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. Consequently, we investigate HP-cycles in equatorial regions, which is the assumed origin of this signal.

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

We present first results of a larger project which has the overall objective to characterize the HP-signal during and beyond the Mid-Pleistocene Transition (MPT) at Site 663. The connection of (half-)precession to eccentricty implies a weaker influence of HP during the MPT, as the major driver of climate forcing during this period is the 41-kyr obliquity cycle. Further objectives of the investigations will be to link the orbital patterns of Site 663 to terrestrial records, e.g. from the ICDP project on Lake Bosumtwi (Ghana). This will contribute to a better understanding of paleoenvironmental processes in Equatorial Africa.