, 03 May 1998 02:06:24 -0600

Here's the rest of my presentation of Bob Gastaldo's paper (A CASE
LYCOPOD-DOMINATED FLOATING PEAT MATS). My comments will follow in a
third post.


The first two paragraphs review the evidence that lycopods were not
hollow during growth and maturation, but rather "hollowed easily after
death due to the degradation of thin-walled cells in a number of tissues
(DiMichele, 1979a, 1981)"

Bob then describes the morphology of lycopod roots, or stigmarian axial
systems, and their relationship to the strata which contain them:

"...The proximal axial systems may depart the base at angles up to 30
degrees and the more distal axes commonly cross-cut bedding at angles of
10 degrees or more. This provides for an intertwining of axes at
multiple levels, rather than the generally viewed concept of
intertwining along a single plane or adjacent planes. The appendages
('rootlets') develop perpendicular to the main axial system and also
cross-cut bedding where bedding is preserved."

"...The preservation of stigmarian axial systems within the underclays
of Euramerican coals can only be interpreted as in growth position and
in place. As discussed previously, the cross-cutting relationships of
the stigmarian axes and appendages precludes interpretation of abiotic
emplacement. If stigmarian axes were abiotically introduced into the
underclay by sinking, the aerenchymatous rootlets as well as the
sediment itself should always demonstrate distortion."

In this paragraph above, Bob points out that if root systems were
pressed into sediment by sinking (abiotic emplacement) rather than
growth in place, the bedding of the sediments would be distorted. In
the next paragraph, he makes the same case for the axial rootlets - that
the rootlets would always be distorted from their normal perpendicular
arrangement if pressed into soft sediment by sinking:

"If a stigmarian axis, perfectly horizontal with perpendicularly
inserted aerenchymatous appendages, was emplaced into the underclay, the
resistance of the sediment with the spirally arranged 'rootlets' would
push them upwards out of their original plane of growth (Figure 5). In
transverse view, then, theoretically only the two appendages inserted
perpendicularly to the horizontal plane would be undisturbed....
Observations and reported occurrences of erect lycopods with attached
stigmarian axial systems do not demonstrate these conditions. Rather,
whether the stigmarian axes are horizontal or inclined, the preserved
rootlets are all essentially perpendicularly inserted on the axis..."

"Examination of underclays results in the observation that there is no
evidence for abiotic disruption of the sediment that would have been
caused by the sinking of the axial system. Since the sediment would
have been unlithified at the time of stigmarian emplacemnet, disruption
of the sediments would have occurred in order to allow for complete
encasement of the axial system in the undreclay. The time for sinking
of the axial system with attached plant body and hypothesized peat would
have been short. This rapid event would have caused compactional and
deformational sedimentary structures such as flame-like structures or
clay injection structures between 'rootlets' in addition to
dispolacement of bedding. Underclays in association with the axial
systems do not demonstrate these features. Rather, the underclays are
disrupted by the growth of the rootlets through the sediment and
accompanying vegetative (coalified compression) remains. In addition,
the emplacement of the lycopod mat with developed peat accumulations
should have generated mud diapers into the base of the coal seam.
Again, the condition is not known. The coal may lie conformably or
unconformably on the underclay."

"Field observations, numerous reports, and descriptions of erect
lycopods support the interpretation that these plants are in situ and
were not transported to their site of deposition. Stump features
displayed by most preserved trees agree with those criteria proposed by
Fritz and Harris (in press) to distinguish in situ from transported
stumps. That the stigmarian axial systems embedded within the underclays
(paleosols) of coals represent stands of lycopods in non-peat and peat
accumulating environments is unquestionable. The assertion that these
lycopods were abiotically, vertically emplaced from a floating habit
cannot be supported by the disposition of the axial systems or the
sedimentary structures accompanying them."


In this section, Bob notes that lycopods trees of moderate size could
attain heights of 14 meters, and that these trees were supposedly
growing in a floating mat in a shallow eperic sea of one to two meters
for tens of kilometers from the shore. Growth of the lycopods would
cause the mat to sink and the rootlets and/or axial systems would
reattach to the sea floor. Bob also offers several other problems for
the floating mat model, such as a stratified water column, and assessory
vegetation (ferns and pteridosperms) not saline tolerant. These are
side issues and not germane to the main thrust of his argument. Bob
then notes that Austin (1979) admitted difficluties with the concept of
a continuously transgressing sea, a mobile floating mat, and continuous
winnowing of the mat producing the 1100 square-kilometer Kentucky No. 12


"Arborescent lycopods...were not hollow trees during growth and
development. Rather, these trees were easily hollowed upon death by
degradation of thin-walled parenchymatous tissues in the trunk, canopy
and stigmarian axial system. Although speculation continues as to the
textural character of these trees, the fact that specimens have been
documented in excess of 38 meters in height attests to the
interpretaiton that these trees were not frail or lightly built. None
of these characters supports the contention of a reduction in weight
allowing for a floating habit."

"Morphological considerations suggest that these plants were adapted to
extreme swampy conditions, and the disposition of the stigmarian axes
within various lithologies can only be interpreted as recording growth
in situ. The variable angle of axial penetration and their
corss-cutting relationships, the helical and undistrubed arrangement of
the 'rootlets', and the abiotically undisturbed sediment surrounding the
axial/appendage system, lend support to their autochthonous character."

"The strata in which these stumps and axial systems are preserved
represent fossil soil horizons with few exceptions. These plants were
tolerant of fresh water to marine conditions, as well as highly reducing
to non-reducing conditions. Stands of trees are documented to have been
established in areas that accumulated sediments including marine
bioclastic limestones, sandstones, siltstones, claystones and peats.
The three-dimensional disposition of the axial system precludes the
general notion of a shallowly buried support system, and this
distribution would have diminished the planar surface area necessary for

"An evaluation of the floating mat hypothesis in perspective
demonstrates the untenable nature of the hypothesis. The divergent
stigmarian axial systems of the mat inhabiting lycopods would encounter
the substrate and allow for reattachment of the mat to the bottom of the
shallow epeiric sea. In slightly deeper environs (up to 2 meters), the
probability that at least the 'rootlets' would reattach to the substrate
is high. Isostatic adjustments of the mat would continue as the forest
matured. The weight of the mature vegetation would probably sink the
mat or at least promote reattachment. The reducing conditions necessary
for near surface peat accumulation would be greatly influenced by
meteoric waters. Fresh water in combination with a tropical climate
would promote deterioration and utilization of the plant debris rather
than continued peat accumulation. Marine transgression would have to
have been at a faster pace than the rate of continuous plant growth and
the mobility of the mat may have precluded large substrate accumulations
of peat via winnowing. The large geographical extent of such a floating
mat is difficult to explain due to the lack any modern analog."