SAMPLING: NETS, GRAB SAMPLES, & CORES GEOL 3213 Micropaleontology

Marine Sampling Devices Nets Grab samplers Corers –Gravity corer –Piston corer Cores –Split lengthwise (working and archival halves) –Photographed –Sampled –Stored in “core libraries”

NETS Bottom trawl net used on the Challenger Plankton nets –Microscopic organisms –Floating (planktic or planktonic) pelagic forms –Base of the marine food web –Major groups Phytoplankton Zooplankton Nets for larger organisms –Different for various depths and organisms –Coarser nets for fish –Dredges for the seafloor

SAMPLING MARINE SURFACE SEDIMENTS “Grab sampler” (="clamshell sampler") –Lowered until it strikes bottom –A release mechanism then closes "cups" –Heavy enough to stay closed when raised –Covers prevent sediment from washing out as raised to surface

SAMPLING MARINE SURFACE SEDIMENTS How a Van Veen-type grab sampler works DOWN TOUCH & RELEASE CLOSE & UP

GRAVITY CORER Main components –1. Nose cone –2. Core catcher –3. Inner plastic liner –4. Steel core barrel –5. Weights (up to a ton or more) –6. Flap (on gravity corer) or piston –7. Tripping arm (on piston corer) –8. Cable to ship

PISTON CORER

DEPLOYING & RETRIEVING PISTON CORERS

CUTTING CORE LINER 40-foot long core liner with core is being cut –Transversely –1.5 m lengths –Before splitting

SPLIT CORE for Study Core is cut in half –Lengthwise –Before study & sampling Turbidites deposited by turbidity currents

CORE LIBRARIES Cores are –Sectioned longitudinally –Placed in trays & photographed –S tored in hermetically sealed cold rooms. Gulf Coast Repository (pictured here) of the Ocean Drilling Program, located at Texas A & M University, stores about 75,000 sections taken from more than 80 kilometers (50 miles) of cores recovered from the Pacific and Indian oceans. Smaller core libraries are maintained at –Scripps –Lamont-Doherty Earth Observatory.

JOIDES Resolution (=SEDCO/BP 471) 470 ft-long and 70 ft-wide drilling ship used for the Ocean Drilling Project (ODP). Derrick towers 202' above the waterline. Computer-controlled dynamic positioning system, supported by 12 powerful thrusters and two main shafts, that maintains its position over a specific location while drilling in water depths up to 27,000'. A 12,000 sq ft, 7-story stack of laboratories and other scientific facilities occupies the areas fore and aft of the derrick. Deploys up to 30,000'of drill string.

JOIDES Resolution": the ship can deploy up to 30,000' of drill string. This view shows pipe being lowered by roughnecks.

JOIDES Resolution": roughnecks handling drill pipe with rotary drill bit.

Rentry Cone JOIDES Resolution": reentry cones are used to reenter an existing hole End of drill string is positioned using either sonar or an underwater television system.

RE-ENTRY TECHNIQUE Computer coordinated Multiple thrusters Sonar TV cameras Funnel

Cores Leave Rig Floor to the “Catwalk” The "JOIDES Resolution": the 30-ft (9.5-m) cores are brought from the rig floor to the “catwalk,” a platform outside the laboratories where core is prepared for analysis.

Sampling Working Half of Cores JOIDES Resolution: scientists take samples from the working half of cores for both shipboard and shore-based analysis. The shipboard curatorial representative inventories all samples and enters the information into a computer. No samples are taken from the archive half.

OFFSHORE OIL & GAS PLATFORMS Drilling –Jackup –Semisubmersible (floating) Production –Non-floating –Floating On Scotian Shelf

OFFSHORE OIL & GAS PLATFORMS Oil production platform in the North Sea

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