Diatoms and paleoenvironmental reconstructions of the last 16,000 years of laguna Potrok Aike (Santa Cruz, Argentina)”

MAIDANA, N. I.

RIO GALLEGOS, SANTA CRUZ

Workshop; Workshop ICDP- PASADO (Potrok Aike Lake Sediment Archive Drilling Project),; 2006

ICDP

Climatic changes are the subject of many multidisciplinary studies all around the world and it is well known the importance of diatoms as valuable diagnostic tools in such kind of studies. The use of these tools implies a deep knowledge of the taxonomy and ecology of the recent species, that will allow us to use them to infer past environmental conditions. The diatomological analysis from a sediment core recovered from the center of Laguna Potrok Aike covering 16,000 years revealed the alternance of the dominance of three planktonic species. Cyclostephanos patagonicus Guerrero & Etchenique dominates in the lower part of the core. This species was found previously only in the type locality (Limay river, northern Patagonia) and it seems to prefer low conductivity waters. Chaetoceros muelleri Lemmermann was found as dominant (37% of relative abundance) only in one sample that overlyes a tephra layer (ca. 8700 y BP). In the upper samples until the present days the dominant species is Cyclotella agassizensis Håkansson & Kling, known only for the type locality (Manitoba Lake, Canada) and Salta province (Argentina). Diatom concentrations fluctuated between 0 to 3 108 frustules gr-1 along the core but  there was a tendency to decrease from the bottom to the top of the core.  Although the correlation studies between diatom species and the other proxys have not been completed yet, our previous results indicate a significative positive correlation between the concentrations of Cyclotella agassizensis and TIC. That would indicate that the higher the abundance of this species within the sediment record is, the lower the lake level was during the time of sedimentation.