GAMMA RAY ATTENUATION POROSITY EVALUATION (GRAPE) DATA

INTRODUCTION

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. During Leg 146 there was

no Boyce correction formula used for the attenuation of

hydrogen in water in high-porosity sediments.

BIBLIOGRAPHY

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.

DATA ITEM FORMATS

The GRAPE data is presented in the following format:

LEG

SITE

HOLE

CORE

CORETYPE

SECTION

TOP_INTERVAL

SUB_BOTTOM_DEPTH

BULK_DENSITY

GAMMA_COUNTS

RUN_NUMBER

EXPLANATION OF THE GRAPE PROCESSED DATA ITEMS

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 app-

roximately 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.

BULK_DENSITY - This is the calculated bulk density in g/cm3

for a specific sample interval in the core section.

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.