Sub - annually resolved Miocene/Pliocene tropical palaeo - climate records from giant clams

Changes in seasonality play an important role in regards to climate changes (e.g. Eldrett
et al.,
2009). To better characterize Miocene/Pliocene tropical climate and environmental change, it is
therefore crucial to reconstruct their variability on a seasonal scale. However, highly time resolve
d
palaeoenvironmental records which allow assessing
tropical intra
-
annual SST variability (like
ENSO or monsoon events) are rare, especially in 'deep
-
time'.
Here, we present high resolution
trace element and stable isotope proxy records from well
-
preserved aragonitic Late Miocene and
Pliocene
Tridacna
spp.
shells, sampled along the coast of East Kalimantan (Indonesia) and Sabah
(Malaysia), respectively. Our multi
-
proxy approach utilizes LA
-
ICPMS El/Ca ratios (e.g. Mg/Ca,
Sr/Ca, Ba/Ca) and micromilled stable isotope profiles (
δ
18
O,
δ
13
C).
Records obtained fr
om our
Miocene specimens show a remarkable agreement in Mg/Ca, Sr/Ca and
δ
18
O and can be aligned
with the shell banding pattern.
δ
18
O intra
-
annual variability indicates a palaeoseasonality of 3
-
4°C
(if interpreted as being temperature
-
controlled only). Ba/
Ca profiles from Pliocene tridacnin shells
are characterized by pronounced, episodically occurring peaks with a high intrashell
reproducibility. Very similar Ba/Ca signals found in modern
Tridacnagigas
have been interpreted
as palaeoproductivity indicators
(Elliot et al., 2009). Records of a modern
Tridacna
spp. from
Sabah are utilized for comparison and calibration purposes
.