Micro Fossils

MicropaleontologyEarth History 1131

MicrofossilsNot necessarily microscopic, but details of a microfossil typically cannot be seen with the naked eyeMany make good index fossils

Common microfossilsForamsRadiolariansDiatoms Conodonts

Common microfossilsProtists

Eukaryotic, single-celled organismsContain forams, radiolarians (pictured below) and diatoms

Common microfossilsForaminifera:

Single-celled, small organisms that either secrete a shell or construct an agglutinated shell.Can be planktonic or benthicFusulinids (pictured below) are common in the fossil record, and very useful for biostratigraphy

Common microfossilsRadiolarians: marine zooplankton

Silica-based testFeed through trapping of food particles

Common microfossilsDiatoms: photosynthetic algae

Silica test

Common microfossilsConodonts: less understood than other microfossils, but very useful for biostratigraphy

Jaw portions (hard parts) are preserved in the fossil recordThermal Alteration Index

Viewing microfossilsThe “big” picture

What can the fossils within a rock specimen tell us about the depositional environment?

Factors include:Rock compositionBathymetryOther influences (biological, chemical, etc.)

Viewing microfossils“Loose specimens”

Can be observed with a hand lens or basic microscope

“Specimens in matrix (rock)”Often viewed in a thin section of a rock (pictured below)