Orbital forcing in Pliocene-Pleistocene Mediterranean lacustrine deposits: dominant expression of eccentricity versus precession

Milankovitch forcing of climate is expressed in the sedimentary record as lithological cycles that can have one or more of four typical periods related to precession (21 kyr), obliquity (41 kyr) and eccentricity (100 and 400 kyr). In several Mediterranean continental successions, striking differences in the expression of particularly precession and eccentricity appear. We present the results of an additional lower Pliocene lacustrine succession from Lupoaia (southern Romania), and compare the cyclic expression in this lignite-siliciclastic basin in detail with the time-equivalent lignite-carbonate basin of Ptolemais (northern Greece), the middle Pleistocene lignite-siliciclastic basin of Megalopolis (southern Greece) and the Miocene carbonate-clay basin of Orera (north eastern Spain). It appears that carbonate basins dominantly express precession, while siliciclastic basins dominantly express eccentricity in their lithological cycles. This can be explained by a more linear response to insolation forcing in carbonate basins than in siliciclastic basins. Alternatively, it can be explained by the low amplitude of 100-kyr eccentricity at the times the carbonate sections were deposited. This reduced 100-kyr amplitude was caused by minima in the 2.35 Myr eccentricity cycle, that co-occurred with the deposition in both carbonate basins. Finally, the expression of 100-kyr eccentricity appears to be independent of glacial cyclicity. (C) 2001 Elsevier Science B.V. All rights reserved.