Trilobite Biostratigraphy of the lower Paleozoic (Cambrian–Ordovician) Joseon Supergroup, Taebaeksan Basin, Korea

Abstract

In Korea, trilobites are among the most intensively studied fossil groups in the past century and provide invaluable information about lower Paleozoic stratigraphy, paleogeography, and tectonics of the Korean Peninsula. Trilobites occur in the lower Paleozoic Joseon Supergroup of the Taebaeksan Basin which was part of the Sino‐Korean Craton in the Paleozoic. The Joseon Supergroup is divided into the Taebaek, Yeongwol, and Mungyeong groups. The Taebaek and Yeongwol groups are richly fossiliferous, while the Mungyeong Group is poorly fossiliferous. Contrasting trilobite faunal contents of the Taebaek and Yeongwol groups resulted in two separate biostratigraphic schemes for the Cambrian–Ordovician of the Taebaeksan Basin. A total of 22 biozones or fossiliferous horizons were recognized in the Taebaek Group; 19 zones were established in the Yeongwol Group; and four biozones were known from the Mungyeong Group. These trilobite biozones of the Taebaeksan Basin indicate the Joseon Supergroup ranges in age from the Cambrian Series 2 to Middle Ordovician and can be correlated well with the formations of North China, South China, and Australia.

Evolution of the Taebaeksan Basin, Korea: I, early Paleozoic sedimentation in an epeiric sea and break‐up of the Sino‐Korean Craton from Gondwana

“…The Taebaek Group was known to have formed in a carbonate‐siliciclastic platform, governed by sea‐level fluctuations (Kwon, Chough, Choi, & Lee, ). A total of 22 trilobite biozones are recognized in the Taebaek Group (Choi, Lee, Lee, Park, & Hong, ) and warrant the assignment of geologic ages from the Cambrian Stage 3 to Darriwilian (Figure ).…”

“…The lowermost Sambangsan Formation is composed of siliciclastic sedimentary rocks, whereas the upper four formations consist predominantly of carbonate rocks. Nineteen trilobite zones were established within the Yeongwol Group (Choi et al, ) and the geologic age of the group can be bracketed within the Cambrian Stage 3 to Darriwilian (Figure ).…”

“…No shelly fossils are recorded in the Jangsan Formation, whilst J. Y. Kim () reports the occurrence of a trace fossil Skolithos in the Myeonsan Formation. In reference to the biostratigraphical information of the overlying Myobong Formation (Choi et al, ), the age of the Jangsan/Myeonsan Formation is assigned to the Cambrian Stage 3 (Figure ).…”

Depositional history, tectonics, and provenance of the Cambrian-Ordovician boundary interval in the western margin of the North China block: Reply

“…In Table 1of Myrow et al (2015Myrow et al ( , p. 1190, we listed the section as containing a "brief unconformity between the uppermost Cambrian and lowermost Ordovician" based on detailed sedimentological and sequence-stratigraphic work of Kwon et al (2006). Lee and Lee state that "Late Furongian to earliest Tremadocian trilobite biozones successively occur across the Hwajeol and Dongjeom formations, which are well correlated to those of North China and other parts of the world (Choi and Chough, 2005;Choi et al, 2016)." Lee and Choi (2007) presented the most detailed biostratigraphic data for the Dongjeom Formation, which has a fossiliferous lower member and sandstonedominated unfossiliferous middle and upper members.…”

Depositional history, tectonics, and provenance of the Cambrian-Ordovician boundary interval in the western margin of the North China block: COMMENT

“…In the Taebaek area of Korea (Taebaeksan Basin), an ~1200-m-thick mixed carbonatesiliciclastic sequence was deposited from the Cambrian Series 2 to the Middle Ordovician (Kwon et al, 2006). The Cambrian-Ordovician boundary lies in the basal part of the Dongjeom Formation, which conformably overlies the Hwajeol Formation (Choi et al, 2016). Evidence of a time gap or sedimentary hiatus across the Cambrian-Ordovician boundary is not recognized in this area, which can be noted from detailed sedimentological and paleontological studies performed in the area over the past 30 yr (e.g., Woo and Park, 1989;Choi et al, 2003Choi et al, , 2016Choi and Chough, 2005;Kwon et al, 2006;Choi, 2007, 2011).…”