Monterey Formation : Microfossils

Large deposits of diatomite have been found in the Monterey Formation. This is a soft chalky marine deposit formed largely from the accumulation of diatom skeletons which have settled to the ocean floor.

Diatomite does not include only diatoms, however, and diatoms are not the only microorganisms known from this formation. Large numbers of foraminifera, silicoflagellates, and even radiolarians have been found and described.

The images below all come from scrapings of algal and vertebrate type fossils viewed on our Environmental SEM. Each image includes a scale bar near the bottom expressing units in micrometers.

Diatomaceous Earth

Scanning view

Although diatomaceous earth looks like a fine white powder to the naked eye, under high magnification it can be seen to consist of jumbled tiny skeletons of microorganisms.

Scanning view

At higher magnification, the delicate beauty of the microfossils becomes apparent.


Diatom cingulum

The cingulum is a broad hoop-shaped portion of a diatom's skeleton. One can be seen here connected to one end of a skeleton.

Diatom side-view

Diatom end-plate

The fine perforations of a diatom skeleton were once used to test the resolution of light microscopes. The detailing is far finer than anything that man could manufacture.


Cannopilus sphaericus

Distephanus speculum (?)

Distephanus speculum

Distephanus speculum