Abstract

Distortion of ocean-bottom cores, as evidenced by thin smear zones along the sides or by the disturbed regions often disclosed by X-radiography, are well known. Evidence was obtained on one mode of core disturbance that cast further doubt upon the utility of the customary surface-operated piston corers for acquiring accurate data on sea-bottom sediment mass physical properties. Inadvertent rupture of a plastic bag of 3 mm diameter lead pellets, part of the equipment used to photograph a piston corer in action, resulted in pellet drag to nearly one meter along the side of one core without significant lithologic drag effects showing up on the X-radiograph of the whole core. This discovery suggests a mode of surficial coarse particle distortion which may be more common than heretofore realized. Consequently, care should be exercised when these types of cores are used for studying the mass physical properties of sea-floor sediments especially when textural and mineralogical parameters are correlated with acoustic properties, and for sound velocity measured normal to the core.

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