Dating rocks on Valentine’s Day!

Valentines Foraminifera with scale bar

DGER geologists Trevor Contreras, Michael Polenz, Annette Patton and Harley Gordon are collaborating with the University of Washington’s Burke Museum to better date Tertiary rock formations along Hood Canal. Just as with macrofossil assemblages, microscopic fossils can be used to correlate an unidentified rock with known units. These tiny fossils pack quite a punch, despite their small size. The species of fossils in a given sample can indicate the specific age of the rock and allow researchers to deduce key information about environmental conditions at the time the microfossils and their accompanying sediments were deposited. Such knowledge provides valuable insight into our understanding of the age and stratigraphy of Tertiary sandstones and mudstones exposed in the current mapping area between Discovery Bay and Quilcene.


Foraminifera, like those pictured here, are members of a group of single-celled protozoans that primarily live in marine environments. The living organisms construct chambered shells in a variety of shapes and sizes, either by secreting a solid calcite shell or by cementing together grains that they pick up from the ocean floor. These organisms are particularly valuable microfossils because they are abundant, diverse, and morphologically distinct. Foraminifera also make useful biostratigraphic markers because most species are benthic (they live on the ocean floor). Unlike many planktonic organisms that float along ocean currents, such species remain geographically confined and form unique and local assemblages of fossils.