My name's Jack and I'm a PhD student
here at the University of Birmingham.
In geology the term salt can encompass any
rock which formed mainly through
evaporation.
This is Rory by the way.
When oceans dry up and evaporate they leave behind
minerals that precipitate out.
The first of those is calcite, which you can find in caves as stalagtites and stalagmites.
The next of them is gypsum. Which you can find on your walls at home.
And then the mineral after that is halite, or table salt.
Which you'll put on your fish and chips on a Friday.
And this is what I
study for my PhD, I study salt.
Let me explain something.
Salt is unique, it's made out of crystals
but its weak.
Once a layer of salt has
formed it will be covered in sediment;
in this case mud.
Salt is incompressible
which means as it gets buried its
buoyancy will remain the same whilst the
rocks around it will become denser.
I'm studying the ways in which the salt
deforms and interacts with the sediments
adjacent to it using magnetics.
As it is buried the base of the salt
sinks but the top of the salt remains at
the surface eventually resulting in
the underground salt structures that can
be kilometers deep, these are called
diapirs. And the process of salt
movement is called a halokinesis.
Salt is also impermeable to fluids and gases,
meaning that it's economically important
when it comes to oil and gas.
But, salt doesn't occur just anywhere around the world.
So I went to nova scotia to study
the Carboniferous age rocks there.
In Nova Scotia I could retrieve halite
samples for magnetic analysis from a
working salt mine. The gypsum at the
surface is at the top of a three
kilometer deep salt diapir and shows
signs of extreme deformation, that can be
related back to geological events of the
past. To study the way the salt has
deformed I had to collect orientated
samples so that our laboratory
measurements could be relocated to
nature. By using drones we can create 3D
models of the structures seen in the
gypsum exposures and this helps us
correlate them across cliff sections.
Now you know how and why I collected the rocks
it's time to get dirty in the lab.
I start by drilling the rock samples into cores.
This Kappabridge rotates the samples in very low magnetic fields
showing us if there
is any alignment of magnetism in the rocks.
This might be due to impurities in
the rock or because of the mineral crystals.
Through 3D modeling I can
compare the magnetic fabrics with the
visible gypsum structures, and to find
out what is producing the magnetism I
use extremely high magnification images
of the sample surfaces.
This PhD is a novel use of an established technique
called anisotropy of magnetic susceptibility.
