New Mexico Geological Society Annual Spring Meeting — Abstracts

Many plants use available elements in the soil, such as silica and calcium, to make biominerals called phytoliths, which can provide structure, aid in defense against predation, and provide mechanisms to deal with environmental stressors. Some plants manufacture morphologically or chemically unique phytoliths and they can be used to identify plant families or species. Pollen, sponge spicules, diatoms, and other biogenic silicate materials have been used as paleoclimate proxies and phytoliths provide a new diagnostic tool to help reconstruct past ecological conditions. These microfossils can be recovered from modern plants, soils, sediments, lacustrine deposits, eolian deposits, archaeological sites, plant fossils, and allochthonous sediment deposits in caves. North American phytolith research is limited, especially in arid regimes. Phytoliths from arid land plants are often of calcic composition, e.g. calcium oxalates, calcite, etc., thus have significantly different properties than their silicate counterparts.

Modern plants from several ecological zones and habitat types in New Mexico and Arizona were collected and analyzed to create a phytolith reference library. Desert plants like cacti, creosote, and yucca yielded several different phytolith morphologies, with primarily calcic minerals. Riparian indicator species such as horsetail, Maximilian’s sunflower, and mulberry manufactured primarily amorphous silica phytoliths with diverse morphologies and smaller amounts of other minerals.

Phytoliths are released into the environment through vegetative decay, fire, herbivore consumption and deposition, and through human usage. They can then be buried or transported by wind, water, animals, or geological events, and usually some amount of weathering takes place along the way. We simulated mechanical weathering of the phytoliths to understand how abrasion would affect the identifiable morphological features and if chemical makeup was a factor in preservability from abrasion. Despite alterations of surface features, most phytoliths of all chemical compositions were still identifiable after the simulated weathering experiments indicating long term preservation potential.