Microfossils – what are they?

A thin blanket of soft white to buff-coloured ooze
covers one-sixth of the Earth’s surface. Seen under the
microscope this sediment can be a truly impressive
sight. It contains countless numbers of tiny shells variously
resembling miniature flügelhorns, shuttlecocks,
water wheels, hip flasks, footballs, garden sieves, space
ships and chinese lanterns. Some of these gleam with
a hard glassy lustre, others are sugary white or strawberry
coloured. This aesthetically pleasing world of
microscopic fossils or microfossils is a very ancient one
and, at the biological level, a very important one.
Any dead organism that is vulnerable to the natural
processes of sedimentation and erosion may be called a
fossil, irrespective of the way it is preserved or of how
recently it died. It is common to divide this fossil world
into larger macrofossils and smaller microfossils, each
kind with its own methods of collection, preparation
and study. This distinction is, in practice, rather arbitrary
and we shall largely confine the term ‘microfossil’
to those discrete remains whose study requires the use
of a microscope throughout. Hence bivalve shells or
dinosaur bones seen down a microscope do not constitute
microfossils. The study of microfossils usually
requires bulk collecting and processing to concentrate
remains prior to study.
The study of microfossils is properly called micropalaeontology.
There has, however, been a tendency to
restrict this term to studies of mineral-walled microfossils
(such as foraminifera and ostracods), as distinct
from palynology the study of organic-walled microfossils
(such as pollen grains, dinoflagellates and
acritarchs). This division, which arises largely from
differences in bulk processing techniques, is again
rather arbitrary. It must be emphasized that macropalaeontology,
micropalaeontology and palynology
share identical aims: to unravel the history of life and
the external surface of the planet. These are achieved
more speedily and with greater reward when they
proceed together.