Re: Clanad's post on page 2 (apologies if already pointed out; I am catching up on this thread)
//and clearly indicate bacterial fossils extending to within a few hundred thousand of years following the estimated creation of Earth (3.8 billions of years ago)//
The opening paragraph of the berkeley article you link to says:
"The cyanobacteria have an extensive fossil record. The oldest known fossils, in fact, are cyanobacteria from Archaean rocks of western Australia, dated 3.5 billion years old. This may be somewhat surprising, since the oldest rocks are only a little older: 3.8 billion years old!"
The difference between 3.8 billion and 3.5 billion is, of course 300 million.
300 million years ago is the era of the supercontinent of Pangea, the collapse of the Carboniferous forests into vast deserts and the start of the Permian. Before the first mammals.
https://en.m.wikipedia.org/wiki/Permian
There is also an indeterminite length of time between first formation of earth and "oldest surviving rocks (exposed on the surface)". Formation of the planet is often stated to be over 4 billion years ago and the cooling and solidification of the surface was somewhat delayed by the "late heavy bombardment". The theory behind moon formation, being caused by a massive impactor, also implies the long-standing existence of a proto earth. Age of oldest known moon rock therefore constrains minimum age of earth.