Phytolith analysis for the Protok Aike Lake Drilling Project: Preliminary results and current studies

ALEJANDRO ZUCOL; MARIANA BREA; ESTEBAN PASSEGGI; MARÍA GABRIELA FERNÁNDEZ PEPI; MARÍA DE LOS MILAGROS COLOBIG; NOELIA PATTERER

Buenos Aires

Workshop; 1ª Reunión Internodos del Proyecto Interdisciplinario Patagonia Austral y 1er Workshop Argentino del Proyecto Potrok Aike Maar Lake Sediment Archive Drilling Project; 2010

Universidad Maimónides- Fundación de Historia Natural Félix de Azara

The preliminary phytolith studies from the Potrok Aike Lake sedimentary sequence were made with SALSA core samples , which included 9 samples from across this drilling section. These samples were sent for analysis by Dr. Nora Maidana (PI of the PASADO project) for the purpose of verifying the presence of siliceous microremains and particularly phytoliths, in order to evaluate the potential information that might be obtained using this approach in the analysis of the Potrok Aike Lake sedimentary sequence. In these preliminary analyses, the phytoliths became the main emphasis and therefore the study of other types of microremains was not included.The results of the preliminary analysis show the presence of various types of silica microremains in all of the analyzed samples. Phytolith distributions show a marked abundance of non-diagnostic elements such elongate prismatic, fan-shaped, and point-shaped phytoliths, as well as a clear abundance of diagnostic elements linked to the microthermic grass lineages (such as pooids, festucoids, stipoids, and danthonioids). These were represented mainly by festucoid boats, crescents, truncated cones, and stipa-type morphotypes. The majority of these grass groups are typical of the Patagonian steppe. For other types of grasses, diagnostic phytolith morphotypes such dumbbell shapes are found in these samples, with highest abundances in the upper samples of the sequence. Panicoid elements are not characteristic of the region's floral composition, and the presence of these megathermic grasses can perhaps be related to an antropical factor. Other diagnostic grass types such as collapsed saddle phytoliths, which can be related to the bambusoid groups, are considered as Andean forest elements, as are some nothofagoid and gymnosperm morphotypes. These distributions, although not considered securely comparable because of the insufficient counting levels applied during this preliminary analysis, do create a pattern that resembles the pattern seen in the paleopalynological records, with Patagonian steppe in the lower core section and Andean forest in the upper section.