Seafloor Geology

Piston cores collected for geochemical evaluation can also be described to identify processes such as the age of mass movement events, and in order to provide a general overview of the sediment characteristics in a block, as well as pinpoint the nature and distribution of geologic hazards for siting of future drilling and submarine production facilities.

Descriptions include annotations of color, lithology, texture, primary and secondary structures. Because of the importance of the calcium carbonate content for deep water facies classification, calcium carbonate content was estimated by reaction with an acid solution.

Paleontological samples are taken from the cores at irregular intervals. Climatically controlled planktonic foraminifera biozones of Ericsson and Wollin (1968), calibrated to the oxygen isotope stages of Emiliani (1966) and their assigned absolute ages are used as a dating tool for the Late Pleistocene.

Calcareous nanno-fossils are used to date sediments older than Late Pleistocene. Sediment cohesion and degree of consolidation are estimated by means of a pocket penetrometer and/or pocket shear vane. Depth of burial was estimated from the shear-strength values by using strength versus depth relationships from numerous geotechnical lab and in-situ measurements.