Abstract
Rational: Organisms that grow a hard carbonate shell or skeleton, such
as foraminifera, corals or molluscs, incorporate trace elements into
their shell during growth that absorbs the environmental change and
biological activity they experienced. These geochemical signals locked
within the carbonate are archives used in proxy reconstructions to study
past environments and climates, to decipher taxonomy of cryptic species
and to resolve evolutionary responses to climatic changes. Methods: Here
we use a laser ablation inductively coupled plasma mass spectrometry
(LA-ICP-MS) as a time resolved acquisition to quantify the elemental
composition of carbonate shells. We present the LABLASTER (Laser
Ablation BLASt Through Endpoint in R) package, which imports a single
time resolved LA-ICP-MS analysis, then detects when the laser has
ablated through the carbonate as a function of change in signal over
time, and outputs key summary statistics. We provide two worked examples
within the package: a planktic foraminifera and a tropical coral.
Results: We present the first R package that improves signal: noise
ratios in data reduction workflows by automating the detection of when
the laser has ablated through a sample using a smoothed time-series and
subsequent removal of off-target data points. The functions are flexible
and adjust dynamically to enhance the signal: noise ratio of the desired
geochemical target. Visualisation tools for manual validation are also
included. Conclusions: LABLASTER increases transparency and
repeatability by algorithmically identifying when the laser has either
ablated fully through a sample or across a mineral boundary and is thus
no longer documenting a geochemical signal associated with the desired
sample. LABLASTER’s focus on better data targeting means more accurate
extraction of biological and geochemical signals.