An early Holocene short climatic event in the northwest Iberian Peninsula inferred from pollen and diatoms

Abstract

Pollen and diatom analyses have been carried out in a 490-cm long core collected from Laguna Lucenza (1420 m a.s.l.; northwest Iberian Peninsula), spanning the last 10,000 yr. Pollen analyses show a decrease in deciduous Quercus pollen percentages and total pollen concentration after radiocarbon date 8350±80 yr BP. The estimated age by linear interpolation for the peak of this event is about 9200 cal yr BP. Diatom analyses have been carried out using the same samples in order to obtain complementary information about past environmental conditions within the water body. Pollen and diatom records show a response to changes in the palaeoenvironmental conditions. Diatom concentrations are relatively low, indicating low productivity within the lake. Fragilaria species are dominant and Fragilaria exigua is notably more abundant than during previous periods. These changes in the diatom community reflect a decrease in lake pH. This would be consistent with longer periods of ice cover and cold conditions in the lake at this time. We interpret this episode as a response to climatic change probably due to climatic deterioration. This interval coincides, at least in part, with an episode of abrupt and short widespread climate change lasting from 9000 to 8000 yr BP.