• Journal of the Korean earth science society
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• v.21 no.4
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• pp.449-468
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• 2000

The Ordovician Chongson Limestone deposited in the carbonate ramp to the rimmed shelf shows diverse diagenetic features. The marine diagenetic feature appears as isopachous cements surrounding ooids and peloids. Meteoric diagenetic features are recrystallized finely and coarsely crystalline calcite, evaporite casts filled with calcite, and isopachous sparry calcite surrounding ooid grains. Shallow burial diagenetic features include wispy seam, microstylolite, and dissolution seam whereas deep burial features include stylolite, burial cements. blocky calcite with twin lamellae, and poikilotopic calcite. Dolomites consist of very finely to finely crystalline mosaic dolomite formed as supratidal dolomite, disseminated dolomite of diverse origin, patchy dolomite formed from bioturbated mottles, and saddle dolomite of burial origin. Silicified features include calcite-replacing quartz and fracture-filling megaquartz. Burial cements characterized by poikilotopic texture show ${\delta}^{18}$O value of -10.4 %$_o$ PDB, ${\delta}^{13}$C value of -1.0%$_o$ PDB and 504ppm Sr, 3643ppm Fe, and 152ppm Mn concentrations. Finely and coarsely crystalline limestones show similar ${\delta}^{18}$O and ${\delta}^{13}$C value to those of burial cements; however, they show lower Sr and higher Fe and Mn concentrations than burial cements. This suggests that very finely and coarsely crystalline limestones were recrystallized in freshwater and then they were readjusted geochemically in the burial setting whereas the burial cements were formed in relatively high temperature and low water/rock ratio conditions. Very finely and finely crystalline mosaic dolomites with ${\delta}^{18}$O value of -8.2%$_o$ PDB, ${\delta}^{13}$C value of -1.9 %$_o$ PDB, and 213ppm Sr, 3654ppm Fe, and 114ppm Mn concentrations, respectively are interpreted to have been formed penecontemporaneously in supratidal flat and then recrystallized in the low water/rock ratio burial environment. Geochemical data suggest that the low water/rock ratio burial environment was the dominant diagenetic setting in the Chongson Limestone. The Chongson Limestone has experienced marine and meteoric diagenesis during early diagenesis. With deposition of Haengmae and Hoedongri formations part of the Chongson Limestone was buried beneath these formations and it experienced shallow burial diagenesis. During the Devonian the Chongson Limestone was tectonically deformed and subaerially exposed. During the Carboniferous to the Permian about 3.3km thick Pyongan Supergroup was deposited on the Chongson Limestone and the Chongson Limestone was in deep burial depths and stylolite, burial cements, blocky calcite and saddle dolomite were formed. After this burial event the Chongson Limestone was subaerially exposed during the Mesozoic and Cenozoic by three periods of tectonic disturbance including Songnim, Daebo and Bulguksa disturbance. Since the Bulguksa disturbance during Cretaceous and early Tertiary the Chongson Limestone has been subaerially exposed.