Million years ago , abbreviated as Mya , Myr (megayear) or Ma (megaannum), is a unit of time equal to 1,000,000 years (i.e. 1 × 10 years), or approximately 31.6 teraseconds .
5-829: The Navesink Formation is a 66 to 70 mya greensand glauconitic marl and sand geological formation in New Jersey . It is known for its Cretaceous period fossil shell beds and dinosaur bones. The Navesink Formation, named after Navesink, New Jersey , is typically found above the Mount Laurel Formation and under the Red Bank Formation . There is a 5 mya gap between the Navesink and Mount Laurel Formations. The Navesink varies in depth from 45 feet (14 m) to 65 feet (20 m) across its range from Sandy Hook to Pennsville . The Navesink has
10-521: 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 a milliyear (a thousandth of a year, or 8 hours). On this side of the debate, one avoids myr and simply adds ago explicitly (or adds BP ), as in: The Cretaceous started 145 Ma ago and ended 66 Ma ago, lasting for 79 Ma. In this case, "79 Ma" means only
15-431: 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 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
20-705: The highest radon gas potential of the New Jersey geologic formations. There are several locations where the Navesink Formation is visible including Poricy Park in Middletown, New Jersey which has several exposures along Poricy Brook. There is also exposure in Big Brook Park in Marlboro, NJ. Mya (unit) Myr is in common use in fields such as Earth science and cosmology . Myr
25-433: 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 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
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