One place microfossils accumulate is the abyssal floor of the ocean, more than half of the earth's surface, which is buried under a blanket of microfossil-rich formations that slowly accumulates like a rain of dust. Changes in the abundance and types of microfossils from year to year, over millions of years of undisturbed accumulation, makes an exquisitely detailed record of climate change, plate tectonics, and biological evolution. Such marker horizons allow geological events in different parts of the world to be related in a global earth history. Microfossil data also revealed that changes in sea levels, temperature, and glacial advances were synchronous worldwide, proving the reality of global climate changes more accurately than geochemical dating methods. Recently, micropaleontology has documented how oscillations in the earth's orbit and tilt have created cyclic variation in global climate, especially during the Ice Ages.
Microfossils are vital to oil exploration.
Because of their tiny size and great abundance, they occur unbroken in the rock fragments brought up by drilling into the deeply-buried ocean formations and lake beds where oil is found. The characteristic fossils from each formation enable geologists to unravel the geometry of the strata far beneath the surface, tracing the domes and traps that may hold oil. The condition of the fossils, as well, indicates whether the petroleum source rocks have been buried and heated sufficiently to generate oil from trapped organic matter. The organic matter itself is almost entirely from ancient micro-organisms. Important groups of microfossils are also found among animals and plants, for instance the ostracodes , tiny free-swimming crustaceans in the same family as barnacles.