WHAT
TINY THINGS CAN TELL US
The
science of Micropalaeontology is the study of microfossils,
the microscopic remains of animals, plants and protists
belonging mostly to biological groups of simple organisation
(single cell) and less than a millimetre in size. Thus,
microfossils, unlike other kinds of fossils, are not grouped
according to their relationships to one another, but only
because of their generally small size and methods of study.
For example, fossils of bacteria, foraminifera, diatoms,
very small invertebrate shells or skeletons, spores and
pollen, and tiny bones and teeth of large
vertebrates, among others, can be called microfossils.
Micropalaeontology is perhaps the largest branch of paleontology,
with many specialists world-wide. Because of their small
size and frequently very high numerical abundance in rocks
and sediments, microfossils are the most
commonly used fossils for applied research. They are extremely
useful in age-dating, correlation and palaeoenvironmental
reconstruction, all important in the oil, mining, engineering,
and environmental industries, as
well as in general geology.
Microfossils
span the marine environment from the abyssal plains of
the deep sea to the salt marshes of the inter-tidal zone,
the freshwater aquatic environments of rivers and lakes
and the terrestrial realm. These organisms were extraordinarily
abundant and diverse in the past and continue to be so
in modern environments, in many cases forming the primary
elements in organic productivity cycles and food chains.
The production of these organisms is a basic component
of the global biogeochemical system, intimately linked
to present and past environmental change.
Some
of the more important groups of microfossils include:
Foraminifera, Coccolithophores, Spores and Pollen, Dinoflagellates,
Radiolarians, Diatoms, Ostracodes and Conodonts.
THE
K/T BOUNDARY
A bad moment in time
The
K/T Boundary is what we call the violent and sudden passing
in Earth’s history from the Cretaceous (K) Period,
the age of the dinosaurs, to the Tertiary (T) Period.
The
violent passing from one period to another occurred when
an asteroid hit the Earth about 65 million years, destroying
most marine and terrestrial life, including the dinosaurs.
The 10km wide asteroid fell on what today is the Yucatan
Peninsula of Mexico and blasted a 180km wide crater into
the earth. The heat and vapours incinerated North America,
destroying life there. Light and temperature changed so
drastically that 90% to 95% of the plankton became extinct.
Out of the few organisms that survived, life evolved as
we know it today.
Micropalaeontologists
have used deep sea cores, like the one recovered 2000
km from Florida in 1997 by JOIDES Resolution, in order
to explain why the dinosaurs became extinct.
In
this core we can see: a) in the lower part, pre-extinction
sediments that contained microfossils from the age of
the dinosaurs, b) in the middle, dust, ashes and other
material blasted from the collision, and c) at the top,
sediments containing microfossils of organisms that survived
or evolved afterwards.
Our
results come primarily from the study of the microfossils
in this core. Most of them belong to the category of foraminiferida,
microscopic single-celled marine organisms that floated
in the oceans. Look at the border of the showcase for
some of them in extreme close-up.
|
Did
you know there is a place on the planet where you
can walk on the ocean floor without getting wet?
It’s the island of Aphrodite, Cyprus. Cyprus
is actually a piece of the ocean floor that was thrown
up on the surface 100 million years ago in the Cretaceous
period. The island contains younger sediments allowing
micropalaeontologists to take larger sections of ocean
sediment from the surface for study, rather than drilling
deep-sea cores. |
CHALK
& THE CHANNEL TUNNEL
When plankton, tiny sea creatures, die, their remains
are deposited on the ocean floor. These remains are pressed
together as more as deposited on top of them, forming
what we call chalk. This means that areas like the White
Cliffs of Dover or the chalk fields in Sussex, Kent, and
the Downs must have once been at the bottom of the sea.
Chalk
was deposited 100 million years ago in the Cretaceous
period, when dinosaurs still roamed the planet. The tiny
creatures are identified today as foraminifera and nannofossils.
You can see enlarged photos of them taken from a Scanning
Electron Microscope all around this showcase.
Chalk
can be found in the north west part of Europe and Austin,
Texas.
It is not always white, as one might think, but can also
be reddish or greyish. When chalk contains more clay it
is grey – we call this Chalk Marl. Bands of this
kind of chalk are ideal for tunnelling because they are
more impermeable to water and possess the best properties
to core through. The construction of the Channel Tunnel,
between Folkstone and Coquelles, followed a Chalk Marl
horizon. The tunnelling machines were guided by its characteristic
microfossils.
PETROLEUM
One of the most important applications of micropaleontology
today is in oil exploration.
Petroleum
is derived from decayed phytoplankton, microorganisms
that live in the sea. When phytoplankton die, they sink
to the sea floor where they begin to accumulate. The deposited
phytoplankton is covered by other sediments and pushed
deeper into the crust of the Earth, where it is subjected
to higher pressures and temperatures. Only then will phytoplankton
change structure and become kerogen, heavy oil and finally
light oil, which is used for petroleum. This complex process
means that not all formerly marine environments will yield
petroleum.
The
remains of phytoplankton, microfossils, in petroleum-bearing
rocks undergo changes in colour because of heat. Micropaleontologists
study their alteration in colour to define possible areas
for oil exploration. When these fossilised microorganisms
are pale or orange the sediment is immature, when they
are brown the rocks are mature, indicating oil, and when
the fossils are black, they indicate gas.
ODP
The
Ocean Drilling Programme is an international partnership
of research institutions and scientists that study the
evolution and structure of the Earth. Eight international
members were added to the original 18 American Joint Ocean
Institutions in DATE. Today more than 20 countries fund
the research activities of ODP.
The drill ship JOIDES Resolution (Joint Oceanographic
Institutions Drilling Explorative Ship) is the main focus
of ODP. It is a transformed petroleum drilling ship built
in 1978 in Halifax, refitted in 1984 and equipped with
fine onboard laboratories. Every year the ship will go
on 6 two-month expeditions around the oceans. The task
of the ship’s crew is to drill cores, long cylindrical
holes 10cm in diameter and 9.5m in length, to a depth
of 8.2 km in the ocean floor.
In
1995, JOIDES Resolution sailed to Cote d’Ivoire
and Ghana with both tectonic and paleoceanographic objectives.
Scientists onboard (including Micropalaeontologists) helped
determine the timing of the separation of South America
from Africa to around 100 million years ago.
The
importance of the knowledge ODP contributes to our understanding
of the Earth can be compared to that of NASA for the exploration
of space.
Microfossils
To
learn more about Micropalaeontology and the stories they
can tell, and to look through a microscope at real specimens,
please visit the exhibition.
Resources
Micropalaeontology
at UCL
