Middle Cambrian siliceous sponge-calcimicrobe buildups (Daegi Formation, Korea): Metazoan buildup constituents in the aftermath of the Early Cambrian extinction event Jongsun Hong a, 1 , Seong-Hyeon Cho a, 1 , Suk-Joo Choh a, ⁎, Jusun Woo b, 2 , Dong-Jin Lee c, 3 a Department of Earth and Environmental Sciences, Korea University, Seoul 136–713, Republic of Korea b Division of Polar Earth-System Sciences, Korea Polar Research Institute, Incheon 406–840, Republic of Korea c Department of Earth and Environmental Sciences, Andong National University, Andong 760–749, Republic of Korea abstract article info Article history: Received 26 November 2011 Received in revised form 21 January 2012 Accepted 23 January 2012 Available online 31 January 2012 Editor: B. Jones Keywords: Middle Cambrian (Series 3) Metazoan-microbial buildup Siliceous sponge Epiphyton Numerous decimetre- to metre-scale carbonate buildups dominated by siliceous sponges and the calcimic- robe Epiphyton are reported from the Middle Cambrian (Series 3) Daegi Formation of Korea. These siliceous sponge-Epiphyton buildups consist predominantly of grey micritic boundstones with dark clots and/or white clumps. The boundstones contain sponge spicule networks interpreted as the calcified remains of siliceous sponges. The white clumps and dark clots in the boundstones represent variously preserved Epiphyton. Siliceous sponges form constructional pore space and are commonly encrusted by Epiphyton. The sponges were probably the primary frame-builders, providing substrates for the attachment and subsequent growth of Epiphyton. Epiphyton is considered to be a binder when covering the surface of siliceous sponges, and a subordinate frame-builder when filling depositional voids created by siliceous sponges or growing on top of other Epiphyton growth bundles. The siliceous sponge-Epiphyton buildups of the Daegi Formation show similarities to previously described Late Cambrian (Furongian) anthaspidellid-calcimicrobe buildups from Iran and the USA. Together with recently reported examples from the Zhangxia Formation of eastern China, the sponge–Epiphyton buildups from Korea represent some of the oldest metazoan-calcimicrobe buildups, after the extinction of most archaeo- cyaths at the end of the Early Cambrian (Series 2). This implies that the incorporation of metazoans in Middle Cambrian (Series 3) carbonate buildups occurred much earlier than previously known. The buildup-forming siliceous sponges described in this study demonstrate that their role in Early Phanerozoic carbonate buildups has been grossly underestimated. © 2012 Elsevier B.V. All rights reserved. 1. Introduction The first metazoan-bearing carbonate buildups appeared in the early Neoproterozoic (Neuweiler et al., 2009), followed by those built by archaeocyath-calcimicrobe associations in the Early Cambrian (Terreneuvian and Series 2) (Rowland and Gangloff, 1988; Rowland and Shapiro, 2002). Renalcis-dominated archaeocyath-calcimicrobe buildups initially appeared on the Siberian Platform in the middle Early Cambrian (late Terreneuvian; Tommotian) and became widespread during the late Early Cambrian (early to middle Series 2; Atdabanian and Botomian), occurring throughout both Gondwana and Laurentia (Kruse et al., 1995; Riding and Zhuravlev, 1995). These buildups consisted of metazoans such as archaeocyaths, radiocyaths, coralo- morphs, cribricyaths, and siliceous sponges, together with various calci- microbes, including Epiphyton, Renalcis, Girvanella and Botomaela (James and Gravestock, 1990; Wood et al., 1993; Wood, 1999; Rowland and Shapiro, 2002). Toward the end of the Early Cambrian (Series 2), metazoan-calcimicrobe buildups were composed of archaeocyaths of reduced diversity, as well as the calcimicrobes Renalcis, Epiphyton, Girvanella, and Serligia (Kobluk and James, 1979; James and Klappa, 1983; Rowland and Shapiro, 2002). The end-Early Cambrian (Series 2) extinction of archaeocyaths dramatically changed the characteristics of carbonate buildups (Zhuravlev, 1996)(Fig. 1); after the extinction, Middle Cambrian (Series 3) to earliest Ordovician carbonate buildups are typically dominated by the calcimicrobes Renalcis, Girvanella, and Epiphyton (Heckel, 1974; Wood, 1999; Rowland and Shapiro, 2002; Webby, 2002). Metazoans such as anthaspidellid sponges are sparse in Late Cambrian (Furongian) buildups (Table 1). In this study we document and assess buildups from the Middle Cambrian (Series 3) Daegi Formation of Korea, which represent some of the first metazoan-calcimicrobe buildups to occur after the end-Early Cambrian (Series 2) archaeocyath extinction. The buildups Sedimentary Geology 253-254 (2012) 47–57 ⁎ Corresponding author. Tel.: + 82 2 3290 3180. E-mail addresses: bulgeun@korea.ac.kr (J. Hong), meosi@naver.com (S.-H. Cho), sjchoh@korea.ac.kr (S.-J. Choh), jusunwoo@kopri.re.kr (J. Woo), djlee@andong.ac.kr (D.-J. Lee). 1 Fax: +82 2 3290 3189. 2 Fax: +82 3 2260 6243. 3 Fax: +82 5 4822 5467. 0037-0738/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.sedgeo.2012.01.011 Contents lists available at SciVerse ScienceDirect Sedimentary Geology journal homepage: www.elsevier.com/locate/sedgeo