The Gamma Ray Attenuation Porosity Evaluation (GRAPE) data files contains information generated onboard JOIDES Resolution by the shipboard physical properties scientists and technicians. Each whole round core section is moved along a horizontal Multi-Sensor Track (MST) where successive intervals are continuously bombarded by a beam of radiation.
Gamma rays which transmit through the entire core are detected and counted. The amount of gamma radiation transmitted through the core is inversely proportional to the bulk density of the rock or sediment.
The GRAPE data files represent measurements obtained from all cores from a given hole. Each record in the data file represents a density/porosity evaluation measurement at a given point in the whole round core.
Boyce, R.E., 1976. Definitions and laboratory techniques of compressional sound velocity parameters and water-wet content, wet-bulk density, and porosity parameters by gravimetric and gamma ray attenuation techniques. In: Schlanger, S.O., et al., 1976, Initial Reports of the Deep Sea Drilling Project, vol. 33: Washington (U.S. Government Printing Office) pp. 931-958.
Explanatory Notes chapters, 1986 - present. In Proceedings of the Ocean Drilling Program, Initial Reports.
LEG - Number identifying the cruise.
SITE - Number identifying the site. A site is the position of a beacon around which holes are drilled.
HOLE - Letter identifying the hole.
CORE - Number identifying the core. Cores are numbered serially from the top of the hole downward.
CORETYPE - A letter code identifying the drill bit/coring method used to retrieve the core. The coretype codes are:
B - Drill Bit
C - Center Bit
D - Positive Displacement
H - Hydraulic Piston Core
M - Miscellaneous
N - Downhole Mud Motor (Navidrill)
P - Pressure Core Barrel
R - Rotary
S - Side Wall Core
W - Wash Core
X - Extended Core Barrel
SECTION - A core is cut into 1.5 meter long sections that are numbered serially from the top of the core. A core with full recovery will have 7 sections and a core catcher and be approximately 9.8 meters long.
TOP_INTERVAL - Distance in centimeters from the top of the section to the top of the sample interval.
SUB_BOTTOM_DEPTH - Distance in meters from the seafloor to the top of the sample interval.
DENSITY - This is the calculated bulk density in g/cm3 for a specific sample interval in the core section.
BOYCE_CORRECTED_DENSITY - This is the corrected density.
GAMMA_COUNTS - The cumulative transmitted gamma ray count detected by the GRAPE apparatus over a specific sample interval.
RUN_NUMBER - Each run of the MST is given a number which increments by one with every test.