Magnetic parameters and their palaeoclimatic implications?the sediment record of the last 15 500 cal. BP from Laguna Potrok Aike (Argentina)

M.A. IRURZUN, M.J. ORGEIRA, C.S.G. GOGORZA, A.M. SINITO, R. COMPAGNUCCI AND B. ZOLITSCHKA

GEOPHYSICAL JOURNAL INTERNATIONAL

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2014 p. 1 - 17

0956-540X

Lake sediments are excellent sources of palaeoenvironmental and palaeoclimatic infor mation because t hey provide continuous and high-resolution r ecords. South America is of par ticular interest because i t i s t he only l andmass t hat stretches southward i nto t he Pacific and Atlantic Oceans towards Antarctica. The aim of this study is to explore t he relationship of magnetic parameters with elemental and palaeobiological data of Laguna Potrok Aike to develop a model of lake-level changes and related hydrological and climatic fluctuations. M agnetic measurements were perfor med on subsamples from 15 500 cal. BP t o t he present, and associated rock magnetic parameters were calculated to infer magnetic mineralogy, concentration and g r ain size. According to the model, parameters dependent on magnetic concentration and g r ain s ize are directly related t o l ake-level changes. During dr y periods, t he remanent coercivity displays high values, whereas the propor tion of magnetite is relatively low. Low percentages of g r eigite are obser ved, indicating t hat the water of the l ake was stratified at least f our times during t he studied period, at approximately 10 300, 8900, 8500 and 8300 cal. BP. The preser vation of g r eigite by inhibiting its complete t ransfor mation i nto pyrite is associated with a r apid b urial that occurs with high sedimentation r ates. Ther mal s tratification could be caused by a s light cooling i n t he area triggered by a weakening of the Westerlies and/or low activity of the s un, sum t o t he effect of a flood of melt water i n t he Nor t h Atlantic.