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for an age mixes unit systems, and tempts capitalization errors: "million" need not be capitalized, but "mega" must be; "ma" would technically imply a
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The "ago" is implied, so that any such year number "X Ma" between 66 and 145 is "Cretaceous", for good reason. But the counter argument is that having
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In this case, "79 Ma" means only a quantity of 79 million years, without the meaning of "79 million years ago".
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seen in geology, it is usually "Myr" (a unit of mega-years). In astronomy, it is usually "Myr" (Million years).
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The
Cretaceous started 145 Ma ago and ended 66 Ma ago, lasting for 79 Ma.
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The
Cretaceous started 145 Ma and ended 66 Ma, lasting for 79 Myr.
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In geology, a debate remains open concerning the use of
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134:(million years ago) versus using only the term
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34:"Myr" redirects here. For other uses, see
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240:"Discussion of GSA Time Unit Conventions"
84:Myr is in common use in fields such as
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267:"Push to define year sparks time war"
16:Unit of time equal to 1,000,000 years
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265:Biever, Celeste (April 27, 2011).
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72:years), or approximately 31.6
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29:one million (disambiguation)
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138:. In either case, the term
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27:. For 1,000,000 BC, see
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62:1,000,000 years
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150:ISO 80000-3
74:teraseconds
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186:), as in:
23:song, see
349:Astronomy
298:April 28,
214:Megaannum
170:milliyear
109:astronomy
107:, but in
90:cosmology
60:equal to
244:web page
198:See also
146:ISO 31-1
96:that is
19:For the
387:Geology
311:Portals
281:Bibcode
105:geology
122:Debate
64:(i.e.
361:Stars
148:(now
80:Usage
21:Adele
300:2011
216:(Ma)
88:and
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166:Mya
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