Abstract:
Orbital, stochastic, and geologic influences were considered for ODP site 806, Ontong Java Plateau. The orbital influence was obtained by transforming July insolation at 65 degrees north to sea-level using a physically consistent ice growth concept. The transform assumes that ice growth is constant but that melting is dependent on insolation, the size of the ice sheet and the average size of the ice sheet over the previous 57 k.y. The resulting sea-level template is similar in time and frequency domains to the observed oxygen isotope signal. Red noise was superimposed on the insolation curve before application of the transform. Red noise has little effect on precession and obliquity, however the 100 k.y. eccentricity signal is increasingly blurred as red noise is increased beyond 15% of the signal; and the amplitude of the 100 k.y. peak increases. At the Ontong Java Plateau sedimentation rates are higher during glacial periods. A linear relation between sea-level and sedimentation rate was imposed on the sea-level template, generated with a pure climatic signal. The time series, stretched during glacials, destroys the precession and obliquity signals. The short-eccentricity signal shifts towards shorter wavelengths. Occasional, random slumping events occurred at site 806 removing sediment from the plateau. This was simulated with removal of randomly distributed patches of sediment from the climate template. The size of the package removed was given a red-noise distribution. Increased erosion results in decreased spectral resolution at all frequencies, particularly when the events are concentrated over a smaller number of locations.