Abstract

Vesicular sand is composed of air bubbles trapped in sand. The vesicles flatten with depth due to the weight of overburden. This paper describes a method of studying the degree of compaction with depth. To quantify sphericity vesicles were compared with the Rittenhouse visual estimation chart and a division between vesicles and non-vesicles (channel-pores) made. The vesicles were divided by the chart into spherical, ellipsoidal, or flattened vesicles. Size of vesicles was taken to be a function of density--the smaller the size, the more vesicles per unit area. Degree of compaction was quantified by recording decreasing mean sphericity of the vesicles with depth, decreasing percentages of vesicles to channel pores and of spherical to flattened vesicles with depth. Flattening occurred suddenly rather than steadily with depth, due to the strength of the vesicles being overcome by the sediment load. The lower level of vesicle existence was due, however, not to destruction by weight of overburden but through poorly-aerated saturated sand inhibiting vesicle formation.

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