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You can't calculate how much 87Sr was present at the beginning without first *assuming* that it is relatively proportional w/ 84Sr, 86Sr & 88Sr. Because of this assumption, you are *assuming* the amount of 87Sr that was present when the isochron was formed. Maybe that doesn't qualify as an assumption in your mind, but it does in mine.

No. You know that it does not exceed 7%, because that's the current abundance, and it's increasing with time. We understand isotope fractionation processes pretty well, and we know they're very weak for a divalent ion like Sr²⁺. We also can extrapolate back the abundance of ⁸⁷Sr to the time the rock was formed, based on the known concentration of ⁸⁷Rb in the lithosphere. There will be some error associated with that, but not much, becuase the abundance of ⁸⁷Sr is quite low in the first place, and it is formed very slowly. So you certainly know it's in a very narrow range somewhat below 7% of all strontium. So if you know the abundance of the other isotopes, you can calculate the initial abundance of ⁸⁷Sr at any time in the earth's history, probably to better than 1% accuracy.

And yes, they did find excess helium. You do the same thing when you assume how much helium should be present. Why criticize your opponent for the same thing that you do?

No, they did not. They found less helium than must have been produced by radioactive decay. We know how much helium was produced, because we know the amount of uranium that decayed to lead.

See Setterfield. Setterfield is a fruit-loop whose ideas have ben rejected by the scientific community and even by the more respectable YECcers.

When 3 of 8 isochron samples by Dalrymple return dates of 34 billion years, there are no good 'independent' reasons for discarding these anomalies.

Let's look at what he actually said, shall we? The final example listed in Table 2 is a supposed 34 billion-year Rb-Sr isochron age on diabase of the Pahrump Group from Panamint Valley, California, and is referenced to a book by Faure and Powell (50). Again, Woodmorappe (134) badly misrepresents the facts. The “isochron” that Woodmorappe (134) refers to is shown in Figure 6 as it appears in Faure and Powell (50). The data do not fall on any straight line and do not, therefore, form an isochron. The original data are from a report by Wasserburg and others (130), who plotted the data as shown but did not draw a 34-billion-year isochron on the diagram. The “isochrons” lines were drawn by Faure and Powell (50) as “reference isochrons” solely for the purpose of showing the magnitude of the scatter in the data.

As discussed above, one feature of the Rb-Sr isochron diagram is that, to a great extent, it is self-diagnostic. The scatter of the data in Figure 6 shows clearly that the sample has been an open system to 87Sr (and perhaps to other isotopes as well) and that no meaningful Rb-Sr age can be calculated from these data. This conclusion was clearly stated by both Wasserburg and others (130) and by Faure and Powell (50). The interpretation that the data represent a 34 billion-year isochron is solely Woodmorappe’s (134) and is patently wrong.

The only difference is that science hasn't figured out all of the problems w/ isochron dating yet. But they are starting to come out and that's not good for you.

The two references you've given citing 'problems' are 17 and 22 years old. Hardly 'starting to come out'!

No, you don't. You *assume* that it is equally distributed and you *assume* that it is increasing at the same rate. More assumptions than you can shake a stick at.

And yes, the 34 billion year examples do not 'form an isochron' because they are thrown out. The reason that they are thrown out is because they do not form an isochron (a linear distribution).

Circular reasoning and truth by definition.

Setterfield is a fruit-loop whose ideas have ben rejected by the scientific community and even by the more respectable YECcers.

YEC'ist Fruit Loops, anyone?