John Solum

With Ron's agreement, this thread is a spin off of the "Care and Feeding of the Kitty" thread dedicated to flood geology.

You’re welcome. Do you accept radiometric dating as valid? If not, would you tell me why.

The presence of aquifers, and the pressure in them, doesn’t provide any evidence for a layer of water under the crust. As I pointed out before, and as you agreed, we understand how aquifers form, and they don’t have anything to do with the mantle. We know where the water comes from, we know how the pressures are generated, and the mantle doesn’t play a role. Something else to keep in mind is that aquifers are very shallow features. Continental crust is ~30-40km thick, water aquifers are confined to the upper 3 km or so, oil wells can be up to 7km (that’s a different topic, and besides I don’t know if these have any water in them). Oceanic crust is thinner (~7km), but the aquifers you suggest could be evidence of a layer of subcrustal water are on continents. I don’t know how deep the deepest oil well in the ocean is, my guess is ~4km below the sea floor (but I don’t know for sure). So, if we know where the water in aquifers comes from (we do) and we know how the pressures are generated (we do) and neither of those phenomena has anything to do with the mantle how is it possible that aquifers could support such an idea?

Which “non Christian” (I’d prefer the term non-creationist, but that’s a minor point) scientific theory advocates the presence of a layer of subcrustal water? I’ve not heard of one. I’m familiar with two creationist arguments: Walt Brown’s hydroplates (he makes elementary geologic errors) and John Baumgardner (who is forced to resort to miracles to explain how the heat generated by his model is dissipated).

A final thought to consider is that there was no time when faults didn’t exist in the earth’s crust. There are remnants of mountain ranges over two billion years old, and (clearly) there are mountains forming today. So, even if a layer of subcrustal water could exist, there’s no way to keep it contained.

The following comments weren’t addressed at me, but I’m going to comment on them anyway.


There are no geologic theories that try to show the Flood didn’t happen. That’s an argument that was settled in the early 19th century. If you want to say that the Green River varves are post flood, then the flood had to happen before ~55 million years ago (since the Green River formation is Eocene). The point is that there’s no evidence for a global flood anywhere in the geologic record. By and large, the rock record is best explained through the operation of processes that are similar to those in operation today. The rocks, almost without exception, look just like deposits that are forming today. I’m not arguing that rates are constant, they weren’t, but that doesn’t change my conclusion.

Don’t berate yourself for being unfamiliar with geology, no one here is an expert in all fields. You’ve got a great opportunity to learn more about area’s you’re unfamiliar with, and I think you should take it. I'm a geologist, and I learn a lot about nongeological topics from this message board.

There aren’t “good scientists” in other fields research the flood. Creationist research is characterized by the mischaracterization of conventional scientists (for example, the out-of-context quotations of conventional scientists), and the refusal to discard refuted ideas (for example, thrust faults are physically impossible or the geologic column is based on circular reasoning). Creationists have every right to believe their theories, but they don’t have to right to call them scientific because they do not follow the rules of science.

faded_Glory

John,

Just a minor point, aquifers are almost universally sedimentary, porous rocks where the pores are filled with water (usually trapped in the sediment since deposition). In most rocks porosity decreases with depth because of compaction due to the weight of the overlying rocks. At some depth all pores close and there is no room left for water.

Oil is formed in organic-rich shales and migrates from there into porous rocks, replacing the original formation water. Most oil fields contain oil in the shallowest part of the porous layers, but water deeper down (a simple buoyancy effect).

The deepest oil fields are at around 6000 m., usually in carbonates because sandstones don't have much porosity left at such depths. There is no reason why there wouldn't be any aquifers at the same depths - as long as there is preserved porosity.

On of the many problems with 'Flood Geology' and 'Fountains of the Deep' is that it needs an aquifer, ie. a porous layer, which obviously must pre-date the Flood. Most YEC's assume that all sedimentary rocks were laid down in the flood. They thus gloss over the fact that aquifers are sedimentary rocks themselves...

fG

John Solum

You won't get any arguments from me that aquifers are usually sedimentary rocks, but I don't think that the water in aquifers is left over from deposition. The water in aquifers is mobile. Two examples I can think of off the top of my head are the spread of contaminat plumes and springs.

I thought natural gas was in the shallowest parts since it's less dense than oil. Thanks for the information about the water, I knew that water was found in a lot of fields, but I wasn't sure how widespread it was.

