Amorphous silica biomineralizations in soils, paleosoils and sediments in pedesedimentary sequences of the pampean plain, argentina.

OSTERRIETH L. MARGARITA; DONNA, ROBERTO; PAOLICCHI, MICAELA; BENVENUTO, LAURA; FRAYSSINET, CELIA; ALTAMIRANO, STELLA; BORRELLI, L. NATALIA; ALVAREZ, FERNANDA; FERNANDEZ HONAINE, MARIANA

Simposio; The 14th International Symposium on Biomineralization (BIOMIN XIV) From Molecular and Nano-structural Analyses to Environmental Science; 2017

Silicophytoliths are amorphous silica biomineralizations deposited in plant tissues followingdegradation of the tissue, the silicophytoliths are incorporated into the soil, where they can bepreserved and constitute the skeletal fraction of sediments and soils; but a high percentageof them are altered and disappear from the soil system. The grasslands developed from theTertiary in the Pampas, have produced high amounts of silicophytolith. The aim of this studywas to evaluate the quantitative and qualitative of the silicophytolith content in the soil andsediments. Pampean plain region, covers an area of 1,200,000 km2; it is one of the mostfertile regions of the world. Depending on the environmental and pedological conditions,silicophytoliths are affected by diverse taphonomical processes, both in natural and anthropicenvironments. They can be preserved, dissolved or fragmented, and also be transportedby different agents (wind, water, animals and people). Integrated profiles representativeof typical pedoestratigraphic sequences were analyzed. Silicophytoliths were analyzed aspart of the whole mineralogy of the samples, under optical and SEM. The results showedhigh amounts of silicophytoliths which have been affected by several kinds of both physicaland chemical alteration and/or by taphonomic processes of different types and degreesof intensity. All the quantifications measured showed that the content of silicophytolithsdecreased between 50 and 95% from superficial to subsuperficial soil horizons, due topedological processes. The comprehension of the physico-chemical degradation andtransference processes within silicophytolith-plant-soil-environment system is essential inorder 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-physicochemically balanced by the introduction of crops, in relation to the silicon cycle, since theyare also important silicophytolith producers in the SE Pampean agroecosystems