"Relative Dating" or "Absolute Dating" or "Chronometric Dating"

[Tristen]

14 hours ago, teddyv said:

What are these "fundamentally unverifiable assumptions"?

Let's be specific: in the U-Pb method, what are the assumptions here?

 

The first primary assumption is knowledge of the original state of the substance being 'dated'. For example, "in the U-Pb method", we assume that all of the lead isotope (206) comes from decayed uranium since the rock formed. This is not an observation.

Another primary assumption of most dating methods is that some process has continued at an unaltered rate over unobserved time. In "the U-Pb method", there is a series of different kinds of decay whose rate is assumed to be constant over the enormous periods of putative time since the rock supposedly formed. Again, this is assumed based on current measurements, not actually observed over the claimed time frame.

A third fundamental assumption of many dating methods is that the system of the tested substance has been closed to outside influences that may have either contributed, or removed, the tested substances. In "the U-Pb method", that refers to the potential addition or removal of any of the isotopes in the decay chain between uranium and lead.

[Omegaman 3.0]

18 hours ago, Sparks said:

Pangaea is a theory.  There is no evidence of it.

Not to entirely disagree, but I don't think that is quite accurate. Is it a theory? Yes. Is there proof? No. Is there evidence, yes, but it is circumstantial. Basically, the puzzle pieces fit together. I might be wrong in this, not stating it as a fact, but as I recall the continental drift is such that the parts are moving in the right direction, in other words, if we could run the tape backwards, the part seem to have come from where they look like they could be from. In would be interesting to know (and I do not), if the geology from the apparently broken edges, matches (substantially better than form random part of the edges).

By the way, all this time I thought this topic was about dating ones' relatives - should I date my cousin?

[Sparks]

5 hours ago, Omegaman 3.0 said:

Not to entirely disagree, but I don't think that is quite accurate. Is it a theory? Yes. Is there proof? No. Is there evidence, yes, but it is circumstantial. Basically, the puzzle pieces fit together. I might be wrong in this, not stating it as a fact, but as I recall the continental drift is such that the parts are moving in the right direction, in other words, if we could run the tape backwards, the part seem to have come from where they look like they could be from. In would be interesting to know (and I do not), if the geology from the apparently broken edges, matches (substantially better than form random part of the edges).

By the way, all this time I thought this topic was about dating ones' relatives - should I date my cousin?

The puzzle does not fit together. 

If you remove Mexico, Nicaragua, Panama, Costa Rica, Guatemala, Honduras, Belize, and then shrank down Africa by about 40%, it fits together. 

This is the real size of Africa.  Most USA maps and globes show Africa shrunken down, probably for this dumb theory.  The truth is that most continents would fit within the boundaries of Africa.

[believeinHim]

7 hours ago, Omegaman 3.0 said:

Not to entirely disagree, but I don't think that is quite accurate. Is it a theory? Yes. Is there proof? No. Is there evidence, yes, but it is circumstantial. Basically, the puzzle pieces fit together. I might be wrong in this, not stating it as a fact, but as I recall the continental drift is such that the parts are moving in the right direction, in other words, if we could run the tape backwards, the part seem to have come from where they look like they could be from. In would be interesting to know (and I do not), if the geology from the apparently broken edges, matches (substantially better than form random part of the edges).

By the way, all this time I thought this topic was about dating ones' relatives - should I date my cousin?

Loll, No that is not what this is about @Omegaman 3.0! The thread kind of got derailed ! 

[believeinHim]

Absolute dating is the process of determining an age on a specified chronology in archaeology and geology. Some scientists prefer the terms chronometric or calendar dating, as use of the word "absolute" implies an unwarranted certainty of accuracy.

[teddyv]

16 hours ago, Omegaman 3.0 said:

Not to entirely disagree, but I don't think that is quite accurate. Is it a theory? Yes. Is there proof? No. Is there evidence, yes, but it is circumstantial. Basically, the puzzle pieces fit together. I might be wrong in this, not stating it as a fact, but as I recall the continental drift is such that the parts are moving in the right direction, in other words, if we could run the tape backwards, the part seem to have come from where they look like they could be from. In would be interesting to know (and I do not), if the geology from the apparently broken edges, matches (substantially better than form random part of the edges).

By the way, all this time I thought this topic was about dating ones' relatives - should I date my cousin?

Pangaea is a consequence of Plate Tectonic theory. Continental drift, by the way, is generally no longer used.

Plate tectonics is essentially the underpinning theory of modern geology. One could also claim that geology is really an applied science since it is really a consequence of physics and chemistry.

Pangaea is supported through various strands of evidence, including the geological belts that can be seen in West Africa and northern South America. As an exploration geologist, the gold belts in Ghana are similar in style and age to those in Venezuela. These all date to Proterozoic time, so well before the breakup occurred.Fossil evidence shows common species prior to the breakup followed by a divergence of species once the split was great enough to separate populations. Remanent magnetics is another common line of evidence that is often used. Other mountain belts are noted that share commonalities like the Appalachians with the Highlands inn Scotland.

