Yes, but it’s relatively unlikely to go back a billion years given how geologically active our planet is and how fast microbes can mutate.
The oldest I can think of are the Movile Cave [1] which was isolated for 5.5 million years before it was discovered and Lake Vostok [2] which has been isolated for tens of millions of years.
The oldest I can think of are the Movile Cave [1] which was isolated for 5.5 million years before it was discovered and Lake Vostok [2] which has been isolated for tens of millions of years.
[1] https://en.m.wikipedia.org/wiki/Movile_Cave
[2] https://en.m.wikipedia.org/wiki/Lake_Vostok