Silicophytolith Studies in South America and Argentina: 147 Scope and Limitations for Paleoenvironmental Reconstruction 1489 of the Marine Isotope Stage 3 (MIS3)

OSTERRIETH, MARGARITA; ALVAREZ, M FERNANDA; FERNÁNDEZ HONAINE, MARIANA; ERRA, GEORGINA

Marine Isotope Stage 3 in Southern South America, 60 KA B.P.-30 KA B.P.

SPRINGER

Año: 2016; p. 321 - 352

Silicophytoliths are amorphous silica biominerals deposited in intracellular or extracellular spaces of planttissues. Due to their taxonomic value and their high preservation in a variety of soils and sediments, theyare widely used as indicators of past plant communities. Numerous phytolith studies show the presence ofpast grass-dominated ecosystems in the Late Cenozoic, including changes between glacial and interglacialperiods. Studies in South America are scarce, particularly those associated to the temporal intervalcorresponding to the Marine Isotopic Stage 3 (MIS3). A synthesis of silicophytolith studies onpedosedimentary sequences of MIS3 age in South America is herein presented and, particularly, our ownwork carried out in Argentina. Integrated profiles? representatives of typical pedostratigraphic sequencesfrom two regional geomorphological units (Mesopotamia and the Pampean Plain) were analyzed. Samplesfrom pedostratigraphic sequences were subjected to routine analysis. Silicophytoliths were extracted afterthe elimination of carbonates, organic matter, and clay; and their morphologies were described underoptical and scanning electron microscopes (SEMs). Profiles from both regions show the presence ofconspicuous paleopedological levels, developed in the MIS3 interval. C3 grasses (Pooideae and/orPanicoideae subfamilies) and, in a lesser proportion, C4 grasses (Chloridoideae and/or Panicoideaesubfamilies) were present in both areas. This indicates the development of mesothermal grass-dominatedecosystems, which nowadays grow mainly in warm-temperate regions. Within the MIS3, frequent climaticenvironmental variations during the Late Pleistocene may have led to a fluctuation in biogeographicconnections between the Mesopotamian region and other parts of South America, closely linked to theChaco-Pampean plain and, at other times, to inter-tropical regions.