New high resolution pollen, charcoal and sclerochronological records from Northern Patagonian Lakes

62. BIANCHI, M. M., A. L. SOLDATI, D. E. JACOB & B. R. SCHOENE

Bonn, Alemania

Congreso; . XII International palynological Congress; 2008

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-US;} @page Section1 {size:21.0cm 842.0pt; margin:70.9pt 2.0cm 70.9pt 3.0cm; mso-header-margin:0cm; mso-footer-margin:0cm; mso-paper-source:0;} div.Section1 {page:Section1;} --> New high resolution pollen, charcoal and sclerochronological records from Northern Patagonian lakes   XII International Palynological Congress 30 August- 5 September, Bonn, Germany.   M. M. Bianchi1, A. L. Soldati2, D. E. Jacob2 and B. R. Schoene2   1 INIBIOMA, CONICET, Bariloche, Argentina. 2 Institut für Geowissenschaften, Universität Mainz, D-55099 Mainz, Germany.   Quaternary palynologists have been active for almost a century in Northern Patagonia. Pioneer studies relying on pollen as a regional stratigraphic tool gave place to interpretations of the vegetation response to environmental and climatic changes since glacier retreat in the region ca. 17,000 cal years B.P. More recently, a variety of proxy-records were added to the initial pollen sequences and palaeoclimate studies were enhanced under international collaborative research programs. Studies concentrated on sensitive spots within two major watersheds, discharging either to the South Atlantic Ocean (Río Limay) or to the South Pacific Ocean (Río Manso) and introduction of new methods for recovery and analysis of lake sediments facilitated the obtainment of lake sediment proxies including sedimentological, geochemical and biological data. Therefore, a more detailed picture of landscape and ecosystem transformations could be achieved which suggests a steeper west-east precipitation gradient during the Full Glacial, a reorganization of the regional drainage system during the Late Glacial and significant shifts of the forest-steppe ecotone during Holocene times. This well-studied area therefore provides an excellent framework to test and develop new high-resolution proxy archives which will complement and extend the existing proxy-records. We are evaluating shells of the fresh water clam Diplodon ch. patagonicus from Northern Patagonian lakes for their potential as an environmental proxy archive and complement this study with high resolution pollen and charcoal studies of short sediment cores from the same lakes. The mussel shells consist of aragonite and grow in annular increments reaching a life span of more than 90 years. Modified dendrochronological methods (Schoene et al. 2002) show periodicities of 2.5, 7 to 9 and 15 years which can be matched with recurring climatic parameters in the area. High resolution pollen and charcoal records from short cores covering the water-mud interface and dated with 210Pb and 137Cs, show fluctuations in Nothofagus – Austrocedrus forest environments as well as regional (background) charcoal trends but no evidence of fires (peaks) during the last century at the two studied lakes in both watersheds.   Schoene et al. (2002): The Veliger 45(1): 45-54.