A note about this land are being too small, I suspect what that might derived from, is that the reconstruction would be based on the cratons - the cores of continental crust (i.e. Canadian Shield, Man shield). This would ignore any add-on island arcs or new plutonism and volcanism that would extend the margins of many of the cratons. 

For example, in BC, the edge of the North American craton is at the Rock Mountain Trench, a NW-trending valley that runs close to the BC-Alberta border. It heads into the Yukon becoming the Tintina Trench. East of the trench are the Paleozoic sediments that make of the Canadian Rockies which overlie the granitic core.

West of the trench, British Columbia consists of a series of belts called terranes. These are a series of "docked" geological packages of common ages and related volcanism and plutonism. Think of an island arc system like Japan or New Zealand. These were added onto the North American plate as the plate collided with the Pacific plate. We have at least 10 identified distinct terranes in BC. Quesnellia and Stikinia are some of the larger ones are known to host certain types of deposits of comparable ages. Dating of intrusives shows a consistent pattern of Late Cretaceous plutonism from the US border to Alaska. These were a response to the subduction of the oceanic plate.

Sorry if that the tl;dr.

[teddyv]

18 hours ago, Tristen said:

The first primary assumption is knowledge of the original state of the substance being 'dated'. For example, "in the U-Pb method", we assume that all of the lead isotope (206) comes from decayed uranium since the rock formed. This is not an observation.

Interesting.

Zircons, being the primary source for U-Pb dating are chosen for several particular reasons. When crystallizing, their crystal lattice strongly rejects lead but accommodates uranium. I don't have technical papers at hand for this, but such an observation should be able to be demonstrated in a laboratory. Elemental properties, I would think, should not be that debatable. Zircons are quite immune to contamination as well due to other physical properties. These are observations.

So at formation, there is virtually no lead and only uranium. Any lead subsequently detected in the sample would be daughter product. These are observations.

Additionally, I understand, checks can be made using U235 decay chain. These are observations.

18 hours ago, Tristen said:

Another primary assumption of most dating methods is that some process has continued at an unaltered rate over unobserved time. In "the U-Pb method", there is a series of different kinds of decay whose rate is assumed to be constant over the enormous periods of putative time since the rock supposedly formed. Again, this is assumed based on current measurements, not actually observed over the claimed time frame.

This argument seems to take something radiometric dating and make a claim in complete isolation from other strands of scientific observations. Just looking at the Andromeda galaxy some 2+ million ly away indicates that the universe has been operating normally over 2 million years ago. If the universe, and the speed of light are operating normally, then radioactive decay (which is intrinsically tied to the speed of light) is operating normally. 

If reality is unreliable the YEC and modern sciences are 

18 hours ago, Tristen said:

A third fundamental assumption of many dating methods is that the system of the tested substance has been closed to outside influences that may have either contributed, or removed, the tested substances. In "the U-Pb method", that refers to the potential addition or removal of any of the isotopes in the decay chain between uranium and lead.

As aforementioned, zircons are quite good at maintaining a closed system even with subsequent reheating and metamorphism.

 

The fact that geologists have used, still use and will continue to use radiometric methods, is because they work. U-Pb is the preferred one because of the properties of zircons. Isochron plotting adds additional veracity.

[teddyv]

An Aside and not directed at anyone:

I mentioned in a previous post that geology, is underpinned by chemistry and physics. I have seen little of these sciences are ever questioned by YEC-adherents, which tend to focus on the astronomical, geological and biological sciences (for obvious reasons). For example, most mineral deposits are formed by hydrothermal fluid flows and these are driven by mundane, explainable physical processes of temperature and pressure gradients. You can't really speed these up though. It's an area that seems completely ignored by the YEC groups. Regional metamorphism is another area that has not received an significant attention. These are big factors to consider in geology. I'd like to see some attention on that rather than rehashing the Grand Canyon nonsense over and over.

[Sparks]

12 hours ago, teddyv said:

Pangaea is a consequence of Plate Tectonic theory. Continental drift, by the way, is generally no longer used.

Pangaea is the theory that didn't work out, so of course it's no longer used. 

[Tristen]

22 hours ago, teddyv said:

Interesting.

Zircons, being the primary source for U-Pb dating are chosen for several particular reasons. When crystallizing, their crystal lattice strongly rejects lead but accommodates uranium. I don't have technical papers at hand for this, but such an observation should be able to be demonstrated in a laboratory. Elemental properties, I would think, should not be that debatable. Zircons are quite immune to contamination as well due to other physical properties. These are observations.

So at formation, there is virtually no lead and only uranium. Any lead subsequently detected in the sample would be daughter product. These are observations.

Additionally, I understand, checks can be made using U235 decay chain. These are observations.

This argument seems to take something radiometric dating and make a claim in complete isolation from other strands of scientific observations. Just looking at the Andromeda galaxy some 2+ million ly away indicates that the universe has been operating normally over 2 million years ago. If the universe, and the speed of light are operating normally, then radioactive decay (which is intrinsically tied to the speed of light) is operating normally. 

