LACUSTRINE OXYGEN ISOTOPES OF OSTRACODS, CHIRONOMIDS AND AQUATIC MACROPHYTES AS PALEOCLIMATE PROXIES. RESULTS FROM A CALIBRATION STUDY IN PATAGONIA

MAYR, C., LAPRIDA, C., LÜCKE, A., MASSAFERRO, J., MARTÍN, R. S., RAMON-MERCAU, J., WISSEL, H.

Medellin

Simposio; LOTRED-SA 3rd International Symposium ?Climate change and human impact in Central and South America over the last 2000 years: Observation and Models?; 2014

PAGES

Carbonate, chitine, and cellulose of lacustrine organisms can provide important paleohydrologic and paleoclimatic information as they store isotopic information of their host waters. The isotope ratio of inflows, climatic parameters and the water balance of a lake affect its oxygen-isotope composition. Moreover, temperature-dependent isotopic fractionation, isotopic disequilibrium, and ?vital effects? can influence oxygen isotope composition of biogenic proxies to varying degrees. Therefore it is crucial for paleoclimate reconstructions using these proxies to quantify these effects thoroughly. In a case study the isotopic composition (18O, 2H) of water from 41 lakes and ponds as well as 26 rivers and brooks in southern Patagonia was determined. Lake water isotope values plot along a line with a slope of 5 in 2H versus 18O space and span a range of more than 20 per mile. Ostracods were sampled at 11, submerged aquatic macrophytes at 32, and chironomid head capsules at 6 of these sites for oxygen isotope analyses. 18O values of ostracod calcite, chironomid chitin, and macrophyte cellulose all reflected the oxygen isotopic composition of host water. However, slopes and significance of correlations between these components and host waters were influenced to varying degrees by temperature-dependent isotope fractionation and vital effects. Host-water isotopic composition was best reflected by 18O values of aquatic moss cellulose while ostracod calcite exhibited clear interspecific differences and a clear temperature effect. The results provide a database for water temperature as well as host-water isotope quantification using lacustrine oxygen isotope proxies in appropriate sediment records.