Re: Meaning of the Geological Column

Zoe wrote:

On Wed, 28 Feb 2007 03:56:26 GMT, John Harshman
<jharshman.diespamdie@xxxxxxxxxxx> wrote:


Zoe wrote:


After reading those posts that were informative about the geological
column - thanks to those who know enough to respond informatively -
here is what I have learned so far.

1. The geological column does not exist in its entirety anywhere in
the world. Do I have that correct now?

Yes. But even that statement is odd, because of ambiguity as to what
"the geological column" means. If it indeed means a record of continuous
deposition, moment by moment, or even year by year, there are very few
formations that fill that bill, let alone the whole column. Deposition
is episodic, meaning that you can go years with nothing much happening
and then have one big storm that deposits a bunch. This is true on all
time scales. So the most complete records may have more missing time
than present time.

Now there are localities that have been touted as having the "complete
geological column", but all that means is that they have at least some
rocks from each period from Cambrian to Tertiary.

I don't understand what you mean by "some rocks from EACH period" are
in certain localities, and yet you don't think that the geological
column is found anywhere in its entirety. If rocks from each period
are found in a certain locality, then you have the entire geological
column in that locality.

Perhaps I should have said "each Period", capital P. The geological time
scale is broken into Eons, Eras, Periods, Epochs, and Ages, e.g. the
Maastrichtian Age of the Late Cretaceous Epoch of the Cretaceous Period
of the Mesozoic Era of the Phanerozoic Eon. There are only ten Periods
in the Phanerozoic: Cambrian, Ordovician, Silurian, Devonian,
Carboniferous (which some references split in two, but never mind),
Permian, Triassic, Jurassic, Cretaceous, Paleogene, and Neogene (or you
might prefer the older division of Tertiary and Quaternary for the last
two). I'm saying that there are places with some rocks from each of
these Periods. But Periods last many millions of years. The rocks
representing a Period may be missing a large portion of the time in that
Period.

At least you and Steven J. agree, but I don't know how you manage to
deny and admit at the same time.

I'm not sure what I'm denying and admitting, but I can be fairly assured
that it all stems from confusion on your part.

2. Robert Carnegie explains that the column can be pulled together by
connecting layers horizontally worldwide. Correct so far?

No. You can't do that worldwide for all layers. Any layer, for example,
that formed in Australia after its separation from Antarctica can't
possibly be continuously connected horizontally to any layer outside
Australia.

so have you decided which layers formed pre-breakup and post-breakup?

Yes. These events are pretty well dated.

However, horizontal connections can be made over long
distances, and across oceans if the continents in question were
connected when the rocks formed.

well, since much of the geological column (where do you draw your
lines?) supposedly formed during a time period when the continents
were joined together, you can indeed have the layers worldwide. Which
is what seems to be the case, for I see that rocks in North America
are given the same period name as rocks in the Old World.

Again, you are highly confused. You don't need worldwide layers to have
layers of the same age on different continents. And by the way there
never was a time when all the land was connected. Even Pangaea was
missing some bits, and at any rate the depositional basins were never
all continuous anyway, even during Pangaea. Finally, Pangaea was a
transitory phenomenon, and the continents were separate both before and
after.

3. Carlson enlarges on Carnegie's description by likening this method
of connecting layers to a filing cabinet in which the files are
separated but can be ordered alphabetically.

An observation: The ordering of files according to the alphabet
implies prior knowledge of the alphabet. So, to compare the ordering
of the column to the ordering of files alphabetically, implies that
there is some standard used against which the ordering of scattered
rock layers occurs. If that standard is not the ToE, then what is
it?

There is no standard. You compare sequences of layers to each other. The
characteristics of individual layers are many, and there are many
possible orderings. So if you see a layer of type A atop a layer of type
B atop a layer of type C in one place, and layers of types B, C, and D
in another, then a complete sequence of ABCD is a good inference. It's
much more complicated than that, but this is the general idea.

once again, the Jurassic "layer" is not atop the Triassic "layer" atop
the Permian "layer." How have you managed to get these widely scatted
sites to sit atop each other?

Note that the Jurassic is not necessarily one layer, and layers can
cross period boundaries. But you are wrong about your basic notion.
There are many places in which a Jurassic layer (or layers) is in fact
atop a Triassic layer atop a Permian layer. This happens, for example,
in the sediments of Zion Canyon.

Do sites in other locations have
identical fossils and identical materials, and thus you feel confident
that they can be placed earlier or later in time, regardless of
whether the site is stacked or not?

In many cases, yes. Stratigraphy is a complicated discipline that makes
use of many sorts of data to correlate and date rocks. Index fossils and
lithology (the word for physical characteristics of rocks) are among these.

Among the characteristics of layers, of course, are the index fossils
found in them.

apparently, index fossils all range around a certain level of
complexity, ammonites, shells, trilobites. What about fossils for
more recent strata? Do you have them appearing in orderly layers to
match that progression nicely ordered on paper?

