RAZD: how does ANY of the dating techniques explained in the opening post determine their starting benchmark date?
What is the
external check used to determine deep time accuracy?
I propose that you have none because none can exist. The only external benchmark date available to calendar history applies to calendar history exclusively (2140 BC; two star alignments and the fixed in stone descending passage in the Great Pyramid interlock once every 26,000 years).
What you have is rocks dating fossils and fossils dating rocks based on a guess by Charles Lyell in the 19th century as to when the Cretaceous period ended. That guess is still ballpark close to the accepted date of the end of the Cretaceous based on modern radio dating. This is nothing less than a miracle. And needless to say Lyell's guess in the 19th century is the beginning "benchmark" date or dating that modern evolutionists accepted and built upon. In addition, Charles Darwin ignored the experts in his day (Lord Kelvin) and augmented fantastically the age of the Earth in accordance to the needs of modification evolution. Again, this is the "benchmark" dating that modern radio dating is built upon. Again, this is nothing less than a miracle that a guess and a arbitrary augmentation to be confirmed by modern radio dating.
Ray