Abstract: Mass Physical and Engineering Properties of "Glacial" Sediments of Voring Plateau, Norwegian Sea

Richard W. Faas

During Leg 38 of the Deep Sea Drilling Project in the Norwegian-Greenland Sea, six holes were drilled into the Voring Plateau, a relatively flat feature, 1,200 m deep, lying west of the Norwegian continent. The inner part of the plateau contains a thick sedimentary sequence, perhaps as much as 4 km of predominantly terrigenous sediment, and hole 341 encountered methane, ethane, and soluble hydrocarbons in middle Miocene sediments.

Three holes drilled through "glacial" sediments (339, 340, 341) provided nearly continuous sections which made it possible to determine unit-weight, water-content, porosity, and shear-strength changes with depth. A shear-strength profile through predominantly terrigenous sediments in the upper 25 m of hole 341 shows a rapid increase (from 29.8 g/sq cm to 65.0 g/sq cm) within the first 8 m. Shear strength increases regularly to 137.9 g/sq cm at 30-m depth.

Anomalously high values of sonic velocity, unit weight, and low water contents in the "glacial" sediments of hole 339, located over an Oligocene-cored clay diapir, are believed to have resulted from compaction and dewatering of the sediments by vertical stresses from below, generated by the rising diapir. Similar sediments adjacent to the diapir show normally expectable sonic velocities and mass physical properties. Abnormally high values of mass physical properties and sonic velocities in the uppermost deposits of hole 339 may indicate that vertical diapiric movement is presently occurring. Alternatively, the sediments may be overconsolidated older material exposed through erosion and/or nondeposition of younger "glacial" sediments over the diapir.

AAPG Search and Discovery Article #90961©1978 AAPG Annual Convention and Exhibition, Oklahoma City, Oklahoma