Just my two-cents worth on a couple of points.
>> 2. The occurrence of igneous plutons and batholiths within Phanerozoic
>> sedimentary strata of such a size as to require, using standard
>> thermodynamic calculations, that the bodies would take tens of
>> millions
>> of years to cool (depending upon their size, of course). How does
>> one have rapid sedimentation with a thick gabbroic sill in the middle
>> of the package of sedimentary rocks?
>
>Glenn has shared some of his calculation on this, and others have offered
>alternative viewpoints. I am no geophysicist, but I know that water
>conducts heat well, and there are many earth processes that require
>tremendous amounts of heat. Clearly the oceans have not boiled away in
>the past. The marine environment has been stable enough to maintain life,
>despite extensive extinctions. And land areas (if they took tens of
>millions of years to cool, would they be devoid of life all that time?)
>have supported its biota as well. I don't think we have all the answers
>about heat balance.
>
Perhaps yes, perhaps no, but I did some rough calculations awhile back and
discovered that if all the carbonate rocks had been laid down during the
Deluge, the amount of heat released would have raised the surface
temperature of the earth to over 1000 degrees Celsius during the flood year.
I leave it to your imagination as to what effect this would have on the Ark
and on the earth's biosphere as a whole.
>
>>
>> 4. How does one get thick halite (salt) or gypsum layers in the middle
>> of Paleozoic sedimentary rocks?
>
>How do you get halite layers on the surface? They are usually not pure
>halite, and not very thick. You would have to evaporate many feet of sea
>water to get layers like we find in the column, and it wouldn't be pure
>halite -- or pure gypsum.
>
Which is what happened when the Mediterranean Sea dried up, not once but
perhaps as many as a dozen times. This at least accounts for the halite
layers found in the Mediterranean basin today. A similar process also seems
to have created the Gulf of Mexico halite deposits.
>
>> How exactly do evaporite minerals form in flood waters?
>
>I don't pretend to know exactly! To get pure deposits, you would have to
>have pure precipitates from pure brines. Brines still come out from the
>ocean floor. Temperature changes and other factors induce supersaturation
>and precipitation. This suggests some interesting experiments.
>
First of all, the deposits are not pure: they contain plankton, pollen and
volcanic dust, among other impurities, exactly what you would expect if the
deposits had been formed by evaporation. Secondly, brines are not "still"
coming out of the ocean floor, nor is there any evidence that they ever had.
This was first verified by Project FAMOUS in 1974 (Strahler, _Science and
Earth History_, pg 230) and has been continuously verified since. It was
found that sea floor vents were depositing tremendous amounts of iron,
manganese, copper and zinc sulfates, oxides and silicates, but there was
also no evidence of sodium chloride deposition in any form. The only known
cases of concentrated brines occur in places like the Red Sea, and these are
formed by the concentration of sea water through evaporation. As Strahler
himself points out, ãin the light of a great deal of firm information as to
what actually goes on at submarine spreading plate boundaries,ä vague
notions of juvenile salt deposition from magmatic brines are unacceptable.
Thirdly, salt does not precipitate; it crystallizes. This may sound
trivial, but in fact crystallization and precipitation are two very
different chemical processes. Precipitates are by and large insoluble,
which is why they can settle out of solution to form thick layers under the
right conditions. Salt is not insoluble, and unlike precipitation the
process of crystallization involves striking a balance between the amount of
salt in solution and the amount out of solution. Salt crystals can only
exist in water when the water is saturated; at any less concentration the
crystals would dissolve until the water became saturated, or there were no
more crystals.
The maximum solubility of salt in "cold" water (say room temperature) is 357
g/L; the maximum solubility of salt in "hot" water is 391 g/L. As such,
the magmatic brines would have had to have at least this amount of salt in
them, so that when the brines mixed with the surrounding sea water and
cooled, the solubility of the brines would drop to a value lower than their
concentration, thus supersaturating them and allowing for some of the salt
to crystallize out. Unfortunately, only the amount of salt needed to reduce
the brine concentration to that of the current solubility value would
crystallize out; the rest would remain in solution, saturating the water.
In other words, only some 34 g/L would crystallize out, which is not enough
to create the halite deposits known to be present in the geologic column.
On top of that, because the normal ocean salt content is only about 26 g/L,
in the process of cooling the brines would become diluted, so that their
concentrations would fall below the "cold" maximum solubility levels, which
in turn means no crystallization. Before crystallization could occur on a
large enough scale to form massive layers of halite, the entire flood would
have be saturated with salt. This means that either the brines would have
had to have been super-super-supersaturated or they would have had to
constitute the bulk of the flood, perhaps even the entirety of the flood.
So how did these brines acquire that much salt, how did it stay solublized,
and why are the modern oceans not saturated with salt or nearly so?
Fourthly, even if salt could have "precipitated" from supersaturated brines,
it would not have formed halite. For one thing, halite is created when
dewatering lithifies the accumulated salt, and dewatering cannot occur
underwater. For another, the turbulence created by the mixing of the brines
with the flood water would initially keep the salt suspended, and would mix
it with the sediments rather than form a separate bed, creating a special
type of salt-saturated sediment called sabkha, now found only in deserts, or
as a result of over-irrigation (Strahler, pg 228). Since there are no
extensive sabkha layers in the geological record, I believe it is safe to
say that submarine brines had nothing to do with forming halite deposits.
Kevin L. O'Brien