Separation of sedimentary phytoliths from other biogenic silica particles for triple oxygen isotope analysis

Area of Science:

• Paleobotany
• Geochemistry
• Paleoclimatology

Background:

• Phytoliths, silica bodies from plants, are crucial for reconstructing past vegetation.
• Oxygen isotopes in phytoliths can reveal past atmospheric relative humidity (RH).
• Contamination from diatoms and sponge spicules in sediments biases isotopic RH reconstructions.

Purpose of the Study:

• To develop and test a filtration protocol for concentrating phytoliths.
• To assess the suitability of processed samples for triple oxygen isotope analysis.
• To improve the accuracy of paleo-RH reconstructions from African lake and peat sediments.

Main Methods:

• Developed a filtration protocol to separate phytoliths from sediment matrices.
• Applied the protocol to 31 lacustrine and peat sediment samples from West and Central Africa.
• Analyzed changes in phytolith concentration and proportion using microscopy and mass balance equations.

Main Results:

• Phytolith concentrations increased in 23 out of 31 samples after filtration.
• The protocol effectively removed contaminating diatom frustules and sponge spicules.
• Twenty-nine samples achieved phytolith proportions >40%, suitable for isotopic analysis.

Conclusions:

• The developed filtration protocol is effective for concentrating phytoliths in challenging sedimentary environments.
• This method enhances the reliability of phytolith-based paleo-RH reconstructions.
• The processed samples are suitable for ¹⁷O-excess measurements, advancing paleoclimatic studies in Africa.