Subject: What does AFDW (ash-free dry weight) show?

I've seen numerous reports where oceanographers have used the term AFDW 
(Ash-free dry weight) when discussing their sediment samples.   
Considering the technique is quite different to simple dry weight 
measurements, I wondered what AFDW measurements depicted.   I suspect that 
it might be something to do with measuring the organic content of the 
sediment, can anyone shed any light on it for me?

Thank you.

Re: What does AFDW (ash-free dry weight) show?