(Table 1) Textural characteristics of sediments at DSDP Leg 71 Holes

In conjunction with a study of ice-rafted detritus (IRD), textural analyses were carried out on Miocene to Quaternary sediments at Sites 511, 512, 513, and 514. Grain-size statistics were computed for the <62.5 µm fraction in order to identify changes in current velocity; the sand fraction was omitted from these determinations because it consists primarily of ice-raft and biogenic components. The contributions by terrigenous sediment in the 62.5-250 µm and the >250 µm fractions were determined.

(Table 1) Geochemistry at DSDP Hole 71-511

Transformation of aragonite to calcite and of high-magnesian to low-magnesian calcite is accompanied by a substantial increase in volume which produces cone-in-cone texture by tangential compression. Internal stresses stored within in the sediment could not be released until the core was extracted; then material and mounting medium expanded spontaneously.