Jino Park

Revised stratigraphy of the Xiazhen Formation (Upper Ordovician) at Zhuzhai, South China, based on palaeontological and lithological data

Lee, D.-C., Park, J., Woo, J., Kwon, Y.K., Lee, J.-G., Guan, L., Sun, N., Lee, S.-B., Liang, K., Liu, L., Rhee, C.-W., Choh, S.-J., Kim, B.-S. & Lee, D.-J., September 2012. Revised stratigraphy of the Xiazhen Formation (Upper Ordovician) at Zhuzhai, South China, based on palaeontological and lithological data. Alcheringa 36, 393–412. ISSN 0311-5518. Three exposures of the Upper Ordovician Xiazhen Formation at Zhuzhai, Yushan, Jiangxi Province, China are re-measured and described in detail. Comparison of palaeontological and lithological data from the exposures (designated sub-sections ZU1, ZU2 and ZU3) reveals that the sub-sections overlap stratigraphically. Nearly identical assemblages of trilobites and brachiopods occur in mudstones of ZU1 and ZU3, whereas a different assemblage occurs in those of ZU2. Identical coral species occur in the overlapped intervals of ZU1 and ZU2, and ZU1 and ZU3, respectively. In addition, a distinctive identical lithological succession consisting of brachiopod-bearing nodular limestone at the base to coral floatstone at the top is evident in the overlapped interval of ZU1 and ZU2; prism-cracked algal laminites are found in the same interval; and bioclastic limestone beds, which represent bioherms consisting mainly of corals and stromatoporoids, occur in both ZU1 and ZU3. A thrust fault system appears to be responsible for the repetition in the subsections, and the faulting was probably due to the major post-Ordovician structural movements exerted on the Zhe-Gan Platform of the Jiangnan Region of the South China Block. Dong-Chan Lee [dclee@hit.ac.kr], Department of Heritage Studies, Daejeon Health Sciences College, 300-711, Daejeon, Republic of Korea; Jino Park [jinopark@korea.ac.kr], Suk-Joo Choh [sjchoh@korea.ac.kr], Department of Earth and Environmental Sciences, Korea University, 136-701, Seoul, Republic of Korea; Jusun Woo [jusunwoo@kopri.re.kr], Division of Polar Earth-System Sciences, Korea Polar Research Institute, 406-840, Incheon, Republic of Korea; Yi Kyun Kwon [kyk70@kigam.re.kr], Marine and Petroleum Division, Korea Institutue of Geoscience and Mineral Resources, 305-350, Daejeon, Republic of Korea; Jeong-Gu Lee [leejg@mest.go.kr], Seung-Bae Lee [sblee@mest.go.kr], Exhibition Planning and Coordination Division, Gwacheon National Science Museum, 427-060, Gwacheon, Republic of Korea; Liming Guan [glm.1103218@yahoo.com], Ning Sun [sun@andong.ac.kr], Kun Liang [ibcaskun@126.com], Lu Liu [liulu323@hotmail.com], Department of Earth and Environmental Sciences, Andong National University, 760-749, Andong, Republic of Korea; Dong-Jin Lee [djlee@andong.ac.kr], Department of Earth and Environmental Sciences, Andong National University, 760-749, Andong, Republic of Korea and College of Earth Science, Jilin University, Changchun 130061, PR China; Chul-Woo Rhee [gloryees@chungbuk.ac.kr], Department of Earth and Environmental Sciences, Chungbuk National University, 361-763, Cheongju, Republic of Korea; Byong-Song Kim [kbs1972@163.com], Department of Resources Exploration Engineering, Kim Chaek University of Technology, Pyongyang, Democratic Peoples Republic of Korea and College of Earth Science, Jilin University, Changchun 130061, PR China. Received 16.10.2011, revised 4.1.2012, accepted 16.1.2012.

Early labechiid stromatoporoids of the Yeongheung Formation (Middle Ordovician), Yeongwol Group, mideastern Korean Peninsula: Part I. Environmental distribution

This study examines depositional facies and environmental significance of early labechiid stromatoporoids in the Yeongheung Formation (late Middle Ordovician), Yeongwol Group in the mideastern part of the Korean Peninsula. The formation is composed of five depositional facies: lime mudstone to wackestone (LM/W), peloidal, intraclastic and bioclastic packstone to grainstone (P/G), laminated dolomitic lime mudstone (LMdl), algal laminite (La), and oolitic packstone to grainstone (P/Go). Three types of shallowing upward cycles in the succession are identified, including subtidal (LM/W–P/G), subtidal to peritidal (LM/W–P/G–LMdl–La), and peritidal cycles (LMdl–La). The stromatoporoids occur exclusively in the packstone to grainstone (P/G) facies of the subtidal cycle. These early labechiids inhabited on a grainy substrate under moderate- to high-energy conditions, conforming to the previous notion that stromatoporoids primarily occupied level-bottom or reefs, surrounded by grainy calcareous sediments during the Middle Ordovician.

Early labechiid stromatoporoids of the Yeongheung Formation (Middle Ordovician), Yeongwol Group, mideastern Korean Peninsula: Part II. Systematic paleontology and paleogeographic implications

Three species belonging to two genera of labechiid stromatoporoids are described from the Yeongheung Formation (Darriwilian, Middle Ordovician), Yeongwol Group of the Taebaeksan Basin, mid-eastern Korean Peninsula. Sixteen stromatoporoid-bearing stratigraphic intervals have been recognized in the Namgyo section. All stromatoporoids occur in the peloidal and bioclastic packstone to grainstone facies. Labechia yeongwolense sp. nov. is the dominant species, occurring throughout the lower and middle parts of the section. In contrast, Labechiella mingshankouensis is restricted to the lower-middle part and Labechiella regularis occurs mostly in the upper part of the section. The occurrence of the early labechiids in the Yeongwol Group is suggestive of a close biogeographic affinity with the Liaoning and Shandong provinces of northeastern China.