Re: Meaning of the Geological Column

On Mar 10, 12:07 pm, John Harshman <jharshman.diespam...@xxxxxxxxxxx>
wrote:
Zoe wrote:
On 6 Mar 2007 17:45:52 -0800, "hersheyh" <hershe...@xxxxxxxxx> wrote:

snip>

zoe wrote:

However, with that out of the way, my question remains unanswered. I
am not questioning the correctness of the superposition of the layers.

Of course you are. You are claiming that because there is no single
site that has all the layers in order that means that a complete
geological column cannot be generated or would not be useful or
meaningful if it were.

what claims have I made, Howard? All I've been doing so far is asking
how geologists went about pulling the current version of the
geological column together.

Don't be disingenuous, Zoe. You know you have an agenda. You want to
show that the geological column doesn't really exist, and everything you
say works toward that purpose, and everything you read is interpreted
through that lens (and it's quite a distorting lens, which prevents you
from understanding most of what people tell you).

I am questioning what characteristics are recognized that allow you to
consistently label a layer D or I or L or M, and so forth.

A pattern of *specific* fossils is what allows the designation of the
layers.

do you have an example of what a pattern of specific higher fossils
would look like, such as the Dimetrodon and Eryops, found in the Ural
Mountains, the Tyrannosaurus and Triceratops, found in North America,
whose ancestors apparently evolved to higher forms like the antelope
and gazelle and primates as found in Africa? How has this pattern
been established?

Once again you confuse biostratigraphy with evolution. Index fossils,
which is what helps to establish the ordering of strata, have nothing to
do with evolution. So all this talk of "higher fossils" is nonsense in
context. Now, after we have determined the ordering, correlations, and
dating of strata, we can learn much about evolution by looking at the
fossils in those strata. But the ones you find interesting are not index
fossils and are not used in biostratigraphy.

By the way, your foray into evolution was nonsense on its face. You
could as well have drawn a line connecting any random set of species.
Though in fact Dimetrodon is not extremely far from the lineage leading
(after quite a long time and many intermediates) to gazelles and
primates; at least it's a synapsid. But this is a completely new
question. Once you start asking about evolution, you are no longer
asking how the geological column is assembled, but what we do with it
after it's assembled.

Some have said that the rock type is not what gives the layer its
characteristics. Therefore, rock type is not the equivalent of a D or
an L or an M.

With some exceptions. Remember that all that is required is a unique
identifier that allows specification. The iridium rich clay layer at
the K-T boundary is uniquely identifiable by virtue of its placement
between K and T and its richness in iridium. And the banded irons and
certain other minerals that could only form under the low O2
conditions of the early earth are also uniquely situateable in the
geological column on the basis of the rock type.

these two formations seem like indisputable benchmarks for a certain
period of time world over, yes. What are the other benchmarks that
allow you to use them for corroboration of the evolutionary concept?

You don't need worldwide benchmarks, as long as there are ways of
correlating strata. There is however one more set of worldwide
benchmarks: magnetic reversal intervals. And radiometric dates, though
local, are objectively equivalent whereever in the world you find them.
However, much correlation is done by matching site A with nearby site B,
and matching B with C, and so on until you get a chain of correlatable
sites relating A to Z, even though A and Z may have no features that can
directly correlate them.

Others have said that it is not the fossils that identify the layers.

Who said that? Fossil distribution is extremely useful (in a very
practical way) in identifying layers. Ask your local petrochemical
exploration company.

petrochemical exploration companies don't look for the fossils of
dinosaurs or other higher life forms in performing their search, do
they. Their benchmarks are no higher than sea shells, from what I can
see.

Again this obsession with the meaningless "higher". You're asking about
the correlation and dating of the geological column. Don't confuse that
with evolution. As long as you're confused about this you can't learn
anything. You need to get rid of all the stuff you know that ain't so
before you can understand what anyone is saying here.

Anyway, "sea shells" and other "lower" forms are found throughout the
geological column from top to bottom. They're plentiful, unlike
vertebrates, and so make the best index fossils. Mammals, mostly their
teeth, are common enough in some places to be used as index fossils, and
North American Cenozoic terrestrial deposits can be ordered by time into
ages (called "land mammal ages") using fossil teeth. These must then be
correlated with marine deposits and with other regions of the world.



Therefore, the labels of D or L or M are not the equivalent of fossil
types.

