Amorphous silica biomineralizations in soils, paleosoils and sediments in pedosedimentary sequences of the pampean plain, Argentina.

OSTERRIETH, MARGARITA; DONNA, ROBERTO; PAOLICCHI, MICAELA; BENVENUTO, MARIA LAURA; ALTAMIRANO, STELLA MARIS; FRAYSSINET CELIA; BORRELLI, NATALIA; ALVAREZ, M FERNANDA; FERNÁNDEZ HONAINE, MARIANA

Tsukuba

Simposio; 14th International Symposium of Biomineralization; 2017

Silicophytoliths are amorphous silica biomineralizations deposited in plant tissues. Following degradation of the tissue, the silicophytoliths are incorporated into the soil, where they can be preserved and constitute the skeletal fraction of sediments and soils; but a high percentage of them are altered and disappear from the soil system. The grasslands developed from the Tertiary in the Pampas, have produced high amounts of silicophytoliths. The aim of this study was to evaluate the quantitative and qualitative of the silicophytolith content in the soil and sediments. Pampean plain region, covers an area of 1,200,000 km2; it is one of the most fertile regions of the world. Depending on the environmental and pedological conditions, silicophytoliths are affected by diverse taphonomical processes, both in natural and anthropic environments. They can be preserved, dissolved or fragmented, and also be transported by different agents (wind, water, animals and people). Integrated profiles representative of typical pedoestratigraphic sequences were analyzed. Silicophytoliths were analyzed as part of the whole mineralogy of the samples, under optical and SEM. The results showed high amounts of silicophytoliths which have been affected by several kinds of both physical and chemical alteration and/or by taphonomic processes of different types and degrees of intensity. All the quantifications measured showed that the content of silicophytoliths decreased between 50 and 95% from superficial to subsuperficial soil horizons, due to pedological processes. The comprehension of the physico-chemical degradation and transference processes within silicophytolith-plant-soil-environment system is essential in order to evaluate the role of taphonomical processes in the biogeochemical cycle of silicon. Finally, it is proposed that the displacement of native grasslands may be bio-physico-chemically balanced by the introduction of crops, in relation to the silicon cycle, since they are also important silicophytolith producers in the SE Pampean agroecosystems.