Re: The Santana Formation - Rapid or Slow Burial?


Richard Forrest wrote:
Seanpit wrote:
Richard Forrest wrote:
Seanpit wrote:
Richard Forrest wrote:

Where on Earth is your anoxic lake/ocean notion preserving
fossils to the degree and extent that we see in the fossil record?

Lagoa Vermelha, Brazil
http://www.blackwell-synergy.com/links/doi/10.1046/j.1365-3091.2003.00550.x

Come on now. Only microorganisms live in the coastal lagoon of Lagoa
Vermelha, Brazil. I'm talking about fossilized macroorganisms in fine
condition - like fish, other vertebrates, etc.

You need to do a bit more reading about the Santana Formation. The
Santana Formation of Brazil contains fish whose gills and muscles are
so perfectly preserved that geologists believe they were completely
fossilized within five hours of death. The foremost expert on these
Brazilian fossils, Dr David Martill, has called this "the Medusa
effect", after the creature of Greek mythology who could instantly turn
people to stone just by looking at them.

Well, whopedee do! You can look stuff up on the internet.

I've talked to Dave Martill, who I know well, about these fish. I've
read the papers about these fish which describe how the soft tissues
are replaced by permineralising bacteria. Dave showed me some of the
first SEM pictures showing these structures well before any paper on
the subject was published, and I even made a small contribution to the
paper by pointing him at a study made in the Florida Everglades in
which bird feathers became partially mineralised in a matter of weeks
in some locations because such bacteria are present.

What turns these organisms to stone is the presence of autolithifying
bacteria, which you would know if you had read the literature on the
subject, or talked to the scientists who are involved in the study of
such processes. One of my PhD supervisiors, Sarah Ga***, is studying
similar processes in exceptionally well-preserved Ordovician faunas
from South Africa.

I have spent many hours discussing the taphonomic processes in black
shales with Dave, Sarah and others in the context of interpreting the
preservation of fossil plesiosaur I am describing as part of my PhD
thesis.

Since you've read these papers, why did you argue that the Santana
Formation was the result of anoxic conditions? Martill himself says
that, "There is evidence of scavenging of many of the exceptionally
preserved Santana specimens suggesting that anoxic and rapid burial
modes are not applicable here."

David M. 1990. Macromolecular resolution of fossilized muscle tissue
from an elopomorph fish. Nature 346:171-172

"Many miles beyond the edges of this plateau, patches or pockets of
Santana are found. The broad range of this formation, the evidences of
rapid sedimentation and preservation, the quick cementation of the
nodules with enclosed fish fossils, and the mixture of fresh-water and
marine organisms, has been surprising to paleontologists and geologists
who have tried without much success to encompass all these requirements
in an estuarine environment that was stirred up by a catastrophic
tsunami. The resulting sediments could have been a mixture of marine,
brackish, and fresh-water sediments, and the fauna caught and buried
also could have come from these three major types of environments. Yet
the absence of typical bay and estuary invertebrate organisms is a
problem for this model.

The evaporite layer and the fine-grained flat-lying shales could
suggest quiet conditions and the passage of time. However, water of
sufficient depth can allow for quiet sedimentation even when a major
storm is ravaging the surface. Most evaporites, contrary to the name,
probably were not produced gradually by long continued evaporation.
Evaporites can readily be transported. It is most unlikely that the
fish fixed within the concretions were originally living normally in
water directly above a salt deposit (gypsum). Some of the concretions
lie directly upon the gypsum. Also there does not seem to be a
transition from the underlying shale sheets to the massive evaporite as
would be expected if the origin of the gypsum were truly by
evaporation.

The unnatural mixture and the rapid stratigraphic shifts of fauna seem
to require catastrophic water transport into the area. The large
geographic extent precludes a local event."

http://www.grisda.org/georpts/gr13.htm

Such conditions on such a wide scale are almost certainly related to a
catastrophic event of some kind. As described above, the "evaporates"
are probably also the result of some sort of rather sudden catastrophic
event - not the result of long periods of time in normal estuaries or
anoxic lagoons.

I'm not saying that rapid sedimentary burial is the only means of
fossilization. However, pristine fossilization must be the result of
very rapid/catastrophic conditions in order to preserve such details in
such relatively large creatures - especially on such large scales.

Fish simply do not fossilize in modern "anoxic lakes" like they did in
the past. Some pictures of the Santana Fossils can be seen at:
http://www.uoguelph.ca/zoology/rush/zoo402www/ichthyology7.html

They are surprisingly well preserved. They show excellent scale, fin,
and eye socket preservation. This seems rather strange to me because
many fish float when they die and rapidly decompose, even while
sinking. The scales are the first to go. They are also heavily
scavenged before there is a chance to be buried if burial does not
occur rapidly.

A description of how these fish were fossilized in this Brazilian lake
reads, "Rhacolepis lived in a shallow marine environment. Fossil
specimens found today were fish that died and were quickly covered with
silt or mud."

As it turns out, the Santana "lake" was not thought to be "anoxic" at
all. Here is a description of this "environment": In the Early
Cretaceous period the Santana Formation was deposited in warm, shallow,
salty lagoons close to land." Clearly then, the generally pristine
condition of the fossilized fish in the Santana Formation speaks for a
very rapid burial of living or very recently killed fish.

It is the conditions of the bottom of the lake, which are essentially
soft, anoxic muds which allow fishes which have dropped to the bottom
to be preserved in this way. The fish sink into the soupy substrate at
the bottom of the lake. Note that fish *DO* sink to the bottom when
they die: they float to the top when decomposition gasses expand in
their body cavities.Down in Portsmouth where Dave works, they have
tanks of water in which fish, birds and tortoises are decaying
naturally so that they can study the processes by which such fossils
are formed. The stench is appalling.

Unless very rapidly preserved by very unusual conditions a dead fish
sinking to the bottom of a lake or lagoon is going to bloat and float
very quickly, decay, and be scavenged. Even in the Santana formation,
there is evidence of scavenging - indicating that anoxic conditions
were not significantly in play here. A supersaturated environment was
at play here - one that was created rather suddenly/catastrophically on
a very large scale. This did not happen over a long period of time. It
was a short sudden catastrophic event.

< snip >

Did I miss something? Where are the peat bogs in ichthyosaur
preservation? Where are the peat bogs in the masses of fossil fish
preservation?

No?
Thought not.

LOL - you're just too much. Come one now. We aren't talking about peat
bogs here.

With a bit of subsidence and a marine incursion we would expect these
human remains to become fossilised. The north sea was dry land a few
thousand years ago, and fishermen drag up the bones of mammoths and
other animals from the bottom in large numbers. Some are quite soft and
only partly mineralized, others rock hard and fully mineralised. This
is fossilisation in action.

It's not an explanation for ichthyosaur fossils and large masses of
fish fossils buried in finely grained sediments.

They also drag up lumps of peat bog from the bottom, which contain
wood, insects and other remains of living organisms. I've found bones
of bison and teeth of extinct horses in lumps of this stuff washed up
on the beaches of the east coast of England. In some cases this is
still soft and squishy, in other cases hard and mineralised. There is
no reason why a human body, preserved by the conditions in the peat,
should not be fossilised in one of the these lumps. It would form an
exquisitely preserved fossil of the sort you claim as evidence for a
flood.

Again, evidence for rapid watery burial is all over the place. You
aren't suggesting peat as a means for producing fish fossils and
ichthyosaur fossils - right? Stay on topic now . . .

< snip more of the same >

RF

Sean Pitman
www.DetectingDesign.com

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