Geologic age and depositional environment can be interpreted from both modern- and paleo-marine sediments using calcareous nannofossils (nannos). All nannos are less than 25 microns (0.025 mm), are widely distributed, and typically occur in large quantities, which means that statistically significant counts can be quickly generated for interpretation. The nanno fossil record starts in the mid-Jurassic, and the nature of their rapid evolution makes for an excellent high-resolution chronostratigraphic tool through to the present day. Finally, given the non-ubiquitous nature of microfossils, if one group is absent, you need to be able to use another. 

Nannos are easily collected from sediment cores, cuttings, or field samples; and the amount of sediment that can fit on the tip of a toothpick is all that is needed to prepare a smear slide before examination can begin. Nanno samples are the least time-intensive and most cost-effective to prepare. They are the safest to prepare, too, as no chemical treatment is required. Consider them for your next project!