Stromatolites - Pilbara craton - Western Australia
The Paleoarchean (//; also spelled Palaeoarchaean (Formerly known as early Archean)) is a geologic era within the Archaean. It spans the period of time 3,600 to 3,200 million years ago—the period being defined chronometrically and not referenced to a specific level in a rock section on Earth. The name derives from Greek "Palaios" ancient. The oldest ascertained life form (well-preserved bacteria older than 3,460 million years found in Western Australia) is from this period. 3,480 Ma: Fossils of microbial mat found in 3.48 billion-year-old sandstone discovered in Western Australia.  The first supercontinent Vaalbara formed during this period.