From: Bill Payne (email@example.com)
Date: Tue May 27 2003 - 23:30:08 EDT
On Tue, 27 May 2003 12:26:54 -0400 "bivalve"
I appreciate your thoughtful summary. I'll continue to chew on this, but
my initial gut reaction is that you've listed a number of factors, most
of which seem to be special circumstances that would occur in limited
areas and times.
> Fine layering suggests that bioturbation was very limited. This
> could happen for any of several reasons:
> Bioturbators were globally rare or absent. This seems to be the
> case for the Precambrian into the early Paleozoic, and immediately
> after some mass extinctions.
> The environment was inimical to bioturbators. This includes anoxic
> or dysoxic environments (the latter often anoxic in the sediment),
> tidal flats, extremely unstable sediments (e.g., dunes or sand
> waves), or hypersaline water.
> Net sedimentation was extremely slow, so that only a small amount
> was deposited before the layer was lithified.
> Sedimentation was faster than bioturbation. This can happen in a
> storm or a local flood, for example.
That's the one I, of course, am leaning into. If it can happen in a
local flood, it could also happen in the Flood.
> Or, in environments that are
> not especially conducive to high levels of bioturbation, this may
> not require as much sedimentation. Deep lakes, even if they are not
> anoxic, tend to have a relatively low number of large, active
> bioturbators, and distinct annual layers easily accumulate.
How deep are "deep lakes"? Do you have a reference for this claim? Does
bioturbation occur in the deep ocean?
> Bioturbation may not necessarily totally obliterate all layering.
> If sediment is accumulating more or less continually, with some
> variation in those sedmients that can be detected as layers,
> bioturbation will mix things around a bit but eventually they get
> buried deep enough to no longer get frequent mixing. Thus, although
> the layering is smeared, it may not be totally gone.
But most of the rocks I look at in north Alabama have clear distinct
layers. Your distinction of "fine" layering can be extended to include a
sharp contact between two massive beds.
> There's a whole range in the degree of bioturbation observed in
> sediments. You can look up various references. I think Sue Kidwell
> and Mary Droser are some of the names to look for.
> Remember also that, although fine lamination is found here and there
> throughout the geologic column, extensively bioturbated beds are
> common. You can't honestly claim that the whole geologic column is
> depauperate in bioturbation.
No, and I am not claiming that. I have seen some evidence of what I
suppose are burrows in interbedded Pennsylvanian sands and shales. But
the bedding is still clearly evident. If these layers were subjected to
bioturbation for a week, I would think they would be gone.
> As I am generally looking for beds
> with lots of shells, my collecting emphasizes well-bioturbated
> facies, but I do see a lot of places with plenty of bioturbation. I
> sometimes encounter layers with good lamination. Very many involve
> dark layers, which indicates high organic content. High organic
> content implies low oxygen levels.
> Also, each lamination takes some amount of time to form. With about
> 200,000 laminations in the Castille Formation in western Texas, you
> would have to form one organic rich-organic poor couplet every two
> to three minutes to fit it all into one year. That's just one
The time required is a notion we bring from somewhere else. Somewhere I
have a reference that says these interbeds can be formed spontaneously in
the lab from a single sedimentary event.
> Trying to explain any substantial portion of the geologic column as
> resulting from the Flood requires extremely high sedimentation
> rates, and the fact that organisms frequently had plenty of time to
> burrow around poses a problem for this. On the other hand,
> occasional deposits being deposited rapidly in no way poses a
> problem for an old earth view. The young-earth view is at a
> disadvantage, as anything taking a long period of time is
> incompatible with it, whereas lots of things can happen quickly
> within an old earth model.
As I see it, the old-earth model is at a disadvantage. The geologic
column is replete with bedded strata, and by comparison, very little
evidence of bioturbation. The locally (vertical and/or horizontal)
bioturbated zone in no way poses a problem for YEC.
Can you name any marine and coastal swamp modern analogs, where bedded
strata are being continuously formed with little bioturbation?
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