Age: Miocene-Tortonian.
Location: Coiron, Ardèche, France.
Leaf measures: 6,5 cm x 2 cm
Diatomite leaf. Diatomite is a
siliceous sedimentary rock, formed by diatom microfossils, which are
unicellular aquatic algae that secrete a siliceous skeleton called a frustule.
This piece belongs to an old
collection, which, together with the rest of the specimens, represents a
complete collection of the flora of the Coiron massif.
The Coiron is an ancient basalt
plateau located in the Ardèche, where a dozen "maars" (name given to
volcanic crater lakes) were formed. Diatom deposits that have accumulated at
the bottom of lakes have solidified into a rock called diatomite.
This deposit is 8 million years
old, that is, in the Tortonian stage during the Miocene.
There are few diatom deposits in
the world. Fortunately, this deposit was saved from the glacial erosion of the
Quaternary thanks to a basalt shield formed after the volcanic eruptions and
which, by covering the layers, protected them.
