HR: 1340h
AN: U13B-1146    [Abstracts]
TI: High-Resolution Speleothem Records of Climate Variability from the Northwestern Iberian Peninsula During the Last 30,000 Years
AU: * Moreno, A
EM: moren079@umn.edu
AF: Geology and Geophysics - University of Minnesota, 220 Pillsbury Hall 310 Pillsbury Drive S.E., Minneapolis, MN 55455, United States
AU: * Moreno, A
EM: moren079@umn.edu
AF: Pyrenean Institute of Ecology - CSIC, Avda. Montañana, 1005. Apdo 202, Zaragoza, 50080, Spain
AU: Stoll, H
EM: Heather.M.Stoll@williams.edu
AF: Departamento de Geología - Universidad de Oviedo, C/ Arias de Velasco, s/n, Oviedo, 33005, Spain
AU: Jiménez-Sánchez, M
EM: mjimenez@geol.uniovi.es
AF: Departamento de Geología - Universidad de Oviedo, C/ Arias de Velasco, s/n, Oviedo, 33005, Spain
AU: Valero-Garcés, B L
EM: blas@ipe.csic.es
AF: Pyrenean Institute of Ecology - CSIC, Avda. Montañana, 1005. Apdo 202, Zaragoza, 50080, Spain
AU: Edwards, L
EM: edwar001@umn.edu
AF: Geology and Geophysics - University of Minnesota, 220 Pillsbury Hall 310 Pillsbury Drive S.E., Minneapolis, MN 55455, United States
AU: Ito, E
EM: eito@umn.edu
AF: Geology and Geophysics - University of Minnesota, 220 Pillsbury Hall 310 Pillsbury Drive S.E., Minneapolis, MN 55455, United States
AU: Vadillo, I
EM: vadillo@uma.es
AF: Departamento de Geología - Universidad de Málaga, Avda. Cervantes, 2, Málaga, 29071, Spain
AU: Trigo, R M
EM: rmtrigo@fc.ul.pt
AF: Instituto Geofisico - Universidade de Lisboa, Rua da Escola Politécnica, 58, Lisboa, 1250- 102, Portugal
AU: Cacho, I
EM: icacho@ub.edu
AF: University of Barcelona, C/Martí i Franqués s/n, Barcelona, 28080, Spain
AB: The late Quaternary climatic evolution of the northern Iberian Peninsula has not yet been well documented despite the rich human history of occupation preserved in cave sites and the significance of this location in the modern North Atlantic Oscillation. Existing geomorphologic records suggest that in the northern Iberian Peninsula the maximum glacial extent was reached as much as 10 ka before the last global glacial maximum (LGM), but do not resolve rapid climate changes. Here, we present stable isotope and elemental climate records from two well-dated stalagmites from the northern coast of Spain, which span from 28,000 to 4800 years B.P., with average deposition rates of 20 and 50 mm/ka. The climate variability described by these new speleothem records will be placed in a regional context by comparison with available lacustrine records from nearby mountains. We aim to (1) describe the sequence of climate changes that occurred since the LGM, (2) identify the timing and describe the structure of abrupt climate oscillations and (3) test hypotheses concerning the forcing mechanisms of hydrological variations for the last 30 ka. Oxygen isotopic values, with a total variability of 3 ‰, are highest from 22.8 to 18.2 ka, coinciding with the global LGM. After that, a hiatus was detected ending at 15.4 ka, likely pointing to a cold and dry period without speleothem formation, which may be related to Heinrich Event 1. The postglacial decrease in δ¹⁸O features higher frequency variability including a 0.7 ‰ excursion to lower values during the Younger Dryas (12.8 to 11.8 ka). The Holocene values are lower and ranging 2 ‰, pointing to significant hydrological variability during the last 10 ka. Carbon isotopic values, ranging from -11 to -2 ‰, are very similar to the oxygen profile in both records and along the entire time interval recorded. After testing that calcite was deposited under equilibrium conditions, we suggest a probable common forcing behind the hydrological and soil-vegetation patterns of variation. Our high resolution (48 hour) analysis of oxygen isotopes in modern precipitation at the site reveals a large (6 ‰) range which is highly correlated with the daily CPC NAO index and only weakly correlated with air temperature or precipitation amount. Oxygen isotopes in rain and dripwater might thus be most strongly regulated by the dynamics of precipitation (moisture source and condensation height and temperature), superimposed on the trend in δ¹⁸O of seawater from ice volume effects. Thus, the negative isotopic excursion during the Younger Dryas and those events during the Holocene could reflect precipitation generated under conditions more similar to those characterizing the modern negative NAO phase. Mg/Ca ratios rise sharply after 8000 years BP likely reflecting sea level rise and greater proximity to the coast which increases sea salt aerosol Mg deposition.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1065 Major and trace element geochemistry
DE: 1120 Isotopic disequilibrium dating
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 4958 Speleothems
SC: Union [U]
MN: 2007 Fall Meeting