POC: Kevin Briggs, NRL-SSC


There are 27 Excel files describing geoacoustic core measurements at the SAX99 experiment site. Explanation of the header data and column headings are given here, as well as simplified location information for each core are described below.

The top row of each Excel file gives the Cruise Designation (SJ or PE, depending on the vessel—Seward Johnson or Pelican—from which it was collected), the Station-Subcore Number, and the Date the sample was collected. The designation 20-1 indicates dive number 20, subcore number 1 (in this case, 2 subcores were collected during dive 20).

The second row gives the latitude, longitude, and water depth of the dive site/experiment site.

The next row, row 4, indicates the conditions for which the sediment sound speed is calculated: the temperature, salinity, and water depth on the sea floor at the beginning of the experiment (26 deg, 35 ppt, 19 m) and the acoustic frequency at which the sound speed was measured (400 kHz). The temperature changed during the experiment, but the sound speed has been normalized for comparison purposes (Note: Vp Ratio is independent of temperature, salinity and depth).

Row 5 indicates the diver subcore sample salinity and core inside diameter, which figure in the calculations of the sediment sound velocity.

Row 7 consists of the 13 possible parameters measured on the diver cores and the sediment depth heading. Key to the parameters:

Vp = sediment sound speed in m/s

Vp Ratio = sediment sound speed divided by the overlying water sound speed

alpha = attenuation in dB/m

k = attenuation scaled to frequency in dB/m/kHz (alpha divided by 400)

Porosity = sediment porosity determined by gravimetric methodology, in percent

Density = sediment bulk density calculated from porosity, grain density, and seawater density, in g/cm³.

e = void ratio, determined from the ratio of porosity volume to solid volume

% Gravel = percent gravel by weight (> 2 mm dia.)

% Sand = percent sand by weight (2 mm > wt > .062 mm dia.)

% Silt = percent silt by weight (62 µm > wt > 4 µm dia.)

% Clay = percent clay by weight (< 4 µm dia.)

MGS = mean grain size in phi units calculated by the graphic method of Folk (R.L. Folk, Petrology of Sedimentary Rocks, 1965). Phi = -log2[dia. in mm]

Sorting = inclusive graphic standard deviation in phi units from Folk (R.L. Folk, Petrology of Sedimentary Rocks, 1965)

The locations from which the diver cores were collected:

Low Frequency: PE27-1, PE27-2, SJ42
Lopes (CSS): PE52-2, SJ41
BAMS tower: SJ20-1, 20-2
Seward Johnson: SJ29-4, 29-5, 37-1, 37-2, 65B, 101, 129, 141, 153, 163
APL Penetration: SJ36-1, 36-2, 62-1, 62-2, 100-1, 100-2, 175
Schmidt: 176

The diver core permeability data is contained in SAXperm.xls

1st column = diver core identification
2nd column = mean depth of sample, in cm
3rd column = k, coefficient of permeability, in cm/s
4th column = Kp, intrinsic permeability, in cm²
5th column = Kp, intrinsic permeability, in darcys
6th column = standard deviation in cm/s
7th column = standard deviation in cm²
8th column = standard deviation in darcys

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