6km is pretty close to what I remember, but the fact that the deepest wells are in carbonates surprises me. Carbonates become plastic at lower confining pressures and temperatures than quartz sandstones, and so I'd expect the sandstones to maintain their porosity longer (i.e., deeper). I'd assume that the porosity in carbonates is almost entirely fracutre porosity, while perhaps the porosity in the sandstone is primary. I'd imagine that it's easier to compact the rock and close pores than it is to heal fractures, so maybe that's the reason.

Sounds like a good point to me. It'd be interesting to know what the deepest nonsedimentary aquifer is.

It's pretty well-established that there is unbound water in the crust to a depth of at least 10km (maybe as high as 13-15km), at least along major fault zones (which serve as conduits for fluid migration due to the fracturing of rocks adjacent to the fault). The fact that faults so efficiently "drain" the crust is a large problem that I see with claims of subcrustal water.

[ February 26, 2002: Message edited by: John Solum ]</p>

Kosh

Ouch.

LeftCoast

I think that's correct. I'm not a geologist, nor do I play one on TV, but I seem to recall that the majority of the water that makes up the Ogollala aquifer is left over from the melt-off after the last ice-age. So, when you fly over the plains of the mid-continent US and see all of those circular irrigation patches the water that is being used last saw the light of day during the last ice-age.

Coragyps

There are quite a few oil & gas reservoirs in sandstone at 6 km or so, but all the really deep gas I can think of is, indeed, in carbonates, and for that matter in fractured dolomites. The pore space is probably vugs and fractures. Gas has been found and commercialized at 10 km depth in a few places.
The big reason that I remember for oil not being found that deep is that the higher temperatures way down "crack" it to gas+ graphite or other non-volatiles. Lots of the oil that is deep is also geologically pretty young - US Gulf Coast, for instance, has Miocene deposits at 20,000 feet or so. (Don't those have to be at least 4500 years old? )
Note: attempts to drill your own wildcat based on Coragyps's scattered knowledge of petroleum geology are not advised.

Kosh

Let me just beat Ron to the punch on this one.
Why would the younger oil be deeper than the
older stuff? Ie, if oil is formed from biological
deposits, then the deeper it is, the older it
should be.What are the geological mechanisms that
would make it otherwise?

Coragyps

Duh. Sorry, I wasn't very clear, was I?

The reason, in this case anyway, is that areas like the Gulf Coast have been sites of lots of rapid sedimentation for big portions of the recent past. Out here in West Texas, on the other hand, oil occurs down to maybe 12000 feet, and only gas deeper than that. But the sediments below me are Cretaceous or so, way older than the gulf coast Miocenes. And, in fact, the rocks here have been buried deeper (therefore hotter) than at present, and erosion has brought them back shallower - probably all before the Miocene. So shallow oil here is many times older than deep oil in Tangipahoa Parish, and deep oil here has been subjected to enough time and temperature to cook it into natural gas instead.
There has been some work on quantifying the time+ temperature conditions to do these transformations - the phrase "vitrinite reflectance" somehow comes to mind - but it's been so long since I've looked at that literature that I wouldn't know where to start to get anything in the way of a reference. (Google, of course, but I must go....)

faded_Glory

John,

I understand that springs are basically rain water moving in relatively shallow aquifers in response to pressure gradients. Most formation water in deeper reservoirs appears to be pretty immobile (on 'human timescales', not geological ones!), unless some pressure gradient is created (eg by draining an oil or gas field). On geological time scales, of course, formation water is mobile too as evidenced by dissolution and re-mineralisation, hydrothermal deposits etc. I don't know how much of the deeper formation water is secondary (like more recent influx from the surface, as opposed to primary, originally depositional) but I reckon not a lot?

I believe most clastic reservoirs would have lost their primary porosity when they are buried 6000 m. deep. Where there is still porosity left, it would be because the formation fluids are totally sealed in and cannot escape. Water is basically incompressible, and altough it will start to carry part of the overburden load and attain very high pressures it will keep the pores open.

Carbonates tend to have a much stronger framework than clastics, and can also have secondary (solution) and fracture porosity. This helps to preserve porosity at depth.

Why are we discussing this, anyway ?

fG

Oolon Colluphid

Funny, but there's no sign of Ron...

Oolon