According to some authorities, the era in Old Earth's geologic history from 65 million years ago to the present; according to others, the period from 65 million years ago until the Great Expulsion. It was preceded by the Mesozoic, and followed according to some by the Gaiazoic. During this time Old Earth took on its "modern" aspect; it is sometimes called the "Age of Mammals".
This era saw the emergence of modern mammals, birds, vegetation (especially grasses), the modern look of the continents, and (after an early warm period) a cooling climate. It is divided into the Paleogene and the Neogene periods according to some authorities. Others prefer to mark of the most recent years, including the Pleistocene, Holocene, and Gaiacene epochs, as a third period, called the Quaternary.
Gaiacene Epoch - Text by Stephen Inniss A term used to designate the new geological epoch and ice age on Old Earth from the nanoswarms and the Great Expulsion onwards. Preceded by the Holocene.
Gaiozoic Era - Text by M. Alan Kazlev Used to designate the geological period on Earth from the Great Expulsion onwards. Some prefer to imply a shorter time span, given the implications of the Fermi Paradox, and refer to this period as the Gaiacene Epoch.
Holocene Epoch - Text by M. Alan Kazlev and Stephen Inniss On Old Earth the Holocene ("entirely recent") is the most recent but one epoch in geologic time, lasting from about 12,000 BT (10,000 b.c.e.) to the Great Expulsion. This brief span of time from the birth of agriculture until the end of human baseline dominance on the species' home planet was the Golden Age according to most Anthropist sects. It was preceded by the Pleistocene and succeeded by the Gaiacene.
Paleogene Period - Text by Stephen Inniss In Old Earth paleontology and geology, the first period of the Cenozoic, stretching from 65 to 23 million years before the present and containing the Paleocene, Eocene and Oligocene epochs. It was followed by the Neogene. The Muuh and the Soft Ones established interstellar civilizations during this period, and though there are ruins of Muuh origin on Titan there is no evidence they ever interacted with Earth life and the modern Muuh have no record of any connection with Solsys at all.
Quaternary Period - Text by Stephen Inniss On Old Earth the third period (or second according to some) of the Cenozoic Era on Old Earth beginning 2.8 million years ago. It follows the Neogene (or according to some divisions the Tertiary) period, and consists of the Pleistocene, Holocene, and Gaiacene epochs.