A continuous and
record in bulk
fine-fraction carbonate has been obtained for the late Miocene
and late middle Miocene (5-14 Ma) at 10-cm intervals
(corresponding to an average 6 k.y.). Continuous data are
presented for benthic foraminifers over the interval 57.3
Ma as well as over intervals from ~9.5 to 9.8 Ma and 11 to 13 Ma.
Limited data are also available for planktonic foraminifers over
the same intervals. There is strong orbital-frequency covariance
between
in bulk
fine fraction and
in benthic foraminifers, suggesting that both parameters reflect
variability in the
of dissolved CO2 in the ocean. Spectral analysis of the whole
record for bulk fine
fraction shows strong power in the 400-k.y. and 100-k.y.
eccentricity bands. Benthic
shows variability that probably reflects the
temperature of the deep (3.6 km) Atlantic Ocean water. Bulk
fine-fraction
displays very little high-frequency variability, possibly due to
an original signal having been reduced through isotopic
equilibration with pore water. The origin of the long-term
variability in bulk fine-fraction
, which apparently implies a cooling
centered on about 9.5 Ma, is enigmatic, since this feature is not
evident in the
data
for G. sacculifer.
1Shackleton, N.J., Curry, W.B., Richter, C., and Bralower, T.J. (Eds.), 1997. Proc. ODP, Sci. Results, 154: College Station, TX (Ocean Drilling Program).
2University of Cambridge, Godwin Laboratory, Free School Lane, Cambridge, CB2 3RS, United Kingdom. njs5@cam.ac.uk