Hsü, Kenneth J; Percival, Stephen F Jr; Wright, Ramil; Petersen, Nikolai P (1984): Numerical ages of magnetostratigraphically calibrated biostratigraphic zones at DSDP Leg 73 Holes. PANGAEA, https://doi.org/10.1594/PANGAEA.811128, Supplement to: Hsü, KJ et al. (1984): Numerical ages of magnetostratigraphically calibrated biostratigraphic zones. In: Hsü, KJ; LaBrecque, JL; et al. (eds.), Initial Reports of the Deep Sea Drilling Project (U.S. Govt. Printing Office), 73, 623-635, https://doi.org/10.2973/dsdp.proc.73.124.1984
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Most Cenozoic nannofossil and many foraminiferal zonal boundaries have been accurately determined and magnetostratigraphically calibrated at five Leg 73 boreholes. The numerical ages of the boundaries were computed by assuming a linear seafloor spreading rate and a radiometric age of 66.5 m.y. for the Cretaceous/Tertiary boundary. Alternative magnetostratigraphic ages (given below in parentheses) were obtained by adopting a 63.5 m.y. age for the Cenozoic. Our data confirm previous determinations of the Pleistocene/Pliocene boundary at 1.8 (1.7) m.y. and of the Pliocene/ Miocene boundary at 5.1 (5.0) m.y. The Miocene/Oligocene boundary is placed within Chron C-6C and has a magnetostratigraphic age of 23.8 to 24.0 (22.7 to 22.9) m.y. The Oligocene/Eocene boundary is also very precisely located within Chron C-13-R, with a magnetostratigraphic age of 37.1 to 37.2 (35.5 to 35.6) m.y. The Eocene/Paleocene boundary should be located within an uncored interval of Chron C-24 and have a magnetostratigraphic age of 59.0 (55.4) +/- 0.2 m.y.
The general accord of the magnetostratigraphic and radiometric ages supports the hypothesis that the seafloor spreading rate was linear during the Cenozoic. Two possible exceptions are noted: the middle Miocene radiometric ages are a few million years older, and the early Eocene radiometric ages are several million years younger, than the corresponding magnetostratigraphic ages.
Median Latitude: -27.184989 * Median Longitude: -4.907135 * South-bound Latitude: -29.484200 * West-bound Longitude: -11.666200 * North-bound Latitude: -26.073800 * East-bound Longitude: 3.512300
Date/Time Start: 1980-04-22T00:00:00 * Date/Time End: 1980-05-21T00:00:00
73-519 * Latitude: -26.136700 * Longitude: -11.666200 * Date/Time: 1980-04-22T00:00:00 * Elevation: -3769.0 m * Penetration: 151.6 m * Recovery: 138.1 m * Location: South Atlantic/RIDGE * Campaign: Leg73 * Basis: Glomar Challenger * Device: Drilling/drill rig (DRILL) * Comment: 37 cores; 151.6 m cored; 0 m drilled; 91.1 % recovery
73-521 * Latitude: -26.073800 * Longitude: -10.264500 * Date/Time: 1980-05-02T00:00:00 * Elevation: -4125.0 m * Penetration: 84 m * Recovery: 75.2 m * Location: South Atlantic/HILL * Campaign: Leg73 * Basis: Glomar Challenger * Device: Drilling/drill rig (DRILL) * Comment: 21 cores; 84 m cored; 0 m drilled; 89.5 % recovery
73-521A * Latitude: -26.075700 * Longitude: -10.259800 * Date/Time: 1980-05-02T00:00:00 * Elevation: -4130.0 m * Penetration: 71.1 m * Recovery: 64 m * Location: South Atlantic/HILL * Campaign: Leg73 * Basis: Glomar Challenger * Device: Drilling/drill rig (DRILL) * Comment: 17 cores; 71.1 m cored; 0 m drilled; 90.1 % recovery