Palynology

the study of (mainly fossil) pollen, spores and some other microfossils. It deals primarily with structure, classification and distribution and is used in petroleum exploration, and palaeoclimatology (the study of ancient climates). In the main, the spores and pollen are highly resistant and in some sedimentary sequences are the only fossils that can be used for stratigraphic correlation (matching one rock with a similar rock elsewhere which is of the same age).

Taken from Dictionary of Science