Global Correlation of Basal Triassic Layers in the Light of the First Carbon Isotope Data on the Permian–Triassic Boundary in Northeast Asia

摘要

This paper is dedicated to the global correlation of the marine Permian–Triassic boundary layers based on some published and original data on the δ~(13)C_(org) and δ~(13)C_(carb) values obtained for the section along the Suol Creek (Setorym River, southern Verkhoyansk region). The section includes six carbon-isotope intervals readily distinguished in the corresponding curves obtained for several Permian and Triassic reference sections in Eurasia and North America including palleontologically well substantiated sections of central Iran, Kashmir, and South China. This provides grounds for assuming the Permian–Triassic boundary’s position in the Suol Creek section as being close to the carbon-isotope minimum of Interval IV. In the light of new data, the upper part of the Upper Permian Changhsingian Stage in Siberia is proposed to correspond in range to the Otoceras concavum range zone, and the lower substage of the Lower Triassic Induan Stage, to the Tompophiceras pascoei and Wordieoceras decipiens zones. The Otoceras concavum Zone of the Verkhoyansk region in its new understanding is likely correlative with the upper Changhsingian Hypophiceras triviale Zone of Greenland. Carbon-isotope intervals II, III, IV, and V defined in the Permian–Triassic boundary layers of the Verkhoyansk region, which are traceable in several reference sections of Eurasia and North America, evidently coincide with the period of some intensification of the volcanic activity in the initial late Changhsingian and with the first phases of extensive eruption of Siberian trappes in the terminal Changhsingian and initial Induan ages. New data imply the probable survival of some ammonoid species from the superfamily Otoceratoidea after the mass extinction of organisms in the terminal Permian Epoch.