Ok, now that work is out of the way for the day, I can get back to this:
I'm aware TalkOrigins claims Austin misapplied the method because "Austin sent his samples to a laboratory that clearly states that their equipment cannot accurately measure samples less than two million years old." However if YECs are correct that all fossils are younger than that to begin with, then all laboratories would be incorrectly dating younger material, so that argument doesn't work.
CD013.1: K-Ar dating of Mt. St. Helens dacite
No. What would most likely happen if EVERYTHING was too young to date accurately is that IF we were able to get a reading at all, like Austin did, it would be right around lower limits of the method we were using. This is because there is a certain amount of "noise" in the readings that comes from residue in the tools, and the preparation process which gives a minimal reading in the results. This is accounted for in the "error bars" that are given when quoting an age for a rock.
Now, the reason this is significant is that different isotopes have different minimum ages they can measure (because of the length of their half-lives/decay rate). So, if you measured the same rock with both the Rb/Sr method and with the K/Ar method, you would get two different dates, since they would both test right around the lower limit of the respective method.
What this means is that we would virtually NEVER see concordant dates between multiple methods. In fact, we see concordant dates greater than 90% of the time.
The only way to explain this is if the sample is sufficiently old to date using each of the methods, such that there has been enough decay to get an actual reading.
Secondly, there is evidence of an ancient eruption within the sea killing the dinosaurs.
Ancient Volcanic Eruptions Caused Global Mass Extinction -- ScienceDaily
That's nice. There are several hypotheses about how the dinos went extinct. The vast consensus, however, is that it was due to the meteorite that hit the earth in Mexico 65 million years ago.
Thirdly, Carbon 14 from dinosaur soft tissue fossils has been discovered, even though it shouldn't still exist according to the theory of evolution. Of course, soft tissue wasn't supposed to exist either.
C14 dinos - creation.com
I've already touched on this in a previous post, but I'll add a few things. The "soft tissue" that exists, while surprising, is not as "soft" as creationists would like it to be. It has to be rehydrated, contains no DNA, no carbon 14 (despite claims by the same dude who sent a shellacked dinosaur bone to get tested a couple decades earlier; shellac contains carbon), no collagen, etc.
Secondly, even if, and that's a big if, the C-14 dates were legit, it still does YEC no good. The numbers that the guy came up with are near the upper limits of the carbon dating method. What this means is that it is TRACE amounts of C14. If the earth was only 6000 years old, there should be a full HALF of the carbon content remaining. So where did the rest of it go, if it didn't have time to decay?
Fourth, they do suffer from similar limitations. They rely on the assumption that the daughter isotope levels are known,
First of all, I'm going to assume (because your statement makes no sense if I don't) that you mean that the INITIAL daughter concentration levels are assumed to be zero. Because the PRESENT daughter amounts are actually measured.
But that's ok. We absolutely don't assume that the initial concentration is zero. In fact, it usually is not (although, it is often very close to zero), and WE DON'T NEED IT TO BE. You know why? Because we can DETERMINE what the initial concentrations were. That's the lovely thing about mathematics. Given the values for enough variables, we can figure out the unknown variable. And it just so happens that we can measure all the variables needed to find unknown variable of initial concentration. They do this by plotting a graph, called an isochron.
And we've been able to do that for decades.
that a closed system occurred without variation in the decay process,
We don't assume this at all. In fact, we know that it is often not the case. But guess what? They have developed procedures that can check for that, too. Remember that isochron I told you about? It's a straight line on a graph with its slope representing the age. If the system has not remained closed, the samples WON'T FORM A STRAIGHT LINE.
But that is just one method. Using concordia/discordia graphs with the Pb dating system, we can also check for closed systems. In the Ar/Ar method, we use an age spectrum.
This is actually a great help for geologists because it allows us to even measure metamorphic rock and determine how long ago different geologic events occurred.
and that equally flawed dating methods can crosscheck them.
Oh, but how are they all "equally flawed" in VASTLY different ways to all arrive at the same ages?? How can dendrochronology be wrong in one way, speleothems in another, coral bands in another, icecores in another, C14 in another, lake varves in yet another and all wind up agreeing with each other?
These are all very different methods, with different environmental pressures, in many different parts of the world. Ok, so they are all flawed? Yet, miraculously all flawed DIFFERENTLY, so that they get the same wrong answer. That's one deceptive, trickster god you believe in.