Please use this identifier to cite or link to this item: http://hdl.handle.net/20.500.12136/1822
|Title:||Climate variability revealed by two stalagmites from Northern and South-Western Romania|
Onac, Bogdan Petroniu
|Publisher:||American Geophysical Union|
|Abstract:||We present two stable isotope records of climate variability from stalagmites in northern (#1152 from Pestera Izvorul Tausoarelor, Rodna Mountains) and south-western (#POM1 from Pestera Ascunsa, Mehedinti Mountains) Romania. Both cave entrances are located at over 1000 m asl in areas covered by mature beech forests, in continental temperate climate. Superimposed on the present-day climatic conditions are two different climate influences: Atlantic in the north and sub-mediterranean in the south-west. Both stalagmites were dated by means of uranium series on a Thermo Neptune MC-ICP-MS at Centro Nacional de Investigacion sobre la Evolucion Humana (Burgos, Spain) and samples for stable O and C stable isotopes were analysed on a Thermo Delta V IRMS at the Stable Isotope Laboratory, University of South Florida. For the stable isotopes profile, stalagmite 1152 was sampled at an average interval of 100 years , whereas POM1 was sampled at a 30 years interval. The two stalagmites reveal differences in isotopic signature response to climatic variability. When the POM1 δ18O profile is compared to the NGRIP δ18O, a lower variability of its values is evident. Even so, we are still able to distinguish structures similar to Greenland Interstadials (GIs) 7 and 8, the latter being composed of two distinct units. The stalagmite 1152 δ18O profile shows less variability although some of the peaks in the values could be correlated to GIs 4 through 12. The absolute values of these two records vary around an average of -7.5‰, very close to the typical Holocene values from this part of Europe. This may point to an enhanced Mediterranean circulation towards the north during MIS 3. In return, the δ13C values of the two stalagmites are very different and point to large differences in the activity of plants and soil organisms. POM1 values, averaging -5 to -6‰, indicate a C4 type vegetation in the area above the cave, that could belong to alpine meadows. This may document a lowering of the tree limit of at least 500 m compared to Holocene altitudes that was influenced by overall low temperatures and/or by enhanced seasonality in temperatures and water availability. Stalagmite 1152 shows positive δ13C values (0 to 1 ‰) that might be related to a lack or a very low activity of plants and soil organisms, a situation very close to permafrost conditions.|
|Description:||Ponencia presentada en: American Geophysical Union, Fall Meeting, 5-9 de diciembre 2011, San Francisco|
|Appears in Collections:||Congresos, encuentros científicos y estancias de investigación|
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