DSDP/Agecodes 6/86


                ===============================
                =  DEEP SEA DRILLING PROJECT  =
                =           AGECODES          =
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I. INTRODUCTION


    The age codes are integer values which represent specific
    geological ages.  The construct of the code in eight digits
    allows immediate recognition of age level, i.e. era,
    period, epoch, etc.  The codes are used in several DSDP data
    bases which contain age information.  The file contains all
    of the numeric age codes, age names and age mnemonics used
    by the Deep Sea Drilling Project.


II. FORMAT AND FIELD DESCRIPTIONS


A.  DATA FORMAT:      Record length 77 chars


     COLUMN    FIELD                               FORMAT
     ======    ==============================      ======
      1-6      AGE MNEMONIC                        A6
      7-14     AGE CODE                            I8
      15       space                               X1
      16       AGE LEVEL (1-7)                     I1
      17       space                               X1
      18-37    AGE NAME (full name)                A20
      38-43   *UPPER AGE MNEMONIC                  A6
      44-50   *UPPER AGE CODE                      I7
      51       space                               X1
      52-57   *LOWER AGE MNEMONIC                  A6
      58-64   *LOWER AGE CODE                      I7
      65       space                               X1
      66-70    UPPER AGE (million years)           F5.0
      73-77    LOWER AGE (million years)           F5.0


      * NGDC NOTE:  These fields contain all blanks


B. FIELD DESCRIPTIONS


AGE CODE:

     An eight digit integer which represents a specific age.
     The hierarchical code is designed to provide age level
     information as shown below.

                   CODE DIGIT   AGE LEVEL
                   ==========   =============
                      1         (1) ERA
                      2-3       (2) PERIOD
                      4         (3) SUBPERIOD
                      5         (4) EPOCH
                      6         (5) SUBEPOCH
                      7         (6) STAGE
                      8         (7) SUBSTAGE


AGE MNEMONIC:

     An abbreviation of the age name.


AGE (million years):

     The upper and lower absolute age assigned by the DSDP to
     each geological age.  Absolute ages were assigned for
     internal DSDP use only and may be outdated.


NGDC NOTES:

Age code problems of the following types were fixed in the SCREEN,
Smearslide, and Paleontology data files:
     1. Agecodes consisting of a single zero were expanded to eight zeros
     2. Seven-digit agecodes were changed to eight by adding a zero
     3. Non-matching codes in fossil data files were hand-edited
        after checking the Initial Reports volumes (see paleontology
        documentation file).


                                                       DSDP/Agecodes 6/86