The label D or L or M means "This layer and only this layer has the
following suite of fossils at the species or genera or higher level
(which is used is a matter of how big a "layer" or how much time one
is using the fossils to identify). For example, the area I live in
(Bloomington, IN) has much exposed limestone that dates to the middle
Mississippian period, whereas the area to the west starts having
exposed limestones that date to the late Mississippian and early
Pennsylvanian. To you, not being a scientist and all, limestone is
limestone. But in McCormick's Creek park about 18 miles from here,
there is an old limestone quarry that has 3 separate layers of
limestone, each composed of different fossils (mostly small shelly
stuff). The layers are easily identified by the fossils. The layers
are easily distinguishable by the fossils they contain because there
was a long enough time between depositions that the species
composition of the organisms that were layed down had changed.

you use as an example, limestone which, you say, dates to the
Mississippian period.

No. He says that some particular limestone dates to the Mississippian.
There is limestone of all ages.

If rocks, worldwide, date to a particular
period, this seems to imply that during that period of time, there
existed only that type of rock, and this type of rock was deposited
worldwide. Why else would they, as you say, date to a certain period?

Because the particular limestone he mentions has been shown by various
means, including index fossils, to be Mississippian in age. Note the
mention of fossils above?

I have no problem with layer D being younger than layer M, or layer N
being older than layer C. What I want to know is what exactly makes a
layer be recognized as always D or M or N or C? If it is not the
material, and if it is not the fossils in the material, then how do
you recognize the layers sufficiently to order them?

For *sedimentary* layers, it is indeed the fossils that allow one to
recognize them uniquely. You complain that there is no single place
that has deposition from every time

I had no complaints. All I'm doing is asking questions.

If only you were also listening to the answers.

(which never was a requirement of
a geology based on local deposition; but does cause problems for a
single world-wide flood) yet ignore the *fact* that no single fossil
species is found in every sedimentary layer. Not the lightest; not
the one with the thickest shell; none. In fact, most fossils species
are found only in a very narrow band of a single "geological" era.

so how do you explain the arrangement of fossils that cover the entire
span of time from Cambrian to the Cenozoic era? If, in fact, most
fossil species are found only in a very narrow band of a single
geological era, how did you manage to arrange the more complex life
forms in their ascending order, as seen in textbooks and web sites?

What exactly do you mean by "ascending order"? Time? Evolutionary
advancement? I can't tell what you are talking about here. But it's
pretty simple. You can use index fossils (and other means too, but let's
stick with index fossils) to order the geologic column. Not only do
species have short stratigraphic ranges, the ranges also overlap each
other, so you can put them all in order. Once you have arranged the
strata in time, you can find the ages of other, non-index fossils by
seeing where in the assembled column they are. So we can see that the
earliest land animals are Devonian in age, because their earliest
fossils fall into strata we know -- based on prior correlation of strata
with index fossils and other means -- are Devonian in age. Similarly we
know that the earliest mammal (or mammaliaform if you prefer) fossils
are Triassic in age, and the last ornithischians are Cretaceous. And so
on. Once everything is properly dated, we can immediately see that
different groups appear and disappear at different times, and that the
biota changes through time. All species and many groups that are alive
in the Cambrian are not alive in the Neogene, and vice versa. Now we
need an explanation for that observation. Evolution is that explanation,
but in fact simple stratigraphic ordering is not the primary evidence
of its course. Now we have strayed far from the thread topic, though.
And it's because you consistently confuse biostratigraphy with evolution
that we got into this at all.

okay, I'm gathering that index fossils are not indicative of any
evolutionary progression.

Mostly because evolution is only in the business

...

read more »



I believe what she is asking is this:

Ammonites are a well known index fossil that span a huge chunk of
time. Two structures are used for identifying different species, the
Siphuncle and the Septa which is probably also the reason for the
different patterns on their shells. So, I can't remember the periods
exactly but I do remember that an Ammonite who's Siphuncle runs
through the top of the upper spiral is considered older than one who's
Spihuncle is closer to the animals body, which is older again than one
where it runs through multiple chambers and is touching the body. What
Zoe is ctrying not to ask is how those decisions have been made. Why
is an Ammonite with a Siphuncle further from its body older than one
where it's closer? Why is a more modern Ammonite expected to have a
more detailed pattern on it's shell. If evolution doesn't have a goal,
and isn't about a progression from simple to complex, how can anyone
make decisions about which Ammonite is older than another based on its
physiology?

(BTW, I already know the answers ;-)

It's obvious she's asking deliberately obtuse questions so she won't
in-fact have to admit she got a satisfying answer. The more unclear
she can make her questions the more unlikely she'll be proven wrong.


---
Strange


.

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