Experimental setup
A single planktonic foraminifer case study is included in the package as
a worked example. Planktonic foraminifera are unicellular zooplankton
distributed throughout the world’s oceans as a key resource in
understanding Earth’s climate system1, 2 and the
evolution of biodiversity16. The thickness of a
fossilised foraminifera test can vary substantially even within an
individual. Some have thick solid chamber walls while others have a
highly porous structure as a result of species specificities, biological
controls and environmental influences. This natural variability is the
motivation for our development of automated processing methods and thus
better control of geochemical “vital effects” (Kearns et al, submitted
to Paleoceanography and Paleoclimatology ). Foraminifera grow
connected chambers throughout their life with those in the final whorl
accessible for LA-ICP-MS analysis17 (Figure 1). The
case study is from the antepenultimate chamber of Menardella
exilis foraminifera 72, identified hereon as “Foram-72-shot-3”.
The experimental setup is described fully in Kearns et al. (in review).
Briefly major and trace elements in the foraminifera test were analysed
using a New Wave UP193 laser ablation system (ArF source, 30 µm spot
diameter, a fluence of 0.73 J/cm3 and 5 Hz pulse rate)
coupled to an Agilent 8900 triple quadrupole inductively coupled plasma
(ICP-QQQ) mass spectrometer in single quadrupole mode using a He and Ar
gas mixture (900 ml/min) at the University of Southampton. Each laser
spot pattern was sequenced with a 30 s warmup, 50 s laser pulse and 30 s
washout. The default values within this endPoint function are based on
outputs from this setup.
Initial processing of the time resolved acquisition data was performed
within the R environment (version 4.2.2). The first 30 seconds were used
to calculate the background signal and then removed. The next five
seconds were removed as the isotopic signal begins to rise for the laser
has started pulsing but the ablated material is still travelling through
the system piping. As our washout time was enough to purge the system
after each analysis, the duration of this signal rise was regular and
reproducible.