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
• 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
Bottom trawl net used on the Challenger
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
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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
– Stored 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
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(=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
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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
On Scotian Shelf
(floating)
• Production
– Non-floating
– Floating
OFFSHORE OIL & GAS PLATFORMS
• Oil production platform in the North Sea
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