Palynology is the study of organic (i.e., non-mineralised) microfossils, especially those in sediments, either of terrestrial (land), freshwater, or marine (sea) origin. These microfossils are very small, generally falling into the 5 - 500 micro-millimetre range, and are found in rocks of all geological ages, beginning about 1.4 billion years ago in the late Precambrian Eon right up to the present.
The most widely studied groups of microfossils are pollen grains and spores produced by plants. This sub-field of palynology is often called "pollen analysis". Pollen-producing plants first appeared in the late Devonian Period, about 360 million years ago, and have become the dominant plant type over most of the earth. The earliest types of pollen-producing plants were gymnosperms (which means literally "naked seed"), of which the best-known modern group are the conifers, such as spruce and firtrees. Flowering plants, or angiosperms (meaning "enclosed seed" plants), first appeared somewhat later, about 120 million years ago in the early cretaceous period. Because these plants have become increasingly abundant and diverse from the Devonian Period to the present, pollen grains have become more dominant in the geologic record and spores have consequently decreased in abundance. In most modern samples, for instance, pollen grains generally form more than 95 per cent of the sample.
Pollen grains and spores are about the same size, are dispersed and deposited in similar ways, and are often found together. For these reasons, "pollen analysis" refers to the study of both. Pollen analysts look at material from the geologic past and also at today's, production and distribution, of pollen and spores.
Palynology has wide application in the earth and natural sciences. For instance, it can be used to correlate and provide relative ages for layers of rock, mainly in oil exploration (stratigraphic palynology), and to understand vegetation distributions and reconstitution of past vegetation and environments (biogeography) and climate changes of the past (palaeoecology, especially in the quartenary Period). It can be used to investigate what plants were available to people living in past landscapes (archaeopalynology or geoarchaeology), studies of human impact on vegetation and finally genetic and evolutionary studies. Palynology is also used to monitor the production and dispersal of pollen in the atmosphere (allergy studies or aerobiology), to confirm the type and purity of honey and its country of origin (melissopalynology), and, in recent police work, to trace the origin of illegal drug shipments (forensic palynology), correlating deposits and tentative dating.
(Alwynne B. Beaudoin, Canada).