With its unique green color and pellet-like shape, glauconite contrasts remarkably with the surrounding rocks. Currently there are three generally adopted concepts: glauconite is a kind of typical marine sedimentary mineral, special in-situ glauconite is one of the diagnostic minerals indicative of slow depositional rate, weak reduction and deep-water environment, glauconites are often deposited during the transgressive period, and therefore the glauconite-bearing formations in shallow sediments are often regarded as condensed section in the transgressive period. Glauconites are ideal measurement objects of K-Ar and ⁴⁰Ar/³⁹Ar ages. Their genesis, evolution, and sedimentary as well as stratigraphic significance have been widely used. It should be noted that glauconites can be formed in a variety of sedimentary environments, only in-situ glauconites can be used to identify the condensed section, but its age may be younger or older than the real age.