The Tanabe Research Group had studied the Miocene Tanabe Group which consists of shallow marine strata and intercalates no traceable marker layers, with the collaborating research method in the last two decades. The lithostratigraphic divisions of the Tanabe Group were first established in 1984. However, the divisions of the strata in this stratigraphy were based only on the composition of rock types, such as sandstone, alternating beds of sandstone and mudstone, conglomerate, etc., while the sedimentary mechanisms and environments were not well studied. Therefore, the difference between strata deposited by different mechanisms could not be distinguished, if the lithology resembles each other. During the period from 1986 to 1992, the Tanabe Research Group analysed the sedimentary facies of the lower half of the group (the Asso Formation). And since 1993, the author has studied the sedimentary facies of the upper half of the group (the Shirahama Formation). These studies has established the high resolution stratigraphy and reconstructed the paleoenvironments and relative sea level fluctuations in detail. The author emphasizes the necessity of the sedimentary facies analysis for establishing the stratigraphy.
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