FAQ for ISO 19115 and 19115-2
|Crustal Ages of the Ocean Floor - Poster
|The Crustal Ages of the Ocean Floor Poster was created at NGDC using the Crustal Ages
of the Ocean Floor database draped digitally over a relief of the ocean floor database.
The Crustal Ages of the Ocean Floor database was created by a consortia of marine
scientists including Dr. R. Dietmar Muller, Dept. of Geology and Geophysics, University
of Sydney, Australia, Dr. Walter R. Roest, Geological Survey of Canada, Ottawa, Canada,
Dr. Jean-Yves Royer, Lab. de Geodynamique, Villefranche Sur Mer, France, Dr. Lisa
M. Gahagan, Institute for Geophysics, University of Texas, Austin, Texas, and Dr.
John G. Sclater, Scripps Institution of Oceanography, La Jolla, California. This version
of the age grid is based on the geomagnetic time scale of Cande and Kent (1995) for
magnetic anomalies younger than chron 34 (83.5 Ma), and on the time scale from Gradstein
et al, (1994) for older times. The grid node interval is 6 arc-minutes using a self-
consistent set of global isochrons and associated plate reconstruction poles. The
age of each grid node was determined by linear interpolation between adjacent isochrons
in the direction of spreading. Ages for ocean floor between the oldest identified
magnetic anomalies and continental crust were interpolated by estimating the ages
of passive continental margin segments from geological data and published plate models.
The gridded ages of the ocean floor are based on a digital set of isochrons. The isochrons
are based on a large number of marine magnetic anomaly data, satellite altimetry data,
and a self- consistent plate model. The finite rotation poles that the isochrons are
based on and the references to the magnetic anomaly and fracture zone data are documented
in the: University of Texas Institute for Geophysics Technical Report No. 117, 1992,
"A global isochron chart" by J.-Y. Royer, R.D. Muller, L.M. Gahagan, L.A. Lawver,
C.L. Mayes, D. Nurnberg, and J.G. Sclater. Digital age and error grids, files of continent-ocean
boundaries and present day plate boundaries, a C-program to adapt the grid to new
timescales, can be obtained from public ftp sites in North America and Australia.