Palaeoworld 16 (2007) 16–30 Research paper The Capitanian (Permian) Kamura cooling event: The beginning of the Paleozoic–Mesozoic transition Yukio Isozaki a,∗, Hodaka Kawahata b, Kayo Minoshima c a Department of Earth Science and Astronomy, The University of Tokyo, Komaba, Meguro, Tokyo 153-8902, Japan b Graduate School of Frontier Sciences and Ocean Research Institute, The University of Tokyo, Minamidai, Nakano, Tokyo 164-8639, Japan c Geological Survey of Japan, AIST, Tsukuba 305-8567, Japan Received 4 January 2007; received in revised form 12 May 2007; accepted 15 May 2007 Available online 25 May 2007 Abstract 13 The Capitanian (late Guadalupian) high positive plateau interval of carbonate carbon isotope ratio (␦ Ccarb) was recognized lately in a mid-Panthalassan paleo-atoll limestone in Japan as the Kamura event. This unique episode in the late-middle Permian indicates high productivity in the low-latitude superocean likely coupled with resultant global cooling. This event ended shortly before the Guadalupian–Lopingian (middle-late Permian) boundary (ca. 260 Ma); however, its onset time has not been ascertained previously. Through a further analysis of the Wordian (middle Guadalupian) to lower Capitanian interval in the same limestone at 13 Kamura in Kyushu, we have found that the ␦ Ccarb values started to rise over +4.5‰ and reached the maximum of +7.0‰ within the Yabeina (fusuline) Zone of the early-middle Capitanian. Thus the total duration of the Kamura event is estimated over 3–4 million years, given the whole Capitanian ranging for 5.4 million years. This 3–4 million years long unique cooling event occurred clearly after the Gondwana glaciation period (late Carboniferous to early Permian) in the middle of the long-term warming trend toward the Mesozoic. This cooling may have been a direct cause of the end-Guadalupian extinction of low-latitude, warm-water adapted fauna including the large fusulines (Verbeekinidae), gigantic bivalves (Alatoconchidae), and rugose corals (Waagenophyllidae). The 13 Kamura event marks the first sharp excursion of ␦ Ccarb values in the volatile fluctuation interval that lasted for nearly 20 million 13 years from the late-Middle Permian until the early-Middle Triassic. This interval with high volatility in ␦ Ccarb values represents the transition of major climate mode from the late Paleozoic icehouse to the Mesozoic–Cenozoic greenhouse regime. The end- Paleozoic double-phased extinction occurred within this interval and the Capitanian Kamura event is regarded as the prelude to this transition. © 2007 Nanjing Institute of Geology and Palaeontology, CAS. Published by Elsevier Ltd. All rights reserved. Keywords: Guadalupian; C isotope; Panthalassa; Permo-Triassic boundary; Extinction; Productivity 1. Introduction history (e.g., Erwin, 1993, 2006); however, it was not long time ago when its double-phased nature became The terminal Paleozoic mass extinction represents the widely recognized. Jin et al. (1994) and Stanley and greatest in magnitude throughout the Phanerozoic life Yang (1994) first pointed out that the Permian biodi- versity declined in two steps separated clearly from each other; i.e., first at the Middle-Late Permian boundary ∗ (=Guadalupian–Lopingian boundary; G–LB) and sec- Corresponding author. Tel.: +81 3 5454 6608; fax: +81 3 3465 3925. ond at the Permo-Triassic boundary (P–TB) sensu stricto E-mail address: [email protected] (Y. Isozaki). (or Changhsingian–Induan boundary). 1871-174X/$ – see front matter © 2007 Nanjing Institute of Geology and Palaeontology, CAS. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.palwor.2007.05.011 Y. Isozaki et al. / Palaeoworld 16 (2007) 16–30 17 In contrast to the P–TB issue, not much attention mental change and relevant extinction event. A particular has been paid to the G–LB event; however, the signif- emphasis is given to the Kamura event in the context icance of the G–LB event was re-emphasized from a of a long-term change in environmental regime during different aspect relevant to the superocean Panthalassa. the nearly 20 million years of the Paleozoic–Mesozoic The timing of the end-Guadalupian extinction apparently transition. coincides with the onset of the superanoxia in Pantha- lassa, i.e., another global scale geologic phenomenon 2. Geologic setting across the P–TB (Isozaki, 1997a, 2007). In addition to the faunal turnover in mid-oceanic plankton (radiolari- The Permian and Triassic limestone at Kamura ans) detected in deep-sea chert, shallow marine sessile (Takachiho town, Miyazaki prefecture; Fig. 2) in Kyushu benthos (fusulines) also sharply declined in diversity forms a part of an ancient mid-oceanic atoll complex across the G–LB in mid-Panthalassan paleo-atoll com- primarily developed on a mid-oceanic paleo-seamount plex (Isozaki and Ota, 2001; Ota and Isozaki, 2006). (Sano and Nakashima, 1997; Isozaki and Ota, 2001; Ota These positively suggest the global nature of the G–LB and Isozaki, 2006). This limestone, like many other Per- extinction and causal environmental change. mian limestones in Japan, occurs as