Molecular Fossils

There are two types of molecular fossils: those observed with a mass spectrometer and those observed with a microscope. Those observed by mass spectrometer are biomarkers, while those observed by microscope are macromolecular fossils. These molecular fossils are used to reconstruct the material cycle and paleoenvironment of the Earth.

Tree of life with biomarkers

Molecular fossils that can be analyzed by the mass spectrometer. Because of the presence of biomarkers specific to some species, paleoenvironmental reconstructions can be made by reconstructing the distribution of these species with biomarkers.

Acritarch (macromolecular fossils)

The molecular fossils include macromolecular fossils that can be observed under the microscope. Paleoenvironment is inferred from these fossils. This photo shows an ancient acritarch observed under a fluorescence microscope.

Charcoal (macromolecular fossils)

Fire conditions are inferred from the physicochemical state of soot. This photo was taken under reflectance microscope.

GC-MS chromatograms of m/z 191 showing hopanoids in geological samples

Structural isomer ratios reflect the thermal history of the sedimentary rocks. Kinetics and thermodynamics are applied to elucidate such history.

GC-MS Mass spectra of a mixture of archaea-derived biomarkers in geological sample

Mass spectra pattern reveals the presence of multiple archaea-derived tricyclic biphytanes.

Fluorescence spectra of molecular fossils

Spectra obtained by spectroscopic methods (absorbance, reflectance, fluorescence, and Raman) tell us about the physicochemical properties of molecules, such as the electronic and vibrational states of molecular fossils.

Grainstone containing inorganic macromolecular fossils

Carbonate rocks often contain a number of skeletal grains, though carbonate rocks that we handle usually are micrite due to mass extinctions and OAEs. The photo showing fossils of dasycladalean algae and tubiphytes was taken under a transmission microscope.

Related Publication: 

Saito, R., Kaiho, K., Oba, M., Tong, J., Chen, Z.-Q., Tian, L., Takahashi, S., Fujibayashi, M., 2017. Tentative identification of diagenetic products of cyclic biphytanes in sedimentary rocks from the uppermost Permian and Lower Triassic. Organic Geochemistry 111, 144-153.