When I look at cross-sectional diagrams like that of the Grand Canyon
Series (mentioned below), I see Phanerozoic sedements draped like a set of
blankets over the Precambrian rocks below. Of course (as I note below),
that is a limited view, and the Precambrian under much of the Colorado
Plateau isn't very well known at all. I have not adequately considered the
instances of conformable deposition across the Precambrian-Cambrian
boundary. I sometimes wonder how well established (stratigraphically) that
boundary really is.
>> >You also said
>> >....Clearly before the Cambrian Explosion event, but not at any specific
>> >Precambrian horizon. And not with implicit faith in the methods of dating
>> >Precambrian layers.
>>
>> In answer to a question of when Creation occurred, which implied that it
>> should be visible at some geologic horizon (such as the pC-C boundary), I
>> note that it would not be visible at any specific horizon, because
>> burial/fossilization, which would be our visible evidence of life, is
>> necessarily after origin, and not necessarily at origin.
>>
>> >What methods of "dating Precambrian layers" do you not have implicit faith
>> >in?
>>
>> Well, really, all of them, because when the isotope ratios indicate dates
>> that do not match the accepted timeframe (such as K-Ar ratios that "date"
>> older than the accepted age of the earth), alternate explanations for the
>> observed ratios are explained, and I would apply those explanations to the
>> "acceptable" dates as well. It seems circular to me to accept isotope
>> ratios as accurate only if they fit the expected date range.
>
>Any numerical data set will have outliers. If I have 10 assays of the
>same rock
>which give a value for gold of 1 ppb and 1 that has a value of 1 ppm,
>the high
>value is an outlier. It is that which needs to be explained, and if
>there is no
>valid reason for it, rejected as analytical error. Of course if the 11
>assays
>had values all over the place between 1 ppb and 1 ppm then I would
>either have to
>say that there was extreme heterogeneity in the sample, or there was
>something
>suspicious about the lab. It is no different with radiometric dating.
>If a
>geologist rejects a K-Ar age of 800 Ma on a volcanic interbedded with
>Cambrian
>limestones, but accepts one of 520 Ma, it is because there is a
>considerable body
>of evidence that suggests that 800 Ma is too old for the Cambrian. It
>is not
>because someone has arbitrarily decided that the Cambrian should be
>between
>490-540 Ma. I have worked with perhaps a hundred or so radiometric
>dates
>(Ar/Ar, SHRIMP U-Pb, C14) and the results were fundamentally consistent.
>Outliers were clearly outliers, the results were not a smorgasbord from
>which I
>chose the numbers I wanted.
>
It is good to hear from someone who has direct experience with this. I
have heard of some "smorgasboard" examples, and perhaps put too much weight
on that.
>> >Who are you implying has this faith?
>>
>> I believe that most of the people on this list have faith in the accuracy
>> of radiometric dating.
>
>I can't speak for them but based on my experience, I would accept it was
>well.
>of course, there are always exceptions, and I have poured scorn on some
>dates in
>my time as well.
>
>> Does this clarify my words better for you? I don't claim to have all the
>> answers by any means.
>
>Yes it does, thank you. Of course this then generates further
>questions. I
>don't claim all answers either. The fact that neither of us knows all
>the answers does not mean that there are no answers, and that some are
>already known by someone. That is why public discussion before a broad
>audience is good. As for the others is by examining God's world and
>God's
>word that we learn the facts and by honest and humble discussion that we
>refine
>our ideas.
>
Amen.
>>
>> Romans 11:33
>>
>Amen
>
In Christ
Karen