Epsilon-Nd-Signatures and Radiogenic Overprinting in Cold-Water Corals near the Azores

The Azores Front marks the boundary between subtropical and
subpolar water in the North Atlantic. Its position during glacial periods
is debated, tracing it would improve our understanding of glacial ocean
circulation. Neodymium (Nd) isotopes are an important tracer for past and
current water mass mixing. They are however subject to overprinting on
local scales by processes including erosion and volcanic activity.
Cold-water corals incorporate Nd into their skeletons without
fractionation, making them valuable archives. In this work, the epsilon-Nd
of corals from several locations close to the Azores Islands was measured.
The corals were previously dated by U/Th measurements, which revealed ages
between 0.458 and 22.14 ka. The epsilon-Nd measurements found a range of
values between -12.07 and -1.26. The results reveal clear
evidence of radiogenic overprinting, which occurs on decadal timescales
and can most likely be attributed to volcanic activity. The extent and
frequency at which this overprinting occurs does not depend on climate
phases. A part of the samples may represent unaltered seawater values,
these show no evidence of a change in water mass mixing over the last 20
ka.'