A simple climate model of Quaternary glaciations is combined with a simple isotopic model in order to study phase relationships between Δ18O records in deep-sea cores and in ice cores. Power spectra of the model's climatic and isotopic variables show a dominant peak near 100 kyr (1 kyr=1000 years), the continuous background of all paleoclimatic spectra, smaller peaks at the orbital periodicities of 41, 23, and 19 kyr, and additional peaks at 14.7, 13, 11.5, 10.4, and 9.5 kyr. Time lags between the model's isotopic profiles are highly variable; ice core events, identified as sharp maxima or minima, can lead apparently homologous events in the marine record or lag then by a few thousand years. This time domain instability of lags is due to the complexity of the power spectrum, with its continuous component and large number of lines. Since the complex spectrum is present in both model and paleoclimatic data, we expect lag relations in the data to be quiet variable as well. Independent dating of ice cores is preferable therefore to dating by comparison with marine records. Absolute dating can be based on a combination of ice flow models of accelerator mass spectroscopy. Time-averaged cross spectra of independently dated isotopic profiles should be stable and should help us to understand the mechanisms which lead to internal climatic variability. ¿ American Geophysical Union 1988