Palaeoflood record of the Tagus River (Central Spain) during the Late Pleistocene and Holocene

Abstract

Palaeoflood hydrology of the Tagus River (Central Spain) was reconstructed from slackwater deposits and palaeostage indicators in two canyon reaches located at El Puente del Arzobispo in the central part of the catchment (35; 000 km2 in drainage area) and in Alc!antara, at the lower part of the catchment (52; 000 km2 in drainage area) near the Portuguese border. The palaeoflood record, with more than 80 flood events, shows clusters of floods at specific periods from 9440 to 9210 14C yr BP (8540–8110 BC), 8500 to 8000 14C yr BP (7500–7000 BC),B6750 14C yr BP (B5000 BC), 1200 to 950 14C yr BP (AD 785–1205),B410 14C yr BP (AD 1450– 1500), 170 to 80 14C yr BP (AD 1670–1950). The largest flood(s) occurred during the periods 9440 to 9210 14C yr BP, B6750 14C yr BP and 1200 to 950 14C yr BP reaching minimum discharge estimates of between 4000 and 4100 m3 s 1 in the El Puente del Arzobispo reach and 13,700–15; 000 m3 s 1 in the Alc!antara reach. These periods with increased flood magnitude and/or frequency in the Tagus River are strongly related to increased moisture influx and winter precipitation in the Iberian Peninsula, especially in the western zone. Proxy records sensitive to winter precipitation such as lake levels and vegetation changes (indicated by pollen records) are in good agreement with the clusters of floods found in the Tagus River. This flood variability seems to correspond to changes in the prevailing atmospheric circulation pattern affecting the Iberian Peninsula.