Antarctic sediment drifts and Plio-Pleistocene orbital periodicities (ODP Sites 1095, 1096, AND 1101)

Petrophysical datasets and related spectral analysis from Plio-Pleistocene sediments cored on the Western Antarctic continental rise during the Ocean Drilling Program, Leg 178, are discussed. It is shown that in different cores, nonharmonic wavelength peaks, when normalized, exhibit a very high correlation factor with predicted Earth's orbital variations. It is also found that both short (~ 95-125 ky) and long (~ 400 ky) eccentricity periodicities emerge clearly from the signal during the whole Pleistocene, without an evident switch to obliquity at mid-Pleistocene (~ 0.9 Ma), as reported in the literature. This suggests that the lithological parameters, a proxy for glacial cycles, are controlled, directly or indirectly, by astronomically forced processes (Milankovitch cycles). Moreover, the good correlatability among distant coring sites, based on systematic sedimentological variations at intervals of about 140 and 370 ky, allows extension of the results to regional scale.