I don't know what you mean by "a certain level of complexity". You seem
to be retaining the idea that index fossils require some kind of
judgment of "evolutionary advancement". They don't. They're just
objects. Evolution is irrelevant to the use of index fossils. But
stripped of your bizarre language and assumptions, yes, there are index
fossils for strata of all ages.

Note also that "ammonites" are not index fossils. Particular species of
ammonites may be index fossils. And in fact we know the distribution of
ammonites well enough that if you find one, you can say fairly
conclusively that the layer in which you find it is Mesozoic, at least.
But index fossils are more precise.

Is there igneous rock near or within Devonian dig sites that give a
younger age than igneous rock near or within Cambrian or Silurian dig
sites? References, please?

The answer is yes. There are many places in each period that can be
dated radiometrically. Here is a publication I happen to have on hand
that does this for several Cambrian sites at different locations, and so
correlates widely separated Cambrian rocks: Landing, E., S. A. Bowring,
K. L. Davidek, S. R. Westrop, G. Geyer, and W. Heidmaier. 1998. Duration
of the Early Cambrian: U-Pb ages of volcanic ashes from Avalon and
Gondwana. Can. J. Earth Sci. 35:329-338.

you cite a source that dates only Cambrian sites. What about a source
that dates more recent dig sites?

Other periods are dated in the same way. I just happen to have that
paper handy. The methods used are identical.

Does every site worldwide carry a marker igneous rock so that the age
can be applied to the layer near it? If not (and I'm betting probably
not), what other standard is used as the "alphabet" for ordering the
layers?

No. You have been told the "alphabet" before. Pure horizontal continuity
works for many. Index fossils and other characteristics of the rock work
for others.

you have not yet explained how South Germany layers with Devonshire,
with France, with Wales, and so on. Why are your answers so vague and
handwavy.

They aren't. You are merely laboring under a number of serious
misconceptions that prevent you from understanding what is being said.
South Germany doesn't layer with Devonshire. You have been told this
before too: what you're talking about are type localities for particular
formations and Periods. They are the places on which the names were
originally based. But all rocks of a particular age are called Cambrian,
whether they're in Wales or not.

But wait a minute, radioactive dating did not contribute to the
ordering of the layers. The named layers, Silurian, Devonian,
Permiam, Jurassic, et cetera, were in place long before radioactive
dating came along. So we're back to square one. What was the
standard used for ordering the scattered sites according to a fossil
progression from simple to complex?

The scattered sites are not ordered according to a fossil progression
from simple to complex. You have been told this before also. The
standard is complicated; many sorts of evidence were used, and I have
mentioned them already. Characteristics of the rock (including index
fossils), ordering of the rock types in single sections, and horizontal
continuity.

and I've told you before, you have not explained how sites in various
parts of the world come to be layered one on top of the other.

Sites in various parts of the world are not layered one on top of the
other. What made you think they were, or that anyone thought they were?
There are multiple layers at a given site, and they can be correlated
among sites in various ways, among which are the all the ones I have
mentioned.

4. R. McBane, thank you for the example of an index fossil, the
radiolarian. Since radiolarians are not extinct, can they appear in
any level of the geological column? If so, in what way would these
simpler life forms be considered an index to the time they lived in?

It's not "radiolarians" that are index fossils. It's particular species
of radiolarians, each of which has a limited stratigraphic range.

okay, so you apparently have evidence of layers, stacked one on top of
the other, in which radiolarians progressively change. Out with it.

Do you know how to google? I put in radiolarian stratigraphy and here is
what I got. That should do for a start:

http://www.google.com/search?hl=en&q=radiolarian+stratigraphy&btnG=Google+Search

.

Relevant Pages

  • To Jon Harshman -- re geological column
    ... fossils found in the layers. ... down, are they continuously under water, or do they emerge as dry land ... lowest sediment begins to lithify. ... So I would like a scientific, step-by-step explanation of how rocks ...
    (talk.origins)
  • Re: Meaning of the Geological Column
    ... |>>> and say that there are several places where one can find deposits, ... Do you understand that when we say Devonian, ... |>>layers of different rock types that have been designated as Devonian? ... |>>could be missing in a period but not all the rocks from that period. ...
    (talk.origins)
  • Re: Meaning of the Geological Column
    ... layers to lithify lower layers? ... there must have been deposition above any layers that were ... Remember that the rocks both left and right of ... contain the types of fossils that generally, in succesion, span life ...
    (talk.origins)
  • Re: Meaning of the Geological Column
    ... layers to lithify lower layers? ... There's a lot of places where rocks just lie there without any significant ... contain the types of fossils that generally, in succesion, span life ... something to do with evolution. ...
    (talk.origins)
  • Re: Meaning of the Geological Column - correction
    ... Invertebrates are often used as index fossils because they preserve well and are often wide spread and often a specific species only existed during a narrow time period. ... There are many places where there are layers stacked. ... If we went to a site that had only limited sedimentary rock and no fossils and no radioactive markers, it's likely that we could not assign an age to the rocks. ...
    (talk.origins)