The Middle Miocene is a sub-epoch of the Miocene epoch made up of two stages : the Langhian and Serravallian stages. The Middle Miocene is preceded by the Early Miocene .
4-686: The sub-epoch lasted from 15.97 ± 0.05 Ma ( million years ago ) to 11.608 ± 0.005 Ma. During this period, a sharp drop in global temperatures took place. This event is known as the Middle Miocene Climatic Transition . For the purpose of establishing European land mammal ages , this sub-epoch is equivalent to the Astaracian age. This geochronology article is a stub . You can help Misplaced Pages by expanding it . Million years ago Million years ago , abbreviated as Mya , Myr (megayear) or Ma (megaannum),
8-431: Is a unit of time equal to 1,000,000 years (i.e. 1 × 10 years), or approximately 31.6 teraseconds . Myr is in common use in fields such as Earth science and cosmology . Myr is also used with Mya or Ma. Together they make a reference system, one to a quantity, the other to a particular point in a year numbering system that is time before the present . Myr is deprecated in geology , but in astronomy Myr
12-462: Is standard. Where "myr" is seen in geology, it is usually "Myr" (a unit of mega-years). In astronomy, it is usually "Myr" (Million years). In geology, a debate remains open concerning the use of Myr (duration) plus Ma (million years ago) versus using only the term Ma . In either case, the term Ma is used in geology literature conforming to ISO 31-1 (now ISO 80000-3 ) and NIST 811 recommended practices. Traditional style geology literature
16-414: Is written: The Cretaceous started 145 Ma and ended 66 Ma, lasting for 79 Myr. 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 myr for a duration and Mya for an age mixes unit systems, and tempts capitalization errors: "million" need not be capitalized, but "mega" must be; "ma" would technically imply
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