Palaeogeography, Palaeoclimatology, Palaeoecology 499 (2018) 13–21 Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo Middle Permian (Capitanian) seawater 87Sr/86Sr minimum coincided with T disappearance of tropical biota and reef collapse in NE Japan and Primorye (Far East Russia) ⁎ Tomomi Kania, , Yukio Isozakib, Ryutaro Hayashib, Yuri Zakharovc, Alexander Popovc a Faculty of Advanced Science and Technology, Division of Natural Science Earth and Environmental Science, Kumamoto University, 2-39-1, Kurokami, Kumamoto, Japan 850-8555 b Department of Earth Science and Astronomy, The University of Tokyo, Komaba, Tokyo 153-8902, Japan c Far-Eastern Geological Institute, Russian Academy of Sciences (Far Eastern Branch), Stoletija Prospect 159, Vladivostok RU-690022, Russia ARTICLE INFO ABSTRACT Keywords: To investigate the secular changes in Permian seawater chemistry and to constrain the global environmental Seawater changes during the end-Guadalupian (Middle Permian) extinction, we analyzed 87Sr/86Sr ratios in Capitanian Extinction (Upper Guadalupian) shallow-marine limestones in NE Japan and in southern Primorye, Far East Russia. These Guadalupian limestones were deposited on the continental shelf/platform of the northern part of Greater South China, which Limestone faced the northern connecting seaway between the Tethys and Panthalassa. The measured limestone samples Sr isotope were collected from the Capitanian fusuline (Lepidolina)-bearing intervals and overlying beds at Iwaizaki in the South Kitakami belt, NE Japan, and at Senkina Shapka in the Sergeevka belt, southern Primorye. The present analysis of bulk 87Sr/86Sr ratios clarified extremely low 87Sr/86Sr ratios of 0.7068–0.7070 from all measured samples. These Sr isotopic values support a Capitanian age for these strata. The topmost 30 m-thick interval of the Iwaizaki Limestone, in particular, witnessed a stepwise biodiversity decline in the shallow marine warm- water biota and the collapse of the carbonate factory after the reef development during the Capitanian in the northern part of Greater South China. The disappearance of the tropical biota and the collapse of the reef during the late Capitanian suggest that the biotic responses to a significant environmental change appeared relatively earlier at mid-latitudes than in the tropical regions. 1. Introduction throughout the entire the Paleozoic, whereas it tended to increase throughout the Mesozoic-Cenozoic (Fig. 1). The most significant The seawater 87Sr/86Sr ratio is mainly driven by the radiogenic flux change, in particular, an extremely low 87Sr/86Sr ratio interval, oc- from the continental crust and a less radiogenic flux from the mantle. curred in the Middle Permian, which marks the most unusual condition The balance of the fluxes has changed through geological time, and it is in the Phanerozoic Sr cycle in the oceans (Veizer et al., 1999; Korte linked to global-scale changes in tectonics, sea level, continental et al., 2003, 2006; Kani et al., 2008; McArthur et al., 2012). This unique weathering rates, mid-ocean ridge activity, and diagenetic processes “Permian minimum” has occurred in general coevally with the major (e.g., Veizer, 1989; McArthur et al., 2012). The residence time of Sr in mass extinction in the Middle Permian (Guadalupian), which represents seawater is estimated as ca. 3 million years in modern oceans, which is the first major decline in the Permian marine biodiversity, but clearly much longer than the ocean circulation interval; therefore, seawater predates the terminal crisis at the Permo-Triassic boundary (P–TB) 87Sr/86Sr ratios are expected to be uniform worldwide. As the seawater (Stanley and Yang, 1994; Jin et al., 1994; Isozaki and Ota, 2001). The 87Sr/86Sr ratio is potentially recorded in marine carbonates, numerous Guadalupian biocrisis occurred not within a short time but over a studies to date have built a large archive of ancient seawater 87Sr/86Sr prolonged period of a few million years (Clapham et al., 2009). Its cause records, particularly for the Phanerozoic, which indeed demonstrate is still controversial (e.g., Erwin, 2006; Isozaki, 2009; Bond et al., remarkable secular changes through time (e.g., Burke et al., 1982; 2010a, 2010b); nonetheless, the relevant global environmental changes Denison et al., 1994; Martin and MacDougall, 1995; Veizer et al., 1999; no doubt involved significant changes in seawater chemistry including McArthur et al., 2012). The 87Sr/86Sr value generally tended to decline the Sr isotope composition. ⁎ Corresponding author. E-mail address: [email protected] (T. Kani). https://doi.org/10.1016/j.palaeo.2018.03.033 Received 12 September 2017; Received in revised form 26 March 2018; Accepted 26 March 2018 