If reality is unreliable the YEC and modern sciences are 

As aforementioned, zircons are quite good at maintaining a closed system even with subsequent reheating and metamorphism.

 

The fact that geologists have used, still use and will continue to use radiometric methods, is because they work. U-Pb is the preferred one because of the properties of zircons. Isochron plotting adds additional veracity.

 

“Zircons, being the primary source for U-Pb dating are chosen for several particular reasons. When crystallizing, their crystal lattice strongly rejects lead but accommodates uranium. I don't have technical papers at hand for this, but such an observation should be able to be demonstrated in a laboratory”

So firstly, even if this was accurate, you are indeed assuming the original state of the substances being tested (which is my claim). That original state was not observed, but merely assumed based on a subset of current knowledge.

But what you claim is only a partial truth. Zircon crystals can be grown artificially from around 600°C, but lead is only restricted when the temperature gets over 800°C. That allows plenty of scope for lead to remain in zircons, or move into zircons during cooling (all assuming that what holds true in the lab is always reflective of nature).

Furthermore, there are a bunch of other isotopes in the U-to-Pb decay cascade that are not temperature restricted – and so can exist in the zircon at the time of formation. Therefore, even if we agree to assume there was no lead in the tested zircon at the time of formation, that doesn’t mean all the current lead in the zircon decayed from uranium.

Zircons can also undergo recrystallization – allowing for the removal and/or acquisition of lead.

Lead has also recently been demonstrated to be mobile within zircons – concentrated into nanospheres that can generate sampling errors. If lead can be mobile within zircons, can it also move in and out of zircons?

Reversely Discordant errors are also present in the secular data which have only thus far been explained by lead-gaining events.

Presumed ‘older’ zircons are generally assumed to be contaminated with intrusions due to structural deterioration over time – so another potential source of introduced or lost isotopes.

And ultimately, you are assuming a naturalistic origin of these zircons. Who but God knows how much lead would be present in a newly created zircon?

 

“Elemental properties, I would think, should not be that debatable. Zircons are quite immune to contamination as well due to other physical properties. These are observations”

Events witnessed in a lab are indeed “observations”. But when we speculate that these “properties” observed in a lab, necessarily hold true for individual, unobserved cases, over stupendous magnitudes of time beyond the lab, that’s when we logically abandon the province of “observations” and dive head-first, deep into the realm of speculation and assumption.

Just as an aside – I have no problem with making assumptions in science. I only have a problem with failing to recognize the logical distinction between assumption and “observations”. This distinction has logical implications for how much legitimate confidence we can attribute to a claim.

 

“So at formation, there is virtually no lead and only uranium. Any lead subsequently detected in the sample would be daughter product. These are observations”

These are only “observations” if the tested zircon was observed being formed and then tested. Otherwise, it is an assumption. The logical distinction here is really very simple.

 

“Additionally, I understand, checks can be made using U235 decay chain. These are observations”

This is a very general, and wholly Unsupported Assertion. One can not “check” how much Pb206 was in the zircon at formation using the “U235 decay chain”.

 

“This argument seems to take something radiometric dating and make a claim in complete isolation from other strands of scientific observations. Just looking at the Andromeda galaxy some 2+ million ly away indicates that the universe has been operating normally over 2 million years ago. If the universe, and the speed of light are operating normally, then radioactive decay (which is intrinsically tied to the speed of light) is operating normally. If reality is unreliable the YEC and modern sciences are”

What? Sorry, I don’t understand your point here.

Yes, that the measured light has been travelling at a constant rate (and in a straight line) throughout its historical journey is indeed an assumption required to generate a distance and age claim. But that’s not what we are discussing here.

 

“As aforementioned, zircons are quite good at maintaining a closed system even with subsequent reheating and metamorphism”

So based on this understanding, you acknowledge that the method does indeed require assuming a closed system over unimaginable magnitudes of time.

 

“The fact that geologists have used, still use and will continue to use radiometric methods, is because they work. U-Pb is the preferred one because of the properties of zircons”

There is no independent way to verify that “they work”.

 

“Isochron plotting adds additional veracity”

Not really. Isochron dating just moves the first assumption along the path by presuming to be able to plot the original isotope levels (i.e. it still makes assumptions about the original state of the substance being tested). That putative ability to plot the isotopes is itself entirely dependent on other underlying assumptions about the initial state of the rocks being tested.

Ironically, in the context of this debate, Isochron Dating was proposed explicitly to overcome one of the assumptions you are trying to gloss over.

 

To sum-up my response – the claims you’ve made in this post seem to be arguing that your assumptions can be rationally justified. I actually think that’s fair. But it doesn’t change the fact that they are still, logically speaking, assumptions. That means, from the perspective of critical thinking, no one is rationally obligated to your levels of confidence in the U-Pb dating method. If any of the things you are assuming about unobserved history happen to be wrong, then the logic of the dating method collapses entirely.