What is "mesoarchean"

The Mesoarchean (, also spelled Mesoarchaean) is a geologic era within the Archean, spanning . The period is defined chronometrically and is not referenced to a specific level in a rock section on Earth. Fossils from Australia show that stromatolites have lived on Earth since the Mesoarchean. The Pongola glaciation occurred at . The first supercontinent Vaalbara broke up during this time around .