The Ordovician succession of the Taebaek Group (Korea) revisited: old conodont data, new perspectives, and implications

We recompiled available Ordovician conodont data from previous studies for the Taebaek Group of the Taebaeksan Basin, Korea, based on the recently revised Ordovician conodont biostratigraphic scheme for North China. The recompiled Ordovician Taebaek Group conodont data conform well with the middle Tremadocian, lower Floian, and middle Darriwilian biozones of North China. The overall conodont distribution patterns, the occurrence of endemic species found only in North China, and the presence of an Upper Ordovician hiatus reaffirms the close relationship of the Taebaeksan Basin to the North China (Sino-Korean) Block. In addition, the absence of middle Floian to lower Darriwilian conodonts in the Taebaek Group and sudden appearance of abundant middle Darriwilian conodonts raises the possibility of the presence of a hiatus in the Lower Ordovician of the Taebaek Group. The possible disconformity may be located at the uppermost contact of the massive dolostone interval (the basal member) of the Makgol Formation. Lithologic evidence for the discontinuity includes the presence of local brecciation and oversized vuggy pores immediately below the contact and that of numerous dolomitic clasts above the contact.