Sediment cores collected from the seafloor provide valuable information on the character, geochemistry and microbiology of the seabed, as well as a record of environmental processes happening over the last ca. 1.000 to 400.000 years – depending on the length of the core and the rate at which sediment is deposited on the seafloor. This year, the CGB researchers will bring equipment to collect gravity cores (operated from the ship) and push cores (operated by the ROV).
A gravity corer is operated from the ship, by dropping the core sampler into the the sediments. The steel barrel simply uses the pull of gravity to penetrate the seabed, and cores of up to 3 meters can be collected using this technique.
Dropping the gravity corer from the deck of the G.O. Sars.
The sediment core is sampled in plastic liners, so that once the core is back on deck it can be split in two – one half for geochemical and biological samples, and the other half for the archives and core scanning XRF.
CGB researchers looking at a split gravity core.
CGB professor Ingunn Thorseth sampling pore fluids from a gravity core.
Learn more about the gravity sample corer here.
Push cores are collected by the robotic arm of an ROV, that pushes the corer into the sediment. The length of the push core depends on the type of sediment (clay-rich sediments are stickier and usually easier to sample) and the arm of the ROV, but usually varies from 50 to 100 cm. It is particularly useful close to hydrothermal vent sites, where the sediment cover is often limited and precise sampling targets are required.
ROV robot arm pushing the push corers into the sediment.