Paleoclimate Reconstruction in Portugal and the Iberian Margin

April 14th, 2012

Paleoclimate reconstructions for Portugal and the Iberian margin have recently been conducted for the last glacial cycle with the main focus centered on both terrestrial and marine-based data. Portuguese stalagmites provide climatic information through oxygen and carbon isotopes in stalagmite calcite and can be dated using uranium-thorium techniques. One area of particular interest is the climatic response in Iberia to Heinrich-events, the coldest points during glacial stadials having sub-polar climatic conditions and are signaled in the Iberian margin by large influxes of ice-rafted debris. During Heinrich-events the Portuguese stalagmites appear to contain growth hiatuses, suggesting that meteoric precipitation did not reach the cave because of permafrost or other conditions that form an impermeable layer overlying the cave. These data are consistent with marine core data from the Iberian margin that demonstrate extreme cold conditions during Heinrich-events. For example, abundances of the foraminifera N. pachyderma, a sub-polar dwelling, planktic species, correlates with the influx of ice-rafted debris (Heinrich) events. Furthermore, windblown pollen from terrestrial Portugal present in the same marine core data during Heinrich-events is consistent with steppe prairie grasses, vegetation that grows when climatic conditions are relatively cold and dry.

Lucas Anderson, ’12
Grinnell, IA
Major: Geology                                                                                     

Sponsor: Rhawn Denniston

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