Shipboard gamma-ray attenuation porosity evaluator (GRAPE) records from Ocean Drilling Program (ODP) Leg 150 contain inaccuracies in both depth and density caused by pervasive gas expansion voids and other coring disturbances. This paper describes the sequential procedure used to correct Leg 150 GRAPE data and presents corrected GRAPE data for Holes 902D, 903A, 904A, and 906A.
  Corrections to shipboard GRAPE depth records were made for voids and for measurements taken from beyond the end of a section. Corrections to shipboard GRAPE densities were made for (1) narrow core diameters, (2) saline pore fluids, and (3) drill slurry. Records of voids and partially filled voids are identified by implementation of a minimum wet bulk density cutoff obtained from Leg 150 gravimetric density measurements. Records failing to meet the minimum density criterion are identified, tallied, and subtracted from the shipboard GRAPE data on a core-by-core basis. Density corrections for undersized core and for the Compton mass attenuation coefficient of pore-filling fluid are taken from earlier works; a new deterministic method of correcting for drill slurry is derived. Corrected data are shown to closely match gravimetric and downhole log bulk density records and visual estimates of depth corrections.
  Results will be useful to sedimentologists, biostratigraphers, and geophysicists using Leg 150 data. Future physical properties specialists working in gassy sediments should find this work of particular interest.

Date of initial receipt: 17 February 1995
Date of acceptance: 29 August 1995

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