DIGITAL SEAFLOOR SPREADING LINEATIONS FOR THE 
WORLD'S OCEANS

Marine Geology and Geophysics Division
National Geophysical Data Center

    There two data files in this data set.  The first file, wmag.dat, 
contains the locations of sea floor spreading magnetic anomalies.  These 
lineations were digitized from the map entitled Magnetic Lineations of 
World's Ocean Basins [Cande et al., 1989] by Greg Cole of Los Alamos 
National Laboratory.  The northeast Pacific region was updated to include 
lineation data that were not available when the original map was prepared.  
The second data file, wfz.dat, contains the locations of fracture zones and 
other features.  These data are also from the Cande, et al. [1989] map and 
were likewise digitized by G. Cole.  For more information concerning the 
preparation of the map and the sources of the lineations , please consult 
the original reference:

Cande,S.C., J.L. LaBrecque, R.L. Larson, W.C. Pitman, III, X. 
   Golovchenko, and W.F. Haxby, Magnetic Lineations of World's Ocean 
   Basins (map), Amer. Ass. Petrol. Geol., Tulsa, OK, 1989.

    The format of the magnetic lineation data file is now described.  
There is a "header" line with the following FORTRAN format statement 
(I6,A20) followed by a block of longitude/latitude pairs (6F11.6) for each 
continuous lineation segment.  To denote the end of a lineation segement, 
a value of 0.0000 for both the latitude and longitude was inserted in the 
data.  There are from one to three pairs of 0.0000 at the end of a block of 
data.  The following is an example:

     91              10101
 -108.37579   23.81193 -108.44330   23.69625 -108.49670   23.60035

    The header line is composed of two variables, the number of 
longitude/latitude pairs and a label.  The label contains the following 
information:

Char 1:5    Anomaly Id (a single "?" reflects label of data source, "??" 
reflects a guess based on neighboring anomalies, by person digitizing the 
data).

Char 6:15   Alternate location Id (where anomaly crosses boundaries of 
regions) or a common name for a particular lineation, such as "J-
Anomaly".

Char 16:20  Location ID (first digit is Ocean Code, digits 2 and 3 are 
Plate Code, and digits 4 and 5 are Lineation Set Code).  

    For the example above, the lineation segment is represented by 9 
lon/lat pairs, the anomaly ID is 1, the data are in the Pacific Ocean, on the 
Pacific Plate, and are lineation set 1.

    The format of the fracture zone and other features file is  as 
follows:

  -6.000000        7814                 1
  144.75240   25.81667  144.82300   25.70847  144.89140   25.60226

    There is a header line followed by a block of longitude/latitude 
pairs (6F11.6).  The header line in this file is slightly different, it 
contains three variables and has the following FORTRAN format statement 
(G15.7,I6,A20).  The first variable is the feature-type ID, a negative 
"value" indicates that the feature-type label should precede the feature 
label on mapped output (the map labeling reference was included for use 
by the contributor of the data set, G. Cole).  The second variable is the 
number of lon/lat pairs, and the third is the label.  The end of a particular 
feature segementis also represented with one to three pairs of 0.0000 at the 
end of a block of data.  The label is 20 characters long and contains the 
following information:

Char 1:19   Label of feature

Char 20     Ocean Code

    In the example above, the feature is a fracture zone, there are 78 
lon/lat pairs, the fracture zone label is "14", and it is located in the 
Pacific Ocean.

    There are four additional files included with this data set.  They are 
"ocean.lis", a file containing the ocean ID codes, "feature.lis", a file 
of the feature-type ID codes, and "plate.lis", a list of plate names and 
abbreviations.  The fourth file is "ages.lis", this file contains the ages 
of the various lineations as well as the sources of the age information.

For further information or assistance contact:

Dr. David L. Divins
NOAA Mail Code E/GC3
325 Broadway
Boulder, CO 80303

Phone:  (303) 497-6505
Fax:    (303) 497-6513
Email:  dld@mail.ngdc.noaa.gov