It is deduced from the rule of Uniformitarianism which proposed by James Hutton that reconstruction of ancient sedimentary depositional environments necessitates study of their modern analogous. Although modern sedimentary environments have successfully been used as a base for comparison to the ancient ones in last decades, but, many investigators have reached the conclusion that in many instances, such as the structures of ooid cortices, Epeiric seas, nature of geosynclines, and deposition of banded iron formations, etc. the present is hardly key to the past.
Considering this fact, how one can use the results of the studies of the modern sedimentary environments to infer ancient depositional models? the answer to this question goes back to the nature of scientific rezoning that is specific to geology in compare to the other field of science. In physics and chemistry known processes are followed via carefully controlled experiments to see what unknown products will result. Therefore, the reasoning is forward from process to product, but, by contrast, in geology the rock is the known product and processes are the unknowns. In the present article this fact has been evaluated through discussion about the structure of ooios cortices.