Absolute astronomical time

Sapropels and/or carbonate cycles in the Mediterranean Narbone Formation and Trubi Marls were tuned to summer insolation 65° North with a 3-kyr lag between insolation maxima and sapropel (or low-carbonate grey-layer) midpoint. The orbital solution that was used assumes present-day values for dynamical ellipticity and tidal dissipation, and no effects from climate friction. The 3-kyr lag honors a previously noted age difference between a 8.5 ka radiocarbon date from the midpoint of the most recent sapropel S1 and the 65° North summer insolation maximum at 11.5 ka (Lourens et al., 1996).

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