What's the difference between archaean and archean?
Archaean
Definition:
(a.) Ancient; pertaining to the earliest period in geological history.
(n.) The earliest period in geological period, extending up to the Lower Silurian. It includes an Azoic age, previous to the appearance of life, and an Eozoic age, including the earliest forms of life.
Example Sentences:
(1) We formulate the following hypothesis: Life's origin may have occurred during the lower Archaean at a time when the environmental temperature was higher than it is at present.
(2) Hence, the occurrence of sulfate evaporites in Archaean sediments does not necessarily provide testimony of oxidation weathering on the ancient continents and, consequently, of the existence of an atmospheric oxygen reservoir.
(3) Incipient minor differentiation of the isotope pattersn notably of Archaean sulfates may be accounted for by photosynthetic sulfur bacteria rather than by sulfate reducers.
(4) (2) Isotopic evidence of dissimilatory sulfate reduction is first observed in the upper Archaean of the Aldan Shield, Siberia (approximately 3.0 x 10(9) yr) and in the Michipicoten and Woman River banded iron formations of Canada (2.75 x 10(9) yr).
(5) The presently available sedimentary sulfur isotope record for the Precambrian seems to allow the following conclusions: (1) In the Early Archaean, sedimentary delta 34S patterns attributable to bacteriogenic sulfate reduction are generally absent.
(6) (4) With the bulk of sulfate in the Archaean oceans probably produced by photosynthetic sulfur bacteria, the accumulation of SO4(2-) in the ancient seas must have preceded the buildup of appreciable steady state levels of free oxygen.