This study presents new paleoenvironmental data obtained from sedimentary cores from Lago Fagnano, an elongated lake located at 54°S in southernmost South America. Data from palynomorphs (pollen, spores and algae) and associated palynofacies as well as from diatom taxa retrieved from these cores compared with other regional proxies contribute to evaluate the similarities and differences in the climate patterns based on different proxies from southernmost Patagonia. The pollen analysis reveals that a grass steppe environment existed during the early Holocene (11,300-~. 8000. cal. a. BP) followed by a major vegetation change characterized by development of forest-steppe ecotone communities between ~. 8000 and ~. 6500. cal. a. BP, under more humid conditions. Between ~. 6500 and ~. 4000. cal. a. BP, expansion and colonization by Nothofagus forests reflect an increase in effective moisture levels, while openness in the forest communities characterizes the region after ~. 1100. cal. a. BP. The palynological organic matter combined with the algal content reflects hydrological changes occurring in the lake and its nutrient status, probably in close relation with past climate oscillations. All these past ecological changes are closely related to oscillations in precipitation and temperature as a response to the variations in the latitudinal position and/or strength of the Southern Westerlies wind belt during the Holocene.
Bibliographical noteFunding Information:
We acknowledge Robert Dunbar (Stanford University, USA) for the invaluable help and contributions to every aspect of this study and for the use of the capable small research vessel, the R/V Neecho (owned by Stanford). John H. McAndrews (Toronto University, Canada) and Charles L. Turton (Royal Ontario Museum, Canada) are gratefully acknowledged for their valuable help in non-pollen palynomorph identifications. The authors kindly acknowledge Rosanna Martini and Agathe Martignier from the University of Geneva and André Piuz from the Muséum d'Histoire Naturelle de Genève (Switzerland) for their help with SEM imaging. We thank David Mucciarone (Stanford, USA), Steffen Saustrup and Mark Wiederspahn (Institute for Geophysics) and Juan Federico Ponce (CADIC-CONICET) for technical assistance during fieldwork and at later stages of this project. The logistical help, hospitality and assistance during every aspect of the fieldwork of Alejandro, Maria Elena and Gabriel Echeverría from Bahía Torito are also kindly acknowledged. Captains Jorge Ebling and Rafael Quezada are also kindly acknowledged for their help during fieldwork. The Centro Austral de Investigaciones Científicas-Consejo Nacional de Investigaciones Científicas y Técnicas (CADIC-CONICET, Argentina) and the Prefectura Naval Argentina are acknowledged for their logistical support and assistance. This work is part of the project Environmental Changes Down-South (ENDS), supported by the Swiss National Science Foundation grants 200021-100668/1 and 200020-111928/1 to D. Ariztegui and the National Geographic Society (grant CRE 7705-04 ) to J. A. Austin Jr. We also thank the Augustin Lombard Foundation for their financial support (grant to C. Recasens) for the 2006 field campaign.
- Lacustrine sediments
- Multi-proxy analyses
- Paleoenvironment and Paleoclimate reconstruction
- Southern Hemisphere Westerlies
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Earth-Surface Processes