Saturday, January 23, 2010

Olive green mud

A core is coming up every hour now and everyone is busy in their labs. Today we logged green mud with diatoms and gravel. Diatoms are microscopic single-celled algae and the gravel indicates the presence of ice bergs. Sedimentologists make visual observations on the cut face of the core and record these on logging sheets and in the database. We also use a microscope to examine smearslides: smears of mud on glass microscope slides. These smears provide an estimate of how much of the sediment is made up of diatoms and other fossil fragments, and how much is made up of minerals, such as quartz and feldspar (see below). The proportions of each component are changing throughout the core and are caused by changes in the paleoenvironment and paleoclimate of Antarctica. Our target at this site is to drill deep into the sea floor and recover rocks from a time when Antarctica was ice-free with forests on its coasts. So far we have seen evidence of ice rafting in the form of pebbles, so we haven't yet traveled far enough in time to reach our goal.

Photomicrograph of a smearslide with abundant diatom fragments.

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