Of these innumerable life forms, only a few kinds leave solid remains that fossilize, but even these few can be so abundant that in places they form mountains of pure fossil remains. Changes in the abundance and types of microfossils in these micro-thin layers provide an exquisitely detailed record of the geological past, in response to 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 reveal the global synchroneity of changes in sea levels, temperature, and glacial advances, to show the reality of worldwide climate changes more accurately than geochemical dating methods. Recently, micropaleontology has confirmed mathematical predictions that cycles of global climate change, especially during the Ice Ages, are due to oscillations in the earth's orbit and tilt.
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.