DIGITAL ISOCHRONS OF THE WORLD'S OCEAN FLOOR

NGDC crustal age poster
     
Global 
view		 Indian Ocean 
view		 North Atlantic 
view
 
FTP Mirror site in Australia POSTERS

This page accompanies a Data and Analysis Note in the Journal of Geophysical Research (1997) entitled

Digital Isochrons of the World's Ocean Floor by

R. Dietmar MÜLLER  Dept of Geology and Geophysics, University of Sydney, Australia  dietmar@es.usyd.edu.au 
Walter R. ROEST  Geological Survey of Canada, Ottawa, Canada  roest@gsc.nrcan.gc.ca 
Jean-Yves ROYER *  Géosciences Azur, Villefranche-sur-mer, France  jyroyer@univ-brest.fr 
Lisa M. GAHAGAN  Institute for Geophysics, University of Texas, Austin, Texas  lisa@utig.ig.utexas.edu 
John G. SCLATER  Scripps Institution of Oceanography, La Jolla, California  sclater@bullard.ucsd.edu 
*Now at:  Domaines Océaniques, UBO-IUEM, Brest
 

We have created a digital age grid of the ocean floor with a grid node interval of 6 arc-minutes using a self-consistent set of global isochrons and associated plate reconstruction poles. The age at 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.

We have constructed a grid with error estimates for each grid cell as a function of (1) the error of ocean floor ages identified from magnetic anomalies along ship tracks and the age of the corresponding grid cells in our age grid, (2) the distance of a given grid cell to the nearest magnetic anomaly identification, and (3) the gradient of the age grid, i.e. larger errors are associated with high age gradients at fracture zones or other age discontinuities.

Uncertainties in the Ages of the World's Ocean Floor

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.

Selected Isochrons of the ocean floor

The finite rotation poles that the isochrons are based on and the references to the magnetic anomaly and fracture zone data are documented in :

Files available by FTP

The 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 a public ftp site in See here to obtain detailed information about the different files and how to transfer them to your computer. 

Available POSTERS

Copies of a colored, shaded relief map (~34 x 60 in. large) of the
gridded ages can be obtained for US $40 within the USA from: Outside the USA copies of the map can be obtained for CAN $50 from: Peter W. Sloss at NGDC has produced a color poster (24"x32") with 3-D perspectives (NGDC Report MGG-12). For copies and information, contact:
MAJ: 20 Sep 2002 (10:49) http://www-sdt.univ-brest.fr/~jyroyer/Agegrid