an allochthonous The mid-oceanic paleo-atoll carbonates also recorded block incorporated in the Middle-Upper Jurassic disor- secular change in stable carbon isotope composition. ganized mudstone/sandstone of the Jurassic accretionary Musashi et al. (2001, 2007) and Isozaki et al. (2007) complex in the Chichibu belt (the tectonic outlier of the first documented the secular change in carbonate carbon Mino-Tanba belt; Isozaki, 1997b). The limestone blocks 13 isotopic ratio (␦ Ccarb) of mid-Panthalassa across the in the Kamura area retain parts of the primary mid- P–TB and the G–LB, respectively. Besides the bound- oceanic stratigraphy that ranges in age from the Wordian ary negative shifts both at P–TB and G–LB properly (middle Guadalupian) to Norian (Late Triassic) with sev- predicted from previous studies (e.g., Baud et al., 1989; eral sedimentary breaks in the Triassic part (Kambe, Holser et al., 1989; Wang et al., 2004), a unique high 1963; Kanmera and Nakazawa, 1973; Watanabe et al., productivity interval in the Capitanian (late Guadalu- 1979; Koike, 1996; Ota and Isozaki, 2006). pian) was newly detected on the basis of the appreciable The Permian part consists of bioclastic limestone with 13 length of high positive ␦ Ccarb (between +5 and +6‰) a typical Tethyan shallow marine fauna that includes interval (Isozaki et al., 2007; Fig. 1). As such high posi- various fusulines, smaller foraminifera, large-shelled tive values over +5.0‰ are quite rare in the Phanerozoic bivalves, gastropods, brachiopods, rugose corals, and record except for several unique events in the Paleo- calcareous algae. The Permian rocks are stratigraphi- zoic (e.g., Veizer et al., 1999; Saltzman, 2005), they cally divided into the Guadalupian Iwato Formation (ca. named this Capitanian episode the “Kamura event”, 70 m thick) and the overlying Lopingian Mitai Formation emphasizing its significance of global cooling and rele- (ca. 30 m thick). Fusulines are the most abundant, and vant extinction of large fusulines and gigantic bivalves they provide a basis for subdividing the Iwato Formation in low-latitude Panthalassa (Isozaki et al., 2007). In into four biostratigraphic units; i.e., the Neoschwagerina the fusuline-tuned section, the waning history of the Zone, Yabeina Zone, Lepidolina Zone, and a barren inter- Kamura event was clearly documented in high reso- val, in ascending order (Ota and Isozaki, 2006; Isozaki lution, whereas the earlier history including the onset and Igo, in preparation). The overlying Lopingian Mitai timing was not yet revealed, owing to the absence of con- Formation is subdivided into two fusuline zones, i.e., tinuous exposure in the previously studied section. This the Codonofusiella-Reichelina Zone and Palaeofusulina left a big chasm in our understanding of the major envi- Zone (Kanmera and Nakazawa, 1973; Ota and Isozaki, ronmental change in the late Guadalupian, in particular 2006). All these fusuline assemblages and associated the cause and processes of the Kamura cooling event. fossils (rugose corals and large-shelled bivalves of Fam- This study aimed to clarify the earlier stage of the ily Alatoconchidae; Isozaki, 2006) indicate that the Kamura event, particularly focusing on the onset tim- seamount was located in a low-latitude warm-water ing, and to bracket the total duration of the event. In domain in the superocean Panthalassa under a tropical the same Kamura area in Kyushu, Japan, we analyzed climate. 13 ␦ Ccarb chemostratigraphy of two other sections that The Neoschwagerina Zone is correlated with the expose much lower parts of the Guadalupian (Wordian Wordian (middle Guadalupian) of Texas and with the to lower Capitanian) mid-oceanic paleo-atoll carbon- Murgabian in Transcaucasia (Leven, 1996; Wilde et al., 13 ates. This article reports the ␦ Ccarb measurements and 1999), while the Yabeina Zone, Lepidolina Zone, and discusses their implications to the Capitanian environ- most of the barren interval are correlated with the Capi- 18 Y. Isozaki et al. / Palaeoworld 16 (2007) 16–30 13 Fig. 1. Schematic diagram showing the late Guadalupian Kamura event documented by high positive ␦ Ccarb values at Kamura in Japan (modified 13 from Isozaki et al., 2007) (A), and the composite Permian secular curve of ␦ Ccarb values modified from Korte et al. (2005) (B). Road: Roadian, Wor: Wordian. Note that the Guadalupian large fusuline and bivalve fauna became extinct in the middle of the Kamura cooling event, whereas the post-extinction radiation of the Lopingian small fusulines started during the subsequent warming period. In contrast to the waning history of the Kamura event, its onset timing and processes were unknown previously. In (B), two possible paths (broken lines) for the Guadalupian secular 13 change of ␦ Ccarb values were shown by Korte et al. (2005); the lower for the Tethyan domain, the upper for the Delaware basin in Texas. The 13 Capitanian Kamura event recorded much higher positive ␦ Ccarb values between +5.0 and +7.0‰ in Kamura, suggesting the positive excursion of global context in the late Guadalupian.