Well, first off,
cross bedding occurs in many many different formations throughout the world at
dramatically different times from this and does not necessarily mean
catastrophic conditions.
But let's drill down to this point in the article you posted:
Now indeed, when something is as old as the
other evidence would suggest these rocks are, then indeed there should be virtually no 14C.
But, technically speaking 50,000 years represents about 10 half-lives.
The way a half-life works is that each half-life removes HALF of the original radioactive element.
If you start off with 10000 atoms of 14-C, after 1 half-life you will have 5000, after 2 half lives, 2500, so on and so forth.
The equation would be:
Amount 14C Left = Original Amount * (1/2^n)
which means you'll wind up with 0.1% of the original 14C amount.
So if you start off with 10,000 14C atoms, after 10 half-lives (approximately 50,000 years) you will still have 9.8 atoms.
So the statement that after 50,000 years there should be nothing left is wrong. But further, to the point, there is
contamination issues that can be induced.
Unfortunately the authors of your piece are "short on details" so we don't really know
how much 14C was found, indeed there should be vanishingly small amounts of it.
But then, the specter of contamination always looms in this aspect. Perhaps a good analysis of the STABLE carbon isotopes would be in order to determine possible issues?
Then they go and shoot themselves in the foot:
So they are suggesting atmospheric
contamination? Wouldn't that basically just GUT the whole point they were trying to make about it being young? Contamination will give a
false young age!
I don't see any mention in the geologic literature of the Narrabeen or Hawkesbury sandstones being part of what is called a
turbidite or
Bouma sequence, which would indicate a catastrophic depositional environment, well at least a very high energy one. But I'm not an expert on Gondwanaland geology or Australian geology in general. Hopefully someone on here is.
Turbidite:
geological formations have their origins in turbidity current deposits, deposits from a form of underwater avalanche that are responsible for distributing vast amounts of clastic sediment into the deep ocean. (SOURCE)
Now I'll readily admit I'm not expert on these formations, but just because you have a sandstone with cross-bedding doesn't mean it was necessarily from some world-wide flood. Otherwise you'd have to explain how you can have multiple layers of cross-bedded sandstones separated by either calm water (shales) or even sub-aerial exposure as we find in other places on the planet.
Cross-bedding is
known to occur today in sandstones forming all over the planet. We can watch them form and we can even see soft-sediment cross-bedding and even, gasp, dune-cross bedding where no water is involved whatsoever.
So cross-bedding does not equal "Global Flood". It appears to be quite common.
Still I'd be interested if someone on here is an expert in Australain geology and can address this more fully.