Available online 30 March 2018 0031-0182/ © 2018 Elsevier B.V. All rights reserved. T. Kani et al. Palaeogeography, Palaeoclimatology, Palaeoecology 499 (2018) 13–21 Fig. 1. Overview of secular changes in sea level (modified from Haq and Schutter, 2008) and the seawater Sr isotopic profile during the Phanerozoic (modified from McArthur et al., 2012) with major extinction timings. Previous Sr isotope studies on the Guadalupian-Lopingian boundary et al., 2010), NE Japan and Primorye naturally have pre-Miocene (G-LB) interval were carried out mostly in fossiliferous and thus well- geology with striking similarity. For example, the Sikhote-Alin fold belt dated shallow marine limestone sections deposited in low-latitude areas in southern Primorye comprises some geotectonic units that are (e.g., Denison and Koepnick, 1995; Martin and MacDougall, 1995; equivalent to those found in Japan; the Triassic-Jurassic accretionary Jones et al., 1995; Korte et al., 2006; Kani et al., 2008, 2013). These complexes of the Samarka belt are no doubt correlated with those of the studies confirmed that unusually the low 87Sr/86Sr ratio in seawater (as Ultra-Tanba and Mino-Tanba-Ashio-North Kitakami belt in Japan (e.g., low as 0.7068) persisted throughout the Capitanian Stage of the Gua- Kojima et al., 2000; Kemkin, 2012; Khanchuk et al., 2016). In addition, dalupian Series (the last one-third of the Guadalupian). This extremely Paleozoic granitoids and ophiolite units are common between the two low Sr isotope value naturally reflected a minimum flux from con- regions (e.g., Ishiwatari, 1991; Nevolin et al., 2010; Tsutsumi et al., tinental crust with respect to that from mid-oceanic ridges. For the 2014, 2016; Isozaki et al., 2015, 2017). cause of this unique phenomenon, a conventional explanation might The latest studies on detrital zircons in Paleozoic sandstones in the prefer a high sea level under global warming, which can suppress the South Kitakami belt in NE Japan (Okawa et al., 2013; Isozaki et al., global total weathering/erosion as a result of concealing vast con- 2014) and the Sergeevka belt in Primorye (Isozaki et al., 2017) have tinental coastal zones. Nonetheless, the sea level during the Capitanian confirmed the occurrence of Neoproterozoic grains that suggest the contradictorily recorded the lowest stand of the Phanerozoic (Haq and origin of NE Japan and southern Primorye together in an intimate link Schutter, 2008), suggesting a global cooling instead. Ice coverage and/ with the South China block (Isozaki et al., 2017). The common occur- or the predominance of arid climates under cooling during the Permian rence of Early Paleozoic arc granitoids in the two regions (Nevolin likely accelerated the decrease in the seawater Sr ratio. et al., 2010; Isozaki et al., 2015; Tsutsumi et al., 2016) also supports the For checking the spatiotemporal extent of the Capitanian Sr- interpretation that NE Japan and southern Primorye have been located minimum and its possible relations to the mass extinction, more data along the Pacific margin of Greater South China, i.e., a reconstructed are needed elsewhere with relevant records of biotic responses, parti- continental block composed of the South China block per se in the cularly from non-tropical higher-latitude areas. This study analyzed the mainland China together with SW-NE Japan and southern Primorye Sr isotope ratios of Wordian-Capitanian (Middle-Upper Guadalupian) (Isozaki et al., 2017). During the Permian, the main part of Greater limestones in the South Kitakami belt of northeast Japan, and the South China remained in a low-latitude area under a tropical climate Sergeevka belt in southern Primorye, Far East Russia. The latest ana- with typical warm-water Tethyan fauna, whereas its northern-eastern lyses on detrital zircon geochronology confirmed that both the South extension may have been positioned near the northern connecting Kitakami belt and the Sergeevka belt once formed northeastern exten- seaway between the Tethys and Panthalassa at relatively higher latitude sions of the Paleozoic South China block and have been overlooked for under subtropical conditions (Fig. 2A), probably to the north of the years (Isozaki et al., 2014, 2017; Fig. 2A); thus, the shallow marine North China block (Isozaki et al., 2017). shelf limestones in these two belts were deposited on the shelf/platform As to the Permian shallow marine sequence of continental shelf of Greater South China during the Permian, but likely at slightly higher facies, the South Kitakami belt (Fig. 2C) and the Sergeevka belt latitudes of the subtropical zone in the northern part of South China (Fig. 2D) share almost the same sedimentary packages with similar li- than in the mainland China