The Holocene fluvial chronology of Spain: evidence from a newly compiled radiocarbon database

A critical analysis of 74 radiocarbon dates, selected from a total of 102 published and unpublished dates from Holocene fluvial environments in Spain, has identified a number of periods of increased fluvial activity in Spain, namely: 11,170–10,230; 9630–8785; 7980–6860; 5800–4800; 3880–3085; 2895–1820; 1300–0 cal BP, the latter period reflecting sustained fluvial response to increased human impact. The radiocarbon samples were classified according to type of depositional environment: (a) alluvial overbank, (b) flood basin, (c) alluvial channel gravels, (d) fluvio-torrential deposits and (e) slackwater flood deposits (palaeofloods). Dates from slackwater flood deposits indicated at least five phases of increased frequency of large magnitude floods during the Holocene: 10,855–10,230; 9530–8780; 2880–2430; 975–790; and 520–265 cal yr BP. Flood basin type deposition occurred from 7980 to 4830 cal yr BP. The main clusters of dates from alluvial floodplain deposits occurred at 2750–2150 and 930–520 cal yr BP. The record is discussed in relation to other palaeoenvironmental archives including pollen records of Holocene vegetation change and palaeoclimatic proxies such as the North Atlantic drift ice record. Comparison with the latter indicates that major Holocene flooding coincided with cold climate phases during 9530–9280, 2880–2430 and 520–265 cal yr BP; a cooling phase at 10,855–10,230; and warming phases at 9030–8780 and 975–790 cal yr BP.