Paleoenvironment of the Toropí Formation (Upper Pleistocene), Corrientes province (Mesopotamian Region, Argentina): A phytolith approach

ERRA GEORGINA; OSTERRIETH MARGARITA; ZURITA ALFREDO ; FRANCIA ANALÍA ; CARLINI ALFREDO ARMANDO

QUATERNARY INTERNATIONAL

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2012

1040-6182

Two Pleistocene sedimentary units are recognized in the Corrientes province, Argentina:the Toropí and Yupoí formations. These sediments have proven productive for fossil vertebrates,but few macrofossils have been recovered. To remedy this situation, plant silica (phytoliths)were extracted from the sediments, enabling a direct comparison of paleovegetation data andinformation based on previous study of vertebrates. The studied samples (n=28) come from twoprofiles from the Toropí Stream (28°36´S; 59°02´W), near Bella Vista, Corrientes, from whichtwo Quaternary mammals, Lestodon (Xenarthra) and Hippocamelus (Artiodactyla), havepreviously been excavated. All samples were productive and contained both non-plant biogenicsilica (diatoms, sponge spicular, chrysophyte cysts) and phytoliths. Phytolith assemblages weredominated by morphotypes diagnostic of grasses, in particular C3 pooids, C4chloridoids, and C3or C4 panicoids (or related grasses in the PACMAD clade). Rare phytoliths of palms and otherwoody or herbaceous dicotyledonous angiosperms were also present. This combination of C3 andC4 grasses, and rare palms and other forest indicators, indicates grass-dominated habitats withgroves with palms and other trees/shrubs along rivers, growing under a relatively warm and dryclimate. This mixed plant community reflects shifting biogeographic affinity with the Chaco-Pampean plain and inter-tropical regions, respectively, linked to the frequent climaticenvironmentalfluctuations during the Late Pleistocene.