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In the core lab, the Geotek core splitter cuts sediment cores in half lengthwise using oscillating saws and a wire cutter.

For some projects, scientists want to calculate sediment settling velocity and need to measure particle size using gravity. We use custom-built settling tubes filled with water – three at 2 meters tall (like the one shown here) and one 3 meters tall.

In the carbon analysis laboratory, these three instruments (the UIC CM250) automatically analyze the total carbon, total organic carbon, and total inorganic carbon content of multiple dried sediment samples. 

This Dionex ASE 350 accelerated solvent extractor automatically extracts hydrocarbons for further analysis. We also have a Zymark TurboVap II for sample preparation (not shown).

We add about 20 grams of sediment from a sample to distilled water for particle size analysis. Then we add strong hydrogen peroxide to break down organic matter that makes clay particles stick together. Digestion takes place overnight.

At the USGS Pacific Coastal and Marine Science Center, we have 3 WS Tyler RX-29 Ro-Taps that can dry-sieve coarser samples. This machine automatically rotates and taps the stack of sieves, so that smaller sediment falls through to the next sieve. Weighing the sediment trapped in each sieve gives us sediment size fractions.

The UIC CM5230/CM5015 analyzes total inorganic carbon content. It's less automated than other analyzers, but often easier to use.

Washing a sediment sample through two sieves with distilled water lets us measure the fractions of gravel (bigger than 2 millimeters or -1 phi) and sand (2 millimeters to 63 microns, -1 phi to 4 phi). Smaller sediment passes through the sieves into a standard 1-liter graduated cylinder.

Lab technician Angela Tan takes a sample of the sediment suspended in liquid, for analysis in one of several ways.

The Beckman Coulter LS 13 320 uses laser diffraction to automatically analyze sediment size fractions between 2 millimeters and 0.35 micron (-1 phi to 11.5 phi).

The settling tube is filled with water and a pre-weighed sediment sample of mixed particle sizes is poured onto this brass "gate" at the top of the tube. When the operator flips the switch, the gate opens quickly like a venetian blind, releasing the whole sediment sample into the water column at the same time.

We take most cores and samples straight from the loading dock into a large walk-in refrigerator (about 780 square feet), kept at the international core curation standard of 4° C plus or minus 2° C. Each core and sample must be labeled with an identifier and metadata, which follows the material through processing and analysis.

We slip split cores into a labeled D-tube, and both are stored on specialized core racks in a walk-in sample refrigerator. USGS and non-USGS scientists often use our core and sample archives for new research. Contact the lab manager for access policies and other details.

In the cold storage room at the USGS Pacific Coastal and Marine Science Center, we store cores on large racks that can hold about 4,500 full sized cores or D-tubes with split cores, up to 1.5 meters long.

These track-mounted racks pack together to save space. Cranking a handle moves the aisle between racks for core access.

The back door of the refrigerator connects to our core and sample processing labs.

Each half of a split sediment core is wrapped in plastic to prevent drying and contamination. For long-term storage, we can shrink-wrap one half with a thick film that prevents moisture loss.

Lab technicians create written descriptions of sediment cores, referencing Munsell chart colors and standard phrases.

Sediment cores may be subsampled for further processing and analysis in other labs, like the Sediment Lab which is across the hall from the Core Lab.

The first stop for many sediment cores is the Geotek MSCL or multi-sensor core logger. The logger automatically measures P-wave velocity, magnetic susceptibility, electrical resistivity, and gamma density at intervals from 1 millimeter to 1 centimeter along cores up to 1.5 meters long.

This is the Pacific Coastal and Marine Science Center's Sediment Prep Lab, where sediment samples and core subsamples are prepared for analyses.