Professor Carlos Ribeiro
Departamento de Geociências, CGE, Universidade de Évora
Data: 18 de Janeiro

Hora: 14:30
Local: Anfiteatro 1 - CLAV

Resumo:

Between 10.2 ka and 2.6 ka a fluvial tufa system developed in the Tavira region. The tufa is essentially made of calcite and present an internal layering that result of the precipitation under changing environmental conditions.  

During the HOLOCLIMA project different proxies were used with the purpose of deciphering the paleoclimatic record imprinted in these rocks. The most promising results were the variations of the oxygen isotopic ratio which exhibit a trend of gradual increasing during the time interval under consideration. 

The data on present day precipitation and isotopic composition of meteoric waters supports that the balance between evaporation and precipitation is the main factor controlling the fractionation of oxygen stable isotopes of the meteoric water in this region. The observed increase in 18O/16O values throughout most of the Holocene can then be interpreted as the result of an increase in the amount of evaporation and/or a decrease on the amount of precipitation with the consequent change in the local climate conditions towards a more arid environment. This increase in the evaporation is most likely related to the increase in the atmospheric temperature during the climatic recovery following the Younger Dryas.