Middle-Upper Permian (Maokouan-Wuchiapingian) boundary in mid-oceanic paleo-atoll limestone of Kamura and Akasaka, Japan

Abstract

Abstract:Nearly 10 million years before the Permo-Triassic boundary (PTB; ca. 251 Ma) characterized by the greatest mass extinction in the Phanerozoic, the Middle-Upper Permian boundary marked another big biotic decline almost comparable in magnitude to the PTB event. Two stratigraphic sections spanning across the Maokouan (Middle Permian)-Wuchiapingian (Upper Permian) boundary (MWB) were newly found in paleo-atoll limestone within the Jurassic accretionary complex in Kamura and Akasaka, Japan. These two sections share almost identical litho-and biostratigraphy that records a remarkable biotic extinction of large-shelled fusultnids and a sharp lithologic change exactly across the MWB. These new data, as the first evidence from the shallow-water mid-oceanic realm, suggest that a quick environmental change occurred in a global scale across the MWB. A thin, acidic tuff recognized at the MWB horizon in the paleoatoll limestone has a potential utility as a key bed for global correlation and suggests a possible link between the end-Permian biosphere crisis and the explosive acidic volcanism.

A unique carbon isotope record across the Guadalupian–Lopingian (Middle–Upper Permian) boundary in mid-oceanic paleo-atoll carbonates: The high-productivity “Kamura event” and its collapse in Panthalassa

“…The excavation of primitive mantle materials with low Sr isotope ratio may have been so large in amount probably by plume-related volcanism that the Sr signature by erosional/weathering input of continental material was likely masked completely. The occurrence of a felsic tuff bed at the G-LB horizon suggests the involvement of violent explosive volcanism (Isozaki and Ota, 2001;Isozaki, 2006), on the other hand, coincidence in timing with the basaltic Emeishan traps was pointed out (e.g., Chung et al, 1998). Direct killing mechanisms and relevant processes for changing global environments are still not clear, however, further research from multiple standpoints and in high resolution is needed for the G-LB interval rocks of various facies and in different geologic settings.…”

“…Since these allochthonous limestones occur in several localities in central Honshu to Kyushu with a geographical separation from each other for up to 500 km, they were probably derived not from a single large seamount but from several isolated ones (Isozaki and Ota, 2001). Therefore, the transition from the normal facies to the unique Kinshozan, and vice versa, was common in several paleo-seamount complexes, suggesting that this unique environmental change may have occurred simultaneously on a regional scale in shallow mid-Panthalassa in the late Guadalupian.…”

“…The exotic limestones spanning from Upper Carboniferous to Upper Triassic originated from ancient atolls on paleo-seamount complexes (Kanmera and Nishi, 1983;Isozaki, 1987;Sano, 1988), and some of them preserve intervals not only across the P-TB (Koike, 1996;Sano and Nakashima, 1997;Musashi et al, 2001, in press) but also across the G-LB. Detailed litho-and biostratigraphy of the G-LB interval in such mid-oceanic shallow marine carbonates was recently clarified at the Kamura section in Kyushu (Isozaki and Ota, 2001;Ota and Isozaki, 2006). These studies demonstrated a selective screening of the Guadalupian large-shelled fusulines at the G-LB and following "Lilliput syndrome" sensu lato in the surviving Lopingian taxa in the mid-superocean (Isozaki, 2006) as well as in the Pangean shelf areas.…”

Memories of Pre-Jurassic Lost Oceans: How To Retrieve Them From Extant Lands

“…Following this first discovery of a geologically significant horizon from the pre-Jurassic mid-oceanic paleo-atoll carbonates exposed on land, another significant interval was identified within the Jurassic AC in SW Japan, the Middle-Late Permian boundary (Guadalupian-Lopingian boundary: G-LB; ca. 260 Ma) interval (Isozaki and Ota 2001;Ota and Isozaki 2006).…”

“…The G-LB boundary horizon in the Permian limestone blocks at Kamura in Kyushu and at Akasaka in central Japan was identified by fusuline stratigraphy (Sakagami 1980;Ozawa and Nishiwaki 1992;Zaw Win 1999;Isozaki and Ota 2001;Ota and Isozaki 2006;Fig. 6A).…”