First results of the phytolith analysis from the last glacial maximum in the Laguna Potrok Aike core, Santa Cruz province, Argentina

ZUCOL, A. F; PASSEGGI, E., FERNÁNDEZ PEPI M.G., PATTERER, N. I

La Plata, Buenos Aires

Simposio; XVI Simposio Argentino de Paleobotánica y Palinología; 2015

The Potrok Aike Lake,is a maar lake present in the Plio-Pleistocene back-arc volcanic field (PaliAike Volcanic Field) located in Santa Cruz province (52°S and 70° W; 113 m a.s.l.), Argentina. ThePASADO project is an interdisciplinary scientific project that has successfullydrilled their lacustrine sediments, obtaining a drilling covering a period of 50ka BP. From this sequence, in the present communication, phytolith compositionof a section ranging from 21301.1?27799.3 ka BP (or 2657.6?3381.0 cm deep fromSite 2) has been studied. This section, belonging to the lithological unit C-1,is composed by pelagic laminated silts intercalated with thin fine sand andcoarse silt layers, with poor lamination, and their analysis show the presenceof three phytolith zones: the lower zone (27799.3?24765.2 ka BP) withoutreworked levels and characterized by demarcated high rarefaction in theirphytolith composition andphytolith assemblage that has an abundance of festucoids, pooids, bromoids andarundinoids phytoliths. A middle mixed zone (24572.5?23513.7 ka BP) characterizedwith the presence of reworked level gaps, and a trend to lower rarefaction in upperlevels, as well as scarce relative abundance of the graminoid elementsmentioned above. Some dicot shrub and/or arboreal elements are most abundant inthis zone. The upper zone (23477.6?21301.1 ka BP, with a reworked gap around 22374.3 ka BP) show low phytolith rarefaction and cleardominance of festucoides and dicots shrub and/or arboreal elements, althoughthey are occasionally other graminoid components.