Paleoproterozoic

The Paleoproterozoic Era (also spelled Palaeoproterozoic) is the first of the three sub-divisions (eras) of the Proterozoic eon, and also the longest era of the Earth's geological history, spanning from (2.5–1.6 Ga). It is further subdivided into four geologic periods, namely the Siderian, Rhyacian, Orosirian and Statherian.

Paleoproterozoic surge in atmospheric oxygen

The Siderian () is the first geologic period in the Paleoproterozoic Era and Proterozoic Eon. It lasted from  to  million years ago (Ma), spanning 200 million years, and is followed by the Rhyacian Period. Instead of being based on stratigraphy, these dates are defined chronometrically.

The Rhyacian () is the second geologic period in the Paleoproterozoic Era. It spans 250 million years and lasted from to million years ago (Ma), following the Siderian Period and preceding the Orosirian Period. These dates are defined chronometrically rather than stratigraphically.

The Statherian (; , meaning "stable, firm") is the fourth and final geologic period in the Paleoproterozoic Era, lasting from to million years ago (Ma) and spanning 200 million years. It follows the Orosirian Period and precedes the Calymmian Period, with the latter belonging to the Mesoproterozoic Era. Instead of being based on stratigraphy, these dates are defined chronometrically.

The Orosirian (; , meaning "mountain range") is the third geologic period in the Paleoproterozoic Era. It spans 250 million years and lasted from to million years ago (Ma), following the Rhyacian Period and preceding the Statherian Period. Instead of being based on stratigraphy, these dates are defined chronometrically.

possibly earliest multicellular lifeforms

Paasselkä (earlier Paasivesi, both names roughly mean 'Stone lake') is an oval-shaped lake formed in an eroded impact crater in Southern Savonia, Finland. The lake, which is a part of Orivesi, which is in turn part of the Greater Saimaa, is devoid of islands which makes it different from other lakes in the region. Paasselkä is also unusually deep, 75 m at the deepest point.