Paleoclimatic reconstruction of past interglacial periods and their transitions in the Iberian Peninsula and its surrounding seas
[eng] This study combines cave speleothems and marine sediments to gain an insight into the climate variability of the Iberian Peninsula (IP) and its surrounding seas associated with previous warm interglacial periods. In particular, it centres in the interglacials comprised within the Marine Isotop...
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| Other Authors: | , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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Universitat de Barcelona
2020
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| Online Access: | http://hdl.handle.net/2445/180213 http://hdl.handle.net/10803/672465 |
| Summary: | [eng] This study combines cave speleothems and marine sediments to gain an insight into the climate variability of the Iberian Peninsula (IP) and its surrounding seas associated with previous warm interglacial periods. In particular, it centres in the interglacials comprised within the Marine Isotopic Stages (MIS) 13, 11, 9, 7, and 5, and their associated transitions. The speleothems are used as archives for changes in atmospheric moisture availability by means of stable isotopes and Mg/Ca analysis. The studied speleothems correspond mostly from the Balearic Islands (Minorca and Mallorca) but also from the Pyrenees. Marine conditions for the penultimate termination (T-II) and the MIS 5 have been reconstructed in the base to three sediment cores from three different marine locations around the IP: the Cantabrian Sea, the Alboran Sea, and the Balearic Sea. Surface conditions were explored by means of pair analyses of δ18O and Mg/Ca ratios measured in carbonate shells of the planktonic foraminifera Globigerina bulloides. These measurements let to the reconstruction of Sea Surface Temperatures (SST) and sea water δ18Osw values as a proxy of major changes in the regional precipitation/evaporation balance or as an indicator of the arrival of melting waters. In addition, changes in the intensity of western Mediterranean deep convection are explored through additional measurements of grain size distribution and XRF-geochemical ratios performed in the Balearic core (MD99- 2343). The studied speleothem collection provides a nearly continuous 450 kyr record, unique for the Mediterranean region. Interglacial periods are characterized by light δ13C and low Mg/Ca ratios pointing to enhanced precipitation and climate amelioration that allowed the expansion of the vegetation cover. On the contrary, heavier/higher δ13C and Mg/Ca ratios during glacial stages highlight their dry conditions with reduced vegetation activity. The δ18Ospeleo records reveal also the overall dominance of lighter values during interglacial periods in ... |
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