A REMARKABLE SEA-LEVEL DROP ACROSS THE GUADALUPIAN-LOPINGIAN BOUNDARY (PERMIAN) IN THE LOW-LATITUDES: UNIQUE HIATUS DETECTED ON A MID-PANTHALASSAN PALEO-ATOLL COMPLEX

In order to clarify the global environmental changes relevant to the end-Guadalupian extinction, litho-, bio-, and chemo- stratigraphy (⁸⁷Sr/⁸⁶Sr, δ¹³C_carb) was analyzed for the Middle-Upper Permian low-latitude mid-oceanic paleo-atoll limestones accreted to Japan.

At Akasaka and Ishiyama sections in central Japan, the Capitanian black limestone is overlain by the Wuchiapingian light gray limestone. The transition was marked by a 9 m-thick unit of black-white striped limestone that lacks major shallow marine fossils such as fusulines and rugose corals. The major extinction level of the Capitanian fossils occurred within the topmost part of the black limestone. The black limestone and light gray limestone were both deposited in the subtidal zone, whereas the transition (striped) limestone in the intertidal zone. An irregular erosion surface occurs at the top of the transition unit. This unique erosional record is concordant to the well-known Phanerozoic lowest sea-level occurred around the G-L boundary.

The Capitanian black limestone is totally characterized by extremely low ⁸⁷Sr/⁸⁶Sr ratios and extremely high δ¹³C_carb values. These chemostratigraphic signatures are explained in accordance with the lowest sea level around the G-L boundary in the mid-superocean.

The extremely low ⁸⁷Sr/⁸⁶Sr ratios (< 0.7070), corresponding to the Capitanian minimum, may suggest the development of large continental glaciers that concealed continental crusts under a cool climate in the Capitanian. Likewise, the extremely high d13Ccarb (> +5 permil) recorded the high primary productivity (Kamura) event in the low-latitude Panthalassa ocean, which was possibly driven by the vigorous ocean circulation under a cool climate.

The end-Guadalupian extinction in low-latitude Panthalassa was related likely to the Capitanian cooling event of the global context.