Geological constraints on tidal dissipation in the Messinian: An XRF record of climate variability from Gavdos Island (Greece)

Abstract

The climatic response to astronomical forcing in sedimentary archives provides insights into the effect of tidal dissipation (Td) and dynamical ellipticity (dE) on the astronomical solutions. The astronomical solutions are used to compute insolation and orbital target curves for paleoclimatic research. It is therefore most fundamental to understand their role as phase relations between astronomical forcing and climate response can only be accurately calculated when the Td and dE parameters are known. In this thesis, I determine the average values of tidal dissipation for the Messinian using an XRF record from the sapropel-bearing Metochia section (Gavdos, Greece), using the assumption of a direct response of sapropel formation to insolation. An exceptional palaeoclimate proxy (Fe/Ti) that records humid as well as arid conditions related to the African monsoon is compared with the insolation record of an astronomical solution (La2001) with varying values for the tidal dissipation. It is found that the optimum fit between the proxy data and astronomical model is obtained for the La2001(1,1.1) solution. This value is, however, statically indistinguishable to that of the La2001(1,1.2) and La2001(1,1) solutions. The use of the La2001(1,1.1) solution implies a -2.12 ± 0.03 kyr phase lag for precession and a -2.04 ± for 0.07 kyr for obliquity compared to the commonly used La2004 solution. An additional ~3.5 kyr lag to precession minima is quantified for the diatomites of the Metochia section, which should be taken into account when applying astronomical tuning to other Mediterranean diatomites.