Record Details
Variability of late Neogene eastern equatorial Pacific carbonate sedimentation and global ice volume on timescales from 10,000 years to 1 million years
ScholarsArchive at Oregon State University
| Field | Value |
|---|---|
| Title | Variability of late Neogene eastern equatorial Pacific carbonate sedimentation and global ice volume on timescales from 10,000 years to 1 million years |
| Names |
Hagelberg, Teresa King
(creator) Pisias, Nicklas G. (advisor) |
| Date Issued | 1993-02-03 (iso8601) |
| Note | Graduation date: 1993 |
| Abstract | Sedimentary sections recovered during the Deep Sea Drilling Project and the Ocean Drilling Program provide the opportunity to study the evolution of Neogene climate at high resolution overtime periods spanning millions of years. Two components of the paleodlimatic system, eastern equatorial Pacific carbonate sedimentation and global ice volume, were examined with the common goal of understanding late Neogene climatic variability. Before examining the temporal evolution in detail, stratigraphic continuity of the sedimentary sections was confirmed. Remotely measured sedimentary properties were used to document section continuity between adjacent and overlapping cores at each drill site during ODP Leg 138. This strategy also provided several realizations of the sedimentary process. Multiple realizations of wet bulk density at each of eight drill sites were averaged to produce continuous records having a ~2 cm resolution. Estimates of local sedimentation variability were also developed to confirm that sedimentation rate variations imposed by orbital tuning strategies are within the range of local sedimentation variability that is present. In the eastern equatorial Pacific, wet bulk density is a proxy indicator of calcium carbonate concentration. Eight records spanning the last 6 million years at a ~1000 year resolution were used to investigate spatial and temporal variations in carbonate sedimentation. Two modes of variability in calcium carbonate concentration and carbonate mass accumulation were resolved. The spatial pattern of the dominant mode of variability indicates latitudinal control of carbonate sedimentation. Over the past 6 myr, the dominant mode of variability is highly coherent with changes in insolation. The dominant mode of carbonate sedimentation has consistent spatial patterns in the presence of large oceanographic and tectonic boundary condition changes. A primary control from surface oceanographic processes was inferred. The second mode of variability in carbonate sedimentation may be influenced by processes related to dissolution and noncarbonate dilution. Carbonate sedimentation and ice volume variations are linearly related in the Milankovitch band during the past 4 myr. Evolution of ice volume over the past 2.5 myr was investigated using oxygen isotope records. Third order statistics were used to study the extent of linear relative to nonlinear variations in ice volume. The same statistically significant phase couplings that are present in the time series of solar insolation are also present in the global ice volume record. These results are consistent with a linear response of the climate system to orbital forcing. An evolution in the nature of the phase coupling is seen, with an increase in the asymmetry of the ice volume record over the late Neogene. Coherence between paleoceanographic records and insolation variations has been used as a measure of time scale accuracy. The effects of age model error and amplitude error on estimates of coherence and bicoherence were investigated. Coherence estimates are more robust to amplitude error and time scale error than bicoherence estimates. A test for time scale error which uses the statistical properties of the bispectrum is not applicable to the problem of time scale accuracy in paleoceanography. However, under the assumption of a linear response of climate to insolation in the Milankovitch band, the high sensitivity of bicoherence estimates suggests that bicoherence may be a more sensitive indicator of age model accuracy. |
| Genre | Thesis/Dissertation |
| Topic | Paleoclimatology -- Pacific Ocean |
| Identifier | http://hdl.handle.net/1957/23441 |
