Astronomically-paced changes in paleoproductivity, winnowing, and
mineral flux over Broken Ridge (Indian Ocean) since the Early Miocene
Abstract
A significant shift in Earth’s climate characterizes the Neogene,
transitioning from a single-ice-sheet planet to the current bipolar
configuration. This climate evolution is closely linked to changing
ocean currents, but globally-distributed continuous high-resolution
sedimentary records are needed to fully capture this interaction. The
Ocean Drilling Program (ODP) Site 752, located on Broken Ridge in the
Indian Ocean, provides such a Miocene-to-recent archive. We use X-ray
fluorescence (XRF) core scanning to build an eccentricity-tuned
age-depth model and reconstruct paleoceanographic changes since 23 Ma.
We find two intervals of enhanced productivity, during the early and
middle Miocene (18.5 – 13.7 Ma) and late Pliocene/early Pleistocene (3
– 1 Ma). We also report a mixed eccentricity-obliquity imprint in the
XRF-derived paleoproductivity proxy. In terms of grain size, three
coarsening steps occur between 19.2 – 16 Ma, 10.8 – 8 Ma, and since
2.6 Ma. The steps respectively indicate stronger current winnowing in
response to vigorous Antarctic Intermediate Water flow over Broken Ridge
in the early Miocene, the first transient onset of Tasman Leakage in the
Late Miocene, and the intensification of global oceanic circulation at
the Plio-Pleistocene transition. High-resolution iron and manganese
series provide a detailed Neogene dust record. This study utilized a
single hole from an ODP legacy-site. Nevertheless, we managed to provide
novel perspectives on past Indian Ocean responses to astronomical
forcing. We conclude that Neogene sediments from Broken Ridge harbor the
potential for even more comprehensive reconstructions. Realizing this
potential necessitates re-drilling of these sedimentary archives
utilizing modern drilling strategies.