DSDP/Density-Porosity 5/86

                ===============================
                =  DEEP SEA DRILLING PROJECT  =
                =    DENSITY-POROSITY DATA    =
                ===============================


I.  INTRODUCTION
                                                                 

A.  BACKGROUND AND METHODS
     Water content and density measurements were regularly made
     aboard the Glomar Challenger on core samples selected by the
     shipboard party.  These samples were completed at sea,
     nearly always by the chemistry technician.  One of three
     different techniques was normally used but the specific
     method was not stored in the data record.  The technique may
     be determined, if necessary, by examination of the prime
     data sheets or the appropriate chemistry laboratory
     notebook.  These data are available on microfilm from
     the National Geophysical Data Center.

     Typical records in this data set contain either a complete
     suite of values (Water Content, Porosity, Density, Grain
     Density) or Water Content only, dependent upon the existence
     of a volume measurement.  All calculations were duplicated
     post-cruise by computer and discrepancies with shipboard
     values were rectified.  Except for 5 sites from Leg 96
     (see SALT CORRECTION LEG 96) all data were encoded directly
     from the worksheets used aboard the ship and calculations
     done without a salt correction.


     Syringe Technique (Boyce, 1976)

        Beginning with leg 1 the syringe technique was used for
        soft sediments until it was gradually supplanted by other
        techniques beginning at about Leg 30.  The accuracy of
        the syringe technique was limited because the weight of
        the wet sediment plus its weighing container could not
        exceed one gram.  It continued to be occasionally
        utilised for extremely unconsolidated sediments.


     Chunk Technique (Boyce, 1976; Boyce, 1984)

        The 'chunk' technique (Boyce,1976) was used initially for
        sediments that were too hard for the syringe technique;
        since volume was not measured it yielded only water
        content values.  Sometime just prior to Leg 30 the
        introduction of a triple beam balance, modified for
        making direct weighings of irregularly-shaped samples in
        air and in water, permitted the determination of volume,
        and therefore density and porosity, of any sediment
        sample that would not rapidly disaggregate in water
        (Boyce, 1984.).  Subsequently, appropriate sample size
        was limited only by the capacity of the balance used:
        approximately 300 grams.


     Cylinder Technique (Boyce, 1984)

        The cylinder technique involved sampling the sediments
        with sharpened stainless steel rings of known weight and
        volume and then proceeding as with the syringe technique.
        Until Leg 79 these samples were sent to the sediment
        laboratory at DSDP for processing.  Subsequent to the
        closing of that facility they were processed aboard the
        vessel.


B.  LEGS IN THE DATA SET


     Data type                  Legs
     =======================    =========================
     No Data                    41
     Water content              1-40, 42-96
     Porosity and/or density    2-40, 42-49, 51-86, 88-96


C.  REFERENCES


     Boyce, R. E., 1976.  Definitions and laboratory techniques
     of compressional sound velocity parameters and wet-water
     content, wet-bulk density, and porosity parameters by
     gravimetric and gamma ray attenuation techniques.  In
     Schlanger, S. O., Jackson, E. D., et al., Initial Reports of
     the Deep Sea Drilling Project, Vol. 33:  Washington
     (U.S. Govt. Printing Office), 931-958.

     Boyce, R. E., 1984.  Methods for laboratory-measured
     physical properties.  In Hay, W. W., Sibuet, J. C., et al.,
     Initial Reports of the Deep Sea Drilling Project, Vol. 75
     Part 2:  Washington (U.S. Govt. Printing Office), 1179-1187.

II.  FORMAT AND FIELD DESCRIPTIONS


 A.  DATA FORMAT

     Record length is 68 characters.(26268 records)
     (Originally 80, blank fields removed by NGDC)

     COLUMN    FIELD                                  FORMAT
     ======    ===================================    ======
      1-2      LEG                                    A2
      3-5      SITE                                   A3
      6-6      HOLE                                   A1
      7-9      CORE                                   A3
     10-11     SECTION                                A2
     12-15     TOP INTERVAL DEPTH (centimeters)       F4.1
     16-19     BOTTOM INTERVAL DEPTH (centimeters)    F4.1
     20-27     TOP OF CORE DEPTH (meters)             F8.2
     28-35     SAMPLE DEPTH (meters)                  F8.2
     36-43     WET WATER CONTENT (no units)           F8.2
     44-51     POROSITY (no units)                    F8.2
     52-59     WET BULK DENSITY (g/cc)                F8.2*
     60-67     GRAIN DENSITY (g/cc)                   F8.2*
     68        SALT CORRECTION LEG 96 (* or blank)    A1

     * NGDC note: F8.3 in original documentation, but all data
       follow format F8.2

B. FIELD DESCRIPTIONS

     The definition of leg, site, hole, core and section may be
     found in the explanatory notes.  In addition, the special
     core designations, as well as the methods of sample labeling
     and calculating absolute sample depths are discussed.



INTERVAL DEPTH:

     The depth, in centimeters, within a section at which the top
     or bottom of a measurement was taken.  Values are encoded
     with an implicit decimal point an encoded value of 805
     represents 80.5 centimeters.


CORE DEPTH:

     The subbottom depth in meters to the top of the core.


SAMPLE DEPTH:

     The subbottom depth in meters to the point of measurement.


WET WATER CONTENT:

     Wet water content is the ratio of the mass of water in a
     sediment sample to the mass of that wet sample, multiplied
     by 100.


POROSITY:

     Porosity is the ratio of the volume of the porespace in a
     sediment sample to the volume of that wet sample.  The
     volume of the porespace is directly proportional to the mass
     of water in the sediment sample.


WET BULK DENSITY:

     Wet bulk density is the ratio of the mass of a wet sediment
     sample to the volume of that wet sample, expressed in grams
     per cubic centimeter.


GRAIN DENSITY:

     Grain density is the ratio of the bulk density minus the
     porosity to the complement of the porosity as shown in the
     following equation.

     (Bulk Density - Porosity)/(1 - Porosity)

     The grain density value is inherently inaccurate because of
     its sensitivity to errors in the porosity and density values
     from which it is calculated.


SALT CORRECTION LEG 96:

     There was NO SALT CORRECTION used in calculating the data in
     this database, with one exception:  for five sites drilled
     on Leg 96 the original work sheets were never returned to
     the Data Group.  Therefore it was impossible to check or
     recalculate the data which was reported.  It was labelled
     "SALT CORRECTED".  The salt correction factor used in these
     calculations is unknown.  This applies only to sites:  615,
     617, 621, 623, and 624.  The rest of the values in this
     database, including the remainder of Leg 96, were calculated
     using a pore fluid density of 1.0 grams/cc.


                                       DSDP/Density-Porosity 5/86