The shape of a foraminifer

In the earth sciences, we often need to look at fossils in order to be able to say something about how environments and climate on earth have varied through space and time. Sometimes these fossil are very big, like the skeleton of a Tyrannosaurus rex, or very small, like the shells of planktonic organisms such as foraminifera. Don’t let size deceive you though … we can extract much more information from a tiny shell than we can from a big skeleton.

The image shown here is of a specimen of the planktonic foraminifer species Globigerinoides ruber (d’Orbigny, 1839, more info here). Mind you that this is not a photograph, but a representation of the shape and surface structure produced by a scanning electron microscope.

The shell of this foraminifera consists of calcium carbonate with the chemical formula CaCO3 (Calcium, Carbon & 3x Oxygen). It was formed by the organism itself, by extracting bicarbonate ions from the surrounding sea water.

In the next post, we’ll go over why these foraminifera are so important and look at what exactly stable isotopes are and how these are related to the ice ages.