Cyclostratigraphic investigations with special emphasis on half-precession signals using XRF-data from ODP Site 663 (Eastern Equatorial Atlantic)

The characteristics of half-precession (HP) cycles (~9,000 - 12,000 years) are still poorly understood, despite their appearance in numerous records. Previous studies on European terrestrial and marine records indicate a connection of the HP-signal to low latitudes. Here, we investigate HP-cycles in equatorial regions to study the assumed origin of this signal.

Spectral analysis, evolutive approaches and correlation techniques are used on records from ODP Sites 662 and 663 to identify the HP-signal in elemental ratios reflecting e.g. terrigenuous input and/or bioproductivity. Filters have been designed to remove the classical orbital cycles (eccentricity, obliquity, precession), in order to isolate the HP-signal and to determine the temporal evolution of its presence and amplitude.

We present first results of a larger project which has the overall objective to characterize the HP-signal across the Mid-Pleistocene Transition (MPT) at Sites 662 and 663. Over the course of the MPT, the ~100 kyr-eccentricity cycles supersede the 41-kyr obliquity as the primary driver of climate forcing. As precession is modulated by eccentricity, a similar relationship may be assumed for HP and eccentricity. Our preliminary analyses show an enhanced HP-signal in the younger, 100-kyr eccentricity world, but also in the late MPT which is partly influenced by the 41-kyr obliquity cycle. Cyclostratigraphic investigations of high-resolution XRF data will provide a clearer insight into the presence, amplitude and role of HP during the MPT and the late Pleistocene.