The Taravilla lake and tufa deposits (Central Iberian Range, Spain) as palaeohydrological and palaeoclimatic indicators

Lacustrine and tufa deposits from Laguna de Taravilla (Iberian Range, Guadalajara province, Spain, 40°39′ N, 1°59′ W, 1100 m a.s.l.) have been analyzed using sedimentological, mineralogical, geochemical and palynological techniques. A preliminary chronological framework is presented, based on U/Th, ¹⁴C AMS, ²¹⁰Pb and ¹³⁷Cs analyses. The lacustrine-tufa system developed in a hanging tributary valley of the Upper Tajo River and is composed of a large perched springline tufa build-up, and a barrage tufa dam that impounds Laguna de Taravilla. The Taravilla tufa stable-isotope compositions are similar to other examples in central and southern Spain and they plot in the same field as other lowland European stream tufas. These values are coherent with the range of isotopic compositions measured in the Taravilla spring and lake water. Several sediment cores retrieved from the Laguna de Taravilla have been dated with ¹⁴C AMS and analyzed using a multiproxy approach including magnetic properties, sedimentology, geochemistry, stable isotopes, palynology and ostracode assemblages. Sedimentary facies analyses show the dominance of clastic depositional processes in the lacustrine depositional system and suggest the potential of the sequences as palaeoflood records. Sands and coarse silts reflect periods of increased alluvial activity of the inlet. The dominance of clastic depositional processes and the input of detrital carbonate hinder the use of lake mud stable-isotope compositions as environmental indicators. Phases of increased tufa growth occurred during the Late Pleistocene (Last Glacial to Interglacial transition from oxygen isotopic stage 6 to 5) and during the Late Glacial and Early Holocene. Although the Taravilla chronology does not allow a detailed analysis of flood frequency, the reconstructed evolution is coherent with the palaeoflood history of the Tajo River for the last 2000 years, particularly with an increase during the last 500 years. The increase in flood frequency coincides with other evidence of wetter and colder climate and environmental change in Central Spain and in Europe during the Little Ice Age.