paleoatmosphere

• palaeoatmosphere

paleo- +‎ atmosphere

paleoatmosphere (plural paleoatmospheres)

1. An atmosphere, particularly that of Earth, at some unspecified time in the geological past.
   • 2013, Robert J. Delmas, Ice Core Studies of Global Biogeochemical Cycles, page 384:

     Of the various paleorecords available to science, ice cores from polar and high altitude ice sheets provide the most direct and highest resolution view of paleoatmospheres.

• paleoatmospheric