A MESOZOIC TIME-SCALE

We present an integrated geomagnetic polarity and stratigraphic time s cale for the Triassic, Jurassic, and Cretaceous periods of the Mesozoi c Era, with age estimates and uncertainty limits for stage boundaries. The time scale uses a suite of 324 radiometric dates, including high- resolution Ar-40/Ar-39 age estimates. This framework involves the obse rved ties between (1) radiometric dates, biozones, and stage boundarie s, and (2) between biozones and magnetic reversals on the seafloor and in sediments. Interpolation techniques include maximum likelihood est imation, smoothing cubic spline fitting, and magnetochronology. The ag e estimates for the 31 stage boundaries (in mega-annum) with uncertain ty (millions of years) to 2 standard deviations, and the duration of t he preceding stages (in parentheses) are Maastrichtian/Danian (Cretace ous/Cenozoic) is 65.0 +/- 0.1 Ma (6.3 m.y.), Campanian/Maastrichtian i s 71.3 +/- 0.5 Ma (12.2 m.y.), Santonian/Campanian is 83.5 +/- 0.5 Ma (2.3 m.y.), Coniacian/Santonian is 85.8 +/- 0.5 Ma (3.2 m.y.), Turonia n/Coniacian is 89.0 +/- 0.5 Ma (4.5 m.y.), Cenomanian/Turonian is 93.5 +/- 0.2 Ma (5.4 m.y.), Albian/Cenomanian is 98.9 +/- 0.6 Ma (13.3 m.y .), Aptian/Albian is 112.2 +/- 1.1 Ma (8.8 m.y.), Barremian/Aptian is 121.0 +/- 1.4 Ma (6.0 m.y.), Hauterivian/Barremian is 127.0 +/- 1.6 Ma (5.0 m.y.), Valanginian/Hauterivian is 132.0 +/- 1.9 Ma (5.0 m.y., Be rriasian/Valanginian is 137.0 +/- 2.2 Ma (7.2 m.y.), Tithonian/Berrias ian (Jurassic/Cretaceous) is 144.2 +/- 2.6 Ma (6.5 m.y.), Kimmeridgian /Tithonian is 150.7 +/- 3.0 Ma (3.4 m.y.), Oxfordian/Kimmeridgian is 1 54.1 +/- 3.2 Ma (5.3 m.y.), Callovian/Oxfordian is 159.4 +/- 3.6 Ma (5 .0 m.y.), Bathonian/Callovian is 164.4 +/- 3.8 Ma (4.8 m.y.), Bajocian /Bathonian is 169.2 +/- 4.0 Ma (7.3 m.y.), Aalenian/Bajocian is 176.5 +/- 4.0 Ma (3.6 m.y.), Toarcian/Aalenian is 180.1 +/- 4.0 Ma (9.5 m.y. ), Sinemurian/Pliensbachian is 195.3 +/- 3.9 Ma (6.6 m.y.), Hettangian /Sinemutian is 201.9 +/- 3.9 Ma (3.8 m.y.), Rhaetian/Hettangian (Trias sic/Jurassic) is 205.7 +/- 4.0 Ma (3.9 m.y.), Norian/Rhaetian is 209.6 +/- 4.1 Ma(11.1 m.y.), Camian/Norian is 220.7 +/- 4.4 Ma (6.7 m.y.), Ladinian/Carnian is 227.4 +/- 4.5 Ma (6.9 m.y.), Anisian/Ladinian is 2 34.3 +/- 4.6 Ma (7.4 m.y.), Olenekian/Anisian is 241.7 +/- 4.7 Ma (3.1 m.y.), Induan/Olenekian is 244.8 +/- 4.8 Ma (3.4 m.y.), Tatarian/Indu an (Permian/Triassic) is 248.2 +/- 4.8 Ma. The uncertainty in the rela tive duration of each individual stage is much less than the uncertain ties on the ages of the stage boundaries.