Abstract:
We carried out a detailed rock magnetic and paleomagnetic study of
deep-sea sediments from selected intervals of Site 1233 in order to assess
whether they contain reproducible evidence for submillennial-scale
environmental, climatic, and geomagnetic field variability. Three 1.5-m
sediment intervals from oxygen isotope Stages 1, 2, and 3 were sampled
using continuous U-channels; replicate sediment sequences were collected
from two or three holes in each interval to test for reproducibility.
Rock magnetic and paleomagnetic measurements were made at 1-
cm intervals. Rock magnetic results identify distinctive centennial
(~150–300 yr)- and millennial-scale variability that is probably continuous
over the entire Site 1233 record. They also show evidence for intermittent
multidecadal-scale rock magnetic variability. The rock magnetic
variability allows us to modify the meters composite depth (mcd) correlation
in each of the three high-resolution intervals to permit correlations
between holes at ~5-cm resolution. Paleomagnetic results indicate
that there is also a reproducible pattern of paleomagnetic secular variation
at the centennial to millennial scale. The centennial-scale variability
is dominated by ~5°–10° oscillations in both inclination and
declination with an average interval of ~200–300 yr. Deconvolution
studies and paleomagnetic secular variation (PSV) correlations between
holes both suggest that the PSVs are real and not caused by similar-scale
rock magnetic variability. The paleomagnetic results also document distinctive,
larger-amplitude multicentennial- and millennial-scale directional
variability that is consistent with preliminary shipboard
paleomagnetic studies.
