Taebaek Group (Cambrian-Ordovician) in the Seokgaejae section, Taebaeksan Basin: a refined lower Paleozoic stratigraphy in Korea

Untangling intricate microbial–sponge frameworks: The contributions of sponges to Early Ordovician reefs

“…The Taebaek Group is a subunit of the Joseon Supergroup consisting of 10 lithostratigraphic units (Choi, 1998;Choi and Chough, 2005). The 150-to 250-m-thick Dumugol Formation of the Taebaek Group consists of a sequence of alternating calcareous shale and limestone, which is interpreted to represent inner to outer ramp deposits (Lee and Choi, 1987;Lee and Kim, 1992;Kim and Lee, 1998;Kwon et al, 2003Kwon et al, , 2006Choi et al, 2004;Kwon and Chough, 2005). Trilobite and conodont biozones indicate that the formation is of middle Tremadocian to middle Floian (Early Ordovician) age (Kim et al, 1991;Seo et al, 1994).…”

Conodonts from the Hwajeol Formation (Upper Cambrian) in the Seokgaejae area, southeast margin of the Taebaeksan Basin

“…The upper part consists of nodule-bearing shale, laminated fine-grained sandstone and calcareous shale with limestone pebble conglomerate. Kobayashi (1935) correlated the Hwajeol Formation with the Chaumitian Series (upper part of the Furongian) of China based on his megafossil collection, and Choi et al (2004) and Sohn and Choi (2007) correlated their Asioptychaspis, Quadraticephalus and Mictosaukia faunas with the uppermost Cambrian faunas of North China and Australia.…”

“…The shale-dominant facies includes calcareous shale, nodule-bearing shale and laminated fine-grained sandstone, whereas the carbonate-dominant facies consists of flaser wackestone to packstone, massive grainstone, limestoneshale couplets and limestone pebble conglomerate (Choi et al, 2004). Choi et al (2004) divided the Hwajeol Formation in the Seokgaejae section into three parts, consisting of lower (34 m thick), middle (14 m thick) and upper (ca. 5 m thick) parts.…”

“…Kobayashi (1935) first recognized five megafossil zones in the Upper Cambrian Hwajeol Formation, namely Prochuangia, Chuangia, Kaolishania, Dictyites and Eoorthis zones in stratigraphic order. Recently Choi et al (2004) and Sohn and Choi (2007) recognized Asioptychaspis, Quadraticephalus and Mictosaukia zones from the Hwajeol Formation.…”

“…(B) Detailed geologic map of the Seokgaejae area, showing section locations (A, B), southeast Taebaeksan Basin (modified fromChoi et al, 2004;Kwon and Chough, 2005).…”