COMPARISON OF XRF AND SPECTRAL REFLECTANCE DERIVED CYCLICITY IN PLIOCENE AND PLEISTOCENE SEDIMENTS FROM ODP SITE 693, DRONNING MAUD LAND ANTARCTICA

The objective of this research is to understand the timing and extent of East Antarctic glaciation during parts of the Pliocene and Pleistocene epochs using sediment cores recovered off of Dronning Maud Land. Sediments from ODP Site 693, Cores 8R (Pliocene) and 2R (Pleistocene) were analyzed for mineralogy using whole-core x-ray fluorescence (XRF) spectrometry and fine-faction diffuse spectral reflectance (DSF). Varimax-rotated principal component analysis (VPCA) was used in conjunction with wavelet analysis to identify orbitally-forced sedimentation patterns. An initial spike in temperature followed by gradual cooling characterizes the Pliocene (McKay et al., 2012), whereas the Pleistocene is marked by glaciation/deglaciation cycles, indicating that these two epochs had different dominant orbital cycles.

VPCA was used to identify the underlying structures that describe the variance within each of these two datasets as well as to highlight clusters within the data. The data from the rotated components were then interpolated to provide a constant step between data points and detrended to remove the effects of periodicity out of the scope of the sample size. The formatted data were inputted into the online program Interactive Wavelet Plot. Using the wave power spectrums provided by Interactive Wavelet Plot, peaks were identified and attributed to Milankovitch cycles (obliquity, eccentricity, or precession), as well as possible sub-Milankovitch cycles that appear in the power spectrums of the Pliocene core. Based on the spacing of these peaks we conclude that within the parameters of our dataset, obliquity was dominant during the Pleistocene while eccentricity was dominant during the Pliocene, though obliquity also had a strong signal. Additional research will be presented as we try to identify why our data do not show the usual orbital forcing for these epochs.